Aviation Engines - Design—Construction

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Title: Aviation Engines - Design—Construction—Operation and Repair
Author: Pagé, Victor Wilfred
Language: English
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AVIATION ENGINES

Design--Construction--Operation and Repair

FIRST LIEUT. VICTOR W. PAGÉ, A. S. S. C., U. S. R.

* * * * *

~JUST PUBLISHED~

=AVIATION ENGINES. Their Design, Construction, Operation and Repair.=

By Lieut. VICTOR W. PAGÉ, Aviation Section, S.C.U.S.R.

A practical work containing valuable instructions for aviation
students, mechanicians, squadron engineering officers and all
interested in the construction and upkeep of airplane power
plants. 576 octavo pages. 250 illustrations. Price $3.00.

=AVIATION CHART, or the Location of Airplane Power Plant Troubles Made
Easy.=

By Lieut. VICTOR W. PAGÉ, A.S., S.C.U.S.R.

A large chart outlining all parts of a typical airplane power
plant, showing the points where trouble is apt to occur and
suggesting remedies for the common defects. Intended especially
for aviators and aviation mechanics on school and field duty.
Price 50 cents.

=GLOSSARY OF AVIATION TERMS.=

Compiled by Lieuts. VICTOR W. PAGÉ, A.S., S.C.U.S.R. and PAUL
MONTARIOL of the French Flying Corps on duty at Signal Corps
Aviation School, Mineola, L. I.

A complete glossary of practically all terms used in aviation,
having lists in both French and English, with equivalents in
either language. A very valuable book for all who are about to
leave for duty overseas. Price, cloth, $1.00.

=THE NORMAN W. HENLEY PUBLISHING COMPANY=

2 WEST 45TH ST., NEW YORK

* * * * *

[Illustration: Part Sectional View of Hall-Scott Airplane Motor, Showing
Principal Parts.]

* * * * *

CENSORED

This Book Entitled

AVIATION ENGINES

By LIEUT. VICTOR W. PAGÉ

has been censored by the United States Government, and pages and
parts of pages have been omitted by special instructions from
Washington.

The book has been passed by THE COMMITTEE ON PUBLIC INFORMATION
and is as complete as we can furnish it, and we so advise the
purchaser of it.

THE NORMAN W. HENLEY PUBLISHING COMPANY

* * * * *

AVIATION ENGINES

Design--Construction--Operation and Repair

A Complete, Practical Treatise Outlining Clearly
the Elements of Internal Combustion Engineering
with Special Reference to the Design, Construction,
Operation and Repair of Airplane Power
Plants; Also the Auxiliary Engine Systems, Such
as Lubrication, Carburetion, Ignition and Cooling.

It Includes Complete Instructions for Engine
Repairing and Systematic Location of Troubles,
Tool Equipment and Use of Tools, Also Outlines
the Latest Mechanical Processes.

FIRST LIEUT. VICTOR W. PAGÉ, A. S. S. C., U. S. R.

Assistant Engineering Officer, Signal Corps Aviation School,
Mineola, L. I.

Author of "The Modern Gasoline Automobile," Etc.

[Illustration]

Contains Valuable Instructions for All Aviation Students,
Mechanicians, Squadron Engineering Officers and All Interested in
the Construction and Upkeep of Airplane Power Plants.

New York
The Norman W. Henley Publishing Company
2 West 45th Street
1917

Copyrighted, 1917
By
The Norman W. Henley Publishing Co.

Printed in U. S. A.

All Illustrations in This Book Have Been
Specially Made by the Publishers, and Their
Use, Without Permission, Is Strictly Prohibited

Composition, Electrotyping and Presswork
by the Publishers Printing Co., New York

PREFACE

In presenting this treatise on "Aviation Engines," the writer realizes
that the rapidly developing art makes it difficult to outline all latest
forms or describe all current engineering practice. This exposition has
been prepared primarily for instruction purposes and is adapted for men
in the Aviation Section, Signal Corps, and students who wish to become
aviators or aviation mechanicians. Every effort has been made to have
the engineering information accurate, but owing to the diversity of
authorities consulted and use of data translated from foreign language
periodicals, it is expected that some slight errors will be present. The
writer wishes to acknowledge his indebtedness to such firms as the
Curtiss Aeroplane and Motor Co., Hall-Scott Company, Thomas-Morse
Aircraft Corporation and General Vehicle Company for photographs and
helpful descriptive matter. Special attention has been paid to
instructions on tool equipment, use of tools, trouble "shooting" and
engine repairs, as it is on these points that the average aviation
student is weakest. Only such theoretical consideration of
thermo-dynamics as was deemed absolutely necessary to secure a proper
understanding of engine action after consulting several instructors is
included, the writer's efforts having been confined to the preparation
of a practical series of instructions that would be of the greatest
value to those who need a diversified knowledge of internal-combustion
engine operation and repair, and who must acquire it quickly. The
engines described and illustrated are all practical forms that have been
fitted to airplanes capable of making flights and may be considered
fairly representative of the present state of the art.

VICTOR W. PAGÉ,

_1st Lieut. A. S. S. C., U. S. R_.

MINEOLA, L. I.,

October, 1917.

CONTENTS

PAGES
CHAPTER I

Brief Consideration of Aircraft Types--Essential Requirements of
Aerial Motors--Aviation Engines Must Be Light--Factors Influencing
Power Needed--Why Explosive Motors Are Best--Historical--Main
Types of Internal Combustion Engines 17-36

CHAPTER II

Operating Principles of Two- and Four-Stroke Engines--Four-cycle
Action--Two-cycle Action--Comparing Two- and Four-cycle Types--
Theory of Gas and Gasoline Engine--Early Gas-Engine Forms--
Isothermal Law--Adiabatic Law--Temperature Computations--Heat and
Its Work--Conversion of Heat to Power--Requisites for Best Power
Effect 37-59

CHAPTER III

Efficiency of Internal Combustion Engines--Various Measures of
Efficiency--Temperatures and Pressures--Factors Governing Economy
--Losses in Wall Cooling--Value of Indicator Cards--Compression in
Explosive Motors--Factors Limiting Compression--Causes of Heat
Losses and Inefficiency--Heat Losses to Cooling Water 60-79

CHAPTER IV

Engine Parts and Functions--Why Multiple Cylinder Engines Are Best
--Describing Sequence of Operations--Simple Engines--Four and Six
Cylinder Vertical Tandem Engines--Eight and Twelve Cylinder V
Engines--Radial Cylinder Arrangement--Rotary Cylinder Forms 80-109

CHAPTER V

Properties of Liquid Fuels--Distillates of Crude Petroleum--
Principles of Carburetion Outlined--Air Needed to Burn Gasoline--
What a Carburetor Should Do--Liquid Fuel Storage and Supply--
Vacuum Fuel Feed--Early Vaporizer Forms--Development of Float Feed
Carburetor--Maybach's Early Design--Concentric Float and Jet Type
--Schebler Carburetor--Claudel Carburetor--Stewart Metering Pin
Type--Multiple Nozzle Vaporizers--Two-Stage Carburetor--Master
Multiple Jet Type--Compound Nozzle Zenith Carburetor--Utility of
Gasoline Strainers--Intake Manifold Design and Construction--
Compensating for Various Atmospheric Conditions--How High
Altitude Affects Power--The Diesel System--Notes on Carburetor
Installation--Notes on Carburetor Adjustment 110-154

CHAPTER VI

Early Ignition Systems--Electrical Ignition Best--Fundamentals of
Magnetism Outlined--Forms of Magneto--Zones of Magnetic Influence
--How Magnets are Made--Electricity and Magnetism Related--Basic
Principles of Magneto Action--Essential Parts of Magneto and
Functions--Transformer Coil Systems--True High Tension Type--The
Berling Magneto--Timing and Care--The Dixie Magneto--Spark-Plug
Design and Application--Two-Spark Ignition--Special Airplane
Plug 155-200

CHAPTER VII

Why Lubrication Is Necessary--Friction Defined--Theory of
Lubrication--Derivation of Lubricants--Properties of Cylinder Oils
--Factors Influencing Lubrication System Selection--Gnome Type
Engines Use Castor Oil--Hall-Scott Lubrication System--Oil Supply
by Constant Level Splash System--Dry Crank-Case System Best for
Airplane Engines--Why Cooling Systems Are Necessary--Cooling
Systems Generally Applied--Cooling by Positive Pump Circulation--
Thermo-Syphon System--Direct Air-Cooling Methods--Air-Cooled
Engine Design Considerations 201-232

CHAPTER VIII

Methods of Cylinder Construction--Block Castings--Influence on
Crank-Shaft Design--Combustion Chamber Design--Bore and Stroke
Ratio--Meaning of Piston Speed--Advantage of Off-Set Cylinders--
Valve Location of Vital Import--Valve Installation Practice--Valve
Design and Construction--Valve Operation--Methods of Driving
Cam-Shaft--Valve Springs--Valve Timing--Blowing Back--Lead Given
Exhaust Valve--Exhaust Closing, Inlet Opening--Closing the
Inlet Valve--Time of Ignition--How an Engine is Timed--Gnome
"Monosoupape" Valve Timing--Springless Valves--Four Valves per
Cylinder 233-286

CHAPTER IX

Constructional Details of Pistons--Aluminum Cylinders and Pistons
--Piston Ring Construction--Leak Proof Piston Rings--Keeping Oil
Out of Combustion Chamber--Connecting Rod Forms--Connecting Rods
for Vee Engines--Cam-Shaft and Crank-Shaft Designs--Ball Bearing
Crank-Shafts--Engine Base Construction 287-323

CHAPTER X

Power Plant Installation--Curtiss OX-2 Engine Mounting and
Operating Rules--Standard S. A. E. Engine Bed Dimensions--
Hall-Scott Engine Installation and Operation--Fuel System Rules
--Ignition System--Water System--Preparations to Start Engine--
Mounting Radial and Rotary Engines--Practical Hints to Locate
Engine Troubles--All Engine Troubles Summarized--Location of
Engine Troubles Made Easy 324-375

CHAPTER XI

Tools for Adjusting and Erecting--Forms of Wrenches--Use and Care
of Files--Split Pin Removal and Installation--Complete Chisel Set
--Drilling Machines--Drills, Reamers, Taps and Dies--Measuring
Tools--Micrometer Calipers and Their Use--Typical Tool Outfits
--Special Hall-Scott Tools--Overhauling Airplane Engines--Taking
Engine Down--Defects in Cylinders--Carbon Deposits, Cause and
Prevention--Use of Carbon Scrapers--Burning Out Carbon with
Oxygen --Repairing Scored Cylinders--Valve Removal and Inspection
--Reseating and Truing Valves--Valve Grinding Processes--
Depreciation in Valve Operating System--Piston Troubles--Piston
Ring Manipulation--Fitting Piston Rings--Wrist-Pin Wear--
Inspection and Refitting of Engine Bearings--Scraping Brasses to
Fit--Fitting Connecting Rods--Testing for Bearing Parallelism--
Cam-Shafts and Timing Gears--Precautions in Reassembling Parts 376-456

CHAPTER XII

Aviation Engine Types--Division in Classes--Anzani Engines--Canton
and Unné Engine--Construction of Gnome Engines--"Monosoupape"
Gnome--German "Gnome" Type--Le Rhone Engine--Renault Air-Cooled
Engine--Simplex Model "A" Hispano-Suiza--Curtiss Aviation Motors--
Thomas-Morse Model 88 Engine--Duesenberg Engine--Aeromarine
Six-Cylinder--Wisconsin Aviation Engines--Hall-Scott Engines--
Mercedes Motor--Benz Motor--Austro-Daimler Engine--Sunbeam-Coatalen
--Indicating and Measuring Instruments--Air Starting Systems--
Electric Starting--Battery Ignition 457-571

INDEX 573

LIST OF ILLUSTRATIONS

AVIATION ENGINES

DESIGN--CONSTRUCTION--REPAIR

CHAPTER I

Brief Consideration of Aircraft Types--Essential Requirements of
Aerial Motors--Aviation Engines Must Be Light--Factors
Influencing Power Needed--Why Explosive Motors Are Best--
Historical--Main Types of Internal Combustion Engines.

BRIEF CONSIDERATION OF AIRCRAFT TYPES

The conquest of the air is one of the most stupendous achievements of
the ages. Human flight opens the sky to man as a new road, and because
it is a road free of all obstructions and leads everywhere, affording
the shortest distance to any place, it offers to man the prospect of
unlimited freedom. The aircraft promises to span continents like
railroads, to bridge seas like ships, to go over mountains and forests
like birds, and to quicken and simplify the problems of transportation.
While the actual conquest of the air is an accomplishment just being
realized in our days, the idea and yearning to conquer the air are old,
possibly as old as intellect itself. The myths of different races tell
of winged gods and flying men, and show that for ages to fly was the
highest conception of the sublime. No other agent is more responsible
for sustained flight than the internal combustion motor, and it was only
when this form of prime mover had been fully developed that it was
possible for man to leave the ground and alight at will, not depending
upon the caprices of the winds or lifting power of gases as with the
balloon. It is safe to say that the solution of the problem of flight
would have been attained many years ago if the proper source of power
had been available as all the essential elements of the modern
aeroplane and dirigible balloon, other than the power plant, were known
to early philosophers and scientists.

Aeronautics is divided into two fundamentally different
branches--aviatics and aerostatics. The first comprises all types of
aeroplanes and heavier than air flying machines such as the helicopters,
kites, etc.; the second includes dirigible balloons, passive balloons
and all craft which rise in the air by utilizing the lifting force of
gases. Aeroplanes are the only practical form of heavier-than-air
machines, as the helicopters (machines intended to be lifted directly
into the air by propellers, without the sustaining effect of planes),
and ornithopters, or flapping wing types, have not been thoroughly
developed, and in fact, there are so many serious mechanical problems to
be solved before either of these types of air craft will function
properly that experts express grave doubts regarding the practicability
of either. Aeroplanes are divided into two main types--monoplanes or
single surface forms, and bi-planes or machines having two sets of
lifting surfaces, one suspended over the other. A third type, the
triplane, is not very widely used.

Dirigible balloons are divided into three classes: the rigid, the
semi-rigid, and the non-rigid. The rigid has a frame or skeleton of
either wood or metal inside of the bag, to stiffen it; the semi-rigid is
reinforced by a wire net and metal attachments; while the non-rigid is
just a bag filled with gas. The aeroplane, more than the dirigible and
balloon, stands as the emblem of the conquest of the air. Two reasons
for this are that power flight is a real conquest of the air, a real
victory over the battling elements; secondly, because the aeroplane, or
any flying machine that may follow, brings air travel within the reach
of everybody. In practical development, the dirigible may be the
steamship of the air, which will render invaluable services of a certain
kind, and the aeroplane will be the automobile of the air, to be used by
the multitude, perhaps for as many purposes as the automobile is now
being used.

ESSENTIAL REQUIREMENTS OF AERIAL MOTORS

One of the marked features of aircraft development has been the effect
it has had upon the refinement and perfection of the internal combustion
motor. Without question gasoline-motors intended for aircraft are the
nearest to perfection of any other type yet evolved. Because of the
peculiar demands imposed upon the aeronautical motor it must possess all
the features of reliability, economy and efficiency now present with
automobile or marine engines and then must have distinctive points of
its own. Owing to the unstable nature of the medium through which it is
operated and the fact that heavier-than-air machines can maintain flight
only as long as the power plant is functioning properly, an airship
motor must be more reliable than any used on either land or water. While
a few pounds of metal more or less makes practically no difference in a
marine motor and has very little effect upon the speed or hill-climbing
ability of an automobile, an airship motor must be as light as it is
possible to make it because every pound counts, whether the motor is to
be fitted into an aeroplane or in a dirigible balloon.

Airship motors, as a rule, must operate constantly at high speeds in
order to obtain a maximum power delivery with a minimum piston
displacement. In automobiles, or motor boats, motors are not required to
run constantly at their maximum speed. Most aircraft motors must
function for extended periods at speed as nearly the maximum as
possible. Another thing that militates against the aircraft motor is the
more or less unsteady foundation to which it is attached. The
necessarily light framework of the aeroplane makes it hard for a motor
to perform at maximum efficiency on account of the vibration of its
foundation while the craft is in flight. Marine and motor car engines,
while not placed on foundations as firm as those provided for stationary
power plants, are installed on bases of much more stability than the
light structure of an aeroplane. The aircraft motor, therefore, must be
balanced to a nicety and must run steadily under the most unfavorable
conditions.

AERIAL MOTORS MUST BE LIGHT

The capacity of light motors designed for aerial work per unit of mass
is surprising to those not fully conversant with the possibilities that
a thorough knowledge of proportions of parts and the use of special
metals developed by the automobile industry make possible. Activity in
the development of light motors has been more pronounced in France than
in any other country. Some of these motors have been complicated types
made light by the skillful proportioning of parts, others are of the
refined simpler form modified from current automobile practice. There is
a tendency to depart from the freakish or unconventional construction
and to adhere more closely to standard forms because it is necessary to
have the parts of such size that every quality making for reliability,
efficiency and endurance are incorporated in the design. Aeroplane
motors range from two cylinders to forms having fourteen and sixteen
cylinders and the arrangement of these members varies from the
conventional vertical tandem and opposed placing to the V form or the
more unusual radial motors having either fixed or rotary cylinders. The
weight has been reduced so it is possible to obtain a complete power
plant of the revolving cylinder air-cooled type that will not weigh more
than three pounds per actual horse-power and in some cases less than
this.

If we give brief consideration to the requirements of the aviator it
will be evident that one of the most important is securing maximum power
with minimum mass, and it is desirable to conserve all of the good
qualities existing in standard automobile motors. These are certainty of
operation, good mechanical balance and uniform delivery of
power--fundamental conditions which must be attained before a power
plant can be considered practical. There are in addition, secondary
considerations, none the less desirable, if not absolutely essential.
These are minimum consumption of fuel and lubricating oil, which is
really a factor of import, for upon the economy depends the capacity and
flying radius. As the amount of liquid fuel must be limited the most
suitable motor will be that which is powerful and at the same time
economical. Another important feature is to secure accessibility of
components in order to make easy repair or adjustment of parts possible.
It is possible to obtain sufficiently light-weight motors without
radical departure from established practice. Water-cooled power plants
have been designed that will weigh but four or five pounds per
horse-power and in these forms we have a practical power plant capable
of extended operation.

FACTORS INFLUENCING POWER NEEDED

Work is performed whenever an object is moved against a resistance, and
the amount of work performed depends not only on the amount of
resistance overcome but also upon the amount of time utilized in
accomplishing a given task. Work is measured in horse-power for
convenience. It will take one horse-power to move 33,000 pounds one foot
in one minute or 550 pounds one foot in one second. The same work would
be done if 330 pounds were moved 100 feet in one minute. It requires a
definite amount of power to move a vehicle over the ground at a certain
speed, so it must take power to overcome resistance of an airplane in
the air. Disregarding the factor of air density, it will take more power
as the speed increases if the weight or resistance remains constant, or
more power if the speed remains constant and the resistance increases.
The airplane is supported by air reaction under the planes or lifting
surfaces and the value of this reaction depends upon the shape of the
aerofoil, the amount it is tilted and the speed at which it is drawn
through the air. The angle of incidence or degree of wing tilt regulates
the power required to a certain degree as this affects the speed of
horizontal flight as well as the resistance. Resistance may be of two
kinds, one that is necessary and the other that it is desirable to
reduce to the lowest point possible. There is the wing resistance and
the sum of the resistances of the rest of the machine such as fuselage,
struts, wires, landing gear, etc. If we assume that a certain airplane
offered a total resistance of 300 pounds and we wished to drive it
through the air at a speed of sixty miles per hour, we can find the
horse-power needed by a very simple computation as follows:

The product of 300 pounds resistance times speed of
88 feet per second times 60 seconds in a minute
----------------------------------------------------- = H.P. needed.
divided by 33,000 foot pounds per minute
in one horse-power

The result is the horse-power needed, or

300 × 88 × 60
--------------- = 48 H.P.
33,000

Just as it takes more power to climb a hill than it does to run a car on
the level, it takes more power to climb in the air with an airplane than
it does to fly on the level. The more rapid the climb, the more power it
will take. If the resistance remains 300 pounds and it is necessary to
drive the plane at 90 miles per hour, we merely substitute proper values
in the above formula and we have

300 pounds times 132 feet per second times 60
seconds in a minute
----------------------------------------------- = 72 H.P.
33,000 foot pounds per minute in one
horse-power

The same results can be obtained by dividing the product of the
resistance in pounds times speed in feet per second by 550, which is the
foot-pounds of work done in one second to equal one horse-power.
Naturally, the amount of propeller thrust measured in pounds necessary
to drive an airplane must be greater than the resistance by a
substantial margin if the plane is to fly and climb as well. The
following formulæ were given in "The Aeroplane" of London and can be
used to advantage by those desiring to make computations to ascertain
power requirements:

[Illustration: Fig. 1.--Diagrams Illustrating Computations for
Horse-Power Required for Airplane Flight.]

The thrust of the propeller depends on the power of the motor, and on
the diameter and pitch of the propeller. If the required thrust to a
certain machine is known, the calculation for the horse-power of the
motor should be an easy matter.

The required thrust is the sum of three different "resistances." The
first is the "drift" (dynamical head resistance of the aerofoils), i.e.,
tan [alpha] × lift (_L_), lift being equal to the total weight of
machine (_W_) for horizontal flight and [alpha] equal to the angle of
incidence. Certainly we must take the tan [alpha] at the maximum _K_{y}_
value for minimum speed, as then the drift is the greatest (Fig. 1, A).

Another method for finding the drift is _D_ = _K_ × _AV_^{2}, when we
take the drift again so as to be greatest.

The second "resistance" is the total head resistance of the machine, at
its maximum velocity. And the third is the thrust for climbing. The
horse-power for climbing can be found out in two different ways. I first
propose to deal with the method, where we find out the actual
horse-power wanted for a certain climbing speed to our machine, where

climbing speed/sec. × _W_
H.P. = ---------------------------
550

In this case we know already the horse-power for climbing, and we can
proceed with our calculation.

With the other method we shall find out the "thrust" in pounds or
kilograms wanted for climbing and add it to drift and total head
resistance, and we shall have the total "thrust" of our machine and we
shall denote it with _T_, while thrust for climbing shall be _T_{c}_.

The following calculation is at our service to find out

_V_{c}_ × _W_
this thrust for climbing --------------- = H.P.,
550

H.P. × 550
thence _V_{c}_ = ------------ (1)
_W_

_T_{c}_ × _V_
H.P. = --------------, then from
550

_T_{c}_ × _V_
--------------- × 550
550 _T_{c}_ × _V_
(1) _V_{c}_ = ----------------------- = ---------------, thence,
_W_ _W_

_V_{c}_ × _W_
T_{c} = ---------------.
_V_

Whether _T_ means drifts, head resistance and thrust for climbing, or
drift and head resistance only, the following calculation is the same,
only in the latter case, of course, we must add the horse-power required
for climbing to the result to obtain the total horse-power.

Now, when we know the total thrust, we shall find the horse-power in the
following manner:

_Pr_2[pi]_R_
We know that the H.P. = -------------- in kilograms, or in
75 × 60

_Pr_2[pi]_R_
English measure, H.P. = -------------- (Fig. 1, B)
33,000

where _P_ = pressure in klgs. or lbs.
_r_ = radius on which _P_ is acting.
_R_ = Revolution/min.

_M.R._2[pi]
When _P_ × _r_ = _M_, then H.P. = -------------, thence,
4,500

H.P. × 4,500 716.2 H.P.
_M_ = -------------- = ------------ in meter kilograms,
_R_2[pi] _R_

H.P. 33,000 5253.1 H.P.
or in English system _M_ = ------------- = ------------- in
_R_2[pi] _R_

foot pounds.

Now the power on the circumference of the propeller will be reduced by
its radius, so it will be _M_/_r_ = _p_. A part of _p_ will be used for
counteracting the air and bearing friction, so that the total power on
the circumference of the propeller will be (_M_/_r_) × [eta] = _p_ where
[eta] is the mechanical efficiency of the propeller. Now

[eta]
--------------- = _T_, where [alpha] is taken on the tip of the
_tan_ [alpha]

propeller.

I take [alpha] at the tip, but it can be taken, of course, at any point,
but then in equation _p_ = _M_/_r_, _r_ must be taken only up to this
point, and not the whole radius; but it is more comfortable to take it
at the tip, as

Pitch
_tan_ [alpha] = ---------- (Fig. 1, C).
_r_2[pi]

Now we can write up the equation of the thrust:

716.2 H.P. [eta] 5253.1 H.P. [eta]
-------------------, or in English measure -------------------
_R r tan [alpha]_ _R r tan [alpha]_

_T_ × _R_ × _r tan_ [alpha]
thence H.P. = -----------------------------, or in English measure
716.2[eta]

_T_ × _R_ × _r tan_ [alpha]
-----------------------------.
5253.1[eta]

The computations and formulæ given are of most value to the student
engineer rather than matters of general interest, but are given so that
a general idea may be secured of how airplane design influences power
needed to secure sustained flight. It will be apparent that the
resistance of an airplane depends upon numerous considerations of design
which require considerable research in aerodynamics to determine
accurately. It is obvious that the more resistance there is, the more
power needed to fly at a given speed. Light monoplanes have been flown
with as little as 15 horse-power for short distances, but most planes
now built use engines of 100 horse-power or more. Giant airplanes have
been constructed having 2,000 horse-power distributed in four power
units. The amount of power provided for an airplane of given design
varies widely as many conditions govern this, but it will range from
approximately one horse-power to each 8 pounds weight in the case of
very light, fast machines to one horse-power to 15 or 18 pounds of the
total weight in the case of medium speed machines. The development in
airplane and power plant design is so rapid, however, that the figures
given can be considered only in the light of general averages rather
than being typical of current practice.

WHY EXPLOSIVE MOTORS ARE BEST

Internal combustion engines are best for airplanes and all types of
aircraft for the same reasons that they are universally used as a source
of power for automobiles. The gasoline engine is the lightest known form
of prime mover and a more efficient one than a steam engine, especially
in the small powers used for airplane propulsion. It has been stated
that by very careful designing a steam plant an engine could be made
that would be practical for airplane propulsion, but even with the
latest development it is doubtful if steam power can be utilized in
aircraft to as good advantage as modern gasoline-engines are. While the
steam-engine is considered very much simpler than a gas-motor, the
latter is much more easily mastered by the non-technical aviator and
certainly requires less attention. A weight of 10 pounds per horse-power
is possible in a condensing steam plant but this figure is nearly double
or triple what is easily secured with a gas-motor which may weigh but 5
pounds per horse-power in the water cooled forms and but 2 or 3 pounds
in the air-cooled types. The fuel consumption is twice as great in a
steam-power plant (owing to heat losses) as would be the case in a
gasoline engine of equal power and much less weight.

The internal-combustion engine has come seemingly like an avalanche of a
decade; but it has come to stay, to take its well-deserved position
among the powers for aiding labor. Its ready adaptation to road, aerial
and marine service has made it a wonder of the age in the development of
speed not before dreamed of as a possibility; yet in so short a time,
its power for speed has taken rank on the common road against the
locomotive on the rail with its century's progress. It has made aerial
navigation possible and practical, it furnishes power for all marine
craft from the light canoe to the transatlantic liner. It operates the
machine tools of the mechanic, tills the soil for the farmer and
provides healthful recreation for thousands by furnishing an economical
means of transport by land and sea. It has been a universal mechanical
education for the masses, and in its present forms represents the great
refinement and development made possible by the concentration of the
world's master minds on the problems incidental to internal combustion
engineering.

HISTORICAL

Although the ideal principle of explosive power was conceived some two
hundred years ago, at which time experiments were made with gunpowder as
the explosive element, it was not until the last years of the eighteenth
century that the idea took a patentable shape, and not until about 1826
(Brown's gas-vacuum engine) that a further progress was made in England
by condensing the products of combustion by a jet of water, thus
creating a partial vacuum.

Brown's was probably the first explosive engine that did real work. It
was clumsy and unwieldy and was soon relegated to its place among the
failures of previous experiments. No approach to active explosive effect
in a cylinder was reached in practice, although many ingenious designs
were described, until about 1838 and the following years. Barnett's
engine in England was the first attempt to compress the charge before
exploding. From this time on to about 1860 many patents were issued in
Europe and a few in the United States for gas-engines, but the progress
was slow, and its practical introduction for power came with spasmodic
effect and low efficiency. From 1860 on, practical improvement seems to
have been made, and the Lenoir motor was produced in France and brought
to the United States. It failed to meet expectations, and was soon
followed by further improvements in the Hugon motor in France (1862),
followed by Beau de Rocha's four-cycle idea, which has been slowly
developed through a long series of experimental trials by different
inventors. In the hands of Otto and Langdon a further progress was made,
and numerous patents were issued in England, France, and Germany, and
followed up by an increasing interest in the United States, with a few
patents.

From 1870 improvements seem to have advanced at a steady rate, and
largely in the valve-gear and precision of governing for variable load.
The early idea of the necessity of slow combustion was a great drawback
in the advancement of efficiency, and the suggestion of de Rocha in 1862
did not take root as a prophetic truth until many failures and years of
experience had taught the fundamental axiom that rapidity of action in
both combustion and expansion was the basis of success in explosive
motors.

With this truth and the demand for small and safe prime movers, the
manufacture of gas-engines increased in Europe and America at a more
rapid rate, and improvements in perfecting the details of this cheap and
efficient prime mover have finally raised it to the dignity of a
standard motor and a dangerous rival of the steam-engine for small and
intermediate powers, with a prospect of largely increasing its
individual units to many hundred, if not to the thousand horse-power in
a single cylinder. The unit size in a single cylinder has now reached to
about 700 horse-power and by combining cylinders in the same machine,
powers of from 1,500 to 2,000 horse-power are now available for large
power-plants.

MAIN TYPES OF INTERNAL-COMBUSTION ENGINES

This form of prime mover has been built in so many different types, all
of which have operated with some degree of success that the diversity in
form will not be generally appreciated unless some attempt is made to
classify the various designs that have received practical application.
Obviously the same type of engine is not universally applicable, because
each class of work has individual peculiarities which can best be met by
an engine designed with the peculiar conditions present in view. The
following tabular synopsis will enable the reader to judge the extent of
the development of what is now the most popular prime mover for all
purposes.

A. Internal Combustion (Standard Type)
1. Single Acting (Standard Type)
2. Double Acting (For Large Power Only)
3. Simple (Universal Form)
4. Compound (Rarely Used)
5. Reciprocating Piston (Standard Type)
6. Turbine (Revolving Rotor, not fully developed)

A1. Two-Stroke Cycle
a. Two Port
b. Three Port
c. Combined Two and Three Port
d. Fourth Port Accelerator
e. Differential Piston Type
f. Distributor Valve System

A2. Four-Stroke Cycle
a. Automatic Inlet Valve
b. Mechanical Inlet Valve
c. Poppet or Mushroom Valve
d. Slide Valve
d 1. Sleeve Valve
d 2. Reciprocating Ring Valve
d 3. Piston Valve
e. Rotary Valves
e 1. Disc
e 2. Cylinder or Barrel
e 3. Single Cone
e 4. Double Cone
f. Two Piston (Balanced Explosion)
g. Rotary Cylinder, Fixed Crank (Aerial)
h. Fixed Cylinder, Rotary Crank (Standard Type)

A3. Six-Stroke Cycle

B. External Combustion (Practically Obsolete)
a. Turbine, Revolving Rotor
b. Reciprocating Piston

CLASSIFICATION BY CYLINDER ARRANGEMENT

Single Cylinder
a. Vertical
b. Horizontal
c. Inverted Vertical

Double Cylinder
a. Vertical
b. Horizontal (Side by Side)
c. Horizontal (Opposed)
d. 45 to 90 Degrees V (Angularly Disposed)
e. Horizontal Tandem (Double Acting)

Three Cylinder
a. Vertical
b. Horizontal
c. Rotary (Cylinders Spaced at 120 Degrees)
d. Radially Placed (Stationary Cylinders)
e. One Vertical, One Each Side at an Angle
f. Compound (Two High Pressure, One Low Pressure)

Four Cylinder
a. Vertical
b. Horizontal (Side by Side)
c. Horizontal (Two Pairs Opposed)
d. 45 to 90 Degrees V
e. Twin Tandem (Double Acting)

Five Cylinder
a. Vertical (Five Throw Crankshaft)
b. Radially Spaced at 72 Degrees (Stationary)
c. Radially Placed Above Crankshaft (Stationary)
d. Placed Around Rotary Crankcase (72 Degrees Spacing)

Six Cylinder
a. Vertical
b. Horizontal (Three Pairs Opposed)
c. 45 to 90 Degrees V

Seven Cylinder
a. Equally Spaced (Rotary)

Eight Cylinder
a. Vertical
b. Horizontal (Four Pairs Opposed)
c. 45 to 90 Degrees V

Nine Cylinder
a. Equally Spaced (Rotary)

Twelve Cylinder
a. Vertical
b. Horizontal (Six Pairs Opposed)
c. 45 to 90 Degrees V

Fourteen Cylinder
a. Rotary

Sixteen Cylinder
a. 45 to 90 Degrees V
b. Horizontal (Eight Pairs Opposed)

Eighteen Cylinder
a. Rotary Cylinder

[Illustration: Fig. 2.--Plate Showing Heavy, Slow Speed Internal
Combustion Engines Used Only for Stationary Power in Large Installations
Giving Weight to Horse-Power Ratio.]

[Illustration: Fig. 3.--Various Forms of Internal Combustion Engines
Showing Decrease in Weight to Horse-Power Ratio with Augmenting Speed of
Rotation.]

[Illustration: Fig. 4.--Internal Combustion Engine Types of Extremely
Fine Construction and Refined Design, Showing Great Power Outputs for
Very Small Weight, a Feature Very Much Desired in Airplane Power
Plants.]

Of all the types enumerated above engines having less than eight
cylinders are the most popular in everything but aircraft work. The
four-cylinder vertical is without doubt the most widely used of all
types owing to the large number employed as automobile power plants.
Stationary engines in small and medium powers are invariably of the
single or double form. Three-cylinder engines are seldom used at the
present time, except in marine work and in some stationary forms.
Eight- and twelve-cylinder motors have received but limited application
and practically always in automobiles, racing motor boats or in aircraft.
The only example of a fourteen-cylinder motor to be used to any extent
is incorporated in aeroplane construction. This is also true of the
sixteen- and eighteen-cylinder forms and of twenty-four-cylinder engines
now in process of development.

The duty an engine is designed for determines the weight per
horse-power. High powered engines intended for steady service are always
of the slow speed type and consequently are of very massive
construction. Various forms of heavy duty type stationary engines are
shown at Fig. 2. Some of these engines may weigh as much as 600 pounds
per horse-power. A further study is possible by consulting data given on
Figs. 3 and 4. As the crank-shaft speed increases and cylinders are
multiplied the engines become lighter. While the big stationary power
plants may run for years without attention, airplane engines require
rebuilding after about 60 to 80 hours air service for the fixed cylinder
types and 40 hours or less for the rotary cylinder air-cooled forms.
There is evidently a decrease in durability and reliability as the
weight is lessened. These illustrations also permit of obtaining a good
idea of the variety of forms internal combustion engines are made in.

CHAPTER II

Operating Principles of Two- and Four-Stroke Engines--Four-cycle
Action--Two-cycle Action--Comparing Two- and Four-cycle Types--
Theory of Gas and Gasoline Engine--Early Gas-Engine Forms--
Isothermal Law--Adiabatic Law--Temperature Computations--Heat
and Its Work--Conversion of Heat to Power--Requisites for Best
Power Effect.

OPERATING PRINCIPLES OF TWO- AND FOUR-STROKE CYCLE ENGINES

Before discussing the construction of the various forms of internal
combustion engines it may be well to describe the operating cycle of the
types most generally used. The two-cycle engine is the simplest because
there are no valves in connection with the cylinder, as the gas is
introduced into that member and expelled from it through ports cored
into the cylinder walls. These are covered by the piston at a certain
portion of its travel and uncovered at other parts of its stroke. In the
four-cycle engine the explosive gas is admitted to the cylinder through
a port at the head end closed by a valve, while the exhaust gas is
expelled through another port controlled in a similar manner. These
valves are operated by mechanism distinct from the piston.

[Illustration: Fig. 5.--Outlining First Two Strokes of Piston in
Four-Cycle Engine.]

The action of the four-cycle type may be easily understood if one refers
to illustrations at Figs. 5 and 6. It is called the "four-stroke engine"
because the piston must make four strokes in the cylinder for each
explosion or power impulse obtained. The principle of the gas-engine of
the internal combustion type is similar to that of a gun, i.e., power is
obtained by the rapid combustion of some explosive or other quick
burning substance. The bullet is driven out of the gun barrel by the
pressure of the gas evolved when the charge of powder is ignited. The
piston or movable element of the gas-engine is driven from the closed
or head end to the crank end of the cylinder by a similar expansion of
gases resulting from combustion. The first operation in firing a gun or
securing an explosion in the cylinder of the gas-engine is to fill the
combustion space with combustible material. This is done by a down
stroke of the piston during which time the inlet valve opens to admit
the gaseous charge to the cylinder interior. This operation is shown at
Fig. 5, A. The second operation is to compress this gas which is done by
an upward stroke of the piston as shown at Fig. 5, B. When the top of
the compression stroke is reached, the gas is ignited and the piston is
driven down toward the open end of the cylinder, as indicated at Fig. 6,
C. The fourth operation or exhaust stroke is performed by the return
upward movement of the piston as shown at Fig. 6, D during which time
the exhaust valve is opened to permit the burnt gases to leave the
cylinder. As soon as the piston reaches the top of its exhaust stroke,
the energy stored in the fly-wheel rim during the power stroke causes
that member to continue revolving and as the piston again travels on
its down stroke the inlet valve opens and admits a charge of fresh gas
and the cycle of operations is repeated.

[Illustration: Fig. 6.--Outlining Second Two Strokes of Piston in
Four-Cycle Engine.]

[Illustration: Fig. 7.--Sectional View of L Head Gasoline Engine
Cylinder Showing Piston Movements During Four-Stroke Cycle.]

The illustrations at Fig. 7 show how the various cycle functions take
place in an L head type water cooled cylinder engine. The sections at A
and C are taken through the inlet valve, those at B and D are taken
through the exhaust valve.

The two-cycle engine works on a different principle, as while only the
combustion chamber end of the piston is employed to do useful work in
the four-cycle engine, both upper and lower portions are called upon to
perform the functions necessary to two-cycle engine operation. Instead
of the gas being admitted into the cylinder as is the case with the
four-stroke engine, it is first drawn into the engine base where it
receives a preliminary compression prior to its transfer to the working
end of the cylinder. The views at Fig. 8 should indicate clearly the
operation of the two-port two-cycle engine. At A the piston is seen
reaching the top of its stroke and the gas above the piston is being
compressed ready for ignition, while the suction in the engine base
causes the automatic valve to open and admits mixture from the
carburetor to the crank case. When the piston reaches the top of its
stroke, the compressed gas is ignited and the piston is driven down on
the power stroke, compressing the gas in the engine base.

[Illustration: Fig. 8.--Showing Two-port, Two-cycle Engine Operation.]

When the top of the piston uncovers the exhaust port the flaming gas
escapes because of its pressure. A downward movement of the piston
uncovers the inlet port opposite the exhaust and permits the fresh gas
to bypass through the transfer passage from the engine base to the
cylinder. The conditions with the intake and exhaust port fully opened
are clearly shown at Fig. 8, C. The deflector plate on the top of the
piston directs the entering fresh gas to the top of the cylinder and
prevents the main portion of the gas stream from flowing out through the
open exhaust port. On the next upstroke of the piston the gas in the
cylinder is compressed and the inlet valve opened, as shown at A to
permit a fresh charge to enter the engine base.

[Illustration: Fig. 9.--Defining Three-port, Two-cycle Engine Action.]

The operating principle of the three-port, two-cycle engine is
practically the same as that previously described with the exception
that the gas is admitted to the crank-case through a third port in the
cylinder wall, which is uncovered by the piston when that member reaches
the end of its upstroke. The action of the three-port form can be
readily ascertained by studying the diagrams given at Fig. 9.
Combination two- and three-port engines have been evolved and other
modifications made to improve the action.

THE TWO-CYCLE AND FOUR-CYCLE TYPES

In the earlier years of explosive-motor progress was evolved the two
types of motors in regard to the cycles of their operation. The early
attempts to perfect the two-cycle principle were for many years held in
abeyance from the pressure of interests in the four-cycle type, until
its simplicity and power possibilities were demonstrated by Mr. Dugald
Clerk in England, who gave the principles of the two-cycle motor a broad
bearing leading to immediate improvements in design, which has made
further progress in the United States, until at the present time it has
an equal standard value as a motor-power in some applications as its
ancient rival the four-cycle or Otto type, as demonstrated by Beau de
Rocha in 1862.

Thermodynamically, the methods of the two types are equal as far as
combustion is concerned, and compression may favor in a small degree the
four-cycle type as well as the purity of the charge. The cylinder volume
of the two-cycle motor is much smaller per unit of power, and the
enveloping cylinder surface is therefore greater per unit of volume.
Hence more heat is carried off by the jacket water during compression,
and the higher compression available from this tends to increase the
economy during compression which is lost during expansion.

From the above considerations it may be safely stated that a _lower_
temperature and higher pressure of charge at the beginning of
compression is obtained in the two-cycle motor, greater weight of charge
and greater specific power of higher compression resulting in higher
thermal efficiency. The smaller cylinder for the same power of the
two-cycle motor gives less friction surface per impulse than of the
other type; although the crank-chamber pressure may, in a measure,
balance the friction of the four-cycle type. Probably the strongest
points in favor of the two-cycle type are the lighter fly-wheel and the
absence of valves and valve gear, making this type the most simple in
construction and the lightest in weight for its developed power. Yet,
for the larger power units, the four-cycle type will no doubt always
maintain the standard for efficiency and durability of action.

The distribution of the charge and its degree of mixture with the
remains of the previous explosion in the clearance space, has been a
matter of discussion for both types of explosive motors, with doubtful
results. In Fig. 10, A we illustrate what theory suggests as to the
distribution of the fresh charge in a two-cycle motor, and in Fig. 10, B
what is the probable distribution of the mixture when the piston starts
on its compressive stroke. The arrows show the probable direction of
flow of the fresh charge and burnt gases at the crucial moment.

[Illustration: Fig. 10.--Diagrams Contrasting Action of Two- and
Four-Cycle Cylinders on Exhaust and Intake Stroke.]

In Fig. 10, C is shown the complete out-sweep of the products of
combustion for the full extent of the piston stroke of a four-cycle
motor, leaving only the volume of the clearance to mix with the new
charge and at D the manner by which the new charge sweeps by the
ignition device, keeping it cool and avoiding possibilities of
pre-ignition by undue heating of the terminals of the sparking device.
Thus, by enveloping the sparking device with the pure mixture, ignition
spreads through the charge with its greatest possible velocity, a most
desirable condition in high-speed motors with side-valve chambers and
igniters within the valve chamber.

THEORY OF THE GAS AND GASOLINE ENGINE

The laws controlling the elements that create a power by their expansion
by heat due to combustion, when properly understood, become a matter of
computation in regard to their value as an agent for generating power in
the various kinds of explosive engines. The method of heating the
elements of power in explosive engines greatly widens the limits of
temperature as available in other types of heat-engines. It disposes of
many of the practical troubles of hot-air, and even of steam-engines, in
the simplicity and directness of application of the elements of power.
In the explosive engine the difficulty of conveying heat for producing
expansive effect by convection is displaced by the generation of the
required heat within the expansive element and at the instant of its
useful work. The low conductivity of heat to and from air has been the
great obstacle in the practical development of the hot-air engine;
while, on the contrary, it has become the source of economy and
practicability in the development of the internal-combustion engine.

The action of air, gas, and the vapors of gasoline and petroleum oil,
whether singly or mixed, is affected by changes of temperature
practically in nearly the same ratio; but when the elements that produce
combustion are interchanged in confined spaces, there is a marked
difference of effect. The oxygen of the air, the hydrogen and carbon of
a gas, or vapor of gasoline or petroleum oil are the elements that by
combustion produce heat to expand the nitrogen of the air and the watery
vapor produced by the union of the oxygen in the air and the hydrogen in
the gas, as well as also the monoxide and carbonic-acid gas that may be
formed by the union of the carbon of gas or vapor with part of the
oxygen of the air. The various mixtures as between air and gas, or air
and vapor, with the proportion of the products of combustion left in the
cylinder from a previous combustion, form the elements to be considered
in estimating the amount of pressure that may be obtained by their
combustion and expansive force.

EARLY GAS ENGINE FORMS

The working process of the explosive motor may be divided into three
principal types: 1. Motors with charges igniting at constant volume
without compression, such as the Lenoir, Hugon, and other similar types
now abandoned as wasteful in fuel and effect. 2. Motors with charges
igniting at constant pressure with compression, in which a receiver is
charged by a pump and the gases burned while being admitted to the motor
cylinder, such as types of the Simon and Brayton engine. 3. Motors with
charges igniting at constant volume with variable compression, such as
the later two- and four-cycle motors with compression of the indrawn
charge; limited in the two-cycle type and variable in the four-cycle
type with the ratios of the clearance space in the cylinder. This
principle produces the explosive motor of greatest efficiency.

The phenomena of the brilliant light and its accompanying heat at the
moment of explosion have been witnessed in the experiments of Dugald
Clerk in England, the illumination lasting throughout the stroke; but in
regard to time in a four-cycle engine, the incandescent state exists
only one-quarter of the running time. Thus the time interval, together
with the non-conductibility of the gases, makes the phenomena of a
high-temperature combustion within the comparatively cool walls of a
cylinder a practical possibility.

THE ISOTHERMAL LAW

The natural laws, long since promulgated by Boyle, Gay Lussac, and
others, on the subject of the expansion and compression of gases by
force and by heat, and their variable pressures and temperatures when
confined, are conceded to be practically true and applicable to all
gases, whether single, mixed, or combined.

The law formulated by Boyle only relates to the compression and
expansion of gases without a change of temperature, and is stated in
these words:

_If the temperature of a gas be kept constant, its pressure or elastic
force will vary inversely as the volume it occupies._

It is expressed in the formula P × V = C, or pressure × volume =
constant. Hence, C/P = V and C/V = P.

Thus the curve formed by increments of pressure during the expansion or
compression of a given volume of gas without change of temperature is
designated as the isothermal curve in which the volume multiplied by the
pressure is a constant value in expansion, and inversely the pressure
divided by the volume is a constant value in compressing a gas.

But as compression and expansion of gases require force for their
accomplishment mechanically, or by the application or abstraction of
heat chemically, or by convection, a second condition becomes involved,
which was formulated into a law of thermodynamics by Gay Lussac under
the following conditions: A given volume of gas under a free piston
expands by heat and contracts by the loss of heat, its volume causing a
proportional movement of a free piston equal to 1/273 part of the
cylinder volume for each degree Centigrade difference in temperature, or
1/492 part of its volume for each degree Fahrenheit. With a fixed piston
(constant volume), the pressure is increased or decreased by an increase
or decrease of heat in the same proportion of 1/273 part of its pressure
for each degree Centigrade, or 1/492 part of its pressure for each
degree Fahrenheit change in temperature. This is the natural sequence of
the law of mechanical equivalent, which is a necessary deduction from
the principle that nothing in nature can be lost or wasted, for all the
heat that is imparted to or abstracted from a gaseous body must be
accounted for, either as heat or its equivalent transformed into some
other form of energy. In the case of a piston moving in a cylinder by
the expansive force of heat in a gaseous body, all the heat expended in
expansion of the gas is turned into work; the balance must be accounted
for in absorption by the cylinder or radiation.

THE ADIABATIC LAW

This theory is equally applicable to the cooling of gases by abstraction
of heat or by cooling due to expansion by the motion of a piston. The
denominators of these heat fractions of expansion or contraction
represent the absolute zero of cold below the freezing-point of water,
and read -273° C. or -492.66° = -460.66° F. below zero; and these are
the starting-points of reference in computing the heat expansion in
gas-engines. According to Boyle's law, called the first law of gases,
there are but two characteristics of a gas and their variations to be
considered, _viz_., volume and pressure: while by the law of Gay Lussac,
called the second law of gases, a third is added, consisting of the
value of the absolute temperature, counting from absolute zero to the
temperatures at which the operations take place. This is the _Adiabatic_
law.

The ratio of the variation of the three conditions--volume, pressure,
and heat--from the absolute zero temperature has a certain rate, in
which the volume multiplied by the pressure and the product divided by
the absolute temperature equals the ratio of expansion for each degree.
If a volume of air is contained in a cylinder having a piston and fitted
with an indicator, the piston, if moved to and fro slowly, will
alternately compress and expand the air, and the indicator pencil will
trace a line or lines upon the card, which lines register the change of
pressure and volume occurring in the cylinder. If the piston is
perfectly free from leakage, and it be supposed that the temperature of
the air is kept quite constant, then the line so traced is called an
_Isothermal line_, and the pressure at any point when multiplied by the
volume is a constant, according to Boyle's law,

_pv_ = a constant.

If, however, the piston is moved very rapidly, the air will not remain
at constant temperature, but the temperature will increase because work
has been done upon the air, and the heat has no time to escape by
conduction. If no heat whatever is lost by any cause, the line will be
traced over and over again by the indicator pencil, the cooling by
expansion doing work precisely equalling the heating by compression.
This is the line of no transmission of heat, therefore known as
_Adiabatic_.

[Illustration: Fig. 11.--Diagram Isothermal and Adiabatic Lines.]

The expansion of a gas 1/273 of its volume for every degree Centigrade,
added to its temperature, is equal to the decimal .00366, the
coefficient of expansion for Centigrade units. To any given volume of a
gas, its expansion may be computed by multiplying the coefficient by
the number of degrees, and by reversing the process the degree of
acquired heat may be obtained approximately. These methods are not
strictly in conformity with the absolute mathematical formula, because
there is a small increase in the increment of expansion of a dry gas,
and there is also a slight difference in the increment of expansion due
to moisture in the atmosphere and to the vapor of water formed by the
union of the hydrogen and oxygen in the combustion chamber of explosive
engines.

TEMPERATURE COMPUTATIONS

The ratio of expansion on the Fahrenheit scale is derived from the
absolute temperature below the freezing-point of water (32°) to
correspond with the Centigrade scale; therefore 1/492.66 = .0020297, the
ratio of expansion from 32° for each degree rise in temperature on the
Fahrenheit scale. As an example, if the temperature of any volume of air
or gas at constant volume is raised, say from 60° to 2000° F., the
increase in temperature will be 1940°. The ratio will be 1/520.66 =
.0019206. Then by the formula:

Ratio × acquired temp. × initial pressure = the gauge pressure; and
.0019206 × 1940° × 14.7 = 54.77 lbs.

By another formula, a convenient ratio is obtained by (absolute
pressure)/(absolute temp.) or 14.7/520.66 = .028233; then, using the
difference of temperature as before, .028233 × 1940° = 54.77 lbs.
pressure.

By another formula, leaving out a small increment due to specific heat
at high temperatures:

Atmospheric pressure × absolute temp. + acquired temp.
I. -------------------------------------------------------- =
Absolute temp. + initial temp.

absolute pressure due to the acquired temperature, from which the
atmospheric pressure is deducted for the gauge pressure. Using the
foregoing example, we have (14.7 × 460.66° + 2000°)/(460.66 + 60°) =
69.47 - 14.7 = 54.77, the gauge pressure, 460.66 being the absolute
temperature for zero Fahrenheit.

For obtaining the volume of expansion of a gas from a given increment of
heat, we have the approximate formula:

Volume × absolute temp. + acquired temp.
II. ------------------------------------------ =
Absolute temp. + initial temp.

heated volume. In applying this formula to the foregoing example, the
figures become:

460.66° + 2000°
I. × ----------------- = 4.72604 volumes.
460.66 + 60°

From this last term the gauge pressure may be obtained as follows:

III. 4.72604 × 14.7 = 69.47 lbs. absolute - 14.7 lbs. atmospheric
pressure = 54.77 lbs. gauge pressure; which is the theoretical pressure
due to heating air in a confined space, or at constant volume from 60°
to 2000° F.

By inversion of the heat formula for absolute pressure we have the
formula for the acquired heat, derived from combustion at constant
volume from atmospheric pressure to gauge pressure plus atmospheric
pressure as derived from Example I., by which the expression

absolute pressure × absolute temp. + initial temp.
----------------------------------------------------
initial absolute pressure

= absolute temperature + temperature of combustion, from which the
acquired temperature is obtained by subtracting the absolute
temperature.

Then, for example, (69.47 × 460.66 + 60)/14.7 = 2460.66, and 2460.66 -
460.66 = 2000°, the theoretical heat of combustion. The dropping of
terminal decimals makes a small decimal difference in the result in the
different formulas.

HEAT AND ITS WORK

By Joule's law of the mechanical equivalent of heat, whenever heat is
imparted to an elastic body, as air or gas, energy is generated and
mechanical work produced by the expansion of the air or gas. When the
heat is imparted by combustion within a cylinder containing a movable
piston, the mechanical work becomes an amount measurable by the observed
pressure and movement of the piston. The heat generated by the explosive
elements and the expansion of the non-combining elements of nitrogen and
water vapor that may have been injected into the cylinder as moisture in
the air, and the water vapor formed by the union of the oxygen of the
air with the hydrogen of the gas, all add to the energy of the work from
their expansion by the heat of internal combustion. As against this, the
absorption of heat by the walls of the cylinder, the piston, and
cylinder-head or clearance walls, becomes a modifying condition in the
force imparted to the moving piston.

It is found that when any explosive mixture of air and gas or
hydrocarbon vapor is fired, the pressure falls far short of the pressure
computed from the theoretical effect of the heat produced, and from
gauging the expansion of the contents of a cylinder. It is now well
known that in practice the high efficiency which is promised by
theoretical calculation is never realized; but it must always be
remembered that the heat of combustion is the real agent, and that the
gases and vapors are but the medium for the conversion of inert elements
of power into the activity of energy by their chemical union. The theory
of combustion has been the leading stimulus to large expectations with
inventors and constructors of explosive motors; its entanglement with
the modifying elements in practice has delayed the best development in
construction, and as yet no really positive design of best form or
action seems to have been accomplished, although great progress has been
made during the past decade in the development of speed, reliability,
economy, and power output of the individual units of this comparatively
new power.

One of the most serious difficulties in the practical development of
pressure, due to the theoretical computations of the pressure value of
the full heat, is probably caused by imparting the heat of the fresh
charge to the balance of the previous charge that has been cooled by
expansion from the maximum pressure to near the atmospheric pressure of
the exhaust. The retardation in the velocity of combustion of perfectly
mixed elements is now well known from experimental trials with measured
quantities; but the principal difficulty in applying these conditions to
the practical work of an explosive engine where a necessity for a large
clearance space cannot be obviated, is in the inability to obtain a
maximum effect from the imperfect mixture and the mingling of the
products of the last explosion with the new mixture, which produces a
clouded condition that makes the ignition of the mass irregular or
chattering, as observed in the expansion lines of indicator cards; but
this must not be confounded with the reaction of the spring in the
indicator.

Stratification of the mixture has been claimed as taking place in the
clearance chamber of the cylinder; but this is not a satisfactory
explanation in view of the vortical effect of the violent injection of
the air and gas or vapor mixture. It certainly cannot become a perfect
mixture in the time of a stroke of a high-speed motor of the two-cycle
class. In a four-cycle engine, making 1,500 revolutions per minute, the
injection and compression in any one cylinder take place in one
twenty-fifth of a second--formerly considered far too short a time for a
perfect infusion of the elements of combustion but now very easily taken
care of despite the extremely high speed of numerous aviation and
automobile power-plants.

TABLE I.--EXPLOSION AT CONSTANT VOLUME IN A CLOSED CHAMBER.

=====+================================+======+=======+========+======
Dia- | | Temp.| Time | Ob- | Com-
gram | | of | of | served |puted
Curve| Mixture Injected. |Injec-|Explo- | Gauge |Temp.
Fig. | | tion | sion |Pressure|Fahr.
8. | | Fahr.|Second.| Pounds |
-----+--------------------------------+------+-------+--------+------
_a_ |1 volume gas to 14 volumes air. | 64° | 0.45 | 40. |1,483°
_b_ |1 " " " 13 " " | 51° | 0.31 | 51.5 |1,859°
_c_ |1 " " " 12 " " | 51° | 0.24 | 60. |2,195°
_d_ |1 " " " 11 " " | 51° | 0.17 | 61. |2,228°
_e_ |1 " " " 9 " " | 62° | 0.08 | 78. |2,835°
_f_ |1 " " " 7 " " | 62° | 0.06 | 87. |3,151°
_g_ |1 " " " 6 " " | 51° | 0.04 | 90. |3,257°
_h_ |1 " " " 5 " " | 51° | 0.055 | 91. |3,293°
_i_ |1 " " " 4 " " | 66° | 0.16 | 80. |2,871°
-----+--------------------------------+------+-------+--------+------

In an examination of the times of explosion and the corresponding
pressures in both tables, it will be seen that a mixture of 1 part gas
to 6 parts air is the most effective and will give the highest mean
pressure in a gas-engine. There is a limit to the relative proportions
of illuminating gas and air mixture that is explosive, somewhat
variable, depending upon the proportion of hydrogen in the gas. With
ordinary coal-gas, 1 of gas to 15 parts of air; and on the lower end of
the scale, 1 volume of gas to 2 parts air, are non-explosive. With
gasoline vapor the explosive effect ceases at 1 to 16, and a saturated
mixture of equal volumes of vapor and air will not explode, while the
most intense explosive effect is from a mixture of 1 part vapor to 9
parts air. In the use of gasoline and air mixtures from a carburetor,
the best effect is from 1 part saturated air to 8 parts free air.

TABLE II.--PROPERTIES AND EXPLOSIVE TEMPERATURE OF A MIXTURE OF ONE PART
OF ILLUMINATING GAS OF 660 THERMAL UNITS PER CUBIC FOOT WITH VARIOUS
PROPORTIONS OF AIR WITHOUT MIXTURE OF CHARGE WITH THE PRODUCTS OF A
PREVIOUS EXPLOSION.

[A] Proportion, Air to Gas by Volumes.
[B] Pounds in One Cubic Foot of Mixture.
[C] Specific Heat. Heat Units Required to Raise 1 Lb. 1 Deg.
Fahrenheit. Constant Pressure.
[D] Specific Heat. Heat Units Required to Raise 1 Lb. 1 Deg.
Fahrenheit. Constant Volume.
[E] Heat to Raise One Cubic Foot of Mixture 1 Deg. Fahr.
[F] Heat Units Evolved by Combustion.
[G] Ratio Col. 6/5
[H] Usual Combustion Efficiency.
[I] Usual Rise of Temperature due to Explosion at Constant Volume.

=======+========+======+======+========+======+=======+=====+=====
[A] | [B] | [C] | [D] | [E] | [F] | [G] | [H] | [I]
-------+--------+------+------+--------+------+-------+-----+-----
6 to 1| .074195| .2668| .1913| .014189| 94.28| 6644.6| .465| 3090
7 to 1| .075012| .2628| .1882| .014116| 82. | 5844.4| .518| 3027
8 to 1| .075647| .2598| .1858| .014059| 73.33| 5216.1| .543| 2832
9 to 1| .076155| .2575| .1846| .014013| 66. | 4709.9| .56 | 2637
10 to 1| .076571| .2555| .1825| .013976| 60. | 4293. | .575| 2468
11 to 1| .076917| .2540| .1813| .013945| 55. | 3944. | .585| 2307
12 to 1| .077211| .2526| .1803| .013922| 50.77| 3646.7| .58 | 2115
-------+--------+------+------+--------+------+-------+-----+-----

The weight of a cubic foot of gas and air mixture as given in Col. 2 is
found by adding the number of volumes of air multiplied by its weight,
.0807, to one volume of gas of weight .035 pound per cubic foot and
dividing by the total number of volumes; for example, as in the table, 6
× .0807 = .5192/7 = .074195 as in the first line, and so on for any
mixture or for other gases of different specific weight per cubic foot.
The heat units evolved by combustion of the mixture (Col. 6) are
obtained by dividing the total heat units in a cubic foot of gas by the
total proportion of the mixture, 660/7 = 94.28 as in the first line of
the table. Col. 5 is obtained by multiplying the weight of a cubic foot
of the mixture in Col. 2 by the specific heat at a constant volume (Col.
4), Col. 6/Col. 5 = Col. 7 the total heat ratio, of which Col. 8 gives
the usual combustion efficiency--Col. 7 × Col. 8 gives the absolute rise
in temperature of a pure mixture, as given in Col. 9.

The many recorded experiments made to solve the discrepancy between the
theoretical and the actual heat development and resulting pressures in
the cylinder of an explosive motor, to which much discussion has been
given as to the possibilities of dissociation and the increased specific
heat of the elements of combustion and non-combustion, as well, also, of
absorption and radiation of heat, have as yet furnished no satisfactory
conclusion as to what really takes place within the cylinder walls.
There seems to be very little known about dissociation, and somewhat
vague theories have been advanced to explain the phenomenon. The fact
is, nevertheless, apparent as shown in the production of water and other
producer gases by the use of steam in contact with highly incandescent
fuel. It is known that a maximum explosive mixture of pure gases, as
hydrogen and oxygen or carbonic oxide and oxygen, suffers a contraction
of one-third their volume by combustion to their compounds, steam or
carbonic acid. In the explosive mixtures in the cylinder of a motor,
however, the combining elements form so small a proportion of the
contents of the cylinder that the shrinkage of their volume amounts to
no more than 3 per cent. of the cylinder volume. This by no means
accounts for the great heat and pressure differences between the
theoretical and actual effects.

CONVERSION OF HEAT TO POWER

The utilization of heat in any heat-engine has long been a theme of
inquiry and experiment with scientists and engineers, for the purpose of
obtaining the best practical conditions and construction of heat-engines
that would represent the highest efficiency or the nearest approach to
the theoretical value of heat, as measured by empirical laws that have
been derived from experimental researches relating to its ultimate
volume. It is well known that the steam-engine returns only from 12 to
18 per cent. of the power due to the heat generated by the fuel, about
25 per cent. of the total heat being lost in the chimney, the only use
of which is to create a draught for the fire; the balance, some 60 per
cent., is lost in the exhaust and by radiation. The problem of utmost
utilization of force in steam has nearly reached its limit.

The internal-combustion system of creating power is comparatively new in
practice, and is but just settling into definite shape by repeated
trials and modification of details, so as to give somewhat reliable data
as to what may be expected from the rival of the steam-engine as a prime
mover. For small powers, the gas, gasoline, and petroleum-oil engines
are forging ahead at a rapid rate, filling the thousand wants of
manufacture and business for a power that does not require expensive
care, that is perfectly safe at all times, that can be used in any place
in the wide world to which its concentrated fuel can be conveyed, and
that has eliminated the constant handling of crude fuel and water.

REQUISITES FOR BEST POWER EFFECT

The utilization of heat in a gas-engine is mainly due to the manner in
which the products entering into combustion are distributed in relation
to the movement of the piston. The investigation of the foremost
exponent of the theory of the explosive motor was prophetic in
consideration of the later realization of the best conditions under
which these motors can be made to meet the requirements of economy and
practicability. As early as 1862, Beau de Rocha announced, in regard to
the coming power, that four requisites were the basis of operation for
economy and best effect. 1. The greatest possible cylinder volume with
the least possible cooling surface. 2. The greatest possible rapidity of
expansion. Hence, _high speed_. 3. The greatest possible expansion.
_Long stroke._ 4. The greatest possible pressure at the commencement of
expansion. _High compression._

CHAPTER III

Efficiency of Internal Combustion Engines--Various Measures of
Efficiency--Temperatures and Pressures--Factors Governing
Economy--Losses in Wall Cooling--Value of Indicator Cards--
Compression in Explosive Motors--Factors Limiting Compression--
Causes of Heat Losses and Inefficiency--Heat Losses to Cooling
Water.

EFFICIENCY OF INTERNAL COMBUSTION ENGINES

Efficiencies are worked out through intricate formulas for a variety of
theoretical and unknown conditions of combustion in the cylinder: ratios
of clearance and cylinder volume, and the uncertain condition of the
products of combustion left from the last impulse and the wall
temperature. But they are of but little value, except as a mathematical
inquiry as to possibilities. The real commercial efficiency of a gas or
gasoline-engine depends upon the volume of gas or liquid at some
assigned cost, required per actual brake horse-power per hour, in which
an indicator card should show that the mechanical action of the valve
gear and ignition was as perfect as practicable, and that the ratio of
clearance, space, and cylinder volume gave a satisfactory terminal
pressure and compression: _i.e._, the difference between the power
figured from the indicator card and the brake power being the friction
loss of the engine.

In four-cycle motors of the compression type, the efficiencies are
greatly advanced by compression, producing a more complete infusion of
the mixture of gas or vapor and air, quicker firing, and far greater
pressure than is possible with the two-cycle type previously described.
In the practical operation of the gas-engine during the past twenty
years, the gas-consumption efficiencies per indicated horse-power have
gradually risen from 17 per cent. to a maximum of 40 per cent. of the
theoretical heat, and this has been done chiefly through a decreased
combustion chamber and increased compression--the compression having
gradually increased in practice from 30 lbs. per square inch to above
100; but there seems to be a limit to compression, as the efficiency
ratio decreases with greater increase in compression. It has been shown
that an ideal efficiency of 33 per cent. for 38 lbs., compression will
increase to 40 per cent. for 66 lbs., and 43 per cent. for 88 lbs.
compression. On the other hand, greater compression means greater
explosive pressure and greater strain on the engine structure, which
will probably retain in future practice the compression between the
limits of 40 and 90 lbs. except in super-compression engines intended
for high altitude work where compression pressures as high as 125 pounds
have been used.

In experiments made by Dugald Clerk, in England, with a combustion
chamber equal to 0.6 of the space swept by the piston, with a
compression of 38 lbs., the consumption of gas was 24 cubic feet per
indicated horse-power per hour. With 0.4 compression space and 61 lbs.
compression, the consumption of gas was 20 cubic feet per indicated
horse-power per hour; and with 0.34 compression space and 87 lbs.
compression, the consumption of gas fell to 14.8 cubic feet per
indicated horse-power per hour--the actual efficiencies being
respectively 17, 21, and 25 per cent. This was with a Crossley
four-cycle engine.

VARIOUS MEASURES OF EFFICIENCY

The efficiencies in regard to power in a heat-engine may be divided
into four kinds, as follows: I. The first is known as the _maximum
theoretical efficiency_ of a perfect engine (represented by the
lines in the indicator diagram). It is expressed by the formula
(T_{1} - T_{0})/T_{1} and shows the work of a perfect cycle in an engine
working between the received temperature + absolute temperature (T_{1})
and the initial atmospheric temperature + absolute temperature (T_{0}).
II. The second is the _actual heat efficiency_, or the ratio of the heat
turned into work to the total heat received by the engine. It expresses
the _indicated horse-power_. III. The third is the ratio between the
second or _actual heat efficiency_ and the first or _maximum theoretical
efficiency_ of a perfect cycle. It represents the greatest possible
utilization of the power of heat in an internal-combustion engine. IV.
The fourth is the _mechanical efficiency_. This is the ratio between the
actual horse-power delivered by the engine through a dynamometer or
measured by a brake (brake horse-power), and the indicated horse-power.
The difference between the two is the power lost by engine friction. In
regard to the general heat efficiency of the materials of power in
explosive engines, we find that with good illuminating gas the practical
efficiency varies from 25 to 40 per cent.; kerosene-motors, 20 to 30;
gasoline-motors, 20 to 32; acetylene, 25 to 35; alcohol, 20 to 30 per
cent. of their heat value. The great variation is no doubt due to
imperfect mixtures and variable conditions of the old and new charge in
the cylinder; uncertainty as to leakage and the perfection of
combustion. In the Diesel motors operating under high pressure, up to
nearly 500 pounds, an efficiency of 36 per cent. is claimed.

[Illustration: Fig. 12.--Graphic Diagram Showing Approximate Utilization
of Fuel Burned in Internal-Combustion Engine.]

The graphic diagram at Fig. 12 is of special value as it shows clearly
how the heat produced by charge combustion is expended in an engine of
average design.

On general principles the greater difference between the heat of
combustion and the heat at exhaust is the relative measure of the heat
turned into work, which represents the degree of efficiency without loss
during expansion. The mathematical formulas appertaining to the
computation of the element of heat and its work in an explosive engine
are in a large measure dependent upon assumed values, as the conditions
of the heat of combustion are made uncertain by the mixing of the fresh
charge with the products of a previous combustion, and by absorption,
radiation, and leakage. The computation of the temperature from the
observed pressure may be made as before explained, but for
compression-engines the needed starting-points for computation are very
uncertain, and can only be approximated from the exact measure and value
of the elements of combustion in a cylinder charge.

TEMPERATURES AND PRESSURES

Owing to the decrease from atmospheric pressure in the indrawing charge
of the cylinder, caused by valve and frictional obstruction, the
compression seldom starts above 13 lbs. absolute, especially in
high-speed engines. Col. 3 in the following table represents the
approximate absolute compression pressure for the clearance percentage
and ratio in Cols. 1 and 2, while Col. 4 indicates the gauge pressure
from the atmospheric line. The temperatures in Col. 5 are due to the
compression in Col. 3 from an assumed temperature of 560° F. in the
mixture of the fresh charge of 6 air to 1 gas with the products of
combustion left in the clearance chamber from the exhaust stroke of a
medium-speed motor. This temperature is subject to considerable
variation from the difference in the heat-unit power of the gases and
vapors used for explosive power, as also of the cylinder-cooling effect.
In Col. 6 is given the approximate temperatures of explosion for a
mixture of air 6 to gas 1 of 660 heat units per cubic foot, for the
relative values of the clearance ratio in Col. 2 at constant volume.

TABLE III.--GAS-ENGINE CLEARANCE RATIOS, APPROXIMATE COMPRESSION,
TEMPERATURES OF EXPLOSION AND EXPLOSIVE PRESSURES WITH A MIXTURE OF GAS
OF 660 HEAT UNITS PER CUBIC FOOT AND MIXTURE OF GAS 1 TO 6 OF AIR.

[A] Clearance Per Cent. of Piston Volume.
[B] Ratio (_V_/_V_{c}_) = (_P_ + _C_ Vol.)/Clearance
[C] Approximate Compression from 13 Pounds Absolute.
[D] Approximate Gauge Pressure.
[E] Absolute Temperature of Compression from 560 Deg. Fahrenheit in
Cylinder.
[F] Absolute Temperature of Explosion. Gas, 1 part; Air, 6 parts.
[G] Approximate Explosion Pressure Absolute.
[H] Approximate Gauge Pressure.
[I] Approximate Temperature of Explosion, Fahrenheit.

=====+======+======+=====+======+======+=====+=====+=====
[A] | [B] | [C] | [D] | [E] | [F] | [G] | [H] | [I]
-----+------+------+-----+------+------+-----+-----+-----
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
-----+------+------+-----+------+------+-----+-----+-----
| | Lbs. | | Deg. | Deg. |Lbs. |Lbs. | Deg.
.50 | 3. | 57. | 42. | 822. | 2488 | 169 | 144 | 2027
.444 | 3.25 | 65. | 50. | 846. | 2568 | 197 | 182 | 2107
.40 | 3.50 | 70. | 55. | 868. | 2638 | 212 | 197 | 2177
.363 | 3.75 | 77. | 62. | 889. | 2701 | 234 | 219 | 2240
.333 | 4. | 84. | 69. | 910. | 2751 | 254 | 239 | 2290
.285 | 4.50 | 102. | 88. | 955. | 2842 | 303 | 288 | 2381
.25 | 5. | 114. | 99. | 983. | 2901 | 336 | 321 | 2440
-----+------+------+-----+------+------+-----+-----+-----

FACTORS GOVERNING ECONOMY

In view of the experiments in this direction, it clearly shows that in
practical work, to obtain the greatest economy per effective brake
horse-power, it is necessary: 1st. To transform the heat into work with
the greatest rapidity mechanically allowable. This means high piston
speed. 2d. To have high initial compression. 3d. To reduce the duration
of contact between the hot gases and the cylinder walls to the smallest
amount possible; which means short stroke and quick speed, with a
spherical cylinder head. 4th. To adjust the temperature of the jacket
water to obtain the most economical output of actual power. This means
water-tanks or water-coils, with air-cooling surfaces suitable and
adjustable to the most economical requirement of the engine, which by
late trials requires the jacket water to be discharged at about 200° F.
5th. To reduce the wall surface of the clearance space or combustion
chamber to the smallest possible area, in proportion to its required
volume. This lessens the loss of the heat of combustion by exposure to a
large surface, and allows of a higher mean wall temperature to
facilitate the heat of compression.

LOSSES IN WALL COOLING

In an experimental investigation of the efficiency of a gas-engine under
variable piston speeds made in France, it was found that the useful
effect increases with the velocity of the piston--that is, with the rate
of expansion of the burning gases with mixtures of uniform volumes: so
that the variations of time of complete combustion at constant pressure,
and the variations due to speed, in a way compensate in their
efficiencies. The dilute mixture, being slow burning, will have its time
and pressure quickened by increasing the speed.

Careful trials give unmistakable evidence that the useful effect
increases with the velocity of the piston--that is, with the rate of
expansion of the burning gases. The time necessary for the explosion to
become complete and to attain its maximum pressure depends not only on
the composition of the mixture, but also upon the rate of expansion.
This has been verified in experiments with a high-speed motor, at speeds
from 500 to 2,000 revolutions per minute, or piston speeds of from 16 to
64 feet per second. The increased speed of combustion due to increased
piston speed is a matter of great importance to builders of gas-engines,
as well as to the users, as indicating the mechanical direction of
improvements to lessen the wearing strain due to high speed and to
lighten the vibrating parts with increased strength, in order that the
balancing of high-speed engines may be accomplished with the least
weight.

From many experiments made in Europe and in the United States, it has
been conclusively proved that excessive cylinder cooling by the
water-jacket results in a marked loss of efficiency. In a series of
experiments with a simplex engine in France, it was found that a saving
of 7 per cent. in gas consumption per brake horse-power was made by
raising the temperature of the jacket water from 141° to 165° F. A still
greater saving was made in a trial with an Otto engine by raising the
temperature of the jacket water from 61° to 140° F.--it being 9.5 per
cent. less gas per brake horse-power.

It has been stated that volumes of similar cylinders increase as the
cube of their diameters, while the surface of their cold walls varies as
the square of their diameters; so that for large cylinders the ratio of
surface to volume is less than for small ones. This points to greater
economy in the larger engines. The study of many experiments goes to
prove that combustion takes place gradually in the gas-engine cylinder,
and that the rate of increase of pressure or rapidity of firing is
controlled by dilution and compression of the mixture, as well as by the
rate of expansion or piston speed. The rate of combustion also depends
on the size and shape of the explosion chamber, and is increased by the
mechanical agitation of the mixture during combustion, and still more by
the mode of firing.

VALUE OF INDICATOR CARDS

[Illustration: Fig. 13.--Otto Four-Cycle Card.]

To the uninitiated, indicator cards are considerable of a mystery; to
those capable of reading them they form an index relative to the action
of any engine. An indicator card, such as shown at Fig. 13, is merely a
graphical representation of the various pressures existing in the
cylinder for different positions of the piston. The length is to some
scale that represents the stroke of the piston. During the intake
stroke, the pressure falls below the atmospheric line. During
compression, the curve gradually becomes higher owing to increasing
pressure as the volume is reduced. After ignition the pressure line
moves upward almost straight, then as the piston goes down on the
explosion stroke, the pressure falls gradually to the point of exhaust
valve, opening when the sudden release of the imprisoned gas causes a
reduction in pressure to nearly atmospheric. An indicator card, or a
series of them, will always show by its lines the normal or defective
condition of the inlet valve and passages; the actual line of
compression; the firing moment; the pressure of explosion; the velocity
of combustion; the normal or defective line of expansion, as measured by
the adiabatic curve, and the normal or defective operation of the
exhaust valve, exhaust passages, and exhaust pipe. In fact, all the
cycles of an explosive motor may be made a practical study from a close
investigation of the lines of an indicator card.

[Illustration: Fig. 14.--Diesel Motor Card.]

A most unique card is that of the Diesel motor (Fig. 14), which involves
a distinct principle in the design and operation of internal-combustion
motors, in that instead of taking a mixed charge for instantaneous
explosion, its charge primarily is of air and its compression to a
pressure at which a temperature is attained above the igniting point of
the fuel, then injecting the fuel under a still higher pressure by which
spontaneous combustion takes place gradually with increasing volume over
the compression for part of the stroke or until the fuel charge is
consumed. The motor thus operating between the pressures of 500 and 35
lbs. per square inch, with a clearance of about 7 per cent., has given
an efficiency of 36 per cent. of the total heat value of kerosene oil.

COMPRESSION IN EXPLOSIVE MOTORS

That the compression in a gas, gasoline, or oil-engine has a direct
relation to the power obtained, has been long known to experienced
builders, having been suggested by M. Beau de Rocha, in 1862, and
afterward brought into practical use in the four-cycle or Otto type
about 1880. The degree of compression has had a growth from zero, in the
early engines, to the highest available due to the varying ignition
temperatures of the different gases and vapors used for explosive fuel,
in order to avoid premature explosion from the heat of compression. Much
of the increased power for equal-cylinder capacity is due to compression
of the charge from the fact that the most powerful explosion of gases,
or of any form of explosive material, takes place when the particles are
in the closest contact or cohesion with one another, less energy in this
form being consumed by the ingredients themselves to bring about their
chemical combination, and consequently more energy is given out in
useful or available work. This is best shown by the ignition of
gunpowder, which, when ignited in the open air, burns rapidly, but
without explosion, an explosion only taking place if the powder be
confined or compressed into a small space.

[Illustration: Fig. 15.--Diagram of Heat in the Gas Engine Cylinder.]

In a gas or gasoline-motor with a small clearance or compression
space--with high compression--the surface with which the burning
gases come into contact is much smaller in comparison with the
compression space in a low-compression motor. Another advantage of a
high-compression motor is that on account of the smaller clearance
of combustion space less cooling water is required than with a
low-compression motor, as the temperature, and consequently the
pressure, falls more rapidly. The loss of heat through the water-jacket
is thus less in the case of a high-compression than in that of a
low-compression motor. In the non-compression type of motor the best
results were obtained with a charge of 16 to 18 parts of gas and 100
parts of air, while in the compression type the best results are
obtained with an explosive mixture of 7 to 10 parts of gas and 100 parts
of air, thus showing that by the utilization of compression a weaker
charge with a greater thermal efficiency is permissible.

It has been found that the explosive pressure resulting from the
ignition of the charge of gas or gasoline-vapor and air in the
gas-engine cylinder is about 4-1/2 times the pressure prior to ignition.
The difficulty about getting high compression is that if the pressure is
too high the charge is likely to ignite prematurely, as compression
always results in increased temperature. The cylinder may become too
hot, a deposit of carbon, a projecting electrode or plug body in the
cylinder may become incandescent and ignite the charge which has been
excessively heated by the high compression and mixture of the hot gases
of the previous explosion.

FACTORS LIMITING COMPRESSION

With gasoline-vapor and air the compression should not be raised above
about 90 to 95 pounds to the square inch, many manufacturers not going
above 65 or 70 pounds. For natural gas the compression pressure may
easily be raised to from 85 to 100 pounds per square inch. For gases of
low calorific value, such as blast-furnace or producer-gas, the
compression may be increased to from 140 to 190 pounds. In fact the
ability to raise the compression to a high point with these gases is one
of the principal reasons for their successful adoption for gas-engine
use. In kerosene injection engines the compression of 250 pounds per
square inch has been used with marked economy. Many troubles in regard
to loss of power and increase of fuel have occurred and will no doubt
continue, owing to the wear of valves, piston, and cylinder, which
produces a loss in compression and explosive pressure and a waste of
fuel by leakage. Faulty adjustment of valve movement is also a cause of
loss of power; which may be from tardy closing of the inlet-valve or a
too early opening of the exhaust-valve.

The explosive pressure varies to a considerable amount in proportion to
the compression pressure by the difference in fuel value and the
proportions of air mixtures, so that for good illuminating gas the
explosive pressure may be from 2.5 to 4 times the compression pressure.
For natural gas 3 to 4.5, for gasoline 3 to 5, for producer-gas 2 to 3,
and for kerosene by injection 3 to 6.

The compression temperatures, although well known and easily computed
from a known normal temperature of the explosive mixture, are subject to
the effect of the uncertain temperature of the gases of the previous
explosion remaining in the cylinder, the temperature of its walls, and
the relative volume of the charge, whether full or scant; which are
terms too variable to make any computations reliable or available.

For the theoretical compression temperatures from a known normal
temperature, we append a table of the rise in temperature for the
compression pressures in the following table:

TABLE IV.--COMPRESSION TEMPERATURES FROM A NORMAL TEMPERATURE OF 60
DEGREES FAHRENHEIT.

===============================+==============================
100 lbs. gauge 484° | 60 lbs. gauge 373°
90 lbs. gauge 459° | 50 lbs. gauge 339°
80 lbs. gauge 433° | 40 lbs. gauge 301°
70 lbs. gauge 404° | 30 lbs. gauge 258°
-------------------------------+------------------------------

CHART FOR DETERMINING COMPRESSION PRESSURES

A very useful chart (Fig. 16) for determining compression pressures in
gasoline-engine cylinders for various ratios of compression space to
total cylinder volume is given by P. S. Tice, and described in the
Chilton Automobile Directory by the originator as follows:

[Illustration: Fig. 16.--Chart Showing Relation Between Compression
Volume and Pressure.]

It is many times desirable to have at hand a convenient means for at
once determining with accuracy what the compression pressure will be in
a gasoline-engine cylinder, the relationship between the volume of the
compression space and the total cylinder volume or that swept by the
piston being known. The curve at Fig. 16 is offered as such a means. It
is based on empirical data gathered from upward of two dozen modern
automobile engines and represents what may be taken to be the results as
found in practice. It is usual for the designer to find compression
pressure values, knowing the volumes from the equation

P_{2} = P_{1} (V_{1}/V_{2})^{1.4} 1

which is for adiabatic compression of air. Equation (1) is right enough
in general form but gives results which are entirely too high, as
almost all designers know from experience. The trouble lies in the
interchange of heat between the compressed gases and the cylinder walls,
in the diminution of the exponent (1.4 in the above) due to the lesser
ratio of specific heat of gasoline vapor and in the transfer of heat
from the gases which are being compressed to whatever fuel may enter the
cylinder in an unvaporized condition. Also, there is always some piston
leakage, and, if the form of the equation (1) is to be retained, this
also tends to lower the value of the exponent. From experience with many
engines, it appears that compression reaches its highest value in the
cylinder for but a short range of motor speeds, usually during the
mid-range. Also, it appears that, at those speeds at which compression
shows its highest values, the initial pressure at the start of the
compression stroke is from .5 to .9 lb. below atmospheric. Taking this
latter loss value, which shows more often than those of lesser value,
the compression is seen to start from an initial pressure of 13.9 lbs.
per sq. in. absolute.

Also, experiment shows that if the exponent be given the value 1.26,
instead of 1.4, the equation will embrace all heat losses in the
compressed gas, and compensate for the changed ratio of specific heats
for the mixture and also for all piston leakage, in the average engine
with rings in good condition and tight. In the light of the foregoing,
and in view of results obtained from its use, the above curve is
offered--values of P_{2} being found from the equation

P_{2} = 13.8 (V_{1}/V_{2})^{1.26}

In using this curve it must be remembered that pressures are absolute.
Thus: suppose it is desired to know the volumetric relationships of the
cylinder for a compression pressure of 75 lbs. gauge. Add atmospheric
pressure to the desired gauge pressure 14.7 + 75 = 89.7 lbs. absolute.
Locate this pressure on the scale of ordinates and follow horizontally
across to the curve and then vertically downward to the scale of
abscissas, where the ratio of the combustion chamber volume to the total
cylinder volume is given, which latter is equal to the sum of the
combustion chamber volume and that of the piston sweep. In the above
case it is found that the combustion space for a compression pressure of
75 lbs. gauge will be .225 of the total cylinder volume, or .225 ÷ .775
= .2905 of the piston sweep volume. Conversely, knowing the volumetric
ratios, compression pressure can be read directly by proceeding from the
scale of abscissas vertically to the curve and thence horizontally to
the scale of ordinates.

CAUSES OF HEAT LOSS AND INEFFICIENCY IN EXPLOSIVE MOTORS

The difference realized in the practical operation of an internal
combustion heat engine from the computed effect derived from the values
of the explosive elements is probably the most serious difficulty that
engineers have encountered in their endeavors to arrive at a rational
conclusion as to where the losses were located, and the ways and means
of design that would eliminate the causes of loss and raise the
efficiency step by step to a reasonable percentage of the total
efficiency of a perfect cycle.

An authority on the relative condition of the chemical elements under
combustion in closed cylinders attributes the variation of temperature
shown in the fall of the expansion curve, and the suppression or
retarded evolution of heat, entirely to the cooling action of the
cylinder walls, and to this nearly all the phenomena hitherto obscure in
the cylinder of a gas-engine. Others attribute the great difference
between the theoretical temperature of combustion and the actual
temperature realized in the practical operation of the gas-engine, a
loss of more than one-half of the total heat energy of the combustibles,
partly to the dissociation of the elements of combustion at extremely
high temperatures and their reassociation by expansion in the cylinder,
to account for the supposed continued combustion and extra adiabatic
curve of the expansion line on the indicator card.

[Illustration: Fig. 17.--The Thompson Indicator, an Instrument for
Determining Compressions and Explosion Pressure Values and Recording
Them on Chart.]

The loss of heat to the walls of the cylinder, piston, and clearance
space, as regards the proportion of wall surface to the volume, has
gradually brought this point to its smallest ratio in the concave
piston-head and globular cylinder-head, with the smallest possible space
in the inlet and exhaust passage. The wall surface of a cylindrical
clearance space or combustion chamber of one-half its unit diameter in
length is equal to 3.1416 square units, its volume but 0.3927 of a cubic
unit; while the same wall surface in a spherical form has a volume of
0.5236 of a cubic unit. It will be readily seen that the volume is
increased 33-1/3 per cent. in a spherical over a cylindrical form for
equal wall surfaces at the moment of explosion, when it is desirable
that the greatest amount of heat is generated, and carrying with it the
greatest possible pressure from which the expansion takes place by the
movement of the piston.

[Illustration: Fig. 18.--Spherical Combustion Chamber.]

[Illustration: Fig. 19.--Enlarged Combustion Chamber.]

The spherical form cannot continue during the stroke for mechanical
reasons; therefore some proportion of piston stroke of cylinder volume
must be found to correspond with a spherical form of the combustion
chamber to produce the least loss of heat through the walls during the
combustion and expansion part of the stroke. This idea is illustrated in
Figs. 18 and 19, showing how the relative volumes of cylinder stroke and
combustion chamber may be varied to suit the requirements due to the
quality of the elements of combustion.

Although the concave piston-head shows economy in regard to the relation
of the clearance volume to the wall area at the moment of explosive
combustion, it may be clearly seen that its concavity increases its
surface area and its capacity for absorbing heat, for which there is no
provision for cooling the piston, save its contact with the walls of the
cylinder and the slight air cooling of its back by its reciprocal
motion. For this reason the concave piston-head has not been generally
adopted and the concave cylinder-head, as shown in Fig. 19, with a
flat piston-head is the latest and best practice in airplane engine
construction.

[Illustration: Fig. 20.--Mercedes Aviation Engine Cylinder Section
Showing Approximately Spherical Combustion Chamber and Concave Piston
Top.]

The practical application of the principle just outlined to one of the
most efficient airplane motors ever designed, the Mercedes, is clearly
outlined at Fig. 20.

HEAT LOSSES TO COOLING WATER

The mean temperature of the wall surface of the combustion chamber and
cylinder, as indicated by the temperatures of the circulating water, has
been found to be an important item in the economy of the gas-engine.
Dugald Clerk, in England, a high authority in practical work with the
gas-engine, found that 10 per cent. of the gas for a stated amount of
power was saved by using water at a temperature in which the ejected
water from the cylinder-jacket was near the boiling-point, and ventures
the opinion that a still higher temperature for the circulating water
may be used as a source of economy. This could be made practical in the
case of aviation engines by adjusting the air-cooling surface of the
radiator so as to maintain the inlet water at just below the boiling
point, and by the rapid circulation induced by the pump pressure, to
return the water from the cylinder-jacket a few degrees above the
boiling point. The thermal displacement systems of cooling employed in
automobiles are working under more favorable temperature conditions than
those engines in which cooling is more energetic.

For a given amount of heat taken from the cylinder by the largest volume
of circulating water, the difference in temperature between inlet and
outlet of the water-jacket should be the least possible, and this
condition of the water circulation gives a more even temperature to all
parts of the cylinder; while, on the contrary, a cold-water supply, say
at 60° F., so slow as to allow the ejected water to flow off at a
temperature near the boiling-point, must make a great difference in
temperature between the bottom and top of the cylinder, with a loss in
economy in gas and other fuels, as well as in water, if it is obtained
by measurement.

From the foregoing considerations of losses and inefficiencies, we find
that the practice in motor design and construction has not yet reached
the desired perfection in its cycular operation. Step by step
improvements have been made with many changes in design though many have
been without merit as an improvement, farther than to gratify the
longings of designers for something different from the other thing, and
to establish a special construction of their own. These efforts may in
time produce a motor of normal or standard design for each kind of fuel
that will give the highest possible efficiency for all conditions of
service.

CHAPTER IV

Engine Parts and Functions--Why Multiple Cylinder Engines Are
Best--Describing Sequence of Operations--Simple Engines--Four
and Six Cylinder Vertical Tandem Engines--Eight and Twelve
Cylinder V Engines--Radial Cylinder Arrangement--Rotary Cylinder
Forms.

ENGINE PARTS AND FUNCTIONS

The principal elements of a gas engine are not difficult to understand
and their functions are easily defined. In place of the barrel of the
gun one has a smoothly machined cylinder in which a small cylindrical or
barrel-shaped element fitting the bore closely may be likened to a
bullet or cannon ball. It differs in this important respect, however, as
while the shot is discharged from the mouth of the cannon the piston
member sliding inside of the main cylinder cannot leave it, as its
movements back and forth from the open to the closed end and back again
are limited by simple mechanical connection or linkage which comprises
crank and connection rod. It is by this means that the reciprocating
movement of the piston is transformed into a rotary motion of the
crank-shaft.

The fly-wheel is a heavy member attached to the crank-shaft of an
automobile engine which has energy stored in its rim as the member
revolves, and the momentum of this revolving mass tends to equalize the
intermittent pushes on the piston head produced by the explosion of the
gas in the cylinder. In aviation engines, the weight of the propeller or
that of rotating cylinders themselves performs the duty of a fly-wheel,
so no separate member is needed. If some explosive is placed in the
chamber formed by the piston and closed end of the cylinder and
exploded, the piston would be the only part that would yield to the
pressure which would produce a downward movement. As this is forced down
the crank-shaft is turned by the connecting rod, and as this part is
hinged at both ends it is free to oscillate as the crank turns, and thus
the piston may slide back and forth while the crank-shaft is rotating or
describing a curvilinear path.

[Illustration: Fig. 21.--Side Sectional View of Typical Airplane Engine,
Showing Parts and Their Relation to Each Other. This Engine is an
Aeromarine Design and Utilizes a Distinctive Concentric Valve
Construction.]

In addition to the simple elements described it is evident that a
gasoline engine must have other parts. The most important of these are
the valves, of which there are generally two to each cylinder. One
closes the passage connecting to the gas supply and opens during one
stroke of the piston in order to let the explosive gas into the
combustion chamber. The other member, or exhaust valve, serves as a
cover for the opening through which the burned gases can leave the
cylinder after their work is done. The spark plug is a simple device
which may be compared to the fuse or percussion cap of the cannon. It
permits one to produce an electric spark in the cylinder when the piston
is at the best point to utilize the pressure which obtains when the
compressed gas is fired. The valves are open one at a time, the inlet
valve being lifted from its seat while the cylinder is filling and the
exhaust valve is opened when the cylinder is being cleared. They are
normally kept seated by means of compression springs. In the simple
motor shown at Fig. 5, the exhaust valve is operated by means of a
pivoted bell crank rocked by a cam which turns at half the speed of the
crank-shaft. The inlet valve operates automatically, as will be
explained in proper sequence.

In order to obtain a perfectly tight combustion chamber, both intake and
exhaust valves are closed before the gas is ignited, because all of the
pressure produced by the exploding gas is to be directed against the top
of the movable piston. When the piston reaches the bottom of its power
stroke, the exhaust valve is lifted by means of the bell crank which is
rocked because of the point or lift on the cam. The cam-shaft is driven
by positive gearing and revolves at half the engine speed. The exhaust
valve remains open during the whole of the return stroke of the piston,
and as this member moves toward the closed end of the cylinder it
forces out burned gases ahead of it, through the passage controlled by
the exhaust valve. The cam-shaft is revolved at half the engine speed
because the exhaust valve is raised from its seat during only one stroke
out of four, or only once every two revolutions. Obviously, if the cam
was turned at the same speed as the crank-shaft it would remain open
once every revolution, whereas the burned gases are expelled from the
individual cylinders only once in two turns of the crank-shaft.

WHY MULTIPLE CYLINDER FORMS ARE BEST

Owing to the vibration which obtains from the heavy explosion in the
large single-cylinder engines used for stationary power other forms were
evolved in which the cylinder was smaller and power obtained by running
the engine faster, but these are suitable only for very low powers.

When a single-cylinder engine is employed a very heavy fly-wheel is
needed to carry the moving parts through idle strokes necessary to
obtain a power impulse. For this reason automobile and aircraft
designers must use more than one cylinder, and the tendency is to
produce power by frequently occurring light impulses rather than
by a smaller number of explosions having greater force. When a
single-cylinder motor is employed the construction is heavier than is
needed with a multiple-cylinder form. Using two or more cylinders
conduces to steady power generation and a lessening of vibration. Most
modern motor cars employ four-cylinder engines because a power impulse
may be secured twice every revolution of the crank-shaft, or a total of
four power strokes during two revolutions. The parts are so arranged
that while the charge of gas in one cylinder is exploding, those which
come next in firing order are compressing, discharging the inert gases
and drawing in a fresh charge respectively. When the power stroke is
completed in one cylinder, the piston in that member in which a charge
of gas has just been compressed has reached the top of its stroke and
when the gas is exploded the piston is reciprocated and keeps the
crank-shaft turning. When a multiple-cylinder engine is used the
fly-wheel can be made much lighter than that of the simpler form and
eliminated altogether in some designs. In fact, many modern
multiple-cylinder engines developing 300 horse-power weigh less than the
early single- and double-cylinder forms which developed but one-tenth or
one-twentieth that amount of energy.

DESCRIBING SEQUENCE OF OPERATIONS

Referring to Fig. 22, A, the sequence of operation in a single-cylinder
motor can be easily understood. Assuming that the crank-shaft is turning
in the direction of the arrow, it will be seen that the intake stroke
comes first, then the compression, which is followed by the power
impulse, and lastly the exhaust stroke. If two cylinders are used, it is
possible to balance the explosions in such a way that one will occur
each revolution. This is true with either one of two forms of four-cycle
motors. At B, a two-cylinder vertical engine using a crank-shaft in
which the crank-pins are on the same plane is shown. The two pistons
move up and down simultaneously. Referring to the diagram describing the
strokes, and assuming that the outer circle represents the cycle of
operations in one cylinder while the inner circle represents the
sequence of events in the other cylinder, while cylinder No. 1 is taking
in a fresh charge of gas, cylinder No. 2 is exploding. When cylinder No.
1 is compressing, cylinder No. 2 is exhausting. During the time that the
charge in cylinder No. 1 is exploded, cylinder No. 2 is being filled
with fresh gas. While the exhaust gases are being discharged from
cylinder No. 1, cylinder No. 2 is compressing the gas previously taken.

[Illustration: Fig. 22.--Diagrams Illustrating Sequence of Cycles in
One- and Two-Cylinder Engines Showing More Uniform Turning Effort on
Crank-Shaft with Two-Cylinder Motors.]

The same condition obtains when the crank-pins are arranged at one
hundred and eighty degrees and the cylinders are opposed, as shown at C.
The reason that the two-cylinder opposed motor is more popular than
that having two vertical cylinders is that it is difficult to balance
the construction shown at B, so that the vibration will not be
excessive. The two-cylinder opposed motor has much less vibration than
the other form, and as the explosions occur evenly and the motor is a
simple one to construct, it has been very popular in the past on light
cars and has received limited application on some early, light
airplanes.

To demonstrate very clearly the advantages of multiple-cylinder engines
the diagrams at Fig. 23 have been prepared. At A, a three-cylinder
motor, having crank-pins at one hundred and twenty degrees, which means
that they are spaced at thirds of the circle, we have a form of
construction that gives a more even turning than that possible with a
two-cylinder engine. Instead of one explosion per revolution of the
crank-shaft, one will obtain three explosions in two revolutions. The
manner in which the explosion strokes occur and the manner they overlap
strokes in the other cylinder is shown at A. Assuming that the cylinders
fire in the following order, first No. 1, then No. 2, and last No. 3, we
will see that while cylinder No. 1, represented by the outer circle, is
on the power stroke, cylinder No. 3 has completed the last two-thirds of
its exhaust stroke and has started on its intake stroke. Cylinder No. 2,
represented by the middle circle, during this same period has completed
its intake stroke and two-thirds of its compression stroke. A study of
the diagram will show that there is an appreciable lapse of time between
each explosion.

Three-cylinder engines are not used on aircraft at the present time,
though Bleriot's flight across the British Channel was made with a
three-cylinder Anzani motor. It was not a conventional form, however.
The three-cylinder engine is practically obsolete at this time for any
purpose except "penguins" or school machines that are incapable of
flight and which are used in some French training schools for aviators.

[Illustration: Fig. 23.--Diagrams Demonstrating Clearly Advantages which
Obtain when Multiple-Cylinder Motors are Used as Power Plants.]

FOUR- AND SIX-CYLINDER ENGINES

In the four-cylinder engine operation which is shown at Fig. 23, B, it
will be seen that the power strokes follow each other without loss of
time, and one cylinder begins to fire and the piston moves down just as
soon as the member ahead of it has completed its power stroke. In a
four-cylinder motor, the crank-pins are placed at one hundred and eighty
degrees, or on the halves of the crank circle. The crank-pins for
cylinders No. 1 and No. 4 are on the same plane, while those for
cylinders No. 2 and No. 3 also move in unison. The diagram describing
sequence of operations in each cylinder is based on a firing order of
one, two, four, three. The outer circle, as in previous instances,
represents the cycle of operations in cylinder one. The next one toward
the center, cylinder No. 2, the third circle represents the sequence of
events in cylinder No. 3, while the inner circle outlines the strokes in
cylinder four. The various cylinders are working as follows:

1. 2. 3. 4.

Explosion Compression Exhaust Intake
Exhaust Explosion Intake Compression
Intake Exhaust Compression Explosion
Compression Intake Explosion Exhaust

It will be obvious that regardless of the method of construction, or the
number of cylinders employed, exactly the same number of parts must be
used in each cylinder assembly and one can conveniently compare any
multiple-cylinder power plant as a series of single-cylinder engines
joined one behind the other and so coupled that one will deliver power
and produce useful energy at the crank-shaft where the other leaves off.
The same fundamental laws governing the action of a single cylinder
obtain when a number are employed, and the sequence of operation is the
same in all members, except that the necessary functions take place at
different times. If, for instance, all the cylinders of a four-cylinder
motor were fired at the same time, one would obtain the same effect as
though a one-piston engine was used, which had a piston displacement
equal to that of the four smaller members. As is the case with a
single-cylinder engine, the motor would be out of correct mechanical
balance because all the connecting rods would be placed on crank-pins
that lie in the same plane. A very large fly-wheel would be necessary to
carry the piston through the idle strokes, and large balance weights
would be fitted to the crank-shaft in an effort to compensate for the
weight of the four pistons, and thus reduce vibratory stresses which
obtain when parts are not in correct balance.

There would be no advantage gained by using four cylinders in this
manner, and there would be more loss of heat and more power consumed in
friction than in a one-piston motor of the same capacity. This is the
reason that when four cylinders are used the arrangement of crank-pins
is always as shown at Fig. 23, B--i.e., two pistons are up, while the
other two are at the bottom of the stroke. With this construction, we
have seen that it is possible to string out the explosions so that there
will always be one cylinder applying power to the crank-shaft. The
explosions are spaced equally. The parts are in correct mechanical
balance because two pistons are on the upstroke while the other two are
descending. Care is taken to have one set of moving members weigh
exactly the same as the other. With a four-cylinder engine one has
correct balance and continuous application of energy. This insures a
smoother running motor which has greater efficiency than the simpler
one-, two-, and three-cylinder forms previously described. Eliminating
the stresses which would obtain if we had an unbalanced mechanism and
irregular power application makes for longer life. Obviously a large
number of relatively light explosions will produce less wear and strain
than would a lesser number of powerful ones. As the parts can be built
lighter if the explosions are not heavy, the engine can be operated at
higher rotative speeds than when large and cumbersome members are
utilized. Four-cylinder engines intended for aviation work have been
built according to the designs shown at Fig. 24, but these forms are
unconventional and seldom if ever used.

[Illustration: Fig. 24.--Showing Three Possible Though Unconventional
Arrangements of Four-Cylinder Engines.]

The six-cylinder type of motor, the action of which is shown at Fig. 23,
C, is superior to the four-cylinder, inasmuch as the power strokes
overlap, and instead of having two explosions each revolution we have
three explosions. The conventional crank-shaft arrangement in a
six-cylinder engine is just the same as though one used two
three-cylinder shafts fastened together, so pistons 1 and 6 are on the
same plane as are pistons 2 and 5. Pistons 3 and 4 also travel together.
With the cranks arranged as outlined at Fig. 23, C, the firing order is
one, five, three, six, two, four. The manner in which the power strokes
overlap is clearly shown in the diagram. An interesting comparison is
also made in the diagrams at Fig. 25 and in the upper corner of Fig. 23,
C.

[Illustration: Fig. 25.--Diagrams Outlining Advantages of Multiple
Cylinder Motors, and Why They Deliver Power More Evenly Than Single
Cylinder Types.]

A rectangle is divided into four columns; each of these corresponds to
one hundred and eighty degrees, or half a revolution. Thus the first
revolution of the crank-shaft is represented by the first two columns,
while the second revolution is represented by the last two. Taking the
portion of the diagram which shows the power impulse in a one-cylinder
engine, we see that during the first revolution there has been no power
impulse. During the first half of the second revolution, however, an
explosion takes place and a power impulse is obtained. The last portion
of the second revolution is devoted to exhausting the burned gases, so
that there are three idle strokes and but one power stroke. The effect
when two cylinders are employed is shown immediately below.

[Illustration: Fig. 26.--Diagrams Showing Duration of Events for a
Four-Stroke Cycle, Six-Cylinder Engine.]

Here we have one explosion during the first half of the first revolution
in one cylinder and another during the first half of the second
revolution in the other cylinder. With a four-cylinder engine there is
an explosion each half revolution, while in a six-cylinder engine there
is one and one-half explosions during each half revolution. When six
cylinders are used there is no lapse of time between power impulses, as
these overlap and a continuous and smooth-turning movement is imparted
to the crank shaft. The diagram shown at Fig. 26, prepared by E. P.
Pulley, can be studied to advantage in securing an idea of the
coordination of effort that takes place in an engine of the six-cylinder
type.

ACTUAL DURATION OF DIFFERENT STROKES

[Illustration: Fig. 27.--Diagram Showing Actual Duration of Different
Strokes in Degrees.]

In the diagrams previously presented the writer has assumed, for the
sake of simplicity, that each stroke takes place during half of one
revolution of the crank-shaft, which corresponds to a crank-pin travel
of one hundred and eighty degrees. The actual duration of these strokes
is somewhat different. For example, the inlet stroke is usually a trifle
more than a half revolution, and the exhaust is always considerably
more. The diagram showing the comparative duration of the strokes is
shown at Fig. 27. The inlet valve opens ten degrees after the piston
starts to go down and remains open thirty degrees after the piston has
reached the bottom of its stroke. This means that the suction stroke
corresponds to a crank-pin travel of two hundred degrees, while the
compression stroke is measured by a movement of but one hundred and
fifty degrees. It is common practice to open the exhaust valve before
the piston reaches the end of the power stroke so that the actual
duration of the power stroke is about one hundred and forty degrees,
while the exhaust stroke corresponds to a crank-pin travel of two
hundred and twenty-five degrees. In this diagram, which represents
proper time for the valves to open and close, the dimensions in inches
given are measured on the fly-wheel and apply only to a certain
automobile motor. If the fly-wheel were smaller ten degrees would take
up less than the dimensions given, while if the fly-wheel was larger a
greater space on its circumference would represent the same crank-pin
travel. Aviation engines are timed by using a timing disc attached to
the crank-shaft as they are not provided with fly-wheels. Obviously, the
distance measured in inches will depend upon the diameter of the disc,
though the number of degrees interval would not change.

[Illustration: Fig. 28.--Another Diagram to Facilitate Understanding
Sequence of Functions in Six-Cylinder Engine.]

EIGHT- AND TWELVE-CYLINDER V ENGINES

Those who have followed the development of the gasoline engine will
recall the arguments that were made when the six-cylinder motor was
introduced at a time that the four-cylinder type was considered
standard. The arrival of the eight-cylinder has created similar futile
discussion of its practicability as this is so clearly established as to
be accepted without question. It has been a standard power plant for
aeroplanes for many years, early exponents having been the Antoinette,
the Woolsley, the Renault, the E. N. V. in Europe and the Curtiss in the
United States.

[Illustration: Fig. 29.--Types of Eight-Cylinder Engines Showing the
Advantage of the V Method of Cylinder Placing.]

The reason the V type shown at Fig. 29, A is favored is that the
"all-in-line form" which is shown at Fig. 29, B is not practical for
aircraft because of its length. Compared to the standard four-cylinder
engine it is nearly twice as long and it required a much stronger and
longer crank-shaft. It will be evident that it could not be located to
advantage in the airplane fuselage. These undesirable factors are
eliminated in the V type eight-cylinder motor, as it consists of two
blocks of four cylinders each, so arranged that one set or block is at
an angle of forty-five degrees from the vertical center line of the
motor, or at an angle of ninety degrees with the other set. This
arrangement of cylinders produces a motor that is no longer than a
four-cylinder engine of half the power would be.

[Illustration: Fig. 30.--Curves Showing Torque of Various Engine Types
Demonstrate Graphically Marked Advantage of the Eight-Cylinder Type.]

Apparently there is considerable misconception as to the advantage of
the two extra cylinders of the eight as compared with the six-cylinder.
It should be borne in mind that the multiplication in the number of
cylinders noticed since the early days of automobile development has not
been for solely increasing the power of the engine, but to secure a more
even turning movement, greater flexibility and to eliminate destructive
vibration. The ideal internal combustion motor, is the one having the
most uniform turning movement with the least mechanical friction loss.
Study of the torque outlines or plotted graphics shown at Figs. 25 and
30 will show how multiplication of cylinders will produce steady power
delivery due to overlapping impulses. The most practical form would be
that which more nearly conforms to the steady running produced by a
steam turbine or electric motor. The advocates of the eight-cylinder
engine bring up the item of uniform torque as one of the most important
advantages of the eight-cylinder design. A number of torque diagrams are
shown at Fig. 30. While these appear to be deeply technical, they may be
very easily followed when their purpose is explained. At the top is
shown the torque diagram of a single-cylinder motor of the four-cycle
type. The high point in the line represents the period of greatest
torque or power generation, and it will be evident that this occurs
early in the first revolution of the crank-shaft. Below this diagram is
shown a similar curve except that it is produced by a four-cylinder
engine. Inspection will show that the turning-moment is much more
uniform than in the single cylinder; similarly, the six-cylinder
diagram is an improvement over the four, and the eight-cylinder diagram
is an improvement over the six-cylinder.

[Illustration: Fig. 31.--Diagrams Showing How Increasing Number of
Cylinders Makes for More Uniform Power Application.]

The reason that practically continuous torque is obtained in an
eight-cylinder engine is that one cylinder fires every ninety degrees of
crank-shaft rotation, and as each impulse lasts nearly seventy-five per
cent. of the stroke, one can easily appreciate that an engine that will
give four explosions per revolution of the crank-shaft will run more
uniformly than one that gives but three explosions per revolution, as
the six-cylinder does, and will be twice as smooth running as a
four-cylinder, in which but two explosions occur per revolution of the
crank-shaft. The comparison is so clearly shown in graphical diagrams
and in Fig. 31 that further description is unnecessary.

Any eight-cylinder engine may be considered a "twin-four,"
twelve-cylinder engines may be considered "twin sixes."

[Illustration: Fig. 32.--How the Angle Between the Cylinders of an
Eight- and Twelve-Cylinder V Motor Varies.]

The only points in which an eight-cylinder motor differs from a
four-cylinder is in the arrangement of the connecting rod, as in many
designs it is necessary to have two rods working from the same
crank-pin. This difficulty is easily overcome in some designs by
staggering the cylinders and having the two connecting rod big ends of
conventional form side by side on a common crank-pin. In other designs
one rod is a forked form and works on the outside of a rod of the
regular pattern. Still another method is to have a boss just above the
main bearing on one connecting rod to which the lower portion of the
connecting rod in the opposite cylinder is hinged. As the eight-cylinder
engine may actually be made lighter than the six-cylinder of equal
power, it is possible to use smaller reciprocating parts, such as
pistons, connecting rods and valve gear, and obtain higher engine speed
with practically no vibration. The firing order in nearly every case is
the same as in a four-cylinder except that the explosions occur
alternately in each set of cylinders. The firing order of an
eight-cylinder motor is apt to be confusing to the motorist,
especially if one considers that there are eight possible sequences. The
majority of engineers favor the alternate firing from side to side.
Firing orders will be considered in proper sequence.

[Illustration: Fig. 33.--The Hall-Scott Four-Cylinder 100 Horse-Power
Aviation Motor.]

[Illustration: Fig. 34.--Two Views of the Duesenberg Sixteen Valve
Four-Cylinder Aviation Motor.]

The demand of aircraft designers for more power has stimulated designers
to work out twelve-cylinder motors. These are high-speed motors
incorporating all recent features of design in securing light
reciprocating parts, large valve openings, etc. The twelve-cylinder
motor incorporates the best features of high-speed motor design and
there is no need at this time to discuss further the pros and cons of
the twelve-cylinder versus the eight or six, because it is conceded by
all that there is the same degree of steady power application in the
twelve over the eight as there would be in the eight over the six. The
question resolves itself into having a motor of high power that will
run with minimum vibration and that produces smooth action. This is well
shown by diagrams at Fig. 31. It should be remembered that if an
eight-cylinder engine will give four explosions per revolution of the
fly-wheel, a twelve-cylinder type will give six explosions per
revolution, and instead of the impulses coming 90 degrees crank travel
apart, as in the case of the eight-cylinder, these will come but 60
degrees of crank travel apart in the case of the twelve-cylinder. For
this reason, the cylinders of a twelve are usually separated by 60
degrees while the eight has the blocks spaced 90 degrees apart. The
comparison can be easily made by comparing the sectional views of Vee
engines at Fig. 32. When one realizes that the actual duration of the
power stroke is considerably greater than 120 degrees crank travel, it
will be apparent that the overlapping of explosions must deliver a very
uniform application of power. Vee engines have been devised having the
cylinders spaced but 45 degrees apart, but the explosions cannot be
timed at equal intervals as when 90 degrees separate the cylinder center
lines.

[Illustration: Fig. 35.--The Hall-Scott Six-Cylinder Aviation Engine.]

RADIAL CYLINDER ARRANGEMENTS

[Illustration: Fig. 36.--The Curtiss Eight-Cylinder, 200 Horse-Power
Aviation Engine.]

While the fixed cylinder forms of engines, having the cylinders in
tandem in the four- and six-cylinder models as shown at Figs. 33 to 35
inclusive and the eight-cylinder V types as outlined at Figs. 36 and 37
have been generally used and are most in favor at the present time,
other forms of motors having unconventional cylinder arrangements have
been devised, though most of these are practically obsolete. While many
methods of decreasing weight and increasing mechanical efficiency of a
motor are known to designers, one of the first to be applied to the
construction of aeronautical power plants was an endeavor to group the
components, which in themselves were not extremely light, into a form
that would be considerably lighter than the conventional design. As an
example, we may consider those multiple-cylinder forms in which the
cylinders are disposed around a short crank-case, either radiating from
a common center as at Fig. 38 or of the fan shape shown at Fig. 39. This
makes it possible to use a crank-case but slightly larger than that
needed for one or two cylinders and it also permits of a corresponding
decrease in length of the crank-shaft. The weight of the engine is
lessened because of the reduction in crank-shaft and crank-case weight
and the elimination of a number of intermediate bearings and their
supporting webs which would be necessary with the usual tandem
construction. While there are six power impulses to every two
revolutions of the crank-shaft, in the six-cylinder engine, they are
not evenly spaced as is possible with the conventional arrangement.

[Illustration: Fig. 37.--The Sturtevant Eight-Cylinder, High Speed
Aviation Motor.]

[Illustration: Fig. 38.--Anzani 40-50 Horse-Power Five-Cylinder Air
Cooled Engine.]

In the Anzani form, which is shown at Fig. 38, the crank-case is
stationary and a revolving crank-shaft is employed as in conventional
construction. The cylinders are five in number and the engine develops
40 to 50 H.P. with a weight of 72 kilograms or 158.4 lbs. The cylinders
are of the usual air-cooled form having cooling flanges only part of the
way down the cylinder. By using five cylinders it is possible to have
the power impulses come regularly, they coming 145° crank-shaft travel
apart, the crank-shaft making two turns to every five explosions. The
balance is good and power output regular. The valves are placed
directly in the cylinder head and are operated by a common pushrod.
Attention is directed to the novel method of installing the carburetor
which supplies the mixture to the engine base from which inlet pipes
radiate to the various cylinders. This engine is used on French school
machines.

[Illustration: Fig. 39.--Unconventional Six-Cylinder Aircraft Motor of
Masson Design.]

In the form shown at Fig. 39 six cylinders are used, all being placed
above the crank-shaft center line. This engine is also of the air-cooled
form and develops 50 H. P. and weighs 105 kilograms, or 231 lbs. The
carburetor is connected to a manifold casting attached to the engine
base from which the induction pipes radiate to the various cylinders.
The propeller design and size relative to the engine is clearly shown in
this view. While flights have been made with both of the engines
described, this method of construction is not generally followed and has
been almost entirely displaced abroad by the revolving motors or by the
more conventional eight-cylinder V engines. Both of the engines shown
were designed about eight years ago and would be entirely too small and
weak for use in modern airplanes intended for active duty.

ROTARY ENGINES

[Illustration: Fig. 40.--The Gnome Fourteen-Cylinder Revolving Motor.]

Rotary engines such as shown at Fig. 40 are generally associated with
the idea of light construction and it is rather an interesting point
that is often overlooked in connection with the application of this idea
to flight motors, that the reason why rotary engines are popularly
supposed to be lighter than the others is because they form their own
fly-wheel, yet on aeroplanes, engines are seldom fitted with a fly-wheel
at all. As a matter of fact the Gnome engine is not so light because it
is a rotary motor, and it is a rotary motor because the design that has
been adopted as that most conducive to lightness is also most suited to
an engine working in this way. The cylinders could be fixed and
crank-shaft revolve without increasing the weight to any extent. There
are two prime factors governing the lightness of an engine, one being
the initial design, and the other the quality of the materials employed.
The consideration of reducing weight by cutting away metal is a
subsidiary method that ought not to play a part in standard practice,
however useful it may be in special cases. In the Gnome rotary engine
the lightness is entirely due to the initial design and to the materials
employed in manufacture. Thus, in the first case, the engine is a radial
engine, and has its seven or nine cylinders spaced equally around a
crank-chamber that is no wider or rather longer than would be required
for any one of the cylinders. This shortening of the crank-chamber not
only effects a considerable saving of weight on its own account, but
there is a corresponding saving in the shafts and other members, the
dimensions of which are governed by the size of the crank-chamber. With
regard to materials, nothing but steel is used throughout, and most of
the metal is forged chrome nickel steel. The beautifully steady running
of the engine is largely due to the fact that there are literally no
reciprocating parts in the absolute sense, the apparent reciprocation
between the pistons and cylinders being solely a relative reciprocation
since both travel in circular paths, that of the pistons, however, being
electric by one-half of the stroke length to that of the cylinder.

While the Gnome engine has many advantages, on the other hand the head
resistance offered by a motor of this type is considerable; there is a
large waste of lubricating oil due to the centrifugal force which tends
to throw the oil away from the cylinders; the gyroscopic effect of the
rotary motor is detrimental to the best working of the aeroplane, and
moreover it requires about seven per cent. of the total power developed
by the motor to drive the revolving cylinders around the shaft. Of
necessity, the compression of this type of motor is rather low, and an
additional disadvantage manifests itself in the fact that there is as
yet no satisfactory way of muffling the rotary type of motor. The modern
Gnome engine has been widely copied in various European countries, but
its design was originated in America, the early Adams-Farwell engine
being the pioneer form. It has been made in seven- and nine-cylinder
types and forms of double these numbers. The engine illustrated at Fig.
40 is a fourteen-cylinder form. The simple engines have an odd number of
cylinders in order to secure evenly spaced explosions. In the
seven-cylinder, the impulses come 102.8° apart. In the nine-cylinder
form, the power strokes are spaced 80° apart. The fourteen-cylinder
engine is virtually two seven-cylinder types mounted together, the
cranks being just the same as in a double cylinder opposed motor, the
explosions coming 51.4° apart; while in the eighteen-cylinder model the
power impulses come every 40° cylinder travel. Other rotary motors have
been devised, such as the Le Rhone and the Clerget in France and several
German copies of these various types. The mechanical features of these
motors will be fully considered later.

CHAPTER V

Properties of Liquid Fuels--Distillates of Crude Petroleum--
Principles of Carburetion Outlined--Air Needed to Burn Gasoline
--What a Carburetor Should Do--Liquid Fuel Storage and Supply--
Vacuum Fuel Feed--Early Vaporizer Forms--Development of Float
Feed Carburetor--Maybach's Early Design--Concentric Float and
Jet Type--Schebler Carburetor--Claudel Carburetor--Stewart
Metering Pin Type--Multiple Nozzle Vaporizers--Two-Stage
Carburetor--Master Multiple Jet Type--Compound Nozzle Zenith
Carburetor--Utility of Gasoline Strainers--Intake Manifold
Design and Construction--Compensating for Various Atmospheric
Conditions--How High Altitude Affects Power--The Diesel System--
Notes on Carburetor Installation--Notes on Carburetor
Adjustment.

There is no appliance that has more material value upon the efficiency
of the internal combustion motor than the carburetor or vaporizer which
supplies the explosive gas to the cylinders. It is only in recent years
that engineers have realized the importance of using carburetors that
are efficient and that are so strongly and simply made that there will
be little liability of derangement. As the power obtained from the
gas-engine depends upon the combustion of fuel in the cylinders, it is
evident that if the gas supplied does not have the proper proportions of
elements to insure rapid combustion the efficiency of the engine will be
low. When a gas engine is used as a stationary installation it is
possible to use ordinary illuminating or natural gas for fuel, but when
this prime mover is applied to automobiles or airplanes it is evident
that considerable difficulty would be experienced in carrying enough
compressed coal gas to supply the engine for even a very short trip.
Fortunately, the development of the internal-combustion motor was not
delayed by the lack of suitable fuel.

Engineers were familiar with the properties of certain liquids which
gave off vapors that could be mixed with air to form an explosive gas
which burned very well in the engine cylinders. A very small quantity of
such liquids would suffice for a very satisfactory period of operation.
The problem to be solved before these liquids could be applied in a
practical manner was to evolve suitable apparatus for vaporizing them
without waste. Among the liquids that can be combined with air and
burned, gasoline is the most volatile and is the fuel utilized by
internal-combustion engines.

The widely increasing scope of usefulness of the internal-combustion
motor has made it imperative that other fuels be applied in some
instances because the supply of gasoline may in time become inadequate
to supply the demand. In fact, abroad this fuel sells for fifty to two
hundred per cent. more than it does in America because most of the
gasoline used must be imported from this country or Russia. Because of
this foreign engineers have experimented widely with other substances,
such as alcohol, benzol, and kerosene, but more to determine if they can
be used to advantage in motor cars than in airplane engines.

DISTILLATES OF CRUDE PETROLEUM

Crude petroleum is found in small quantities in almost all parts of the
world, but a large portion of that produced commercially is derived from
American wells. The petroleum obtained in this country yields more of
the volatile products than those of foreign production, and for that
reason the demand for it is greater. The oil fields of this country are
found in Pennsylvania, Indiana, and Ohio, and the crude petroleum is
usually in association with natural gas. This mineral oil is an agent
from which many compounds and products are derived, and the products
will vary from heavy sludges, such as asphalt, to the lighter and more
volatile components, some of which will evaporate very easily at
ordinary temperatures.

The compounds derived from crude petroleum are composed principally of
hydrogen and carbon and are termed "Hydrocarbons." In the crude product
one finds many impurities, such as free carbon, sulphur, and various
earthy elements. Before the oil can be utilized it must be subjected to
a process of purifying which is known as refining, and it is during this
process, which is one of destructive distillation, that the various
liquids are separated. The oil was formerly broken up into three main
groups of products as follows: Highly volatile, naphtha, benzine,
gasoline, eight to ten per cent. Light oils, such as kerosene and light
lubricating oils seventy to eighty per cent. Heavy oils or residuum five
to nine per cent. From the foregoing it will be seen that the available
supply of gasoline is determined largely by the demand existing for the
light oils forming the larger part of the products derived from crude
petroleum. New processes have been recently discovered by which the
lighter oils, such as kerosene, are reduced in proportion and that of
gasoline increased, though the resulting liquid is neither the high
grade, volatile gasoline known in the early days of motoring nor the low
grade kerosene.

PRINCIPLES OF CARBURETION OUTLINED

The process of carburetion is combining the volatile vapors which
evaporate from the hydrocarbon liquids with certain proportions of air
to form an inflammable gas. The quantities of air needed vary with
different liquids and some mixtures burn quicker than do other
combinations of air and vapor. Combustion is simply burning and it may
be rapid, moderate or slow. Mixtures of gasoline and air burn quickly,
in fact the combustion is so rapid that it is almost instantaneous and
we obtain what is commonly termed an "explosion." Therefore the
explosion of gas in the automobile engine cylinder which produces the
power is really a combination of chemical elements which produce heat
and an increase in the volume of the gas because of the increase in
temperature.

If the gasoline mixture is not properly proportioned the rate of
burning will vary, and if the mixture is either too rich or too weak the
power of the explosion is reduced and the amount of power applied to the
piston is decreased proportionately. In determining the proper
proportions of gasoline and air, one must take the chemical composition
of gasoline into account. The ordinary liquid used for fuel is said to
contain about eight-four per cent. carbon and sixteen per cent.
hydrogen. Air is composed of oxygen and nitrogen and the former has a
great affinity, or combining power, with the two constituents of
hydrocarbon liquids. Therefore, what we call an explosion is merely an
indication that oxygen in the air has combined with the carbon and
hydrogen of the gasoline.

AIR NEEDED TO BURN GASOLINE

In figuring the proper volume of air to mix with a given quantity of
fuel, one takes into account the fact that one pound of hydrogen
requires eight pounds of oxygen to burn it, and one pound of carbon
needs two and one-third pounds of oxygen to insure its combustion. Air
is composed of one part of oxygen to three and one-half portions of
nitrogen by weight. Therefore for each pound of oxygen one needs to burn
hydrogen or carbon four and one-half pounds of air must be allowed. To
insure combustion of one pound of gasoline which is composed of hydrogen
and carbon we must furnish about ten pounds of air to burn the carbon
and about six pounds of air to insure combustion of hydrogen, the other
component of gasoline. This means that to burn one pound of gasoline one
must provide about sixteen pounds of air.

While one does not usually consider air as having much weight, at a
temperature of sixty-two degrees Fahrenheit about fourteen cubic feet of
air will weigh a pound, and to burn a pound of gasoline one would
require about two hundred cubic feet of air. This amount will provide
for combustion theoretically, but it is common practice to allow twice
this amount because the element nitrogen, which is the main constituent
of air, is an inert gas and instead of aiding combustion it acts as a
deterrent of burning. In order to be explosive, gasoline vapor must be
combined with definite quantities of air. Mixtures that are rich in
gasoline ignite quicker than those which have more air, but these are
only suitable when starting or when running slowly, as a rich mixture
ignites much quicker than a weak mixture. The richer mixture of gasoline
and air not only burns quicker but produces the most heat and the most
effective pressure in pounds per square inch of piston top area.

The amount of compression of the charge before ignition also has
material bearing on the force of the explosion. The higher the degree of
compression the greater the force exerted by the rapid combustion of the
gas. It may be stated that as a general thing the maximum explosive
pressure is somewhat more than four times the compression pressure prior
to ignition. A charge compressed to sixty pounds will have a maximum of
approximately two hundred and forty pounds; compacted to eighty pounds
it will produce a pressure of about three hundred pounds on each square
inch of piston area at the beginning of the power stroke. Mixtures
varying from one part of gasoline vapor to four of air to others having
one part of gasoline vapor to thirteen of air can be ignited, but the
best results are obtained when the proportions are one to five or one to
seven, as this mixture is said to be the one that will produce the
highest temperature, the quickest explosion, and the most pressure.

WHAT A CARBURETOR SHOULD DO

While it is apparent that the chief function of a carbureting device is
to mix hydrocarbon vapors with air to secure mixtures that will burn,
there are a number of factors which must be considered before describing
the principles of vaporizing devices. Almost any device which permits a
current of air to pass over or through a volatile liquid will produce a
gas which will explode when compressed and ignited in the motor
cylinder. Modern carburetors are not only called upon to supply certain
quantities of gas, but these must deliver a mixture to the cylinders
that is accurately proportioned and which will be of proper composition
at all engine speeds.

[Illustration: Fig. 41.--How Gravity Feed Fuel Tank May Be Mounted Back
of Engine and Secure Short Fuel Line.]

Flexible control of the engine is sought by varying the engine speed by
regulating the supply of gas to the cylinders. The power plant should
run from its lowest to its highest speed without any irregularity in
torque, i.e., the acceleration should be gradual rather than spasmodic.
As the degree of compression will vary in value with the amount of
throttle opening, the conditions necessary to obtain maximum power
differ with varying engine speeds. When the throttle is barely opened
the engine speed is low and the gas must be richer in fuel than when the
throttle is wide open and the engine speed high.

When an engine is turning over slowly the compression has low value and
the conditions are not so favorable to rapid combustion as when the
compression is high. At high engine speeds the gas velocity through the
intake piping is higher than at low speeds, and regular engine action is
not so apt to be disturbed by condensation of liquid fuel in the
manifold due to excessively rich mixture or a superabundance of liquid
in the stream of carbureted air.

LIQUID FUEL STORAGE AND SUPPLY

The problem of gasoline storage and method of supplying the carburetor
is one that is determined solely by design of the airplane. While the
object of designers should be to supply the fuel to the carburetor by as
simple means as possible the fuel supply system of some airplanes is
quite complex. The first point to consider is the location of the
gasoline tank. This depends upon the amount of fuel needed and the space
available in the fuselage.

A very simple and compact fuel supply system is shown at Fig. 41. In
this instance the fuel container is placed immediately back of the
engine cylinder. The carburetor which is carried as indicated is joined
to the tank by a short piece of copper or flexible rubber tubing. This
is the simplest possible form of fuel supply system and one used on a
number of excellent airplanes.

As the sizes of engines increase and the power plant fuel consumption
augments it is necessary to use more fuel, and to obtain a satisfactory
flying radius without frequent landings for filling the fuel tank it is
necessary to supply large containers.

When a very powerful power plant is fitted, as on battle planes of high
capacity, it is necessary to carry large quantities of gasoline. In
order to use a tank of sufficiently large capacity it may be necessary
to carry it lower than the carburetor. When installed in this manner it
is necessary to force fuel out of the tank by air pressure or to pump it
with a vacuum tank because the gasoline tank is lower than the
carburetor it supplies and the gasoline cannot flow by gravity as in the
simpler systems. While the pressure and gravity feed systems are
generally used in airplanes, it may be well to describe the vacuum lift
system which has been widely applied to motor cars and which may have
some use in connection with airplanes as these machines are developed.

STEWART VACUUM FUEL FEED

One of the marked tendencies has been the adoption of a vacuum fuel feed
system to draw the gasoline from tanks placed lower than the carburetor
instead of using either exhaust gas or air pressure to achieve this end.
The device generally fitted is the Stewart vacuum feed tank which is
clearly shown in section at Fig. 42. In this system the suction of a
motor is employed to draw gasoline from the main fuel tank to the
auxiliary tank incorporated in the device and from this tank the liquid
flows to the carburetor. It is claimed that all the advantages of the
pressure system are obtained with very little more complication than is
found on the ordinary gravity feed. The mechanism is all contained in
the cylindrical tank shown, which may be mounted either on the front of
the dash or on the side of the engine as shown.

[Illustration: Fig. 42.--The Stewart Vacuum Fuel Feed Tank.]

The tank is divided into two chambers, the upper one being the filling
chamber and the lower one the emptying chamber. The former, which is at
the top of the device, contains the float valve, as well as the pipes
running to the main fuel container and to the intake manifold. The lower
chamber is used to supply the carburetor with gasoline and is under
atmospheric pressure at all times, so the flow of fuel from it is by
means of gravity only. Since this chamber is located somewhat above the
carburetor, there must always be free flow of fuel. Atmospheric pressure
is maintained by the pipes A and B, the latter opening into the air. In
order that the fuel will be sucked from a main tank to the upper
chamber, the suction valve must be opened and the atmospheric valve
closed. Under these conditions the float is at the bottom and the
suction at the intake manifold produces a vacuum in the tank which draws
the gasoline from the main tank to the upper chamber. When the upper
chamber is filled at the proper height the float rises to the top, this
closing the suction valve and opening the atmospheric valve. As the
suction is now cut off, the lower chamber is filled by gravity owing to
there being atmospheric pressure in both upper and lower chambers. A
flap valve is provided between the two chambers to prevent the gasoline
in the lower one from being sucked back into the upper one. The
atmospheric and suction valves are controlled by the levers C and D,
both of which are pivoted at E, their outer ends being connected by two
coil springs. It is seen that the arrangement of these two springs is
such that the float must be held at the extremity of its movement, and
that it cannot assume an intermediate position.

This intermittent action is required to insure that the upper part of
the tank may be under atmospheric pressure part of the time for the
gasoline to flow to the lower chamber. When the level of gasoline drops
to a certain point, the float falls, thus opening the suction valve and
closing the atmospheric valve. The suction of the motor then causes a
flow of fuel from the main container. As soon as the level rises to the
proper height the float returns to its upper position. It takes about
two seconds for the chamber to become full enough to raise the float, as
but .05 gallon is transferred at a time. The pipe running from the
bottom of the lower chamber to the carburetor extends up a ways, so that
there is but little chance of dirt or water being carried to the float
chamber.

If the engine is allowed to stand long enough so that the tank becomes
empty, it will be replenished after the motor has been cranked over four
or five times with the throttle closed. The installation of the Stewart
Vacuum-Gravity System is very simple. The suction pipe is tapped into
the manifold at a point as near the cylinders as possible, while the
fuel pipe is inserted into the gasoline tank and runs to the bottom of
that member. There is a screen at the end of the fuel pipe to prevent
any trouble due to deposits of sediment in the main container. As the
fuel is sucked from the gasoline tank a small vent must be made in the
tank filler cap so that the pressure in the main tank will always be
that of the atmosphere.

EARLY VAPORIZER FORMS

The early types of carbureting devices were very crude and cumbersome,
and the mixture of gasoline vapor and air was accomplished in three
ways. The air stream was passed over the surface of the liquid itself,
through loosely placed absorbent material saturated with liquid, or
directly through the fuel. The first type is known as the surface
carburetor and is now practically obsolete. The second form is called
the "wick" carburetor because the air stream was passed over or through
saturated wicking. The third form was known as a "bubbling" carburetor.
While these primitive forms gave fairly good results with the early
slow-speed engines and the high grade, or very volatile, gasoline which
was first used for fuel, they would be entirely unsuitable for present
forms of engines because they would not carburate the lower grades of
gasoline which are used to-day, and would not supply the modern
high-speed engines with gas of the proper consistency fast enough even
if they did not have to use very volatile gasoline. The form of
carburetor used at the present time operates on a different principle.
These devices are known as "spraying carburetors." The fuel is reduced
to a spray by the suction effect of the entering air stream drawing it
through a fine opening.

The advantage of this construction is that a more thorough amalgamation
of the gasoline and air particles is obtained. With the earlier types
previously considered the air would combine with only the more volatile
elements, leaving the heavier constituents in the tank. As the fuel
became stale it was difficult to vaporize it, and it had to be drained
off and fresh fuel provided before the proper mixture would be produced.
It will be evident that when the fuel is sprayed into the air stream,
all the fuel will be used up and the heavier portions of the gasoline
will be taken into the cylinder and vaporized just as well as the more
volatile vapors.

[Illustration: Fig. 43.--Marine-Type Mixing Valve, by which Gasoline is
Sprayed into Air Stream Through Small Opening in Air-Valve Seat.]

The simplest form of spray carburetor is that shown at Fig. 43. In this
the gasoline opening through which the fuel is sprayed into the
entering air stream is closed by the spring-controlled mushroom valve
which regulates the main air opening as well. When the engine draws in a
charge of air it unseats the valve and at the same time the air flowing
around it is saturated with gasoline particles through the gasoline
opening. The mixture thus formed goes to the engine through the mixture
passage. Two methods of varying the fuel proportions are provided. One
of these consists of a needle valve to regulate the amount of gasoline,
the other is a knurled screw which controls the amount of air by
limiting the lift of the jump valve.

DEVELOPMENT OF FLOAT-FEED CARBURETOR

The modern form of spraying carburetor is provided with two chambers,
one a mixing chamber through which the air stream passes and mixes with
a gasoline spray, the other a float chamber in which a constant level of
fuel is maintained by simple mechanism. A jet or standpipe is used in
the mixing chamber to spray the fuel through and the object of the float
is to maintain the fuel level to such a point that it will not overflow
the jet when the motor is not drawing in a charge of gas. With the
simple forms of generator valve in which the gasoline opening is
controlled by the air valve, a leak anywhere in either valve or valve
seat will allow the gasoline to flow continuously whether the engine is
drawing in a charge or not. The liquid fuel collects around the air
opening, and when the engine inspires a charge it is saturated with
gasoline globules and is excessively rich. With a float-feed
construction, which maintains a constant level of gasoline at the right
height in the standpipe, liquid fuel will only be supplied when drawn
out of the jet by the suction effect of the entering air stream.

MAYBACH'S EARLY DESIGN

The first form of spraying carburetor ever applied successfully was
evolved by Maybach for use on one of the earliest Daimler engines. The
general principles of operation of this pioneer float-feed carburetor
are shown at Fig. 44, A. The mixing chamber and valve chamber were one
and the standpipe or jet protruded into the mixing chamber. It was
connected to the float compartment by a pipe. The fuel from the tank
entered the top of the float compartment and the opening was closed by a
needle valve carried on top of a hollow metal float. When the level of
gasoline in the float chamber was lowered the float would fall and the
needle valve uncover the opening. This would permit the gasoline from
the tank to flow into the float chamber, and as the chamber filled the
float would rise until the proper level had been reached, under which
conditions the float would shut off the gasoline opening. On every
suction stroke of the engine the inlet valve, which was an automatic
type, would leave its seat and a stream of air would be drawn through
the air opening and around the standpipe or jet. This would cause the
gasoline to spray out of the tube and mix with the entering air stream.

[Illustration: Fig. 44.--Tracing Evolution of Modern Spray Carburetor.
A--Early Form Evolved by Maybach. B.--Phoenix-Daimler Modification of
Maybach's Principle. C--Modern Concentric Float Automatic Compensating
Carburetor.]

The form shown at B was a modification of Maybach's simple device and
was first used on the Phoenix-Daimler engines. Several improvements are
noted in this device. First, the carburetor was made one unit by casting
the float and mixing chambers together instead of making them separate
and joining them by a pipe, as shown at A. The float construction was
improved and the gasoline shut-off valve was operated through leverage
instead of being directly fastened to the float. The spray nozzle was
surrounded by a choke tube which concentrated the air stream around it
and made for more rapid air flow at low engine speeds. A conical piece
was placed over the jet to break up the entering spray into a mist and
insure more intimate admixture of air and gasoline. The air opening was
provided with an air cone which had a shutter controlling the opening so
that the amount of air entering could be regulated and thus vary the
mixture proportions within certain limits.

CONCENTRIC FLOAT AND JET TYPE

The form shown at B has been further improved, and the type shown at C
is representative of modern single jet practice. In this the float
chamber and mixing chamber are concentric. A balanced float mechanism
which insures steadiness of feed is used, the gasoline jet or standpipe
is provided with a needle valve to vary the amount of gasoline supplied
the mixture and two air openings are provided. The main air port is at
the bottom of the vaporizer, while an auxiliary air inlet is provided at
the side of the mixing chamber. There are two methods of controlling the
mixture proportions in this form of carburetor. One may regulate the
gasoline needle or adjust the auxiliary air valve.

SCHEBLER CARBURETOR

A Schebler carburetor, which has been used on some airplane engines, is
shown in Fig. 45. It will be noticed that a metering pin or needle valve
opens the jet when the air valve opens. The long arm of a leverage is
connected to the air valve, while the short arm is connected to the
needle, the reduction in leverage being such that the needle valve is
made to travel much less than the air valve. For setting the amount of
fuel passed or the size of the jet orifice when running with the air
valve closed, there is a screw which raises or lowers the fulcrum of the
lever and there is also a dash control having the same effect by pushing
down the fulcrum against a small spring. A long extension is given to
the venturi tube which is very narrow around the jet orifices, which are
horizontal and shown at A in the drawing. Fuel enters the float chamber
through the union M, and the spring P holds the metering pin upward
against the restraining action of the lever. The air valve may be set by
an easily adjustable knurled screw shown in the drawing, and fluttering
of the valve is prevented by the piston dash pot carried in a chamber
above the valve into which the valve stem projects. The primary air
enters beneath the jet passage and there is a small throttle in the
intake to increase the speed of air flow for starting purposes. The
carburetor is adapted for the use of a hot-air connection to the stove
around the exhaust pipe and it is recommended that such a fitting be
supplied. The lever which controls the supply of air through the primary
air intake is so arranged that if desired it can be connected with a
linkage on the dash or control column by means of a flexible wire.

[Illustration: Fig. 45.--New Model of Schebler Carburetor With Metering
Valve and Extended Venturi. Note Mechanical Connection Between Air Valve
and Fuel Regulating Needle.]

THE CLAUDEL (FRENCH) CARBURETOR

[Illustration: Fig. 46.--The Claudel Carburetor.]

This carburetor is of extremely simple construction, because it has no
supplementary or auxiliary air valve and no moving parts except the
throttle controlling the gas flow. The construction is already shown in
Fig. 46. The spray jet is eccentric with a surrounding sleeve or tube
in which there are two series of small orifices, one at the top and the
other near the bottom. The former are about level with the spray jet
opening. The sleeve surrounding the nozzle is closed at the top. The
air, passing the upper holes in the sleeve, produces a vacuum in the
sleeve, thereby drawing air in through the bottom holes. It is this
moving interior column of air that controls the flow of gasoline from
the nozzle. Owing to the friction of the small passages, the speed of
air flow through the sleeve does not increase as fast as the speed of
air flow outside the sleeve, hence there is a tendency for the mixture
to remain constant. The throttle of this carburetor is of the barrel
type, and the top of the spray nozzle and its surrounding sleeve are
located inside the throttle.

STEWART METERING PIN CARBURETOR

The carburetor shown at Fig. 47 is a metering type in which the vacuum
at the jet is controlled by the weight of the metering valve surrounding
the upright metering pin. The only moving part is the metering valve,
which rises and falls with the changes in vacuum. The air chamber
surrounds the metering valve, and there is a mixing chamber above. As
the valve is drawn up the gasoline passage is enlarged on account of the
predetermined taper on the metering pin, and the air passage also is
increased proportionately, giving the correct mixture. A dashpot at the
bottom of the valve checks flutter. In idling the valve rests on its
seat, practically closing the air and giving the necessary idling
mixture. A passage through the valve acts as an aspirating tube. When
the valve is closed altogether the primary air passes through ducts in
the valve itself, giving the proper amount for idling. The one
adjustment consists in raising or lowering the tapered metering pin,
increasing or decreasing the supply of gasoline. Dash control is
supplied. This pulls down the metering pin, increasing the gasoline
flow. The duplex type for eight- and twelve-cylinder motors is the same
in principle as model 25, but it is a double carburetor synchronized as
to throttle movements, adjustments, etc. The duplex for aeronautical
motors is made of cast aluminum alloy.

[Illustration: Fig. 47.--The Stewart Metering Pin Carburetor.]

MULTIPLE NOZZLE VAPORIZERS

To secure properly proportioned mixtures some carburetor designers have
evolved forms in which two or more nozzles are used in a common mixing
chamber. The usual construction is to use two, one having a small
opening and placed in a small air tube and used only for low speeds,
the other being placed in a larger air tube and having a slightly
augmented bore so that it is employed on intermediate speeds. At high
speeds both jets would be used in series. Some multiple jet carburetors
could be considered as a series of these instruments, each one being
designed for certain conditions of engine action. They would vary from
small size just sufficient to run the engine at low speed to others
having sufficient capacity to furnish gas for the highest possible
engine speed when used in conjunction with the smaller members which
have been brought into service progressively as the engine speed has
been augmented. The multiple nozzle carburetor differs from that in
which a single spray tube is used only in the construction of the mixing
chamber, as a common float bowl can be used to supply all spray pipes.
It is common practice to bring the jets into action progressively by
some form of mechanical connection with the throttle or by automatic
valves.

The object of any multiple nozzle carburetor is to secure greater
flexibility and endeavor to supply mixtures of proper proportions at all
speeds of the engine. It should be stated, however, that while devices
of this nature lend themselves readily to practical application it is
more difficult to adjust them than the simpler forms having but one
nozzle. When a number of jets are used the liability of clogging up the
carburetor is increased, and if one or more of the nozzles is choked by
a particle of dirt or water the resulting mixture trouble is difficult
to detect. One of the nozzles may supply enough gasoline to permit the
engine to run well at certain speeds and yet not be adequate to supply
the proper amount of gas under other conditions. In adjusting a multiple
jet carburetor in which the jets are provided with gasoline regulating
needles, it is customary to consider each nozzle as a distinct
carburetor and to regulate it to secure the best motor action at that
throttle position which corresponds to the conditions under which the
jet is brought into service. For instance, that supplied the primary
mixing chamber should be regulated with the throttle partly closed,
while the auxiliary jet should be adjusted with the throttle fully
opened.

BALL AND BALL TWO-STAGE CARBURETOR

[Illustration: Fig. 48.--The Ball and Ball Two-Stage Carburetor.]

This is a two-stage vaporizing device, hot air being used in the primary
or initial stage of vaporization and cold air in the supplementary
stage. Referring to the sectional illustration at Fig. 48, it will be
seen that there is a hot-air passage with a choke-valve; the primary
venturi appears at B; J is its gasoline jet, and V is a spring-loaded
idling valve in a fixed air opening. These parts constitute the primary
system. In the secondary system A is a cold-air passage, T a butterfly
valve and J a gasoline jet discharging into the cold-air passage. This
system is brought into operation by opening the butterfly T. A
connection between the butterfly T and the throttle, not shown, throws
the butterfly wide open when the throttle is not quite wide open; at all
other times the butterfly is held closed by a spring. The cylindrical
chamber at the right of the mixing chamber has an extension E of reduced
diameter connecting it with the intake manifold through a passage D. A
restricted opening connects the float chamber with the cylindrical
chamber so that the gasoline level is the same in both. A loosely
fitting plunger P in the cylindrical chamber has an upward extension
into the small part of the chamber. O is a small air opening and M is a
passage from the cylindrical chamber to the mixing chamber. Air
constantly passes through this when the carburetor is in operation. The
carburetor is really two in one. The primary carburetor is made up of a
central jet in a venturi passage. The float chamber is eccentric. In the
air passage there is a fixed opening, and additional air is taken in by
the opening through suction of a spring-opposed air valve. The second
stage, which comes into play as soon as the carburetor is called upon
for additional mixture above low medium speeds, is made up of an
independent air passage containing another air valve. As the valve is
opened this jet is uncovered, and air is led past it. For easy starting
an extra passage leads from the float bowl passage to a point above the
throttle. All the suction falls upon this passage when the throttle is
closed. The passage contains a plunger and acts as a pick-up device.
When the vacuum increases the plunger rises and shuts off the flow of
gasoline from the intake passage. As the throttle is opened the vacuum
in the intake passage is broken, and the plunger falls, causing gasoline
to gather above it. This is immediately drawn through the pick-up
passage and gives the desired mixture for acceleration.

MASTER MULTIPLE-JET CARBURETOR

[Illustration: Fig. 49.--The Master Carburetor.]

This carburetor, shown in detail in Figs. 49 and 50, has been very
popular in racing cars and aviation engines because of exceptionally
good pick-up qualities and its thorough atomization of fuel. Its
principle of operation is the breaking up of the fuel by a series of
jets, which vary in number from fourteen to twenty-one, according to
the size of the carburetor. These are uncovered by opening the throttle,
which is curved--a patented feature--to secure the correct progression
of jets. The carburetor has an eccentric float chamber, from which the
gasoline is led to the jet piece from which the jets stand up in a row.
The tops of these jets are closed until the throttle is opened far
enough to pass them, which it does progressively. The air opening is at
the bottom, and the throttle opening is such that a modified venturi is
formed. The throttle is carried in a cylindrical barrel with the jets
placed below it, and the passage from the barrel to the intake is
arranged so that there is no interruption in the flow. For easy starting
a dash-controlled shutter closes off the air, throwing the suction on
the jets, thus giving a rich mixture.

[Illustration: Fig. 50.--Sectional View of Master Carburetor Showing
Parts.]

The only adjustment is for idling, and once that is fixed it need never
be touched. This is in the form of a screw and regulates the position of
the throttle when at idling position. The dash control has high-speed,
normal and rich-starting positions. In installing the Master carburetor
the float chamber may be turned either toward the radiator or driver's
seat. If the float is turned toward the radiator, however, a forward lug
plate should be ordered; otherwise it will be difficult to install the
control. The throttle lever must go all the way to the stop lug or
maximum power will not be secured. In adjusting the idle screw it is
turned in for rich and out for lean.

COMPOUND NOZZLE ZENITH CARBURETOR

[Illustration: Fig. 51.--Sectional View of Zenith Compound Nozzle
Compensating Carburetor.]

The Zenith carburetor, shown at Fig. 51, has become very popular for
airplane engine use because of its simplicity, as mixture compensation
is secured by a compensating compound nozzle principle that works very
well in practice. To illustrate this principle briefly, let us consider
the elementary type of carburetor or mixing valve, as shown in Fig. 52,
A. It consists of a single jet or spraying nozzle placed in the path of
the incoming air and fed from the usual float chamber. It is a natural
inference to suppose that as the speed of the motor increases, both the
flow of air and of gasoline will increase in the same proportion.
Unhappily, such is not the case. There is a law of liquid bodies which
states that the flow of gasoline from the jet increases under suction
faster than the flow of air, giving a mixture which grows richer and
richer--a mixture containing a much higher percentage of gasoline at
high suction than at low. The tendency is shown by the accompanying
curve (Fig. 52, B), which gives the ratio of gasoline to air at varying
speeds from this type of jet. The mixture is practically constant only
between narrow limits and at very high speed. The most common method of
correcting this defect is by putting various auxiliary air valves which,
adding air, tends to dilute this mixture as it gets too rich. It is
difficult with makeshift devices to gauge this dilution accurately for
every motor speed.

[Illustration: Fig. 52.--Diagrams Explaining Action of Baverey Compound
Nozzle Used in Zenith Carburetor.]

Now, if we have a jet which grows richer as the suction increases, the
opposite type of jet is one which would grow leaner under similar
conditions. Baverey, the inventor of the Zenith, discovered the
principle of the constant flow device which is shown in Fig. 52, C. Here
a certain fixed amount of gasoline determined by the opening I is
permitted to flow by gravity into the well J open to the air. The
suction at jet H has no effect upon the gravity compensator I because
the suction is destroyed by the open well J. The compensator, then,
delivers a steady rate of flow per unit of time, and as the motor
suction increases more air is drawn up, while the amount of gasoline
remains the same and the mixture grows poorer and poorer. Fig. 52, D,
shows this curve.

By combining these two types of rich and poor mixture carburetors the
Zenith compound nozzle was evolved. In Fig. 52, E, we have both the
direct suction or richer type leading through pipe E and nozzle G and
the "constant flow" device of Baverey shown at J, I, K and nozzle H. One
counteracts the defects of the other, so that from the cranking of the
motor to its highest speed there is a constant ratio of air and
gasoline to supply efficient combustion.

In addition to the compound nozzle the Zenith is equipped with a
starting and idling well, shown in the cut of Model L carburetor at P
and J. This terminates in a priming hole at the edge of the butterfly
valve, where the suction is greatest when this valve is slightly open.
The gasoline is drawn up by the suction at the priming hole and, mixed
with the air rushing by the butterfly, gives an ideal slow speed
mixture. At higher speeds with the butterfly valve opened further the
priming well ceases to operate and the compound nozzle drains the well
and compensates correctly for any motor speed.

[Illustration: Fig. 53.--The Zenith Duplex Carburetor for Airplane
Motors of the V Type.]

With the coming of the double motor containing eight or twelve cylinders
arranged in two V blocks, the question of good carburetion has been a
problem requiring much study. The single carburetor has given only
indifferent results due to the strong cross suction in the inlet
manifold from one set of cylinders to the other. This naturally led to
the adoption of two carburetors in which each set of cylinders was
independently fed by a separate carburetor. Results from this system
were very good when the two carburetors were working exactly in unison,
but as it was extremely difficult to accomplish this co-operation,
especially where the adjustable type was employed, this system never
gained in favor. The next logical step was the Zenith Duplex, shown at
Fig. 53. This consists of two separate and distinct carburetors joined
together so that a common gasoline float chamber and air inlet could be
used by both. It does away with cross suction in the manifold because
each set of cylinders has a separate intake of its own. It does away
with two carburetors and makes for simplicity. The practical application
of the Zenith carburetor to the Curtiss 90 horse-power OX-2 motor used
on the JN-4 standard training machine is shown at Fig. 54, which
outlines a rear view of the engine in question. The carburetor is
carried low to permit of fuel supply from a gravity tank carried back of
the motor.

[Illustration: Fig. 54.--Rear View of Curtiss OX-2 90 Horse-Power
Airplane Motor Showing Carburetor Location and Hot Air Leads.]

UTILITY OF GASOLINE STRAINERS

Many carburetors include a filtering screen at the point where the
liquid enters the float chamber in order to keep dirt or any other
foreign matter which may be present in the fuel from entering the float
chamber. This is not general practice, however, and the majority of
vaporizers do not include a filter in their construction. It is very
desirable that the dirt should be kept out of the carburetor because it
may get under the float control fuel valve and cause flooding by keeping
it raised from its seat. If it finds its way into the spray nozzle it
may block the opening so that no gasoline will issue or may so constrict
the passage that only very small quantities of fuel will be supplied the
mixture. Where the carburetor itself is not provided with a filtering
screen a simple filter is usually installed in the pipe line between the
gasoline tank and the float chamber.

Some simple forms of filters and separators are shown at Fig. 55. That
at A consists of a simple brass casting having a readily detachable
gauze screen and a settling chamber of sufficient capacity to allow the
foreign matter to settle to the bottom, from which it is drained out by
a pet cock. Any water or dirt in the gasoline will settle to the bottom
of the chamber, and as all fuel delivered to the carburetor must pass
through the wire gauze screen it is not likely to contain impurities
when it reaches the float chamber. The heavier particles, such as scale
from the tank or dirt and even water, all of which have greater weight
than the gasoline, will sink to the bottom of the chamber, whereas
light particles, such as lint, will be prevented from flowing into the
carburetor by the filtering screen.

[Illustration: Fig. 55.--Types of Strainers Interposed Between Vaporizer
and Gasoline Tank to Prevent Water or Dirt Passing Into Carbureting
Device.]

The filtering device shown at B is a larger appliance than that shown at
A, and should be more efficient as a separator because the gasoline is
forced to pass through three filtering screens before it reaches the
carburetor. The gasoline enters the device shown at C through a bent
pipe which leads directly to the settling chamber and from thence
through a wire gauze screen to the upper compartment which leads to the
carburetor. The device shown at D is a combination strainer, drain, and
sediment cup. The filtering screen is held in place by a spring and
both are removed by taking out a plug at the bottom of the device. The
shut-off valve at the top of the device is interposed between the
sediment cup and the carburetor. This separating device is incorporated
with the gasoline tank and forms an integral part of the gasoline supply
system. The other types shown are designed to be interposed between the
gasoline tank and the carburetor at any point in the pipe line where
they may be conveniently placed.

INTAKE MANIFOLD DESIGN AND CONSTRUCTION

On four- and six-cylinder engines and in fact on all multiple-cylinder
forms, it is important that the piping leading from the carburetor to
the cylinders be made in such a way that the various cylinders will
receive their full quota of gas and that each cylinder will receive its
charge at about the same point in the cycle of operations. In order to
make the passages direct the bends should be as few as possible, and
when curves are necessary they should be of large radius because an
abrupt corner will not only impede gas flow but will tend to promote
condensation of the fuel. Every precaution should be taken with
four- and six-cylinder engines to insure equitable gas distribution to
the valve chambers if regular action of the power plant is desired. If
the gas pipe has many turns and angles it will be difficult to charge
all cylinders properly. On some six-cylinder aviation engines, two
carburetors are used because of trouble experienced with manifolds
designed for one carburetor. Duplex carburetors are necessary to secure
the best results from eight- and twelve-cylinder V engines.

The problem of intake piping is simplified to some extent on block
motors where the intake passage is cored in the cylinder casting and
where but one short pipe is needed to join this passage to the
carburetor. If the cylinders are cast in pairs a simple pipe of T or Y
form can be used with success. When the engine is of a type using
individual cylinder castings, especially in the six-cylinder power
plants, the proper application and installation of suitable piping is a
difficult problem. The reader is referred to the various engine designs
outlined to ascertain how the inlet piping has been arranged on
representative aviation engines. Intake piping is constructed in two
ways, the most common method being to cast the manifold of brass or
aluminum. The other method, which is more costly, is to use a built-up
construction of copper or brass tubing with cast metal elbows and Y
pieces. One of the disadvantages advanced against the cast manifold is
that blowholes may exist which produce imperfect castings and which will
cause mixture troubles because the entering gas from the carburetor,
which may be of proper proportions, is diluted by the excess air which
leaks in through the porous casting. Another factor of some moment is
that the roughness of the walls has a certain amount of friction which
tends to reduce the velocity of the gases, and when projecting pieces
are present, such as core wire or other points of metal, these tend to
collect the drops of liquid fuel and thus promote condensation. The
advantage of the built-up construction is that the walls of the tubing
are very smooth, and as the castings are small it is not difficult to
clean them out thoroughly before they are incorporated in the manifold.
The tubing and castings are joined together by hard soldering, brazing
or autogenous welding.

COMPENSATING FOR VARYING ATMOSPHERIC CONDITIONS

The low-grade gasoline used at the present time makes it necessary to
use vaporizers that are more susceptible to atmospheric variations than
when higher grade and more volatile liquids are vaporized. Sudden
temperature changes, sometimes being as much as forty degrees rise or
fall in twelve hours, affect the mixture proportions to some extent, and
not only changes in temperature but variations in altitude also have a
bearing on mixture proportions by affecting both gasoline and air. As
the temperature falls the specific gravity of the gasoline increases
and it becomes heavier, this producing difficulty in vaporizing. The
tendency of very cold air is to condense gasoline instead of vaporizing
it and therefore it is necessary to supply heated air to some
carburetors to obtain proper mixtures during cold weather. In order that
the gas mixtures will ignite properly the fuel must be vaporized and
thoroughly mixed with the entering air either by heat or high velocity
of the gases. The application of air stoves to the Curtiss OX-2 motor is
clearly shown at Fig. 54. It will be seen that flexible metal pipes are
used to convey the heated air to the air intakes of the duplex mixing
chamber.

[Illustration: Fig. 56.--Chart Showing Diminution of Air Pressure as
Altitude Increases.]

HOW HIGH ALTITUDE AFFECTS POWER

Any internal combustion engine will show less power at high altitudes
than it will deliver at sea level, and this has caused a great deal of
questioning. "There is a good reason for this," says a writer in "Motor
Age," "and it is a physical impossibility for the engine to do
otherwise. The difference is due to the lower atmospheric pressure the
higher up we get. That is, at sea level the atmosphere has a pressure of
14.7 pounds per square inch; at 5,000 feet above sea level the pressure
is approximately 12.13 pounds per square inch, and at 10,000 feet it is
10 pounds per square inch. From this it will be seen that the final
pressure attained after the piston has driven the gas into compressed
condition ready for firing is lower as the atmospheric pressure drops.
This means that there is not so much power in the compressed charge of
gas the higher up you get above sea level.

"For example, suppose the compression ratio to be 4-1/2 to 1; in other
words, suppose the air space above the piston to have 4-1/2 times the
volume when the piston is at the bottom of its stroke that it has when
the piston is at the top of the stroke. That is a common compression
ratio for an average motor, and is chosen because it is considered to be
the best for maximum horse-power and in order that the compression
pressure will not be so high as to cause pre-ignition. Knowing the
compression ratio, we can determine the final pressure immediately
before ignition by substituting in the standard formula:

P^{1} = P(V/V^{1})^{1.3}

in which P is the atmospheric pressure; P^{1} is the final pressure, and
V/V^{1} is the compression ratio, therefore P^{1} = 14.7 (4.5)^{1.3} =
104 pounds per square inch, absolute.

"That is, 104 pounds per square inch is the most efficient final
compression pressure to have for this engine at sea level, since it
comes directly from the compression ratio.

"Now supposing we consider that the altitude is 7,000 feet above sea
level. At this height the atmospheric pressure is 11.25 pounds per
square inch, approximately. In this case we can again substitute in the
formula, using the new atmospheric pressure figure. The equation
becomes:

P^{1} = 11.25 (4.5)^{1.3}--79.4 pounds per square inch, absolute.

"Therefore we now have a final compression pressure of only 79.4 pounds
per square inch, which is considerably below the pressure we have just
found to be the most efficient for the motor. The resulting power drop
is evident.

"It should be borne in mind that these final compression pressures are
absolute pressures--that is, they include the atmospheric pressure. In
the first case, to get the pressure above atmospheric you would subtract
14.7 and in the latter 11.25 would have to be deducted. In other words,
where the sea level compression is 89.3 pounds per square inch above the
atmosphere, the same motor will have only a compression pressure of
68.15 pounds per square inch above the atmosphere at 7,000 feet
elevation.

"From the above it is evident that in order to bring the final
compression pressure up to the efficient figure we have determined, a
different compression ratio would have to be used. That is, the final
volume would have to be less, and as it is impossible to vary this to
meet the conditions of altitude, the loss of power cannot be helped
except by the replacing of the standard pistons with some that are
longer above the wrist-pin so as to reduce the space above the pistons
when on top center. Then if the ratio is thereby raised to some such
figures as 5 to 1, the engine will again have its proper final pressure,
but it will still not have as much power as it would have at sea level,
since the horse-power varies directly with the atmospheric pressure,
final compression being kept constant. That is, at 7,000 feet the
horse-power of an engine that had 40 horse-power at sea level would be
equal to

11.25
------- = 30.6 horse-power.
14.7

"If the original compression ratio of 4.5 were retained, the drop in
horse-power would be even greater than this. These computations and
remarks will make it clear that the designer who contemplates building
an airplane for high altitude use should see to it that it is of
sufficient power to compensate for the drop that is inevitable when it
is up in the air. This is often illustrated in stationary gas-engine
installations. An engine that had a sea-level rating amply sufficient
for the work required, might not be powerful enough when brought up
several thousand feet." When one considers that airplanes attain heights
of over 18,000 feet, it will be evident that an ample margin of engine
power is necessary.

THE DIESEL SYSTEM

A system of fuel supply developed by the late Dr. Diesel, a German
chemist and engineer, is attracting considerable attention at the
present time on account of the ability of the Diesel engine to burn
low-grade fuels, such as crude petroleum. In this system the engines are
built so that very high compressions are used, and only pure air is
taken into the cylinder on the induction stroke. This is compressed to a
pressure of about 500 pounds per square inch, and sufficient heat is
produced by this compression to explode a hydrocarbon mixture. As the
air which is compressed to this high point cannot burn, the fuel is
introduced into the cylinder combustion chamber under still higher
compression than that of the compressed air, and as it is injected in a
fine stream it is immediately vaporized because of the heat. Just as
soon as the compressed air becomes thoroughly saturated with the liquid
fuel, it will explode on account of the degree of heat present in the
combustion chamber. Such motors have been used in marine and stationary
applications, but are not practical for airplanes or motor cars because
of lack of flexibility and great weight in proportion to power
developed. The Diesel engine is the standard power plant used in
submarine boats and motor ships, as its efficiency renders it
particularly well adapted for large units.

NOTES ON CARBURETOR INSTALLATION IN AIRPLANES

A writer in "The Aeroplane," an English publication, discourses on some
features of carburetor installation that may be of interest to the
aviation student, so portions of the dissertation are reproduced
herewith.

"Users of airplanes fitted with ordinary type carburetors will
do well to note carefully the way in which these are fitted, for
several costly machines have been burnt lately through the sheer
carelessness of their users. These particular machines were
fitted with a high powered V-type engine, made by a firm which
is famous as manufacturers of automobiles _de luxe_. In these
engines there are four carburetors, mounted in the V between the
cylinders. When the engine is fitted as a tractor, the float
chambers are in front of the jet chambers. Consequently, when
the tail of the machine is resting on the ground, the jets are
lower than the level of the gasoline in the float chamber.

"Quite naturally, the gasoline runs out of the jet, if it is
left turned on when the machine is standing in its normal
position, and trickles into the V at the top of the crank-case.
Thence it runs down to the tail of the engine, where the
magnetos are fitted, and saturates them. If left long enough,
the gasoline manages to soak well into the fuselage before
evaporating. And what does evaporate makes an inflammable gas in
the forward cockpit. Then some one comes along and starts up the
engine. The spark-gap of the magneto gives one flash, and the
whole front of the machine proceeds to give a Fourth of July
performance forthwith. Naturally, one safeguard is to turn the
petrol off directly the machine lands. Another is never to turn
it on till the engine is actually being started up.

"One would be asking too much of the human boy--who is
officially regarded as the only person fit to fly an
aeroplane--if one depended upon his memory of such a detail to
save his machine, though one might perhaps reasonably expect the
older pilots to remember not to forget. Even so, other means of
prevention are preferable, for fire is quite as likely to occur
from just the same cause if the engine happens to be a trifle
obstinate in starting, and so gives the carburetors several
minutes in which to drip--in which operation they would probably
be assisted by air-mechanics 'tickling' them.

"One way out of the trouble is to fit drip tins under the jet
chamber to catch the gasoline as it falls. This is all very well
just to prevent fire while the machine is being started up, but
it will not save it if it is left standing with the tail on the
ground and the petrol turned on, for the drip tins will then
fill up and run over. And if it catches then, the contents of
the drip tins merely add fuel to the fire.

_Reversing Carburetors_

"Yet another way is to turn the carburetors round, so that the
float chambers are behind the jets, and so come below them when
the tail is on the ground, thus cutting off the gasoline low
down in the jets. There seems to be no particular mechanical
difficulty about this, though I must confess that I did not note
very carefully whether the reversal of the float chambers would
make them foul any other fittings on the engine. It has been
argued, however, that doing this would starve the engine of
gasoline when climbing at a steep angle, as the gasoline would
then be lowered in the jets and need more suction to get into
the cylinders. This is rather a pretty point of amateur motor
mechanics to discuss, for, obviously, when the same engine is
used as a 'pusher' instead of a tractor, the jets are in front
of the floats, and there seems to be no falling off in power.

_Starvation of Mixture_

"Moreover, the higher a machine goes the lower is the
atmospheric pressure, and, consequently, the less is the amount
of air sucked in at each induction stroke. This means, of
course, that with the gasoline supply the mixture at high
altitudes is too rich, so that, in order to get precisely the
right mixture when very high up, it is necessary to reduce the
gasoline supply by screwing down the needle valve between the
tank and the carburetor--at least, that has been the experience
of various high-flying pilots. No doubt something might be done
in the way of forced air feed to compensate for reduced
atmospheric pressure, but it remains to be proved whether the
extra weight of mechanism involved would pay for the extra power
obtained. Variable compression might do something, also, to even
things up, but here, also, weight of mechanism has to be
considered.

"In any case, at present, the higher one goes the more the
power of the engine is reduced, for less air means a less volume
of mixture per cylinder, and as the petrol feed has to be
starved to suit the smaller amount of air available, this means
further loss of power. I do not know whether anyone has evolved
a carburetor which automatically starves the gasoline feed when
high up, but it seems possible that when an airplane is sagging
about 'up against the ceiling'--as a French pilot described the
absolute limit of climb for his particular machine--it might be
a good thing to have the jets in front of the float chamber, for
then a certain amount of automatic starvation would take place.

"When a machine is right up at its limiting height, and the
pilot is doing his best to make it go higher still, it is
probably flying with its tail as low as the pilot dares to let
it go, and the lateral and longitudinal controls are on the
verge of vanishing, so that if the carburetor jets are behind
the float chambers there is bound to be an over-rich mixture in
any case. There is even a possibility of a careless or ignorant
pilot carrying on in this tail-down position till one set of
cylinders cuts out altogether, in which case the carburetor
feeding that set may flood over, just as if the machine were on
the ground, and the whole thing may catch fire. Whereas, with
the jets in front of the floats, though the mixture may starve a
trifle, there is, at any rate, no danger of fire through
climbing with the tail down.

_A Diving Danger_

"On the other hand, in a 'pusher' with this type of engine, if
the jets are in their normal position--which is in front of the
floats--there is danger of fire in a dive. That is to say, if
the pilot throttles right down, or switches off and relies on
air pressure on his propeller to start the engine again, so that
the gasoline is flooding over out of the jets instead of being
sucked into the engine, there may be flooding over the magnetos
if the dive is very steep and prolonged. In any case, a long
dive will mean a certain amount of flooding, and, probably, a
good deal of choking and spitting by the engine before it gets
rid of the over-rich mixture and picks up steady firing again.
Which may indicate to young pilots that it is not good to come
down too low under such circumstances, trusting entirely to
their engines to pick up at once and get going before they hit
the ground.

"On the whole, it seems that it might be better practice to set
the carburetors thwartwise of engines, for then jets and floats
would always be at approximately the same level, no matter what
the longitudinal position of the machine, and it is never long
enough in one position at a big lateral angle to raise any
serious carburetor troubles. Car manufacturers who dive
cheerfully into the troubled waters of aero-engine designs are
a trifle apt to forget that their engines are put into positions
on airplanes which would be positively indecent in a motor car.
An angle of 1 in 10 is the exception on a car, but it is common
on an airplane, and no one ever heard of a car going down a hill
of 10 to 1--which is not quite a vertical dive. Therefore, there
is every excuse for a well-designed and properly brought-up
carburetor misbehaving itself in an aeroplane.

"It seems, then, that it is up to the manufacturers to produce
better carburetors--say, with the jet central with the float.
But it also behooves the user to show ordinary common sense in
handling the material at present available, and not to make a
practice of burning up $25,000 worth or so of airplane just
because he is too lazy to turn off his gasoline, or to have the
tail of his machine lifted up while he is tinkering with his
engines."

NOTES ON CARBURETOR ADJUSTMENT

The modern float feed carburetor is a delicate and nicely balanced
appliance that requires a certain amount of attention and care in order
to obtain the best results. The adjustments can only be made by one
possessing an intelligent knowledge of carburetor construction and must
never be made unless the reason for changing the old adjustment is
understood. Before altering the adjustment of the leading forms of
carburetors, a few hints regarding the quality to be obtained in the
mixture should be given some consideration, as if these are properly
understood this knowledge will prove of great assistance in adjusting
the vaporizer to give a good working proportion of fuel and air. There
is some question regarding the best mixture proportions and it is
estimated that gas will be explosive in which the proportions of fuel
vapor and air will vary from one part of the former to a wide range
included between four and eighteen parts of the latter. A one to four
mixture is much too rich, while the one in eighteen is much too lean to
provide positive ignition.

A rich mixture should be avoided because the excessive fuel used will
deposit carbon and will soot the cylinder walls, combustion chamber
interior, piston top and valves and also tend to overheat the motor. A
rich mixture will also seriously interfere with flexible control of the
engine, as it will choke up on low throttle and run well on open
throttle when the full amount of gas is needed. A rich mixture may be
quickly discovered by black smoke issuing from the muffler, the exhaust
gas having a very pungent odor. If the mixture contains a surplus of air
there will be popping sounds in the carburetor, which is commonly termed
"blowing back." To adjust a carburetor is not a difficult matter when
the purpose of the various control members is understood. The first
thing to do in adjusting a carburetor is to start the motor and to
retard the sparking lever so the motor will run slowly leaving the
throttle about half open. In order to ascertain if the mixture is too
rich cut down the gasoline flow gradually by screwing down the needle
valve until the motor commences to run irregularly or misfire. Close the
needle valves as far as possible without having the engine come to a
stop, and after having found the minimum amount of fuel gradually
unscrew the adjusting valve until you arrive at the point where the
engine develops its highest speed. When this adjustment is secured the
lock nut is screwed in place so the needle valve will keep the
adjustment. The next point to look out for is regulation of the
auxiliary air supply on those types of carburetors where an adjustable
air valve is provided. This is done by advancing the spark lever and
opening the throttle. The air valve is first opened or the spring
tension reduced to a point where the engine misfires or pops back in the
carburetor. When the point of maximum air supply the engine will run on
is thus determined, the air valve spring may be tightened by screwing in
on the regulating screw until the point is reached where an appreciable
speeding up of the engine is noticed. If both fuel and air valves are
set right, it will be possible to accelerate the engine speed uniformly
without interfering with regularity of engine operation by moving the
throttle lever or accelerator pedal from its closed to its wide open
position, this being done with the spark lever advanced. All types of
carburetors do not have the same means of adjustment; in fact, some
adjust only with the gasoline regulating needle; others must have a
complete change of spray nozzles; while in others the mixture
proportions may be varied only by adjustment of the quantity of entering
air. Changing the float level is effective in some carburetors, but this
should never be done unless it is certain that the level is not correct.
Full instructions for locating carburetion troubles will be given in
proper sequence.

It is a fact well known to experienced repairmen and motorists that
atmospheric conditions have much to do with carburetor action. It is
often observed that a motor seems to develop more power at night than
during the day, a circumstance which is attributed to the presence of
more moisture in the cooler night air. Likewise, taking a motor from sea
level to an altitude of 10,000 feet involves using rarefied air in the
engine cylinders and atmospheric pressures ranging from 14.7 pounds at
sea level to 10.1 pounds per square inch at the high altitude. All
carburetors will require some adjustment in the course of any material
change from one level to another. Great changes of altitude also have a
marked effect on the cooling system of an airplane. Water boils at 212
degrees F. only at sea level. At an altitude of 10,000 feet it will boil
at a temperature nineteen degrees lower, or 193 degrees F.

In high altitudes the reduced atmospheric pressure, for 5,000 feet or
higher than sea level, results in not enough air reaching the mixture,
so that either the auxiliary air opening has to be increased, or the
gasoline in the mixture cut down. If the user is to be continually at
high altitudes he should immediately purchase either a larger dome or a
smaller strangling tube, mentioning the size carburetor that is at
present in use and the type of motor that it is on, including details as
to the bore and stroke. The smaller strangling tube makes an increased
suction at the spray nozzle; the air will have to be readjusted to meet
it and you can use more auxiliary air, which is necessary. The effect
on the motor without a smaller strangling tube is a perceptible
sluggishness and failure to speed up to its normal crank-shaft
revolutions, as well as failure to give power. It means that about
one-third of the regular speed is cut out. The reduced atmospheric
pressure reduces the power of the explosion, in that there is not the
same quantity of oxygen in the combustion chamber as at sea level; to
increase the amount taken in, you must also increase the gasoline speed,
which is done by an increased suction through the smaller strangling
aperture. Some forms of carburetors are affected more than others by
changes of altitude, which explains why the Zenith is so widely employed
for airplane engine use. The compensating nozzle construction is not
influenced as much by changes of altitude as the simpler nozzle types
are.

CHAPTER VI

Early Ignition Systems--Electrical Ignition Best--Fundamentals
of Magnetism Outlined--Forms of Magneto--Zones of Magnetic
Influence--How Magnets are Made--Electricity and Magnetism
Related--Basic Principles of Magneto Action--Essential Parts of
Magneto and Functions--Transformer Coil Systems--True High
Tension Type--The Berling Magneto--Timing and Care--The Dixie
Magneto--Spark Plug Design and Application--Two-Spark Ignition--
Special Airplane Plug.

EARLY IGNITION SYSTEMS

One of the most important auxiliary groups of the gasoline engine
comprising the airplane power plant and one absolutely necessary to
insure engine action is the ignition system or the method employed of
kindling the compressed gas in the cylinder to produce an explosion and
useful power. The ignition system has been fully as well developed as
other parts of the engine, and at the present time practically all
ignition systems follow principles which have become standard through
wide acceptance.

During the early stages of development of the gasoline engine various
methods of exploding the charge of combustible gas in the cylinder were
employed. On some of the earliest engines a flame burned close to the
cylinder head, and at the proper time for ignition a slide or valve
moved to provide an opening which permitted the flame to ignite the gas
back of the piston. This system was practical only on the primitive form
of gas engines in which the charge was not compressed before ignition.
Later, when it was found desirable to compress the gas a certain degree
before exploding it, an incandescent platinum tube in the combustion
chamber, which was kept in a heated condition by a flame burning in it,
exploded the gas. The naked flame was not suitable in this application
because when the slide was opened to provide communication between the
flame and the gas the compressed charge escaped from the cylinder with
enough pressure to blow out the flame at times and thus cause irregular
ignition. When the flame was housed in a platinum tube it was protected
from the direct action of the gas, and as long as the tube was
maintained at the proper point of incandescence regular ignition was
obtained.

Some engineers utilized the property of gases firing themselves if
compressed to a sufficient degree, while others depended upon the heat
stored in the cylinder-head to fire the highly compressed gas. None of
these methods were practical in their application to motor car engines
because they did not permit flexible engine action which is so
desirable. At the present time, electrical ignition systems in which the
compressed gas is exploded by the heating value of the minute electric
arc or spark in the cylinder are standard, and the general practice
seems to be toward the use of mechanical producers of electricity rather
than chemical batteries.

ELECTRICAL IGNITION BEST

Two general forms of electrical ignition systems may be used, the most
popular being that in which a current of electricity under high tension
is made to leap a gap or air space between the points of the sparking
plug screwed into the cylinder. The other form, which has been almost
entirely abandoned in automobile and which was never used with airplane
engine practice, but which is still used to some extent on marine
engines, is called the low-tension system because current of low voltage
is used and the spark is produced by moving electrodes in the combustion
chamber.

The essential elements of any electrical ignition system, either high or
low tension, are: First, a simple and practical method of current
production; second, suitable timing apparatus to cause the spark to
occur at the right point in the cycle of engine action; third, suitable
wiring and other apparatus to convey the current produced by the
generator to the sparking member in the cylinder.

The various appliances necessary to secure prompt ignition of the
compressed gases should be described in some detail because of the
importance of the ignition system. It is patent that the scope of a work
of this character does not permit one to go fully into the theory and
principles of operation of all appliances which may be used in
connection with gasoline motor ignition, but at the same time it is
important that the elementary principles be considered to some extent in
order that the reader should have a proper understanding of the very
essential ignition apparatus. The first point considered will be the
common methods of generating the electricity, then the appliances to
utilize it and produce the required spark in the cylinder. Inasmuch as
magneto ignition is universally used in connection with airplane engine
ignition it will not be necessary to consider battery ignition systems.

FUNDAMENTALS OF MAGNETISM OUTLINED

To properly understand the phenomena and forces involved in the
generation of electrical energy by mechanical means it is necessary to
become familiar with some of the elementary principles of magnetism and
its relation to electricity. The following matter can be read with
profit by those who are not familiar with the subject. Most persons know
that magnetism exists in certain substances, but many are not able to
grasp the terms used in describing the operation of various electrical
devices because of not possessing a knowledge of the basic facts upon
which the action of such apparatus is based.

Magnetism is a property possessed by certain substances and is
manifested by the ability to attract and repel other materials
susceptible to its effects. When this phenomenon is manifested by a
conductor or wire through which a current of electricity is flowing it
is termed "electro-magnetism." Magnetism and electricity are closely
related, each being capable of producing the other. Practically all of
the phenomena manifested by materials which possess magnetic qualities
naturally can be easily reproduced by passing a current of electricity
through a body which, when not under electrical influence, is not a
magnetic substance. Only certain substances show magnetic properties,
these being iron, nickel, cobalt and their alloys.

The earliest known substance possessing magnetic properties was a stone
first found in Asia Minor. It was called the lodestone or leading stone,
because of its tendency, if arranged so it could be moved freely, of
pointing one particular portion toward the north. The compass of the
ancient Chinese mariners was a piece of this material, now known to be
iron ore, suspended by a light thread or floated on a cork in some
liquid so one end would point toward the north magnetic pole of the
earth. The reason that this stone was magnetic was hard to define for a
time, until it was learned that the earth was one huge magnet and that
the iron ore, being particularly susceptible, absorbed and retained some
of this magnetism.

Most of us are familiar with some of the properties of the magnet
because of the extensive sale and use of small horseshoe magnets as
toys. As they only cost a few pennies every one has owned one at some
time or other and has experimented with various materials to see if they
would be attracted. Small pieces of iron or steel were quickly attracted
to the magnet and adhered to the pole pieces when brought within the
zone of magnetic influence. It was soon learned that brass, copper, tin
or zinc were not affected by the magnet. A simple experiment that serves
to illustrate magnetic attraction of several substances is shown at A,
Fig. 57. In this, several balls are hung from a standard or support, one
of these being of iron, another of steel. When a magnet is brought near
either of these they will be attracted toward it, while the others will
remain indifferent to the magnetic force. Experimenters soon learned
that of the common metals only iron or steel were magnetic.

[Illustration: Fig. 57.--Some Simple Experiments to Demonstrate Various
Magnetic Phenomena and Clearly Outline Effects of Magnetism and Various
Forms of Magnets.]

If the ordinary bar or horseshoe magnet be carefully examined, one end
will be found to be marked N. This indicates the north pole, while the
other end is not usually marked and is the south pole. If the north pole
of one magnet is brought near the south pole of another, a strong
attraction will exist between them, this depending upon the size of the
magnets used and the air gap separating the poles. If the south pole of
one magnet is brought close to the end of the same polarity of the other
there will be a pronounced repulsion of like force. These facts are
easily proved by the simple experiment outlined at B, Fig. 57. A magnet
will only attract or influence a substance having similar qualities. The
like poles of magnets will repel each other because of the obvious
impossibility of uniting two influences or forces of practically equal
strength but flowing in opposite directions. The unlike poles of magnets
attract each other because the force is flowing in the same direction.
The flow of magnetism is through the magnet from south to north and the
circuit is completed by the flow of magnetic influence through the air
gap or metal armature bridging it from the north to the south pole.

FORMS OF MAGNETS AND ZONE OF MAGNETIC INFLUENCE DEFINED

Magnets are commonly made in two forms, either in the shape of a bar or
horseshoe. These two forms are made in two types, simple or compound.
The latter are composed of a number of magnets of the same form united
so the ends of like polarity are laced together, and such a construction
will be more efficient and have more strength than a simple magnet of
the same weight. The two common forms of simple and compound magnets are
shown at C, Fig. 57. The zone in which a magnetic influence occurs is
called the magnetic field, and this force can be graphically shown by
means of imaginary lines, which are termed "lines of force." As will be
seen from the diagram at D, Fig. 57, the lines show the direction of
action of the magnetic force and also show its strength, as they are
closer together and more numerous when the intensity of the magnetic
field is at its maximum. A simple method of demonstrating the presence
of the force is to lay a piece of thin paper over the pole pieces of
either a bar or horseshoe magnet and sprinkle fine iron filings on it.
The particles of metal arrange themselves in very much the manner shown
in the illustrations and prove that the magnetic field actually exists.

The form of magnet used will materially affect the size and area of the
magnetic field. It will be noted that the field will be concentrated to
a greater extent with the horseshoe form because of the proximity of the
poles. It should be understood that these lines have no actual
existence, but are imaginary and assumed to exist only to show the way
the magnetic field is distributed. The magnetic influence is always
greater at the poles than at the center, and that is why a horseshoe or
U-form magnet is used in practically all magnetos or dynamos. This
greater attraction at the poles can be clearly demonstrated by
sprinkling iron filings on bar and U magnets, as outlined at E, Fig. 57.
A large mass gathers at the pole pieces, gradually tapering down toward
the point where the attraction is least.

From the diagrams it will be seen that the flow of magnetism is from one
pole to the other by means of curved paths between them. This circuit is
completed by the magnetism flowing from one pole to the other through
the magnet, and as this flow is continued as long as the body remains
magnetic it constitutes a magnetic circuit. If this flow were
temporarily interrupted by means of a conductor of electricity moving
through the field there would be a current of electricity induced in the
conductor every time it cut the lines of force. There are three kinds of
magnetic circuits. A non-magnetic circuit is one in which the magnetic
influence completes its circuit through some substance not susceptible
to the force. A closed magnetic circuit is one in which the influence
completes its circuit through some magnetic material which bridges the
gap between the poles. A compound circuit is that in which the magnetic
influence passes through magnetic substances and non-magnetic substances
in order to complete its circuit.

HOW IRON AND STEEL BARS ARE MADE MAGNETIC

Magnetism may be produced in two ways, by contact or induction. If a
piece of steel is rubbed on a magnet it will be found a magnet when
removed, having a north and south pole and all of the properties found
in the energizing magnet. This is magnetizing by contact. A piece of
steel will retain the magnetism imparted to it for a considerable length
of time, and the influence that remains is known as residual magnetism.
This property may be increased by alloying the steel with tungsten and
hardening it before it is magnetized. Any material that will retain its
magnetic influence after removal from the source of magnetism is known
as a permanent magnet. If a piece of iron or steel is brought into the
magnetic field of a powerful magnet it becomes a magnet without actual
contact with the energizer. This is magnetizing by magnetic induction.
If a powerful electric current flows through an insulated conductor
wound around a piece of iron or steel it will make a magnet of it. This
is magnetizing by electro-magnetic induction. A magnet made in this
manner is termed an electro-magnet and usually the metal is of such a
nature that it will not retain its magnetism when the current ceases to
flow around it. Steel is used in all cases where permanent magnets are
required, while soft iron is employed in all cases where an intermittent
magnetic action is desired. Magneto field magnets are always made of
tungsten steel alloy, so treated that it will retain its magnetism for
lengthy periods.

ELECTRICITY AND MAGNETISM CLOSELY RELATED

There are many points in which magnetism and electricity are alike. For
instance, air is a medium that offers considerable resistance to the
passage of both magnetic influence and electric energy, although it
offers more resistance to the passage of the latter. Minerals like iron
or steel are very easily influenced by magnetism and easily penetrated
by it. When one of these is present in the magnetic circuit the
magnetism will flow through the metal. Any metal is a good conductor for
the passage of the electric current, but few metals are good conductors
of magnetic energy. A body of the proper metal will become a magnet due
to induction if placed in the magnetic field, having a south pole where
the lines of force enter it and a north pole where they pass out.

We have seen that a magnet is constantly surrounded by a magnetic field
and that an electrical conductor when carrying a current is also
surrounded by a field of magnetic influence. Now if the conductor
carrying a current of electricity will induce magnetism in a bar of iron
or steel, by a reversal of this process, a magnetized iron or steel bar
will produce a current of electricity in a conductor. It is upon this
principle that the modern dynamo or magneto is constructed. If an
electro-motive force is induced in a conductor by moving it across a
field of magnetic influence, or by passing a magnetic field near a
conductor, electricity is said to be generated by magneto-electric
induction. All mechanical generators of the electric current using
permanent steel magnets to produce a field of magnetic influence are of
this type.

BASIC PRINCIPLES OF MAGNETO OUTLINED

The accompanying diagram, Fig. 58, will show these principles very
clearly. As stated on an earlier page, if the lines of force in the
magnetic field are cut by a suitable conductor an electrical impulse
will be produced in that conductor. In this simple machine the lines of
force exist between the poles of a horseshoe magnet. The conductor,
which in this case is a loop of copper wire, is mounted upon a spindle
in order that it may be rotated in the magnetic field to cut the lines
of magnetic influence present between the pole pieces. Both of the ends
of this loop are connected, one with the insulated drum shown upon the
shaft, the other to the shaft. Two metal brushes are employed to collect
the current and cause it to flow through the external circuit. It can
be seen that when the shaft is turned in the direction of the arrow the
loop will cut through the lines of magnetic influence and a current will
be generated therein.

[Illustration: Fig. 58.--Elementary Form of Magneto Showing Principal
Parts Simplified to Make Method of Current Generation Clear.]

The pressure of the current and the amount produced vary in accordance
to the rapidity with which the lines of magnetic influence are cut. The
armature of a practical magneto, therefore, differs materially from that
shown in the diagram. A large number of loops of wire would be mounted
upon this shaft in order that the lines of magnetic influence would be
cut a greater number of times in a given period and a core of iron used
as a backing for the wire. This would give a more rapid alternating
current and a higher electro-motive force than would be the case with a
smaller number of loops of wire.

[Illustration: Fig. 59.--Showing How Strength of Magnetic Influence and
of the Currents Induced in the Windings of Armature Vary with the
Rapidity of Changes of Flow.]

The illustrations at Fig. 59 show a conventional double winding
armature and field magnetic of a practical magneto in part section and
will serve to more fully emphasize the points previously made. If the
armature or spindle were removed from between the pole pieces there
would exist a field of magnetic influence as shown at Fig. 57, but the
introduction of this component provides a conductor (the iron core) for
the magnetic energy, regardless of its position, though the facility
with which the influence will be transmitted depends entirely upon the
position of the core. As shown at A, the magnetic flow is through the
main body in a straight line, while at B, which position the armature
has attained after one-eighth revolution, or 45 degrees travel in the
direction of the arrow, the magnetism must pass through in the manner
indicated. At C, which position is attained every half revolution, the
magnetic energy abandons the longer path through the body of the core
for the shorter passage offered by the side pieces, and the field thrown
out by the cross bar disappears. On further rotation of the armature, as
at D, the body of the core again becomes energized as the magnetic
influence resumes its flow through it. These changes in the strength of
the magnetic field when distorted by the armature core, as well as the
intensity of the energy existing in the field, affect the windings, and
the electrical energy induced therein corresponds in strength to the
rapidity with which these changes in magnetic flow occur. The most
pronounced changes in the strength of the field will occur as the
armature passes from position B to D, because the magnetic field
existing around the core will be destroyed and again re-established.

During the most of the armature rotation the changes in strength will be
slight and the currents induced in the wire correspondingly small; but
at the instant the core becomes remagnetized, as the armature leaves
position C, the current produced will be at its maximum, and it is
necessary to so time the rotation of the armature that at this instant
one of the cylinders is in condition to be fired. It is imperative that
the armature be driven in such relation to the crank-shaft that each
production of maximum current coincides with the ignition point, this
condition existing twice during each revolution of the armature, or at
every 180 degrees travel. Each position shown corresponds to 45 degrees
travel of the armature, or one-eighth of a turn, and it takes just
three-eighths revolution to change the position from A to that shown at
D.

ESSENTIAL PARTS OF A MAGNETO AND THEIR FUNCTIONS

The magnets which produce the influence that in turn induces the
electrical energy in the winding or loops of wire on the armature, and
which may have any even number of opposed poles, are called field
magnets. The loops of wire which are mounted upon a suitable drum and
rotate in the field of magnetic influence in order to cut the lines of
force is called an armature winding, while the core is the metal
portion. The entire assembly is called the armature. The exposed ends of
the magnets are called pole pieces and the arrangement used to collect
the current is either a commutator or a collector. The stationary pieces
which bear against the collector or commutator and act as terminals for
the outside circuit are called brushes. These brushes are often of
copper, or some of its alloys, because copper has a greater electrical
conductivity than any other metal.

These brushes are nearly always of carbon, which is sometimes
electroplated with copper to increase its electrical conductivity,
though cylinders of copper wire gauze impregnated with graphite are
utilized at times. Carbon is used because it is not so liable to cut the
metal of the commutator as might be the case if the contact was of the
metal to metal type. The reason for this is that carbon has the peculiar
property in that it materially assists in the lubrication of the
commutator, and being of soft, unctuous composition, will wear and
conform to any irregularities on the surface of the metal collector
rings.

The magneto in common use consists of a number of horseshoe magnets
which are compound in form and attached to suitable cast-iron pole
pieces used to collect and concentrate the magnetic influence of the
various magnets. Between these pole pieces an armature rotates. This is
usually shaped like a shuttle, around which are wound coils of insulated
wire. These are composed of a large number of turns and the current
produced depends in great measure upon the size of the wire and the
number of turns per coil. An armature winding of large wire will deliver
a current of great amperage, but of small voltage. An armature wound
with very fine wire will deliver a current of high voltage but of low
amperage. In the ordinary form of magneto, such as used for ignition,
the current is alternating in character and the break in the circuit
should be timed to occur when the armature is at the point of its
greatest potential or pressure. Where such a generator is designed for
direct current production the ends of the winding are attached to the
segments of a commutator, but where the instrument is designed to
deliver an alternating current one end of the winding is fastened to an
insulator ring on one end of the armature shaft and the other end is
grounded on the frame of the machine.

The quantity of the current depends upon the strength of the magnetic
field and the number of lines of magnetic influence acting through the
armature. The electro-motive force varies as to the length of the
armature winding and the number of revolutions at which the armature is
rotated.

THE TRANSFORMER SYSTEM USES LOW VOLTAGE MAGNETO

The magneto in the various systems which employ a transformer coil is
very similar to a low-tension generator in general construction, and the
current delivered at the terminals seldom exceeds 100 volts. As it
requires many times that potential or pressure to leap the gap which
exists between the points of the conventional spark plug, a separate
coil is placed in circuit to intensify the current to one of greater
capacity. The essential parts of such a system and their relation to
each other are shown in diagrammatic form at Fig. 60 and as a complete
system at Fig. 61. As is true of other systems the magnetic influence is
produced by permanent steel magnets clamped to the cast-iron pole pieces
between which the armature rotates. At the point of greatest potential
in the armature winding the current is broken by the contact breaker,
which is actuated by a cam, and a current of higher value is induced in
the secondary winding of the transformer coil when the low voltage
current is passed through the primary winding.

[Illustration: Fig. 60.--Diagrams Explaining Action of Low Tension
Transformer Coil and True High Tension Magneto Ignition Systems.]

[Illustration: Fig. 60A.--Side Sectional View of Bosch High-Tension
Magneto Shows Disposition of Parts. End Elevation Depicts Arrangement of
Interruptor and Distributor Mechanism.]

It will be noted that the points of the contact breaker are together
except for the brief instant when separated by the action of the point
of the cam upon the lever. It is obvious that the armature winding is
short-circuited upon itself except when the contact points are
separated. While the armature winding is thus short-circuited there will
be practically no generation of current. When the points are separated
there is a sudden flow of current through the primary winding of the
transformer coil, inducing a secondary current in the other winding,
which can be varied in strength by certain considerations in the
preliminary design of the apparatus. This current of higher potential or
voltage is conducted directly to the plug if the device is fitted to a
single-cylinder engine, or to the distributor arm if fitted to a
multiple-cylinder motor. The distributor consists of an insulator in
which is placed a number of segments, one for each cylinder to be fired,
and so spaced that the number of degrees between them correspond to the
ignition points of the motor. A two-cylinder motor would have two
segments, a three-cylinder, three segments, and so on within the
capacity of the instrument. In the illustration a four-cylinder
distributor is fitted, and the distributing arm is in contact with the
segment corresponding to the cylinder about to be fired.

[Illustration: Fig. 61.--Berling Two-Spark Dual Ignition System.]

TRUE HIGH-TENSION MAGNETOS ARE SELF-CONTAINED

[Illustration: Fig. 62.--Berling Double-Spark Independent System.]

The true high-tension magneto differs from the preceding inasmuch as the
current of high voltage is produced in the armature winding direct,
without the use of the separate coil. Instead of but one coil, the
armature carries two, one of comparatively coarse wire, the other of
many turns of finer wire. The arrangement of these windings can be
readily ascertained by reference to the diagram B, Fig. 60, which shows
the principle of operation very clearly. The simplicity of the ignition
system is evident by inspection of Fig. 62. One end of the primary
winding (coarse wire) is coupled or grounded to the armature core, and
the other passes to the insulated part of the interrupter. While in some
forms the interrupter or contact breaker mechanism does not revolve, the
desired motion being imparted to the contact lever to separate the
points of a revolving cam, in this the cam or tripping mechanism is
stationary and the contact breaker revolves. This arrangement makes it
possible to conduct the current from the revolving primary coil to the
interrupter by a direct connection, eliminating the use of brushes,
which would otherwise be necessary. In other forms of this appliance
where the winding is stationary, the interrupter may be operated by a
revolving cam, though, if desired, the used of a brush at this point
will permit this construction with a revolving winding.

During the revolution of the armature the grounded lever makes and
breaks contact with the insulated point, short-circuiting the primary
winding upon itself until the armature reaches the proper position of
maximum intensity of current production, at which time the circuit is
broken, as in the former instance. One end of the secondary winding
(fine wire) is grounded on the live end of the primary, the other end
being attached to the revolving arm of the distributor mechanism. So
long as a closed circuit is maintained feeble currents will pass through
the primary winding, and so long as the contact points are together this
condition will exist. When the current reaches its maximum value,
because of the armature being in the best position, the cam operates the
interrupter and the points are separated, breaking the short circuit
which has existed in the primary winding.

The secondary circuit has been open while the distributor arm has moved
from one contact to another and there has been no flow of energy through
this winding. While the electrical pressure will rise in this, even if
the distributor arm contacted with one of the segments, there would be
no spark at the plug until the contact points separated, because the
current in the secondary winding would not be of sufficient strength.
When the interrupter operates, however, the maximum primary current will
be diverted from its short circuit and can flow to the ground only
through the secondary winding and spark-plug circuit. The high pressure
now existing in the secondary winding will be greatly increased by the
sudden flow of primary current, and energy of high enough potential to
successfully bridge the gap at the plug is thereby produced in the
winding.

THE BERLING MAGNETO

[Illustration: Fig. 63.--Type DD Berling High Tension Magneto.]

The Berling magneto is a true high tension type delivering two impulses
per revolution, but it is made in a variety of forms, both single and
double spark. Its principle of action does not differ in essentials from
the high tension type previously described. This magneto is used on
Curtiss aviation engines and will deliver sparks in a positive manner
sufficient to insure ignition of engines up to 200 horse-power and at
rotative speeds of the magneto armature up to 4,000 r. p. m. which is
sufficient to take care of an eight-cylinder V engine running up to
2,000 r. p. m. The magneto is driven at crank-shaft speed on
four-cylinder engines, at 1-1/2 times crank-shaft speed on six-cylinder
engines and at twice crank-shaft speed on eight-cylinder V types. The
types "D" and "DD" BERLING Magnetos are interchangeable with
corresponding magnetos of other standard makes. The dimensions of the
four-, six- and eight-cylinder types "D" and "DD" are all the same.

The ideal method of driving the magneto is by means of flexible direct
connecting coupling to a shaft intended for the purpose of driving the
magneto. As the magneto must be driven at a high speed, a coupling of
some flexibility is preferable. The employment of such a coupling will
facilitate the mounting of the magneto, because a small inaccuracy in
the lining up of the magneto with the driving shaft will be taken care
of by the flexible coupling, whereas with a perfectly rigid coupling the
line-up of the magneto must be absolutely accurate. Another advantage of
the flexible coupling is that the vibration of the motor will not be as
fully transmitted to the armature shaft on the magneto as in case a
rigid coupling is used. This means prolonged life for the magneto.

The next best method of driving the magneto is by means of a gear keyed
to the armature shaft. When this method of driving is employed, great
care must be exercised in providing sufficient clearance between the
gear on the magneto and the driving gear. If there should be a tight
spot between these two gears it will react disadvantageously on the
magneto. The third available method is to drive the magneto by means of
a chain. This is the least desirable of the three methods and should be
resorted to only in case of absolute necessity. It is difficult to
provide sufficient clearance when using a chain without rendering the
timing less accurate and positive.

[Illustration: Fig. 64.--Wiring Diagrams of Berling Magneto Ignition
Systems.]

Fig. 64, A shows diagrammatically the circuit of the "D" type two-spark
independent magneto and the switch used with it. In position OFF the
primary winding of the magneto is short-circuited and in this position
the switch serves as an ordinary cut-out or grounding switch. In
position "1" the switch connects the magneto in such a way that it
operates as an ordinary single-spark magneto. In this position one end
of the secondary winding is grounded to the body of the motor. This is
the starting position. In this position of the switch the entire voltage
generated in the magneto is concentrated at one spark-plug instead of
being divided in half. With the motor turning over very slowly, as is
the case in starting, the full voltage generated by the magneto will
not in all cases be sufficient to bridge simultaneously two spark gaps,
but is amply sufficient to bridge one. Also, this position of the switch
tends to retard the ignition and should be used in starting to prevent
back-firing. With the switch in position "2" the magneto applies
ignition to both plugs in each cylinder simultaneously. This is the
normal running position.

Fig. 64, B shows diagrammatically the circuit of the type "DD" BERLING
high-tension two-spark dual magneto. This type is recommended for
certain types of heavy-duty airplane motors, which it is impossible to
turn over fast enough to give the magneto sufficient speed to generate
even a single spark of volume great enough to ignite the gas in the
cylinder. The dual feature consists of the addition to the magneto of a
battery interrupter. The equipment consists of the magneto, coil and
special high-tension switch. The coil is intended to operate on six
volts. Either a storage battery or dry cells may be used.

With the switch in the OFF position, the magneto is grounded, and the
battery circuit is open. With the switch in the second or battery
position marked "BAT," one end of the secondary winding of the magneto
is grounded, and the magneto operates as a single-spark magneto
delivering high-tension current to the inside distributor, and the
battery circuit being closed the high-tension current from the coil is
delivered to the outside distributor. In this position the battery
current is supplied to one set of spark plugs, no matter how slowly the
motor is turned over, but as soon as the motor starts, the magneto
supplies current as a single-spark magneto to the other set of the
spark-plugs. After the engine is running, the switch should be thrown to
the position marked "MAG." The battery and coil are then disconnected,
and the magneto furnishes ignition to both plugs in each cylinder. This
is the normal running position. Either a non-vibrating coil type "N-1"
is furnished or a combined vibrating and non-vibrating coil type
"VN-1."

SETTING BERLING MAGNETO

The magneto may be set according to one of two different methods, the
selection of which is, to some extent, governed by the characteristics
of the engine, but largely due to the personal preference on the part of
the user. In the first method described below, the most advantageous
position of the piston for fully advanced ignition is determined in
relation to the extreme advanced position of the magneto. In this case,
the fully retarded ignition will not be a matter of selection, but the
timing range of the magneto is wide enough to bring the fully retarded
ignition after top-center position of the piston. The second method for
the setting of the magneto fixes the fully retarded position of the
magneto in relation to that position of the piston where fully retarded
ignition is desired. In this case, the extreme advance position of the
magneto will not always correspond with the best position of the piston
for fully advanced ignition, and the amount of advance the magneto
should have to meet ideal requirements in this respect must be
determined by experiment.

_First Method:_

1. Designate one cylinder as cylinder No. 1.

2. Turn the crank-shaft until the piston in cylinder No. 1 is in the
position where the fully advanced spark is desired to occur.

3. Remove the cover from the distributor block and turn the armature
shaft in the direction of rotation of the magneto until the distributor
finger-brush comes into such a position that this brush makes contact
with the segment which is connected to the cable terminal marked "1."
This is either one of the two bottom segments, depending upon the
direction of rotation.

4. Place the cam housing in extreme advance, i.e., turn the cam housing
until it stops, in the direction opposite to the direction of rotation
of the armature. With the cam housing in this position, open the cover.

5. With the armature in the approximate position as described in "3,"
turn the armature slightly in either direction to such a point that the
platinum points of the magneto interrupter will just begin to open at
the end of the cam, adjacent to the fibre lever on the interrupter.

6. With this exact position of the armature, fix the magneto to the
driving member of the engine.

_Second Method:_

1. Designate one cylinder as cylinder No. 1.

2. Turn the crank-shaft until the piston in cylinder No. 1 is in the
position at which the fully retarded spark is desired to occur.

3. Same as No. 3 under First Method.

4. Place the cam housing in extreme retard, i.e., turn the cam housing
until it stops, in the same direction as the direction of rotation of
the armature. With the cam housing in this position, open the cover.

5. Same as No. 5 under First Method.

6. Same as No. 6 under First Method.

WIRING THE MAGNETO

The wiring of the magneto is clearly shown by wiring diagram.

First determine the sequence of firing for the cylinders and then
connect the cables to the spark plug in the cylinders in proper
sequence, beginning with cylinder No. 1 marked on the distributor block.

The switch used with the independent type must be mounted in such a
manner that there will be a metallic connection between the frame of the
magneto and the metal portion of the switch.

It is advisable to use a separate battery, either storage or dry cells,
as a source of current for the dual equipment. Connecting to the same
battery that is used with the generator and other electrical equipment
may cause trouble, as a "ground" in this battery causes the coil to
overheat.

CARE AND MAINTENANCE

_Lubrication:_

Use only the very best of oil for the oil cups.

Put five drops of oil in the oil cup at the driving end of the magneto
for every fifty hours of actual running.

Put five drops of oil in the oil cup at the interrupter end of the
magneto, located at one side of the cam housing, for every hundred hours
of actual running.

Lubricate the embossed cams in the cam housing with a thin film of
vaseline every fifty hours of actual running. Wipe off all superfluous
vaseline. Never use oil in the interrupter. Do not lubricate any other
part of the interrupter.

_Adjusting the Interrupter:_

With the fibre lever in the center of one of the embossed cams, as at
Fig. 65, the opening between the platinum contacts should be not less
than .016" and not more than .020". The gauge riveted to the adjusting
wrench should barely be able to pass between the contacts when fully
open. The platinum contacts must be smoothed off with a very fine file.
When in closed position, the platinum contacts should make contact with
each other over their entire surfaces.

When inspecting the interrupter, make sure that the ground brush in the
back of the interrupter base is making good contact with the surface on
which it rubs.

_Cleaning the Distributor:_

The distributor block cover should be removed for inspection every
twenty-five hours of actual running and the carbon deposit from the
distributor finger-brush wiped off the distributor block by rubbing with
a rag or piece of waste dipped in gasoline or kerosene. The
high-tension terminal brush on the side of the magneto should also be
carefully inspected for proper tension.

LOCATING TROUBLE

Trouble in the ignition system is indicated by the motor "missing,"
stopping entirely, or by inability to start.

It is safe to assume that the trouble is not in the magneto, and the
carburetor, gasoline supply and spark-plugs should first be
investigated.

[Illustration: Fig. 65.--The Berling Magneto Breaker Box Showing Contact
Points Separated and Interruptor Lever on Cam.]

If the magneto is suspected, the first thing to do is to determine if it
will deliver a spark. To determine this, disconnect one of the
high-tension leads from the spark-plug in one of the cylinders and place
it so that there is approximately 1/16" between the terminal and the
cylinder frame.

Open the pet cocks on the other cylinders to prevent the engine from
firing and turn over the engine until the piston is approaching the end
of the compression stroke in the cylinder from which the cable has been
removed. Set the magneto in the advance position and rapidly rock the
engine over the top-center position, observing closely if a spark occurs
between the end of the high-tension cable and the frame.

If the magneto is of the dual type, the trouble may be either in the
magneto or in the battery or coil system, therefore disconnect the
battery and place the switch in the position marked "MAG." The magneto
will then operate as an independent magneto and should spark in the
proper manner. After this the battery system should be investigated. To
test the operation of the battery and coil, examine all connections,
making sure that they are clean and tight, and then with the switch, in
the "BAT," rock the piston slowly back and forth. If a type "VN-1" coil
is used, a shower of sparks should jump between the high-tension cable
terminal and the cylinder frame when the piston is in the correct
position for firing. If no spark occurs, remove the cover from the coil
and see that the vibrating tongue is free. If a type "N-1" coil is used,
a single spark will occur. The battery should furnish six volts when
connected to the coil, and this should also be verified.

If the coil still refuses to give a spark and all connections are
correct, the coil should be replaced and the defective coil returned to
the manufacturer.

If both magneto and coil give a spark when tested as just described, the
spark-plugs should be investigated. To do this, disconnect the cables
and remove the spark-plugs. Then reconnect the cables to the plugs and
place them so that the frame portions of the plugs are in metallic
connection with the frame of the motor. Then turn over the motor, thus
revolving the magneto armature, and see if a spark is produced at the
spark gaps of the plugs.

The most common defects in spark-plugs are breaking down of the
insulation, fouling due to carbon, or too large or small a spark gap. To
clean the plugs a stiff brush and gasoline should be used. The spark
gap should be about 1/32" and never less than 1/64". Too small a gap may
have been caused by beads of metal forming due to the heat of the spark.
Too long a gap may have been caused by the points burning off.

If the magneto and spark plugs are in good condition and the engine does
not run satisfactorily, the setting should be verified according to
instructions previously given, and, if necessary, readjusted.

[Illustration: Fig. 66.--The Dixie Model 60 for Six-Cylinder Airplane
Engine Ignition.]

Be careful to observe that both the type "VN-1" and type "N-1" coils are
so arranged that the spark occurs on the opening of the contacts of the
timer. As this is just the reverse of the usual operation, it should be
carefully noted when any change in the setting of the timer is made. The
timer on the dual type magneto is adjusted so that the battery spark
occurs about 5° later than the magneto spark. This provides an
automatic advance as soon as the switch is thrown to the magneto
position "MAG." This relative timing can be easily adjusted by removing
the interrupter and shifting the cam in the direction desired.

THE DIXIE MAGNETO

[Illustration: Fig. 67.--Installation Dimensions of Dixie Model 60
Magneto.]

The Dixie magneto, shown at Fig. 66, operates on a different principle
than the rotary armature type. It is used on the Hall-Scott and other
aviation engines. In this magneto the rotating member consists of two
pieces of magnetic material separated by a non-magnetic center piece.
This member constitutes true rotating poles for the magnet and rotates
in a field structure, composed of two laminated field pieces, riveted
between two non-magnetic rings. The bearings for the rotating poles are
mounted in steel plates, which lie against the poles of the magnets.
When the magnet poles rotate, the magnetic lines of force from each
magnet pole are carried directly to the field pieces and through the
windings, without reversal through the mass of the rotating member and
with only a single air gap. There are no losses by flux reversal in the
rotating part, such as take place in other machines, and this is said
to account for the high efficiency of the instrument.

[Illustration: Fig. 68.--The Rotating Elements of the Dixie Magneto.]

And this "Mason Principle" involved in the operation of the Dixie is
simplified by a glance at the field structure, consisting of the
non-magnetic rings, assembled to which are the field pieces between
which the rotating poles revolve (see Fig. 68). Rotating between the
limbs of the magnets, these two pieces of magnetic material form true
extensions to the poles of the magnets, and are, in consequence,
_always_ of the _same_ polarity. It will be seen there is no reversal of
the magnetism through them, and consequently no eddy current or
hysteresis losses which are present in the usual rotor or inductor
types. The simplicity features of construction stand out prominently
here, in that there are no revolving windings, a detail entirely
differing from the orthodox high-tension instrument. This simplicity
becomes instantly apparent when it is found that the circuit breaker,
instead of revolving as it does in other types, is stationary and that
the whole breaker mechanism is exposed by simply turning the cover
spring aside and removing cover. This makes inspection and adjustment
particularly simple, and the fact that no special tool is necessary for
adjustment of the platinum points--an ordinary small screw-driver is the
whole "kit of tools" needed in the work of disassembling or
assembling--is a feature of some value.

[Illustration: Fig. 69.--Suggestions for Adjusting and Dismantling Dixie
Magneto. A--Screw Driver Adjusts Contact Points. B--Distributor Block
Removed. C--Taking off Magnets. D--Showing How Easily Condenser and High
Tension Windings are Removed.]

With dust- and water-protecting casing removed, and one of the magnets
withdrawn, as in Fig. 69, the winding can be seen with its core resting
on the field pole pieces and the primary lead attached to its side. An
important feature of the high-tension winding is that the heads are of
insulating material, and there is not the tendency for the high-tension
current to jump to the side as in the ordinary armature type magneto.
The high-tension current is carried to the distributor by means of an
insulated block with a spindle, at one end of which is a spring brush
bearing directly on the winding, thus shortening the path of the
high-tension current and eliminating the use of rubber spools and
insulating parts. The moving parts of the magneto need never be
disturbed if the high-tension winding is to be removed. This winding
constitutes all of the magneto windings, no external spark coil being
necessary. The condenser is placed directly above the winding and is
easily removable by taking out two screws, instead of being placed in an
armature where it is inaccessible except to an expert, and where it
cannot be replaced except at the factory whence it emanated.

CARE OF THE DIXIE MAGNETO

The bearings of the magneto are provided with oil cups and a few drops
of light oil every 1,000 miles are sufficient. The breaker lever should
be lubricated every 1,000 miles with a drop of light oil, applied with a
tooth-pick. The proper distance between the platinum points when
separated should not exceed .020 or one-fiftieth of an inch. A gauge of
the proper size is attached to the screwdriver furnished with the
magneto. The platinum contacts should be kept clean and properly
adjusted. Should the contacts become pitted, a fine file should be used
to smooth them in order to permit them to come into perfect contact. The
distributor block should be removed occasionally and inspected for an
accumulation of carbon dust. The inside of the distributor block should
be cleaned with a cloth moistened with gasoline and then wiped dry with
a clean cloth. When replacing the block, care must be exercised in
pushing the carbon brush into the socket. Do not pull out the carbon
brushes in the distributor because you think there is not enough tension
on the small brass springs. In order to obtain the most efficient
results, the normal setting of the spark-plug points should not exceed
.025 of an inch, and it is advisable to have the gap just right before a
spark-plug is inserted.

The spark-plug electrodes may be easily set by means of the gauge
attached to the screwdriver. _The setting of the spark-plug points is an
important function which is usually overlooked, with the result that the
magneto is blamed when it is not at fault._

TIMING OF THE DIXIE MAGNETO

[Illustration: Fig. 69A.--Sectional Views Outlining Construction of
Dixie Magneto with Compound Distributor for Eight-Cylinder Engine
Ignition.]

In order to obtain the utmost efficiency from the engine, the magneto
must be correctly timed to it. This operation is usually performed when
the magneto is fitted to the engine at the factory. The correct setting
may vary according to individuality of the engine, and some engines
may require an earlier setting in order to obtain the best results.
However, should the occasion arise to retime the magneto, the procedure
is as follows: Rotate the crank-shaft of the engine until one of the
pistons, preferably that of cylinder No. 1, is 1/16 of an inch ahead of
the end of the compression stroke. With the timing lever in full retard
position, the driving shaft of the magneto should be rotated in the
direction in which it will be driven. The circuit breaker should be
closely observed and when the platinum contact points are about to
separate, the drive gear or coupling should be secured to the drive
shaft of the magneto. Care should be taken not to alter the position of
the magneto shaft when tightening the nut to secure the gear or
coupling, after which the magneto should be secured to its base. Remove
the distributor block and determine which terminal of the block is in
contact with the carbon brush of the distributor finger and connect with
plug wire leading to No. 1 cylinder to this terminal. Connect the
remaining plug wires in turn according to the proper sequence of firing
of the cylinders. (See the wiring diagram for a typical six-cylinder
engine at Fig. 70.) A terminal on the end of the cover spring of the
magneto is provided for the purpose of connecting the wire leading to a
ground switch for stopping the engine.

A special model or type of magneto is made for V engines which use a
compound distributor construction instead of the simple type on the
model illustrated and a different interior arrangement permits the
production of four sparks per revolution of the rotors. This makes it
possible to run the magneto slower than would be possible with the
two-spark form. The application of two compound distributor magnetos of
this type to a Thomas-Morse 135 horse-power motor of the eight-cylinder
V pattern is clearly shown at Fig. 71.

[Illustration: Fig. 70.--Wiring Diagram of Dixie Magneto Installation on
Hall-Scott Six-Cylinder 125 Horse-Power Aeronautic Motor.]

SPARK-PLUG DESIGN AND APPLICATION

[Illustration: Fig. 71.--How Magneto Ignition is Installed on
Thomas-Morse 135 Horse-Power Motor.]

With the high-tension system of ignition the spark is produced by a
current of high voltage jumping between two points which break the
complete circuit, which would exist otherwise in the secondary coil and
its external connections. The spark-plug is a simple device which
consists of two terminal electrodes carried in a suitable shell member,
which is screwed into the cylinder. Typical spark-plugs are shown in
section at Fig. 72 and the construction can be easily understood. The
secondary wire from the coil is attached to a terminal at the top of a
central electrode member, which is supported in a bushing of some form
of insulating material. The type shown at A employs a molded porcelain
as an insulator, while that depicted at B uses a bushing of mica. The
insulating bushing and electrode are housed in a steel body, which is
provided with a screw thread at the bottom, by which means it is screwed
into the combustion chamber.

[Illustration: Fig. 72.--Spark-Plug Types Showing Construction and
Arrangement of Parts.]

When porcelain is used as an insulating material it is kept from direct
contact with the metal portion by some form of yielding packing, usually
asbestos. This is necessary because the steel and porcelain have
different coefficients of expansion and some flexibility must be
provided at the joints to permit the materials to expand differently
when heated. The steel body of the plug which is screwed into the
cylinder is in metallic contact with it and carries sparking points
which form one of the terminals of the air gap over which the spark
occurs. The current entering at the top of the plug cannot reach the
ground, which is represented by the metal portion of the engine, until
it has traversed the full length of the central electrode and overcome
the resistance of the gap between it and the terminal point on the
shell. The porcelain bushing is firmly seated against the asbestos
packing by means of a brass screw gland which sets against a flange
formed on the porcelain, and which screws into a thread at the upper
portion of the plug body.

The mica plug shown at B is somewhat simpler in construction than that
shown at A. The mica core which keeps the central electrode separated
from the steel body is composed of several layers of pure sheet mica
wound around the steel rod longitudinally, and hundreds of stamped steel
washers which are forced over this member and compacted under high
pressure with some form of a binding material between them. Porcelain
insulators are usually molded from high-grade clay and are approximately
of the shapes desired by the designers of the plug. The central
electrode may be held in place by mechanical means such as nuts,
packings, and a shoulder on the rod, as shown at A. Another method
sometimes used is to cement the electrode in place by means of some form
of fire-clay cement. Whatever method of fastening is used, it is
imperative that the joints be absolutely tight so that no gas can escape
at the time of explosion. Porcelain is the material most widely used
because it can be glazed so that it will not absorb oil, and it is
subjected to such high temperature in baking that it is not liable to
crack when heated.

The spark-plugs may be screwed into any convenient part of the
combustion chamber, the general practice being to install them in the
caps over the inlet valves, or in the side of the combustion chamber, so
the points will be directly in the path of the entering fresh gases from
the carburetor.

Other insulating materials sometimes used are glass, steatite (which is
a form of soapstone) and lava. Mica and porcelain are the two common
materials used because they give the best results. Glass is liable to
crack, while lava or the soapstone insulating bushings absorb oil. The
spark gap of the average plug is equal to about 1/32 of an inch for coil
ignition and 1/40 of an inch when used in magneto circuits. A simple
gauge for determining the gap setting is the thickness of an ordinary
visiting card for magneto plugs, or a space equal to the thickness of a
worn dime for a coil plug. The insulating bushings are made in a number
of different ways, and while details of construction vary, spark-plugs
do not differ essentially in design. The dimensions of the standardized
plug recommended by the S. A. E. are shown at Fig. 73.

[Illustration: Fig. 73.--Standard Airplane Engine Plug Suggested by S.
A. E. Standards Committee.]

It is often desirable to have a water-tight joint between the
high-tension cable and the terminal screw on top of the insulating
bushing of the spark-plug, especially in marine applications. The plug
shown at C, Fig. 72, is provided with an insulating member or hood of
porcelain, which is secured by a clip in such a manner that it makes a
water-tight connection. Should the porcelain of a conventional form of
plug become covered with water or dirty oil, the high-tension current is
apt to run down this conducting material on the porcelain and reach the
ground without having to complete its circuit by jumping the air gap and
producing a spark. It will be evident that wherever a plug is exposed to
the elements, which is often the case in airplane service, that it
should be protected by an insulating hood which will keep the insulator
dry and prevent short circuiting of the spark. The same end can be
attained by slipping an ordinary rubber nipple over the porcelain
insulator of any conventional plug and bringing up one end over the
cable.

TWO-SPARK IGNITION

On most aviation engines, especially those having large cylinders, it is
sometimes difficult to secure complete combustion by using a
single-spark plug. If the combustion is not rapid the efficiency of the
engine will be reduced proportionately. The compressed charge in the
cylinder does not ignite all at once or instantaneously, as many assume,
but it is the strata of gas nearest the plug which is ignited first.
This in turn sets fire to consecutive layers of the charge until the
entire mass is aflame. One may compare the combustion of gas in the
gas-engine cylinder to the phenomenon which obtains when a heavy object
is thrown into a pool of still water. First a small circle is seen at
the point where the object has passed into the water, this circle in
turn inducing other and larger circles until the whole surface of the
pool has been agitated from the one central point. The method of
igniting the gas is very similar, as the spark ignites the circle of gas
immediately adjacent to the sparking point, and this circle in turn
ignites a little larger one concentric with it. The second circle of
flame sets fire to more of the gas, and finally the entire contents of
the combustion chamber are burning.

While ordinarily combustion is sufficiently rapid with a single plug so
that the proper explosion is obtained at moderate engine speeds, if the
engine is working fast and the cylinders are of large capacity more
power may be obtained by setting fire to the mixture at two different
points instead of but one. This may be accomplished by using two
sparking-plugs in the cylinder instead of one, and experiments have
shown that it is possible to gain from twenty-five to thirty per cent.
in motor power at high speed with two-spark plugs, because the
combustion of gas is accelerated by igniting the gas simultaneously in
two places. The double-plug system on airplane engines is also a
safeguard, as in event of failure of one plug in the cylinder the other
would continue to fire the gas, and the engine will continue to function
properly.

In using magneto ignition some precautions are necessary relating to
wiring and also the character of the spark-plugs employed. The conductor
should be of good quality, have ample insulation, and be well protected
from accumulations of oil, which would tend to decompose rubber
insulation. It is customary to protect the wiring by running it through
the conduits of fiber or metal tubing lined with insulating material.
Multiple strand cables should be used for both primary and secondary
wiring, and the insulation should be of rubber at least 3/16 inch thick.

The spark-plugs commonly used for battery and coil ignition cannot
always be employed when a magneto is fitted. The current produced by the
mechanical generator has a greater amperage and more heat value than
that obtained from transformer coils excited by battery current. The
greater heat may burn or fuse the slender points used on some battery
plugs and heavier electrodes are needed to resist the heating effect of
the more intense arc. While the current has greater amperage it is not
of as high potential or voltage as that commonly produced by the
secondary winding of an induction coil, and it cannot overcome as much
of a gap. Manufacturers of magneto plugs usually set the spark points
about 1/64 of an inch apart. The most efficient magneto plug has a
plurality of points so that when the distance between one set becomes
too great the spark will take place between one of the other pairs of
electrodes which are not separated by so great an air space.

[Illustration: Fig. 74.--Special Mica Plug for Aviation Engines.]

SPECIAL PLUGS FOR AIRPLANE WORK

Airplane work calls for special construction of spark-plugs, owing to
the high compression used in the engines and the fact that they are
operated on open throttle practically all the time, thus causing a great
deal of heat to be developed. The plug shown at Fig. 74 was recently
described in "The Automobile," and has been devised especially for
airplane engines and automobile racing power plants. The core C is built
up of mica washers, and has square shoulders. As mica washers of
different sizes may be used, and accurate machining, such as is
necessary with conical clamping surfaces, is not required, the plug can
be produced economically. The square shoulders of the core afford two
gasket seats, and when the core is clamped in the shell by means of
check nut E, it is accurately centered and a tight joint is formed. This
construction also makes a shorter plug than where conical fits are used,
thus improving the heat radiation through the stem. The lower end of the
shell is provided with a baffle plate O, which tends to keep the oil
away from the mica. There are perforations L in this baffle plate to
prevent burnt gases being pocketed behind the baffle plate and
pre-igniting the new charge. This construction also brings the firing
point out into the firing chamber of the engine, and has all the other
advantages of a closed-end plug. The stem P is made of brass or copper,
on account of their superior heat conductivity, and the electrode J is
swedged into the bottom of the stem, as shown at K, in a secure manner.

The shell is finned, as shown at G, to provide greater heat radiating
surface. There is also a fin F at the top of the stem, to increase the
radiation of heat from the stem and electrode. The top of this finned
portion is slightly countersunk, and the stem is riveted into same,
thereby reducing the possibility of leakage past the threads on the
stem. This finned portion is necked at A to take a slip terminal.

In building up the core a small section of washers, I, is built up
before the mica insulating tube D is placed on. This construction gives
a better support to section I. Baffle plate O is bored out to allow the
electrode J to pass through, and the clearance between baffle plate and
electrode is made larger than the width of the gap between the firing
points, so that there is no danger of the spark jumping from the
electrode to the baffle plate.

This plug will be furnished either with or without the finned portion,
to meet individual requirements. The manufacturers lay special stress
upon the simplicity of construction and upon the method of clamping,
which is claimed to make the plug absolutely gas-tight.

CHAPTER VII

Why Lubrication Is Necessary--Friction Defined--Theory of
Lubrication--Derivation of Lubricants--Properties of Cylinder
Oils--Factors Influencing Lubrication System Selection--Gnome
Type Engines Use Castor Oil--Hall-Scott Lubrication System--Oil
Supply by Constant Level Splash System--Dry Crank-Case System
Best for Airplane Engines--Why Cooling Systems Are Necessary--
Cooling Systems Generally Applied--Cooling by Positive Pump
Circulation--Thermo-Syphon System--Direct Air-Cooling Methods--
Air-Cooled Engine Design Considerations.

WHY LUBRICATION IS NECESSARY

The importance of minimizing friction at the various bearing surfaces of
machines to secure mechanical efficiency is fully recognized by all
mechanics, and proper lubricity of all parts of the mechanism is a very
essential factor upon which the durability and successful operation of
the motor car power plant depends. All of the moving members of the
engine which are in contact with other portions, whether the motion is
continuous or intermittent, of high or low velocity, or of rectilinear
or continued rotary nature, should be provided with an adequate supply
of oil. No other assemblage of mechanism is operated under conditions
which are so much to its disadvantage as the motor car, and the tendency
is toward a simplification of oiling methods so that the supply will be
ample and automatically applied to the points needing it.

In all machinery in motion the members which are in contact have a
tendency to stick to each other, and the very minute projections which
exist on even the smoothest of surfaces would have a tendency to cling
or adhere to each other if the surfaces were not kept apart by some
elastic and unctuous substance. This will flow or spread out over the
surfaces and smooth out the inequalities existing which tend to produce
heat and retard motion of the pieces relative to each other.

A general impression which obtains is that well machined surfaces are
smooth, but while they are apparently free from roughness, and no
projections are visible to the naked eye, any smooth bearing surface,
even if very carefully ground, will have a rough appearance if examined
with a magnifying glass. An exaggerated condition to illustrate this
point is shown at Fig. 75. The amount of friction will vary in
proportion to the pressure on the surfaces in contact and will augment
as the loads increase; the rougher surfaces will have more friction than
smoother ones and soft bodies will produce more friction than hard
substances.

FRICTION DEFINED

Friction is always present in any mechanism as a resisting force that
tends to retard motion and bring all moving parts to a state of rest.
The absorption of power by friction may be gauged by the amount of heat
which exists at the bearing points. Friction of solids may be divided
into two classes: sliding friction, such as exists between the piston
and cylinder, or the bearings of a gas-engine, and rolling friction,
which is that present when the load is supported by ball or roller
bearings, or that which exists between the tires or the driving wheels
and the road. Engineers endeavor to keep friction losses as low as
possible, and much care is taken in all modern airplane engines to
provide adequate methods of lubrication, or anti-friction bearings at
all points where considerable friction exists.

THEORY OF LUBRICATION

The reason a lubricant is supplied to bearing points will be easily
understood if one considers that these elastic substances flow between
the close fitting surfaces, and by filling up the minute depressions in
the surfaces and covering the high spots act as a cushion which absorbs
the heat generated and takes the wear instead of the metallic bearing
surface. The closer the parts fit together the more fluid the lubricant
must be to pass between their surfaces, and at the same time it must
possess sufficient body so that it will not be entirely forced out by
the pressure existing between the parts.

[Illustration: Fig. 75.--Showing Use of Magnifying Glass to Demonstrate
that Apparently Smooth Metal Surfaces May Have Minute Irregularities
which Produce Friction.]

Oils should have good adhesive, as well as cohesive, qualities. The
former are necessary so that the oil film will cling well to the
surfaces of the bearings; the latter, so the oil particles will cling
together and resist the tendency to separation which exists all the time
the bearings are in operation. When used for gas-engine lubrication the
oil should be capable of withstanding considerable heat in order that it
will not be vaporized by the hot portions of the cylinder. It should
have sufficient cold test so that it will remain fluid and flow readily
at low temperature. Lubricants should be free from acid, or alkalies,
which tend to produce a chemical action with metals and result in
corrosion of the parts to which they are applied. It is imperative that
the oil be exactly the proper quality and nature for the purpose
intended and that it be applied in a positive manner. The requirements
may be briefly summarized as follows:

First--It must have sufficient body to prevent seizing of the parts to
which it is applied and between which it is depended upon to maintain an
elastic film, and yet it must not have too much viscosity, in order to
minimize the internal or fluid friction which exists between the
particles of the lubricant itself.

Second--The lubricant must not coagulate or gum; must not injure the
parts to which it is applied, either by chemical action or by producing
injurious deposits, and it should not evaporate readily.

Third--The character of the work will demand that the oil should not
vaporize when heated or thicken to such a point that it will not flow
readily when cold.

Fourth--The oil must be free from acid, alkalies, animal or vegetable
fillers, or other injurious agencies.

Fifth--It must be carefully selected for the work required and should be
a good conductor of heat.

DERIVATION OF LUBRICANTS

The first oils which were used for lubricating machinery were obtained
from animal and vegetable sources, though at the present time most
unguents are of mineral derivation. Lubricants may exist as fluids,
semifluids, or solids. The viscosity will vary from light spindle or
dynamo oils, which have but little more body than kerosene, to the
heaviest greases and tallows. The most common solid employed as a
lubricant is graphite, sometimes termed "plumbago" or "black lead." This
substance is of mineral derivation.

The disadvantage of oils of organic origin, such as those obtained from
animal fats or vegetable substances, is that they will absorb oxygen
from the atmosphere, which causes them to thicken or become rancid.
Such oils have a very poor cold test, as they solidify at comparatively
high temperatures, and their flashing point is so low that they cannot
be used at points where much heat exists. In most animal oils various
acids are present in greater or less quantities, and for this reason
they are not well adapted for lubricating metallic surfaces which may be
raised high enough in temperature to cause decomposition of the oils.

Lubricants derived from the crude petroleum are called "Oleonaphthas"
and they are a product of the process of refining petroleum through
which gasoline and kerosene are obtained. They are of lower cost than
vegetable or animal oil, and as they are of non-organic origin, they do
not become rancid or gummy by constant exposure to the air, and they
will have no corrosive action on metals because they contain no
deleterious substances in chemical composition. By the process of
fractional distillation mineral oils of all grades can be obtained. They
have a lower cold and higher flash test and there is not the liability
of spontaneous combustion that exists with animal oils.

The organic oils are derived from fatty substances, which are present in
the bodies of all animals and in some portions of plants. The general
method of extracting oil from animal bodies is by a rendering process,
which consists of applying sufficient heat to liquefy the oil and then
separating it from the tissue with which it is combined by compression.
The only oil which is used to any extent in gas-engine lubrication that
is not of mineral derivation is castor oil. This substance has been used
on high-speed racing automobile engines and on airplane power plants. It
is obtained from the seeds of the castor plant, which contain a large
percentage of oil.

Among the solid substances which may be used for lubricating purposes
may be mentioned tallow, which is obtained from the fat of animals, and
graphite and soapstone, which are of mineral derivation. Tallow is
never used at points where it will be exposed to much heat, though it
is often employed as a filler for greases used in transmission gearing
of autos. Graphite is sometimes mixed with oil and applied to cylinder
lubrication, though it is most often used in connection with greases in
the landing gear parts and for coating wires and cables of the airplane.
Graphite is not affected by heat, cold, acids, or alkalies, and has a
strong attraction for metal surfaces. It mixes readily with oils and
greases and increases their efficiency in many applications. It is
sometimes used where it would not be possible to use other lubricants
because of extremes of temperature.

The oils used for cylinder lubrication are obtained almost exclusively
from crude petroleum derived from American wells. Special care must be
taken in the selection of crude material, as every variety will not
yield oil of the proper quality to be used as a cylinder lubricant. The
crude petroleum is distilled as rapidly as possible with fire heat to
vaporize off the naphthas and the burning oils. After these vapors have
been given off superheated steam is provided to assist in distilling.
When enough of the light elements have been eliminated the residue is
drawn off, passed through a strainer to free it from grit and earthy
matters, and is afterwards cooled to separate the wax from it. This is
the dark cylinder oil and is the grade usually used for steam-engine
cylinders.

PROPERTIES OF CYLINDER OILS

The oil that is to be used in the gasoline engine must be of high
quality, and for that reason the best grades are distilled in a vacuum
that the light distillates may be separated at much lower temperatures
than ordinary conditions of distilling permit. If the degree of heat is
not high the product is not so apt to decompose and deposit carbon. If
it is desired to remove the color of the oil which is caused by free
carbon and other impurities it can be accomplished by filtering the oil
through charcoal. The greater the number of times the oil is filtered,
the lighter it will become in color. The best cylinder oils have flash
points usually in excess of 500 degrees F., and while they have a high
degree of viscosity at 100 degrees F. they become more fluid as the
temperature increases.

The lubricating oils obtained by refining crude petroleum may be divided
into three classes:

First--The natural oils of great body which are prepared for use by
allowing the crude material to settle in tanks at high temperature and
from which the impurities are removed by natural filtration. These oils
are given the necessary body and are free from the volatile substances
they contain by means of superheated steam which provides a source of
heat.

Second--Another grade of these natural oils which are filtered again at
high temperatures and under pressure through beds of animal charcoal to
improve their color.

Third--Pale, limpid oils, obtained by distillation and subsequent
chemical treatment from the residuum produced in refining petroleum to
obtain the fuel oils.

Authorities agree that any form of mixed oil in which animal and mineral
lubricants are combined should never be used in the cylinder of a gas
engine as the admixture of the lubricants does not prevent the
decomposition of the organic oil into the glycerides and fatty acids
peculiar to the fat used. In a gas-engine cylinder the flame tends to
produce more or less charring. The deposits of carbon will be much
greater with animal oils than with those derived from the petroleum base
because the constituents of a fat or tallow are not of the same volatile
character as those which comprise the hydro-carbon oils which will
evaporate or volatilize before they char in most instances.

FACTORS INFLUENCING LUBRICATION SYSTEM SELECTION

The suitability of oil for the proper and efficient lubrication of all
internal combustion engines is determined chiefly by the following
factors:

1. Type of cooling system (operating temperatures).

2. Type of lubricating system (method of applying oil to the moving
parts).

3. Rubbing speeds of contact surfaces.

Were the operating temperatures, bearing surface speeds and lubrication
systems identical, a single oil could be used in all engines with equal
satisfaction. The only change then necessary in viscosity would be that
due to climatic conditions. As engines are now designed, only three
grades of oil are necessary for the lubrication of all types with the
exception of Knight, air-cooled and some engines which run continuously
at full load. In the specification of engine lubricants the feature of
load carried by the engine should be carefully considered.

_Full Load Engines._

1. Marine.
2. Racing automobile.
3. Aviation.
4. Farm tractor.
5. Some stationary.

_Variable Load Engines._

1. Pleasure automobile.
2. Commercial vehicle.
3. Motor cycle.
4. Some stationary.

Of the forms outlined, the only one we have any immediate concern about
is the airplane power plant. The Platt & Washburn Refining Company, who
have made a careful study of the lubrication problem as applied to all
types of engines, have found a peculiar set of conditions to apply to
oiling high-speed constant-duty or "full-load" engines. Modern airplane
engines are designed to operate continuously at a fairly uniform high
rotative speed and at full load over long periods of time. As a sequence
to this heavy duty the operating temperatures are elevated. For the
sake of extreme lightness in weight of all parts, very thin alloy steel
aluminum or cast iron pistons are fitted and the temperature of the thin
piston heads at the center reaches anywhere between 600° and 1,400°
Fahr., as in automobile racing engines. Freely exposed to such intense
heat hydro-carbon oils are partially "cracked" into light and heavy
products or polymerized into solid hydro-carbons. From these facts it
follows that only heavy mineral oils of low carbon residue and of the
greatest chemical purity and stability should be used to secure good
lubrication. In all cases the oil should be sufficiently heavy to assure
the highest horse-power and fuel and oil economy compatible with perfect
lubrication, avoiding, at the same time, carbonization and ignition
failure. When aluminum pistons are used their superior heat-conducting
properties aid materially in reducing the rate of oil destruction.

The extraordinary evolutions described by airplanes in flight make it a
matter of vital necessity to operate engines inclined at all angles to
the vertical as well as in an upside-down position. To meet this
situation lubricating systems have been elaborated so as to deliver an
abundance of oil where needed and to eliminate possible flooding of
cylinders. This is done by applying a full force feed system,
distributing oil under considerable pressure to all working parts.
Discharged through the bearings, the oil drains down to the suction side
of a second pump located in the bottom of the base chamber. This pump
being of greater capacity than the first prevents the accumulation of
oil in the crank-case, and forces it to a separate oil reservoir-cooler,
whence it flows back in rapid circulation to the pump feeding the
bearings. With this arrangement positive lubrication is entirely
independent of engine position. The lubricating system of the
Thomas-Morse aviation engines, which is shown at Fig. 76, is typical of
current practice.

[Illustration: Fig. 76.--Pressure Feed Oiling System of Thomas Aviation
Engine Includes Oil Cooling Means.]

GNOME TYPE ENGINES USE CASTOR OIL

The construction and operation of rotative radial cylinder engines
introduce additional difficulties of lubrication to those already
referred to and merit especial attention. Owing to the peculiar
alimentation systems of Gnome type engines, atomized gasoline mixed with
air is drawn through the hollow stationary crank-shaft directly into the
crank-case which it fills on the way to the cylinders. Therein lies the
trouble. Hydrocarbon oils are soon dissolved by the gasoline and washed
off, leaving the bearing surfaces without adequate protection and
exposed to instant wear and destruction. So castor oil is resorted to as
an indispensable but unfortunate compromise. Of vegetable origin, it
leaves a much more bulky carbon deposit in the explosion chambers than
does mineral oil and its great affinity for oxygen causes the formation
of voluminous gummy deposit in the crank-case. Engines employing it need
to be dismounted and thoroughly scraped out at frequent intervals. It is
advisable to use only unblended chemically pure castor oil in rotative
engines, first by virtue of its insolubility in gasoline and second
because its extra heavy body can resist the high temperature of
air-cooled cylinders.

HALL-SCOTT LUBRICATION SYSTEM

[Illustration: Fig. 77.--Diagram of Oiling System, Hall-Scott Type A 125
Horse-Power Engine.]

The oiling system of the Hall-Scott type A-5 125 horse-power engine is
clearly shown at Fig. 77. It is completely described in the instruction
book issued by the company from which the following extracts are
reproduced by permission. Crank-shaft, connecting rods and all other
parts within the crank-case and cylinders are lubricated directly or
indirectly by a force-feed oiling system. The cylinder walls and wrist
pins are lubricated by oil spray thrown from the lower end of connecting
rod bearings. This system is used only upon A-5 engines. Upon A-7a and
A-5a engines a small tube supplies oil from connecting rod bearing
directly upon the wrist pin. The oil is drawn from the strainer located
at the lowest portion of the lower crank-case, forced around the main
intake manifold oil jacket. From here it is circulated to the main
distributing pipe located along the lower left hand side of upper
crank-case. The oil is then forced directly to the lower side of
crank-shaft, through holes drilled in each main bearing cup. Leakage
from these main bearings is caught in scuppers placed upon the cheeks of
the crank-shafts furnishing oil under pressure to the connecting rod
bearings. A-7a and A-5a engines have small tubes leading from these
bearings which convey the oil under pressure to the wrist pins.

A bi-pass located at the front end of the distributing oil pipe can be
regulated to lessen or raise the pressure. By screwing the valve in, the
pressure will raise and more oil will be forced to the bearings. By
unscrewing, pressure is reduced and less oil is fed. A-7a and A-5a
engines have oil relief valves located just off of the main oil pump in
the lower crank-case. This regulates the pressure at all times so that
in cold weather there will be no danger of bursting oil pipes due to
excessive pressure. If it is found the oil pressure is not maintained at
a high enough level, inspect this valve. A stronger spring will not
allow the oil to bi-pass so freely, and consequently the pressure will
be raised; a weaker spring will bi-pass more oil and reduce the oil
pressure materially. Independent of the above-mentioned system, a small,
directly driven rotary oiler feeds oil to the base of each individual
cylinder. The supply of oil is furnished by the main oil pump located in
the lower crank-case. A small sight-feed regulator is furnished to
control the supply of oil from this oiler. This instrument should be
placed higher than the auxiliary oil distributor itself to enable the
oil to drain by gravity feed to the oiler. If there is no available
place with the necessary height in the front seat of plane, connect it
directly to the intake L fitting on the oiler in an upright position. It
should be regulated with full open throttle to maintain an oil level in
the glass, approximately half way.

An oil pressure gauge is provided. This should be run to the pilot's
instrument board. The gauge registers the oil pressure upon the
bearings, also determining its circulation. Strict watch should be
maintained of this instrument by pilot, and if for any reason its hand
should drop to 0 the motor should be immediately stopped and the trouble
found before restarting engine. Care should be taken that the oil does
not work up into the gauge, as it will prevent the correct gauge
registering of oil pressure. The oil pressure will vary according to
weather conditions and viscosity of oil used. In normal weather, with
the engine properly warmed up, the pressure will register on the oil
gauge from 5 to 10 pounds when the engine is turning from 1,275 to 1,300
r. p. m. This does not apply to all aviation engines, however, as the
proper pressure advised for the Curtiss OX-2 motor is from 40 to 55
pounds at the gauge.

The oil sump plug is located at the lowest point of the lower
crank-case. This is a combination dirt, water and sediment trap. It is
easily removed by unscrewing. Oil is furnished mechanically to the
cam-shaft housing under pressure through a small tube leading from the
main distributing pipe at the propeller end of engine directly into the
end of cam-shaft housing. The opposite end of this housing is amply
relieved to allow the oil to rapidly flow down upon cam-shaft, magneto,
pinion-shaft, and crank-shaft gears, after which it returns to lower
crank-case. An outside overflow pipe is also provided to carry away the
surplus oil.

DRAINING OIL FROM CRANK-CASE

The oil strainer is placed at the lowest point of the lower crank-case.
This strainer should be removed after every five to eight hours running
of the engine and cleaned thoroughly with gasoline. It is also advisable
to squirt distillate up into the case through the opening where the
strainer has been removed. Allow this distillate to drain out thoroughly
before replacing the plug with strainer attached. Be sure gasket is in
place on plug before replacing. Pour new oil in through either of the
two breather pipes on exhaust side of motor. Be sure to replace strainer
screens if removed. If, through oversight, the engine does not receive
sufficient lubrication and begins to heat or pound, it should be stopped
immediately. After allowing engine to cool pour at least three gallons
of oil into oil sump. Fill radiator with water after engine has cooled.
Should there be apparent damage, the engine should be thoroughly
inspected immediately without further running. If no obvious damage has
been done, the engine should be given a careful examination at the
earliest opportunity to see that the running without oil has not burned
the bearings or caused other trouble.

Oils best adapted for Hall-Scott engines have the following properties:
A flash test of not less than 400° F.; viscosity of not less than 75 to
85 taken at 21° F. with Saybolt's Universal Viscosimeter.

_Zeroline heavy duty oil_, manufactured by the Standard Oil Company of
California; also,

_Gargoyle mobile B oil_, manufactured by the Vacuum Oil Company, both
fulfill the above specifications. One or the other of these oils can be
obtained all over the world.

Monogram extra heavy is also recommended.

OIL SUPPLY BY CONSTANT LEVEL SPLASH SYSTEM

The splash system of lubrication that depends on the connecting rod to
distribute the lubricant is one of the most successful and simplest
forms for simple four- and six-cylinder vertical automobile engines, but
is not as well adapted to the oiling of airplane power plants for
reasons previously stated. If too much oil is supplied the surplus will
work past the piston rings and into the combustion chamber, where it
will burn and cause carbon deposits. Too much oil will also cause an
engine to smoke and an excess of lubricating oil is usually manifested
by a bluish-white smoke issuing from the exhaust.

A good method of maintaining a constant level of oil for the successful
application of the splash system is shown at Fig. 78. The engine base
casting includes a separate chamber which serves as an oil container and
which is below the level of oil in the crank-case. The lubricant is
drawn from the sump or oil container by means of a positive oil pump
which discharges directly into the engine case. The level is maintained
by an overflow pipe which allows all excess lubricant to flow back into
the oil container at the bottom of the cylinder. Before passing into the
pump again the oil is strained or filtered by a screen of wire gauze and
all foreign matter removed. Owing to the rapid circulation of the oil it
may be used over and over again for quite a period of time. The oil is
introduced directly into the crank-case by a breather pipe and the level
is indicated by a rod carried by a float which rises when the container
is replenished and falls when the available supply diminishes. It will
be noted that with such system the only apparatus required besides the
oil tank which is cast integral with the bottom of the crank-case is a
suitable pump to maintain circulation of oil. This member is always
positively driven, either by means of shaft and universal coupling or
direct gearing. As the system is entirely automatic in action, it will
furnish a positive supply of oil at all desired points, and it cannot be
tampered with by the inexpert because no adjustments are provided or
needed.

DRY CRANK-CASE SYSTEM BEST FOR AIRPLANE ENGINES

[Illustration: Fig. 78.--Sectional View of Typical Motor Showing Parts
Needing Lubrication and Method of Applying Oil by Constant Level Splash
System. Note also Water Jacket and Spaces for Water Circulation.]

In most airplane power plants it is considered desirable to supply the
oil directly to the parts needing it by suitable leads instead of
depending solely upon the distributing action of scoops on the
connecting rod big ends. A system of this nature is shown at Fig. 77.
The oil is carried in the crank-case, as is common practice, but the
normal oil level is below the point where it will be reached by the
connecting rod. It is drawn from the crank-case by a plunger pump which
directs it to a manifold leading directly to conductors which supply the
main journals. After the oil has been used on these points it drains
back into the bottom of the crank-case. An excess is provided which is
supplied to the connecting rod ends by passages drilled into the webs of
the crank-shaft and part way into the crank-pins as shown by the dotted
lines. The oil which is present at the connecting rod crank-pins is
thrown off by centrifugal force and lubricates the cylinder walls and
other internal parts. Regulating screws are provided so that the amount
of oil supplied the different points may be regulated at will. A relief
check valve is installed to take care of excess lubricant and to allow
any oil that does not pass back into the pipe line to overflow or
bi-pass into the main container.

[Illustration: Fig. 79.--Pressure Feed Oil-Supply System of Airplane
Power Plants has Many Good Features.]

A simple system of this nature is shown graphically in a phantom view of
the crank-case at Fig. 79, in which the oil passages are made specially
prominent. The oil is taken from a reservoir at the bottom of the engine
base by the usual form of gear oil pump and is supplied to a main feed
manifold which extends the length of the crank-case. Individual
conductors lead to the five main bearings, which in turn supply the
crank-pins by passages drilled through the crank-shaft web. In this
power plant the connecting rods are hollow section bronze castings and
the passage through the center of the connecting rod serves to convey
the lubricant from the crank-pins to the wrist-pins. The cylinder walls
are oiled by the spray of lubricant thrown off the revolving crank-shaft
by centrifugal force. Oil projection by the dippers on the connecting
rod ends from constant level troughs is unequal upon the cylinder walls
of the two-cylinder blocks of an eight- or twelve-cylinder V engine.
This gives rise, on one side of the engine, to under-lubrication, and,
on the other side, to over-lubrication, as shown at Fig. 80, A. This
applies to all modifications of splash lubricating systems.

When a force-feed lubricating system is used, the oil, escaping past the
cheeks of both ends of the crank-pin bearings, is thrown off at a
tangent to the crank-pin circle in all directions, supplying the
cylinders on both sides with an equal quantity of oil, as at Fig. 80, B.

WHY COOLING SYSTEMS ARE NECESSARY

The reader should understand from preceding chapters that the power of
an internal-combustion motor is obtained by the rapid combustion and
consequent expansion of some inflammable gas. The operation in brief is
that when air or any other gas or vapor is heated, it will expand and
that if this gas is confined in a space which will not permit expansion,
pressure will be exerted against all sides of the containing chamber.
The more a gas is heated, the more pressure it will exert upon the walls
of the combustion chamber it confines. Pressure in a gas may be
created by increasing its temperature and inversely heat may be created
by pressure. When a gas is compressed its total volume is reduced and
the temperature is augmented.

[Illustration: Fig. 80.--Why Pressure Feed System is Best for
Eight-Cylinder Vee Airplane Engines.]

The efficiency of any form of heat engine is determined by the power
obtained from a certain fuel consumption. A definite amount of energy
will be liberated in the form of heat when a pound of any fuel is
burned. The efficiency of any heat engine is proportional to the power
developed from a definite quantity of fuel with the least loss of
thermal units. If the greater proportion of the heat units derived by
burning the explosive mixture could be utilized in doing useful work,
the efficiency of the gasoline engine would be greater than that of any
other form of energizing power. There is a great loss of heat from
various causes, among which can be cited the reduction of pressure
through cooling the motor and the loss of heat through the exhaust
valves when the burned gases are expelled from the cylinder.

The loss through the water jacket of the average automobile power plant
is over 50 per cent. of the total fuel efficiency. This means that more
than half of the heat units available for power are absorbed and
dissipated by the cooling water. Another 16 per cent. is lost through
the exhaust valve, and but 33-1/3 per cent. of the heat units do useful
work. The great loss of heat through the cooling systems cannot be
avoided, as some method must be provided to keep the temperature of the
engine within proper bounds. It is apparent that the rapid combustion
and continued series of explosions would soon heat the metal portions of
the engine to a red heat if some means were not taken to conduct much of
this heat away. The high temperature of the parts would burn the
lubricating oil, even that of the best quality, and the piston and rings
would expand to such a degree, especially when deprived of oil, that
they would seize in the cylinder. This would score the walls, and the
friction which ensued would tend to bind the parts so tightly that the
piston would stick, bearings would be burned out, the valves would warp,
and the engine would soon become inoperative.

[Illustration: Fig. 81.--Operating Temperatures of Automobile Engine
Parts Useful as a Guide to Understand Airplane Power Plant Heat.]

The best temperature to secure efficient operation is one on which
considerable difference of opinion exists among engineers. The fact that
the efficiency of an engine is dependent upon the ratio of heat
converted into useful work compared to that generated by the explosion
of the gas is an accepted fact. It is very important that the engine
should not get too hot, and on the other hand it is equally vital that
the cylinders be not robbed of too much heat. The object of cylinder
cooling is to keep the temperature of the cylinder below the danger
point, but at the same time to have it as high as possible to secure
maximum power from the gas burned. The usual operating temperatures of
an automobile engine are shown at Fig. 81, and this can be taken as an
approximation of the temperatures apt to exist in an airplane engine of
conventional design as well when at ground level or not very high in the
air. The newer very high compression airplane engines in which
compressions of eight or nine atmospheres are used, or about 125 pounds
per square inch, will run considerably hotter than the temperatures
indicated.

COOLING SYSTEMS GENERALLY APPLIED

There are two general systems of engine cooling in common use, that in
which water is heated by the absorption of heat from the engine and then
cooled by air, and the other method in which the air is directed onto
the cylinder and absorbs the heat directly instead of through the medium
of water. When the liquid is employed in cooling it is circulated
through jackets which surround the cylinder casting and the water may be
kept in motion by two methods. The one generally favored is to use a
positive circulating pump of some form which is driven by the engine to
keep the water in motion. The other system is to utilize a natural
principle that heated water is lighter than cold liquid and that it will
tend to rise to the top of the cylinder when it becomes heated to the
proper temperature and cooled water takes its place at the bottom of the
water jacket.

Air-cooling methods may be by radiation or convection. In the former
case the effective outer surface of the cylinder is increased by the
addition of flanges machined or cast thereon, and the air is depended on
to rise from the cylinder as heated and be replaced by cooler air. This,
of course, is found only on stationary engines. When a positive air
draught is directed against the cylinder by means of the propeller slip
stream in an airplane, cooling is by convection and radiation both.
Sometimes the air draught may be directed against the cylinder walls by
some form of jacket which confines it to the heated portions of the
cylinder.

COOLING BY POSITIVE WATER CIRCULATION

[Illustration: Fig. 82.--Water Cooling of Salmson Seven-Cylinder Radial
Airplane Engine.]

A typical water-cooling system in which a pump is depended upon to
promote circulation of the cooling liquid is shown at Figs. 82 and 83.
The radiator is carried at the front end of the fuselage in most cases,
and serves as a combined water tank and cooler, but in some cases it is
carried at the side of the engine, as in Fig. 84, or attached to the
central portion of the aerofoil or wing structure. It is composed of an
upper and lower portion joined together by a series of pipes which may
be round and provided with a series of fins to radiate the heat, or
which may be flat in order to have the water pass through in thin sheets
and cool it more easily. Cellular or honeycomb coolers are composed of a
large number of bent tubes which will expose a large area of surface to
the cooling influence of the air draught forced through the radiator
either by the forward movement of the vehicle or by some type of fan.
The cellular and flat tube types have almost entirely displaced the
flange tube radiators which were formerly popular because they cool the
water more effectively, and may be made lighter than the tubular
radiator could be for engines of the same capacity.

[Illustration: Fig. 83.--How Water Cooling System of Thomas Airplane
Engine is Installed in Fuselage.]

The water is drawn from the lower header of the radiator by the pump and
is forced through a manifold to the lower portion of the water jackets
of the cylinder. It becomes heated as it passes around the cylinder
walls and combustion chambers and the hot water passes out of the top of
the water jacket to the upper portion of the radiator. Here it is
divided in thin streams and directed against comparatively cool metal
which abstracts the heat from the water. As it becomes cooler it falls
to the bottom of the radiator because its weight increases as the
temperature becomes lower. By the time it reaches the lower tank of the
radiator it has been cooled sufficiently so that it may be again passed
around the cylinders of the motor. The popular form of circulating pump
is known as the "centrifugal type" because a rotary impeller of
paddle-wheel form throws water which it receives at a central point
toward the outside and thus causes it to maintain a definite rate of
circulation. The pump is always a separate appliance attached to the
engine and driven by positive gearing or direct-shaft connection. The
centrifugal pump is not as positive as the gear form, and some
manufacturers prefer the latter because of the positive pumping
features. They are very simple in form, consisting of a suitable cast
body in which a pair of spur pinions having large teeth are carried. One
of these gears is driven by suitable means, and as it turns the other
member they maintain a flow of water around the pump body. The pump
should always be installed in series with the water pipe which conveys
the cool liquid from the lower compartment of the radiator to the
coolest portion of the water jacket.

[Illustration: Fig. 84.--Finned Tube Radiators at the Side of Hall-Scott
Airplane Power Plant Installed in Standard Fuselage.]

WATER CIRCULATION BY NATURAL SYSTEM

Some automobile engineers contend that the rapid water circulation
obtained by using a pump may cool the cylinders too much, and that the
temperature of the engine may be reduced so much that the efficiency
will be lessened. For this reason there is a growing tendency to use the
natural method of water circulation as the cooling liquid is supplied to
the cylinder jackets just below the boiling point and the water issues
from the jacket at the top of the cylinder after it has absorbed
sufficient heat to raise it just about to the boiling point.

As the water becomes heated by contact with the hot cylinder and
combustion-chamber walls it rises to the top of the water jacket, flows
to the cooler, where enough of the heat is absorbed to cause it to
become sensibly greater in weight. As the water becomes cooler, it falls
to the bottom of the radiator and it is again supplied to the water
jacket. The circulation is entirely automatic and continues as long as
there is a difference in temperature between the liquid in the water
spaces of the engine and that in the cooler. The circulation becomes
brisker as the engine becomes hotter and thus the temperature of the
cylinders is kept more nearly to a fixed point. With the thermosyphon
system the cooling liquid is nearly always at its boiling point, whereas
if the circulation is maintained by a pump the engine will become cooler
at high speed and will heat up more at low speed.

With the thermosyphon, or natural system of cooling, more water must be
carried than with the pump-maintained circulation methods. The water
spaces around the cylinders should be larger, the inlet and discharge
water manifolds should have greater capacity, and be free from sharp
corners which might impede the flow. The radiator must also carry more
water than the form used in connection with the pump because of the
brisker pump circulation which maintains the engine temperature at a
lower point. Consideration of the above will show why the pump system is
almost universally used in connection with airplane power plant cooling.

DIRECT AIR-COOLING METHODS

The earliest known method of cooling the cylinder of gas-engines was by
means of a current of air passed through a jacket which confined it
close to the cylinder walls and was used by Daimler on his first
gas-engine. The gasoline engine of that time was not as efficient as the
later form, and other conditions which materialized made it desirable to
cool the engine by water. Even as gasoline engines became more and more
perfected there has always existed a prejudice against air cooling,
though many forms of engines have been used, both in automobile and
aircraft applications where the air-cooling method has proven to be very
practical.

The simplest system of air cooling is that in which the cylinders are
provided with a series of flanges which increase the effective radiating
surface of the cylinder and directing an air-current from a fan against
the flanges to absorb the heat. This increase in the available radiating
surface of an air-cooled cylinder is necessary because air does not
absorb heat as readily as water and therefore more surface must be
provided that the excess heat be absorbed sufficiently fast to prevent
distortion of the cylinders. Air-cooling systems are based on a law
formulated by Newton, which is: "The rate for cooling for a body in a
uniform current of air is directly proportional to the speed of the air
current and the amount of radiating surface exposed to the cooling
effect."

AIR-COOLED ENGINE DESIGN CONSIDERATIONS

[Illustration: Fig. 85.--Anzani Testing His Five-Cylinder Air Cooled
Aviation Motor Installed in Bleriot Monoplane. Note Exposure of Flanged
Cylinders to Propeller Slip Stream.]

There are certain considerations which must be taken into account in
designing an air-cooled engine, which are often overlooked in those
forms cooled by water. Large valves must be provided to insure rapid
expulsion of the flaming exhaust gas and also to admit promptly the
fresh cool mixture from the carburetor. The valves of air-cooled engines
are usually placed in the cylinder-head, in order to eliminate any
pockets or sharp passages which would impede the flow of gas or retain
some of the products of combustion and their heat. When high power is
desired multiple-cylinder engines should be used, as there is a certain
limit to the size of a successful air-cooled cylinder. Much better
results are secured from those having small cubical contents because the
heat from small quantities of gas will be more quickly carried off than
from greater amounts. All successful engines of the aviation type which
have been air-cooled have been of the multiple-cylinder type.

An air-cooled engine must be placed in the fuselage, as at Fig. 85, in
such a way that there will be a positive circulation of air around it
all the time that it is in operation. The air current may be produced by
the tractor screw at the front end of the motor, or by a suction or
blower fan attached to the crank-shaft as in the Renault engine or by
rotating the cylinders as in the Le Rhone and Gnome motors. Greater care
is required in lubrication of the air-cooled cylinders and only the best
quality of oil should be used to insure satisfactory oiling.

The combustion chambers must be proportioned so that distribution of
metal is as uniform as possible in order to prevent uneven expansion
during increase in temperature and uneven contraction when the cylinder
is cooled. It is essential that the inside walls of the combustion
chamber be as smooth as possible because any sharp angle or projection
may absorb sufficient heat to remain incandescent and cause trouble by
igniting the mixture before the proper time. The best grades of cast
iron or steel should be used in the cylinder and piston and the machine
work must be done very accurately so the piston will operate with
minimum friction in the cylinder. The cylinder bore should not exceed
4-1/2 or 5 inches and the compression pressure should never exceed 75
pounds absolute, or about five atmospheres, or serious overheating will
result.

As an example of the care taken in disposing of the exhaust gases in
order to obtain practical air-cooling, some cylinders are provided with
a series of auxiliary exhaust ports uncovered by the piston when it
reaches the end of its power stroke. The auxiliary exhaust ports open
just as soon as the full force of the explosion has been spent and a
portion of the flaming gases is discharged through the ports in the
bottom of the cylinder. Less of the exhaust gases remains to be
discharged through the regular exhaust member in the cylinder-head and
this will not heat the walls of the cylinder nearly as much as the
larger quantity of hot gas would. That the auxiliary exhaust port is of
considerable value is conceded by many designers of fixed and fan-shaped
air-cooled motors for airplanes.

Among the advantages stated for direct air cooling, the greatest is the
elimination of cooling water and its cooling auxiliaries, which is a
factor of some moment, as it permits considerable reduction in
horse-power-weight ratio of the engine, something very much to be
desired. In the temperate zone, where the majority of airplanes are
used, the weather conditions change in a very few months from the warm
summer to the extreme cold winter, and when water-cooled systems are
employed it is necessary to add some chemical substance to the water to
prevent it from freezing. The substances commonly employed are
glycerine, wood alcohol, or a saturated solution of calcium chloride.
Alcohol has the disadvantage in that it vaporizes readily and must be
often renewed. Glycerine affects the rubber hose, while the calcium
chloride solution crystallizes and deposits salt in the radiator and
water pipes.

One of the disadvantages of an air-cooling method, as stated by those
who do not favor this system, is that engines cooled by air cannot be
operated for extended periods under constant load or at very high speed
without heating up to such a point that premature ignition of the charge
may result. The water-cooling systems, at the other hand, maintain the
temperature of the engine more nearly constant than is possible with an
air-cooled motor, and an engine cooled by water can be operated under
conditions of inferior lubrication or poor mixture adjustment that would
seriously interfere with proper and efficient cooling by air.

Air-cooled motors, as a rule, use less fuel than water-cooled engines,
because the higher temperature of the cylinder does not permit of a full
charge of gas being inspired on the intake stroke. As special care is
needed in operating an air-cooled engine to obtain satisfactory results
and because of the greater difficulty which obtains in providing proper
lubrication and fuel mixtures which will not produce undue heating, the
air-cooled system has but few adherents at the present time, and
practically all airplanes, with but very few exceptions, are provided
with water-cooled power plants. Those fitted with air-cooled engines are
usually short-flight types where maximum lightness is desired in order
to obtain high speed and quick climb. The water-cooled engines are best
suited for airplanes intended for long flights. The Gnome, Le Rhone and
Clerget engines are thoroughly practical and have been widely used in
France and England. These are rotary radial cylinder types. The Anzani
is a fixed cylinder engine used on training machines, while the Renault
is a V-type engine made in eight- and twelve-cylinder V forms that has
been used on reconnaissance and bombing airplanes with success. These
types will be fully considered in proper sequence.

CHAPTER VIII

Methods of Cylinder Construction--Block Castings--Influence on
Crank-Shaft Design--Combustion Chamber Design--Bore and Stroke
Ratio--Meaning of Piston Speed--Advantage of Off-Set Cylinders--
Valve Location of Vital Import--Valve Installation Practice--
Valve Design and Construction--Valve Operation--Methods of
Driving Cam-Shaft--Valve Springs--Valve Timing--Blowing Back--
Lead Given Exhaust Valve--Exhaust Closing, Inlet Opening--
Closing the Inlet Valve--Time of Ignition--How an Engine Is
Timed--Gnome "Monosoupape" Valve Timing--Springless Valves--Four
Valves per Cylinder.

The improvements noted in the modern internal combustion motors have
been due to many conditions. The continual experimenting by leading
mechanical minds could have but one ultimate result. The parts of the
engines have been lightened and strengthened, and greater power has been
obtained without increasing piston displacement. A careful study has
been made of the many conditions which make for efficient motor action,
and that the main principles are well recognized by all engineers is
well shown by the standardization of design noted in modern power
plants. There are many different methods of applying the same principle,
and it will be the purpose of this chapter to define the ways in which
the construction may be changed and still achieve the same results. The
various components may exist in many different forms, and all have their
advantages and disadvantages. That all methods are practical is best
shown by the large number of successful engines which use radically
different designs.

METHODS OF CYLINDER CONSTRUCTION

One of the most important parts of the gasoline engine and one that has
material bearing upon its efficiency is the cylinder unit. The cylinders
may be cast individually, or in pairs, and it is possible to make all
cylinders a unit or block casting. Some typical methods of cylinder
construction are shown in accompanying illustrations. The appearance of
individual cylinder castings may be ascertained by examination of the
Hall-Scott airplane engine. Air-cooled engine cylinders are always of
the individual pattern.

Considered from a purely theoretical point of view, the individual
cylinder casting has much in its favor. It is advanced that more uniform
cooling is possible than where the cylinders are cast either in pairs or
three or four in one casting. More uniform cooling insures that the
expansion or change of form due to heating will be more equal. This is
an important condition because the cylinder bore must remain true under
all conditions of operation. If the heating effect is not uniform, which
condition is liable to obtain if metal is not evenly distributed, the
cylinder may become distorted by heat and the bore be out of truth. When
separate cylinders are used it is possible to make a uniform water space
and have the cooling liquid evenly distributed around the cylinder. In
multiple cylinder castings this is not always the rule, as in many
instances, especially in four-cylinder block motors where compactness is
the main feature, there is but little space between the cylinders for
the passage of water. Under such circumstances the cooling effect is not
even, and the stresses which obtain because of unequal expansion may
distort the cylinder to some extent. When steel cylinders are made from
forgings, the water jackets are usually of copper or sheet steel
attached to the forging by autogenous welding; in the case of the latter
and, in some cases, the former may be electro-deposited on the
cylinders.

BLOCK CASTINGS

[Illustration: Fig. 86.--Views of Four-Cylinder Duesenberg Airplane
Engine Cylinder Block.]

The advantage of casting the cylinders in blocks is that a motor may be
much shorter than it would be if individual castings were used. It is
admitted that when the cylinders are cast together a more compact,
rigid, and stronger power plant is obtained than when cast separately.
There is a disadvantage, however, in that if one cylinder becomes
damaged it will be necessary to replace the entire unit, which means
scrapping three good cylinders because one of the four has failed. When
the cylinders are cast separately one need only replace the one that has
become damaged. The casting of four cylinders in one unit is made
possible by improved foundry methods, and when proper provision is made
for holding the cores when the metal is poured and the cylinder casts
are good, the construction is one of distinct merit. It is sometimes the
case that the proportion of sound castings is less when cylinders are
cast in block, but if the proper precautions are observed in molding and
the proper mixtures of cast iron used, the ratio of defective castings
is no more than when cylinders are molded individually. As an example of
the courage of engineers in departing from old-established rules, the
cylinder casting shown at Fig. 86 may be considered typical. This is
used on the Duesenberg four-cylinder sixteen-valve 4-3/4" × 7" engine
which has a piston displacement of 496 cu. in. At a speed of 2,000
r.p.m., corresponding to a piston speed of 2,325 ft. per min., the
engine is guaranteed to develop 125 horse-power. The weight of the model
engine without gear reduction is 436 lbs., but a number of refinements
have been made in the design whereby it is expected to get the weight
down to 390 lbs. The four cylinders are cast from semi-steel in a single
block, with integral heads. The cylinder construction is the same as
that which has always been used by Mr. Duesenberg, inlet and exhaust
valves being arranged horizontally opposite each other in the head.
There are large openings in the water jacket at both sides and at the
ends, which are closed by means of aluminum covers, water-tightness
being secured by the use of gaskets. This results in a saving in weight
because the aluminum covers can be made considerably lighter than it
would be possible to cast the jacket walls, and, besides, it permits of
obtaining a more nearly uniform thickness of cylinder wall, as the cores
can be much better supported. The cooling water passes completely around
each cylinder, and there is a very considerable space between the two
central cylinders, this being made necessary in order to get the large
bearing area desirable for the central bearing.

It is common practice to cast the water jackets integral with the
cylinders, if cast iron or aluminum is used, and this is also the most
economical method of applying it because it gives good results in
practice. An important detail is that the water spaces must be
proportioned so that they are equal around the cylinders whether these
members are cast individually, in pairs, threes or fours. When cylinders
are cast in block form it is good practice to leave a large opening in
the jacket wall which will assist in supporting the core and make for
uniform water space. It will be noticed that the casting shown at Fig.
86 has a large opening in the side of the cylinder block. These openings
are closed after the interior of the casting is thoroughly cleaned of
all sand, core wire, etc., by brass, cast iron or aluminum plates. These
also have particular value in that they may be removed after the motor
has been in use, thus permitting one to clean out the interior of the
water jacket and dispose of the rust, sediment, and incrustation which
are always present after the engine has been in active service for a
time.

Among the advantages claimed for the practice of casting cylinders in
blocks may be mentioned compactness, lightness, rigidity, simplicity of
water piping, as well as permitting the use of simple forms of inlet and
exhaust manifolds. The light weight is not only due to the reduction of
the cylinder mass but because the block construction permits one to
lighten the entire motor. The fact that all cylinders are cast together
decreases vibration, and as the construction is very rigid, disalignment
of working parts is practically eliminated. When inlet and exhaust
manifolds are cored in the block casting, as is sometimes the case, but
one joint is needed on each of these instead of the multiplicity of
joints which obtain when the cylinders are individual castings. The
water piping is also simplified. In the case of a four-cylinder block
motor but two pipes are used; one for the water to enter the cylinder
jacket, the other for the cooling liquid to discharge through.

INFLUENCE ON CRANK-SHAFT DESIGN

[Illustration: Fig. 87.--Twin-Cylinder Block of Sturtevant Airplane
Engine is Cast of Aluminum, and Has Removable Cylinder Head.]

The method of casting the cylinders has a material influence on the
design of the crank-shaft as will be shown in proper sequence. When four
cylinders are combined in one block it is possible to use a two-bearing
crank-shaft. Where cylinders are cast in pairs a three-bearing
crank-shaft is commonly supplied, and when cylinders are cast as
individual units it is thought necessary to supply a five-bearing
crank-shaft, though sometimes shafts having but three journals are used
successfully. Obviously the shafts must be stronger and stiffer to
withstand the stresses imposed if two supporting bearings are used than
if a larger number are employed. In this connection it may be stated
that there is less difficulty in securing alignment with a lesser number
of bearings and there is also less friction. On the other hand, the
greater the number of points of support a crank-shaft has the lighter
the webs can be made and still have requisite strength.

COMBUSTION CHAMBER DESIGN

[Illustration: Fig. 88.--Aluminum Cylinder Pair Casting of Thomas 150
Horse-Power Airplane Engine is of the L Head Type.]

Another point of importance in the design of the cylinder, and one which
has considerable influence upon the power developed, is the shape of the
combustion chamber. The endeavor of designers is to obtain maximum power
from a cylinder of certain proportions, and the greater energy obtained
without increasing piston displacement or fuel consumption the higher
the efficiency of the motor. To prevent troubles due to pre-ignition it
is necessary that the combustion chamber be made so that there will be
no roughness, sharp corners, or edges of metal which may remain
incandescent when heated or which will serve to collect carbon deposits
by providing a point of anchorage. With the object of providing an
absolutely clean combustion chamber some makers use a separable head
unit to their twin cylinder castings, such as shown at Fig. 87 and Fig.
88. These permit one to machine the entire interior of the cylinder and
combustion chamber. The relation of valve location and combustion
chamber design will be considered in proper sequence. These cylinders
are cast of aluminum, instead of cast iron, as is customary, and are
provided with steel or cast iron cylinder liners forced in the soft
metal casting bores.

BORE AND STROKE RATIO

A question that has been a vexed one and which has been the subject of
considerable controversy is the proper proportion of the bore to the
stroke. The early gas engines had a certain well-defined bore to stroke
ratio, as it was usual at that time to make the stroke twice as long as
the bore was wide, but this cannot be done when high speed is desired.
With the development of the present-day motor the stroke or piston
travel has been gradually shortened so that the relative proportions of
bore and stroke have become nearly equal. Of late there seems to be a
tendency among designers to return to the proportions which formerly
obtained, and the stroke is sometimes one and a half or one and
three-quarter times the bore.

Engines designed for high speed should have the stroke not much longer
than the diameter of the bore. The disadvantage of short-stroke engines
is that they will not pull well at low speeds, though they run with
great regularity and smoothness at high velocity. The long-stroke engine
is much superior for slow speed work, and it will pull steadily and with
increasing power at low speed. It was formerly thought that such engines
should never turn more than a moderate number of revolutions, in order
not to exceed the safe piston speed of 1,000 feet per minute. This old
theory or rule of practice has been discarded in designing high
efficiency automobile racing and aviation engines, and piston speeds
from 2,500 to 3,000 feet per minute are sometimes used, though the
average is around 2,000 feet per minute. While both short- and
long-stroke motors have their advantages, it would seem desirable to
average between the two. That is why a proportion of four to five or six
seems to be more general than that of four to seven or eight, which
would be a long-stroke ratio. Careful analysis of a number of foreign
aviation motors shows that the average stroke is about 1.2 times the
bore dimensions, though some instances were noted where it was as high
as 1.7 times the bore.

MEANING OF PISTON SPEED

The factor which limits the stroke and makes the speed of rotation so
dependent upon the travel of the piston is piston speed. Lubrication is
the main factor which determines piston speed, and the higher the rate
of piston travel the greater care must be taken to insure proper oiling.
Let us fully consider what is meant by piston speed.

Assume that a motor has a piston travel or stroke of six inches, for the
sake of illustration. It would take two strokes of the piston to cover
one foot, or twelve inches, and as there are two strokes to a revolution
it will be seen that this permits of a normal speed of 1,000 revolutions
per minute for an engine with a six-inch stroke, if one does not exceed
1,000 feet per minute. If the stroke was only four inches, a normal
speed of 1,500 revolutions per minute would be possible without
exceeding the prescribed limit. The crank-shaft of a small engine,
having three-inch stroke, could turn at a speed of 2,000 revolutions per
minute without danger of exceeding the safe speed limit. It will be seen
that the longer the stroke the slower the speed of the engine, if one
desires to keep the piston speed within the bounds as recommended, but
modern practice allows of greatly exceeding the speeds formerly thought
best.

ADVANTAGES OF OFF-SET CYLINDERS

[Illustration: Fig. 90.--Cross Section of Austro-Daimler Engine, Showing
Offset Cylinder Construction. Note Applied Water Jacket and Peculiar
Valve Action.]

Another point upon which considerable difference of opinion exists
relates to the method of placing the cylinder upon the crank-case--i.e.,
whether its center line should be placed directly over the center of the
crank-shaft, or to one side of center. The motor shown at Fig. 90 is an
off-set type, in that the center line of the cylinder is a little to
one side of the center of the crank-shaft. Diagrams are presented at
Fig. 91 which show the advantages of off-set crank-shaft construction.
The view at A is a section through a simple motor with the conventional
cylinder placing, the center line of both crank-shaft and cylinder
coinciding. The view at B shows the cylinder placed to one side of
center so that its center line is distinct from that of the crank-shaft
and at some distance from it. The amount of off-set allowed is a point
of contention, the usual amount being from fifteen to twenty-five per
cent. of the stroke. The advantages of the off-set are shown at Fig. 91,
C. If the crank turns in direction of the arrow there is a certain
resistance to motion which is proportional to the amount of energy
exerted by the engine and the resistance offered by the load. There are
two thrusts acting against the cylinder wall to be considered, that due
to explosion or expansion of the gas, and that which resists the motion
of the piston. These thrusts may be represented by arrows, one which
acts directly in a vertical direction on the piston top, the other
along a straight line through the center of the connecting rod. Between
these two thrusts one can draw a line representing a resultant force
which serves to bring the piston in forcible contact with one side of
the cylinder wall, this being known as side thrust. As shown at C, the
crank-shaft is at 90 degrees, or about one-half stroke, and the
connecting rod is at 20 degrees angle. The shorter connecting rod would
increase the diagonal resultant and side thrusts, while a longer one
would reduce the angle of the connecting rod and the side thrust of the
piston would be less. With the off-set construction, as shown at D, it
will be noticed that with the same connecting-rod length as shown at C
and with the crank-shaft at 90 degrees of the circle that the
connecting-rod angle is 14 degrees and the side thrust is reduced
proportionately.

[Illustration: Fig. 91.--Diagrams Demonstrating Advantages of Offset
Crank-Shaft Construction.]

Another important advantage is that greater efficiency is obtained from
the explosion with an off-set crank-shaft, because the crank is already
inclined when the piston is at top center, and all the energy imparted
to the piston by the burning mixture can be exerted directly into
producing a useful turning effort. When a cylinder is placed directly on
a line with the crank-shaft, as shown at A, it will be evident that some
of the force produced by the expansion of the gas will be exerted in a
direct line and until the crank moves the crank throw and connecting rod
are practically a solid member. The pressure which might be employed in
obtaining useful turning effort is wasted by causing a direct pressure
upon the lower half of the main bearing and the upper half of the
crank-pin bushing.

Very good and easily understood illustrations showing advantages of the
off-set construction are shown at E and F. This is a bicycle
crank-hanger. It is advanced that the effort of the rider is not as well
applied when the crank is at position E as when it is at position F.
Position E corresponds to the position of the parts when the cylinder is
placed directly over the crank-shaft center. Position F may be compared
to the condition which is present when the off-set cylinder construction
is used.

VALVE LOCATION OF VITAL IMPORT

It has often been said that a chain is no stronger than its weakest
link, and this is as true of the explosive motor as it is of any other
piece of mechanism. Many motors which appeared to be excellently
designed and which were well constructed did not prove satisfactory
because some minor detail or part had not been properly considered by
the designer. A factor having material bearing upon the efficiency of
the internal combustion motor is the location of the valves and the
shape of the combustion chamber which is largely influenced by their
placing. The fundamental consideration of valve design is that the gases
be admitted and discharged from the cylinder as quickly as possible in
order that the speed of gas flow will not be impeded and produce back
pressure. This is imperative in obtaining satisfactory operation in any
form of motor. If the inlet passages are constricted the cylinder will
not fill with explosive mixture promptly, whereas if the exhaust gases
are not fully expelled the parts of the inert products of combustion
retained dilute the fresh charge, making it slow burning and causing
lost power and overheating. When an engine employs water as a cooling
medium this substance will absorb the surplus heat readily, and the
effects of overheating are not noticed as quickly as when air-cooled
cylinders are employed. Valve sizes have a decided bearing upon the
speed of motors and some valve locations permit the use of larger
members than do other positions.

While piston velocity is an important factor in determinations of power
output, it must be considered from the aspect of the wear produced upon
the various parts of the motor. It is evident that engines which run
very fast, especially of high power, must be under a greater strain than
those operating at lower speeds. The valve-operating mechanism is
especially susceptible to the influence of rapid movement, and the
slower the engine the longer the parts will wear and the more reliable
the valve action.

[Illustration: Fig. 92.--Diagram Showing Forms of Cylinder Demanded by
Different Valve Placings. A--T Head Type, Valves on Opposite Sides. B--L
Head Cylinder, Valves Side by Side. C--L Head Cylinder, One Valve in
Head, Other in Pocket. D--Inlet Valve Over Exhaust Member, Both in Side
Pocket. E--Valve-in-the-Head Type with Vertical Valves. F--Inclined
Valves Placed to Open Directly into Combustion Chamber.]

As will be seen by reference to the accompanying illustration, Fig. 92,
there are many ways in which valves may be placed in the cylinder. Each
method outlined possesses some point of advantage, because all of the
types illustrated are used by reputable automobile manufacturers. The
method outlined at Fig. 92, A, is widely used, and because of its shape
the cylinder is known as the "T" form. It is approved for automobile use
for several reasons, the most important being that large valves can be
employed and a well-balanced and symmetrical cylinder casting obtained.
Two independent cam-shafts are needed, one operating the inlet valves,
the other the exhaust members. The valve-operating mechanism can be very
simple in form, consisting of a plunger actuated by the cam which
transmits the cam motion to the valve-stem, raising the valve as the cam
follower rides on the point of the cam. Piping may be placed without
crowding, and larger manifolds can be fitted than in some other
constructions. This has special value, as it permits the use of an
adequate discharge pipe on the exhaust side with its obvious advantages.
This method of cylinder construction is never found on airplane engines
because it does not permit of maximum power output.

On the other hand, if considered from a viewpoint of actual heat
efficiency, it is theoretically the worst form of combustion chamber.
This disadvantage is probably compensated for by uniformity of expansion
of the cylinder because of balanced design. The ignition spark-plug may
be located directly over the inlet valve in the path of the incoming
fresh gases, and both valves may be easily removed and inspected by
unscrewing the valve caps without taking off the manifolds.

The valve installation shown at C is somewhat unusual, though it
provides for the use of valves of large diameter. Easy charging is
insured because of the large inlet valve directly in the top of the
cylinder. Conditions may be reversed if necessary, and the gases
discharged through this large valve. Both methods are used, though it
would seem that the free exhaust provided by allowing the gases to
escape directly from the combustion chamber through the overhead valve
to the exhaust manifold would make for more power. The method outlined
at Fig. 92, F and at Fig. 90 is one that has been widely employed on
large automobile racing motors where extreme power is required, as well
as in engines constructed for aviation service. The inclination of the
valves permits the use of large valves, and these open directly into the
combustion chamber. There are no pockets to retain heat or dead gas, and
free intake and outlet of gas is obtained. This form is quite
satisfactory from a theoretical point of view because of the almost
ideal combustion chamber form. Some difficulty is experienced, however,
in properly water-jacketing the valve chamber which experience has shown
to be necessary if the engine is to have high power.

The motor shown at Fig. 92, B and Fig. 88 employs cylinders of the "L"
type. Both valves are placed in a common extension from the combustion
chamber, and being located side by side both are actuated from a common
cam-shaft. The inlet and exhaust pipes may be placed on the same side of
the engine and a very compact assemblage is obtained, though this is
optional if passages are cored in the cylinder pairs to lead the gases
to opposite sides. The valves may be easily removed if desired, and the
construction is fairly good from the viewpoint of both foundry man and
machinist. The chief disadvantage is the limited area of the valves and
the loss of heat efficiency due to the pocket. This form of combustion
chamber, however, is more efficient than the "T" head construction,
though with the latter the use of larger valves probably compensates for
the greater heat loss. It has been stated as an advantage of this
construction that both manifolds can be placed at the same side of the
engine and a compact assembly secured. On the other hand, the
disadvantage may be cited that in order to put both pipes on the same
side they must be of smaller size than can be used when the valves are
oppositely placed. The "L" form cylinder is sometimes made more
efficient if but one valve is placed in the pocket while the other is
placed over it. This construction is well shown at Fig. 92, D and is
found on Anzani motors.

[Illustration: Fig. 93.--Sectional View of Engine Cylinder Showing Valve
and Cage Installation.]

The method of valve application shown at Fig. 87 is an ingenious method
of overcoming some of the disadvantages inherent with valve-in-the-head
motors. In the first place it is possible to water-jacket the valves
thoroughly, which is difficult to accomplish when they are mounted in
cages. The water circulates directly around the walls of the valve
chambers, which is superior to a construction where separate cages are
used, as there are two thicknesses of metal with the latter, that of the
valve-cage proper and the wall of the cylinder. The cooling medium is in
contact only with the outer wall, and as there is always a loss of heat
conductivity at a joint it is practically impossible to keep the
exhaust valves and their seats at a uniform temperature. The valves may
be of larger size without the use of pockets when seating directly in
the head. In fact, they could be equal in diameter to almost half the
bore of the cylinder, which provides an ideal condition of charge
placement and exhaust. When valve grinding is necessary the entire head
is easily removed by taking off six nuts and loosening inlet manifold
connections, which operation would be necessary even if cages were
employed, as in the engine shown at Fig. 93.

[Illustration: Fig. 94.--Diagrams Showing How Gas Enters Cylinder
Through Overhead Valves and Other Types. A--Tee Head Cylinder. B--L Head
Cylinder. C--Overhead Valve.]

[Illustration: Fig. 95.--Conventional Methods of Operating Internal
Combustion Motor Valves.]

At Fig. 94, A and B, a section through a typical "L"-shaped cylinder is
depicted. It will be evident that where a pocket construction is
employed, in addition to its faculty for absorbing heat, the passage of
gas would be impeded. For example, the inlet gas rushing in through the
open valve would impinge sharply upon the valve-cap or combustion head
directly over the valve and then must turn at a sharp angle to enter the
combustion chamber and then at another sharp angle to fill the
cylinders. The same conditions apply to the exhaust gases, though they
are reversed. When the valve-in-the-head type of cylinder is employed,
as at C, the only resistance offered the gas is in the manifold. As far
as the passage of the gases in and out of the cylinder is concerned,
ideal conditions obtain. It is claimed that valve-in-the-head motors are
more flexible and responsive than other forms, but the construction has
the disadvantage in that the valves must be opened through a rather
complicated system of push rods and rocker arms instead of the simpler
and direct plunger which can be used with either the "T" or "L" head
cylinders. This is clearly outlined in the illustrations at Fig. 95,
where A shows the valve in the head-operating mechanism necessary if the
cam-shaft is carried at the cylinder base, while B shows the most direct
push-rod action obtained with "T" or "L" head cylinder placing.

[Illustration: Fig. 96.--Examples of Direct Valve Actuation by Overhead
Cam-Shaft. A--Mercedes. B--Hall-Scott. C--Wisconsin.]

[Illustration: Fig. 97.

CENSORED]

[Illustration: Fig. 98.

CENSORED]

The objection can be easily met by carrying the cam-shaft above the
cylinders and driving it by means of gearing. The types of engine
cylinders using this construction are shown at Fig. 96, and it will be
evident that a positive and direct valve action is possible by following
the construction originated by the Mercedes (German) aviation engine
designers and outlined at A. The other forms at B and C are very clearly
adaptations of this design. The Hall-Scott engine at Fig. 97 is depicted
in part section and no trouble will be experienced in understanding the
bevel pinion and gear drive from the crank-shaft to the overhead
cam-shaft through a vertical counter-shaft. A very direct valve action
is used in the Duesenberg engines, one of which is shown in part section
at Fig. 98. The valves are parallel with the piston top and are actuated
by rocker arms, one end of which bears against the valve stem, and the
other rides the cam-shaft.

[Illustration: Fig. 99.--Sectional Views Showing Arrangement of Novel
Concentric Valve Arrangement Devised by Panhard for Aerial Engines.]

The form shown at Fig. 99 shows an ingenious application of the
valve-in-the-head idea which permits one to obtain large valves. It has
been used on some of the Panhard aviation engines and on the American
Aeromarine power plants. The inlet passage is controlled by the sliding
sleeve which is hollow and slotted so as to permit the inlet gases to
enter the cylinder through the regular type poppet valve which seats in
the exhaust sleeve. When the exhaust valve is operated by the tappet rod
and rocker arm the intake valve is also carried down with it. The
intake gas passage is closed, however, and the burned gases are
discharged through the large annular passage surrounding the sleeve.
When the inlet valve leaves its seat in the sleeve the passage of cool
gas around the sleeve keeps the temperature of both valves to a low
point and the danger of warping is minimized. A dome-shaped combustion
chamber may be used, which is an ideal form in conserving heat
efficiency, and as large valves may be installed the flow of both fresh
and exhaust gases may be obtained with minimum resistance. The intake
valve is opened by a small auxiliary rocker arm which is lifted when the
cam follower rides into the depression in the cam by the action of the
strong spring around the push rod. When the cam follower rides on the
high point the exhaust sleeve is depressed from its seat against the
cylinder. By using a cam having both positive and negative profiles, a
single rod suffices for both valves because of its push and pull action.

VALVE DESIGN AND CONSTRUCTION

Valve dimensions are an important detail to be considered and can be
determined by several conditions, among which may be cited method of
installation, operating mechanism, material employed, engine speed
desired, manner of cylinder cooling and degree of lift desired. A review
of various methods of valve location has shown that when the valves are
placed directly in the head we can obtain the ideal cylinder form,
though larger valves may be used if housed in a separate pocket, as
afforded by the "T" head construction. The method of operation has much
to do with the size of the valves. For example, if an automatic inlet
valve is employed it is good practice to limit the lift and obtain the
required area of port opening by augmenting the diameter. Because of
this a valve of the automatic type is usually made twenty per cent.
larger than one mechanically operated. When both are actuated by cam
mechanism, as is now common practice, they are usually made the same
size and are interchangeable, which greatly simplifies manufacture. The
relation of valve diameter to cylinder bore is one that has been
discussed for some time by engineers. The writer's experience would
indicate that they should be at least half the bore, if possible. While
the mushroom type or poppet valve has become standard and is the most
widely used form at the present time, there is some difference of
opinion among designers as to the materials employed and the angle of
the seat. Most valves have a bevel seat, though some have a flat
seating. The flat seat valve has the distinctive advantage of providing
a clear opening with lesser lift, this conducing to free gas flow. It
also has value because it is silent in operation, but the disadvantage
is present that best material and workmanship must be used in their
construction to obtain satisfactory results. As it can be made very
light it is particularly well adapted for use as an automatic inlet
valve. Among other disadvantages cited is the claim that it is more
susceptible to derangement, owing to the particles of foreign matter
getting under the seat. With a bevel seat it is argued that the foreign
matter would be more easily dislodged by the gas flow, and that the
valve would close tighter because it is drawn positively against the
bevel seat.

Several methods of valve construction are the vogue, the most popular
form being the one-piece type; those which are composed of a head of one
material and stem of another are seldom used in airplane engines because
they are not reliable. In the built-up construction the head is usually
of high nickel steel or cast iron, which metals possess good
heat-resisting qualities. Heads made of these materials are not likely
to warp, scale, or pit, as is sometimes the case when ordinary grades of
machinery steel are used. The cast-iron head construction is not popular
because it is often difficult to keep the head tight on the stem. There
is a slight difference in expansion ratio between the head and the stem,
and as the stem is either screwed or riveted to the cast-iron head the
constant hammering of the valve against its seat may loosen the joint.
As soon as the head is loose on the stem the action of the valve becomes
erratic. The best practice is to machine the valves from tungsten steel
forgings. This material has splendid heat-resisting qualities and will
not pit or become scored easily. Even the electrically welded head to
stem types which are used in automobile engines are not looked upon with
favor in the aviation engine. Valve stem guides and valve stems must be
machined very accurately to insure correct action. The usual practice in
automobile engines is shown at Fig. 100.

[Illustration: Fig. 100.--Showing Clearance Allowed Between Valve Stem
and Valve Stem Guide to Secure Free Action.]

VALVE OPERATION

The methods of valve operation commonly used vary according to the type
of cylinder construction employed. In all cases the valves are lifted
from their seats by cam-actuated mechanism. Various forms of
valve-lifting cams are shown at Fig. 101. As will be seen, a cam
consists of a circle to which a raised, approximately triangular member
has been added at one point. When the cam follower rides on the circle,
as shown at Fig. 102, there is no difference in height between the cam
center and its periphery and there is no movement of the plunger. As
soon as the raised portion of the cam strikes the plunger it will lift
it, and this reciprocating movement is transmitted to the valve stem by
suitable mechanical connections.

[Illustration: Fig. 101.--Forms of Valve-Lifting Cams Generally
Employed. A--Cam Profile for Long Dwell and Quick Lift. B--Typical Inlet
Cam Used with Mushroom Type Follower. C--Average Form of Cam.
D--Designed to Give Quick Lift and Gradual Closing.]

The cam forms outlined at Fig. 101 are those commonly used. That at A is
used on engines where it is desired to obtain a quick lift and to keep
the valve fully opened as long as possible. It is a noisy form, however,
and is not very widely employed. That at B is utilized more often as an
inlet cam while the profile shown at C is generally depended on to
operate exhaust valves. The cam shown at D is a composite form which has
some of the features of the other three types. It will give the quick
opening of form A, the gradual closing of form B, and the time of
maximum valve opening provided by cam profile C.

[Illustration: Fig. 102.--Showing Principal Types of Cam Followers which
Have Received General Application.]

The various types of valve plungers used are shown at Fig. 102. That
shown at A is the simplest form, consisting of a simple cylindrical
member having a rounded end which follows the cam profile. These are
sometimes made of square stock or kept from rotating by means of a key
or pin. A line contact is possible when the plunger is kept from
turning, whereas but a single point bearing is obtained when the plunger
is cylindrical and free to revolve. The plunger shown at A will follow
only cam profiles which have gradual lifts. The plunger shown at B is
left free to revolve in the guide bushing and is provided with a flat
mushroom head which serves as a cam follower. The type shown at C
carries a roller at its lower end and may follow very irregular cam
profiles if abrupt lifts are desired. While forms A and B are the
simplest, that outlined at C in its various forms is more widely used.
Compound plungers are used on the Curtiss OX-2 motors, one inside the
other. The small or inner one works on a cam of conventional design, the
outer plunger follows a profile having a flat spot to permit of a pull
rod action instead of a push rod action. All the methods in which levers
are used to operate valves are more or less noisy because clearance must
be left between the valve stem and the stop of the plunger. The space
must be taken up before the valve will leave its seat, and when the
engine is operated at high speeds the forcible contact between the
plunger and valve stem produces a rattling sound until the valves become
heated and expand and the stems lengthen out. Clearance must be left
between the valve stems and actuating means. This clearance is clearly
shown in Fig. 103 and should be .020" (twenty thousandths) when engine
is cold. The amount of clearance allowed depends entirely upon the
design of the engine and length of valve stem. On the Curtiss OX-2
engines the clearance is but .010" (ten thousandths) because the valve
stems are shorter. Too little clearance will result in loss of power or
misfiring when engine is hot. Too much clearance will not allow the
valve to open its full amount and will disturb the timing.

[Illustration: Fig. 103.--Diagram Showing Proper Clearance to Allow
Between Adjusting Screw and Valve Stems in Hall-Scott Aviation Engines.]

METHODS OF DRIVING CAM-SHAFT

Two systems of cam-shaft operation are used. The most common of these is
by means of gearing of some form. If the cam-shaft is at right angles to
the crank-shaft it may be driven by worm, spiral, or bevel gearing. If
the cam-shaft is parallel to the crank-shaft, simple spur gear or chain
connection may be used to turn it. A typical cam-shaft for an
eight-cylinder V engine is shown at Fig. 104. It will be seen that the
sixteen cams are forged integrally with the shaft and that it is
spur-gear driven. The cam-shaft drive of the Hall-Scott motor is shown
at Fig. 97.

[Illustration: Fig. 104.--Cam-Shaft of Thomas Airplane Motor Has Cams
Forged Integral. Note Split Cam-Shaft Bearings and Method of Gear
Retention.]

While gearing is more commonly used, considerable attention has been
directed of late to silent chains for cam-shaft operation. The ordinary
forms of block or roller chain have not proven successful in this
application, but the silent chain, which is in reality a link belt
operating over toothed pulleys, has demonstrated its worth. The tendency
to its use is more noted on foreign motors than those of American
design. It first came to public notice when employed on the
Daimler-Knight engine for driving the small auxiliary crank-shafts which
reciprocated the sleeve valves. The advantages cited for the application
of chains are, first, silent operation, which obtains even after the
chains have worn considerably; second, in designing it is not necessary
to figure on maintaining certain absolute center distances between the
crank-shaft and cam-shaft sprockets, as would be the case if
conventional forms of gearing were used. On some forms of motor
employing gears, three and even four members are needed to turn the
cam-shaft. With a chain drive but two sprockets are necessary, the chain
forming a flexible connection which permits the driving and driven
members to be placed at any distance apart that the exigencies of the
design demand. When chains are used it is advised that some means for
compensating chain slack be provided, or the valve timing will lag when
chains are worn. Many combination drives may be worked out with chains
that would not be possible with other forms of gearing. Direct gear
drive is favored at the present time by airplane engine designers
because they are the most certain and positive means, even when a number
of gears must be used as intermediate drive members. With overhead
cam-shafts, bevel gears work out very well in practice, as in the
Hall-Scott motors and others of that type.

VALVE SPRINGS

[Illustration: Fig. 105.--Section Through Cylinder of Knight Motor,
Showing Important Parts of Valve Motion.]

Another consideration of importance is the use of proper valve-springs,
and particular care should be taken with those, of automatic valves. The
spring must be weak enough to allow the valve to open when the suction
is light, and must be of sufficient strength to close it in time at high
speeds. It should be made as large as possible in diameter and with a
large number of convolutions, in order that fatigue of the metal be
obviated, and it is imperative that all springs be of the same strength
when used on a multiple-cylinder engine. Practically all valves used to
control the gas flow in airplane engines are mechanically operated. On
the exhaust valve the spring must be strong enough so that the valve
will not be sucked in on the inlet stroke. It should be borne in mind
that if the spring is too strong a strain will be imposed on the
valve-operating mechanism, and a hammering action produced which may
cause deformation of the valve-seat. Only pressure enough to insure that
the operating mechanism will follow the cam is required. It is common
practice to make the inlet and exhaust valve springs of the same
tension when the valves are of the same size and both mechanically
operated. This is done merely to simplify manufacture and not because it
is necessary for the inlet valve-spring to be as strong as the other.
Valve springs of the helical coil type are generally used, though
torsion or "scissors" springs and laminated or single-leaf springs are
also utilized in special applications. Two springs are used on each
valve in some valve-in-the-head types; a spring of small pitch diameter
inside the regular valve-spring and concentric with it. Its function is
to keep the valve from falling into the cylinder in event of breakage of
the main spring in some cases, and to provide a stronger return action
in others.

[Illustration: Fig. 106.--Diagrams Showing Knight Sleeve Valve Action.]

KNIGHT SLIDE VALVE MOTOR

The sectional view through the cylinder at Fig. 105 shows the Knight
sliding sleeves and their actuating means very clearly. The diagrams at
Fig. 106 show graphically the sleeve movements and their relation to the
crank-shaft and piston travel. The action may be summed up as follows:
The inlet port begins to open when the lower edge of the opening of the
outside sleeve which is moving down passes the top of the slot in the
inner member also moving downwardly. The inlet port is closed when the
lower edge of the slot in the inner sleeve which is moving up passes the
top edge of the port in the outer sleeve which is also moving toward the
top of the cylinder. The inlet opening extends over two hundred degrees
of crank motion. The exhaust port is uncovered slightly when the lower
edge of the port in the inner sleeve which is moving down passes the
lower edge of the portion of the cylinder head which protrudes in the
cylinder. When the top of the port in the outer sleeve traveling toward
the bottom of the cylinder passes the lower edge of the slot in the
cylinder wall the exhaust passage is closed. The exhaust opening extends
over a period corresponding to about two hundred and forty degrees of
crank motion. The Knight motor has not been applied to aircraft to the
writer's knowledge, but an eight-cylinder Vee design that might be
useful in that connection if lightened is shown at Fig. 107. The main
object is to show that the Knight valve action is the only other besides
the mushroom or poppet valve that has been applied successfully to high
speed gasoline engines.

VALVE TIMING

It is in valve timing that the greatest difference of opinion prevails
among engineers, and it is rare that one will see the same formula in
different motors. It is true that the same timing could not be used with
motors of different construction, as there are many factors which
determine the amount of lead to be given to the valves. The most
important of these is the relative size of the valve to the cylinder
bore, the speed of rotation it is desired to obtain, the fuel
efficiency, the location of the valves, and other factors too numerous
to mention.

[Illustration: Fig. 107.--Cross Sectional View of Knight Type Eight
Cylinder V Engine.]

Most of the readers should be familiar with the cycle of operation of
the internal combustion motor of the four-stroke type, and it seems
unnecessary to go into detail except to present a review. The first
stroke of the piston is one in which a charge of gas is taken into the
motor; the second stroke, which is in reverse direction to the first, is
a compression stroke, at the end of which the spark takes place,
exploding the charge and driving the piston down on the third or
expansion stroke, which is in the same direction as the intake stroke,
and finally, after the piston has nearly reached the end of this stroke,
another valve opens to allow the burned gases to escape, and remains
open until the piston has reached the end of the fourth stroke and is in
a position to begin the series over again. The ends of the strokes are
reached when the piston comes to a stop at either top or bottom of the
cylinder and reverses its motion. That point is known as a center, and
there are two for each cylinder, top and bottom centers, respectively.

All circles may be divided into 360 parts, each of which is known as a
degree, and, in turn, each of these degrees may be again divided into
minutes and seconds, though we need not concern ourselves with anything
less than the degree. Each stroke of the piston represents 180 degrees
travel of the crank, because two strokes represent one complete
revolution of three hundred and sixty degrees. The top and bottom
centers are therefore separated by 180 degrees. Theoretically each phase
of a four-cycle engine begins and ends at a center, though in actual
practice the inertia or movement of the gases makes it necessary to
allow a lead or lag to the valve, as the case may be. If a valve opens
before a center, the distance is called "lead"; if it closes after a
center, this distance is known as "lag." The profile of the cams
ordinarily used to open or close the valves represents a considerable
time in relation to the 180 degrees of the crank-shaft travel, and the
area of the passages through which the gases are admitted or exhausted
is quite small owing to the necessity of having to open or close the
valves at stated times; therefore, to open an adequately large passage
for the gases it is necessary to open the valves earlier and close them
later than at centers.

That advancing the opening of the exhaust valve was of value was
discovered on the early motors and is explained by the necessity of
releasing a large amount of gas, the volume of which has been greatly
raised by the heat of combustion. When the inlet valves were
mechanically operated it was found that allowing them to lag at closing
enabled the inspiration of a greater volume of gas. Disregarding the
inertia or flow of the gases, opening the exhaust at center would enable
one to obtain full value of the expanding gases the entire length of the
piston stroke, and it would not be necessary to keep the valve open
after the top center, as the reverse stroke would produce a suction
effect which might draw some of the inert charge back into the cylinder.
On the other hand, giving full consideration to the inertia of the gas,
opening the valve before center is reached will provide for quick
expulsion of the gases, which have sufficient velocity at the end of the
stroke, so that if the valve is allowed to remain open a little longer,
the amount of lag varying with the opinions of the designer, the
cylinder is cleared in a more thorough manner.

BLOWING BACK

When the factor of retarded opening is considered without reckoning the
inertia of the gases, it would appear that if the valve were allowed to
remain open after center had passed, say, on the closing of the inlet,
the piston, having reversed its motion, would have the effect of
expelling part of the fresh charge through the still open valve as it
passed inward at its compression stroke. This effect is called blowing
back, and is often noted with motors where the valve settings are not
absolutely correct, or where the valve-springs or seats are defective
and prevent proper closing.

This factor is not of as much import as might appear, as on closer
consideration it will be seen that the movement of the piston as the
crank reaches either end of the stroke is less per degree of angular
movement than it is when the angle of the connecting rod is greater.
Then, again, a certain length of time is required for the reversal of
motion of the piston, during which time the crank is in motion but the
piston practically at a standstill. If the valves are allowed to remain
open during this period, the passage of the gas in or out of the
cylinder will be by its own momentum.

LEAD GIVEN EXHAUST VALVE

The faster a motor turns, all other things being equal, the greater the
amount of lead or advance it is necessary to give the opening of the
exhaust valve. It is self-evident truth that if the speed of a motor is
doubled it travels twice as many degrees in the time necessary to lower
the pressure. As most designers are cognizant of this fact, the valves
are proportioned accordingly. It is well to consider in this respect
that the cam profile has much to do with the manner in which the valve
is opened; that is, the lift may be abrupt and the gas allowed to escape
in a body, or the opening may be gradual, the gas issuing from the
cylinder in thin streams. An analogy may be made with the opening of any
bottle which contains liquid highly carbonated. If the cork is removed
suddenly the gas escapes with a loud pop, but, on the other hand, if the
bottle is uncorked gradually, the gas escapes from the receptacle in
thin streams around the cork, and passage of the gases to the air is
accomplished without noise. While the second plan is not harsh, it is
slower than the former, as must be evident.

EXHAUST CLOSING, INLET OPENING

A point which has been much discussed by engineers is the proper
relation of the closing of the exhaust valve and the opening of the
inlet. Theoretically they should succeed each other, the exhaust closing
at upper dead center and the inlet opening immediately afterward. The
reason why a certain amount of lag is given the exhaust closing in
practice is that the piston cannot drive the gases out of the cylinder
unless they are compressed to a degree in excess of that existing in the
manifold or passages, and while toward the end of the stroke this
pressure may be feeble, it is nevertheless indispensable. At the end of
the piston's stroke, as marked by the upper dead center, this
compression still exists, no matter how little it may be, so that if the
exhaust valve is closed and the inlet opened immediately afterward, the
pressure which exists in the cylinder may retard the entrance of the
fresh gas and a certain portion of the inert gas may penetrate into the
manifold. As the piston immediately begins to aspirate, this may not be
serious, but as these gases are drawn back into the cylinder the fresh
charge will be diluted and weakened in value. If the spark-plug is in a
pocket, the points may be surrounded by this weak gas, and the explosion
will not be nearly as energetic as when the ignition spark takes place
in pure mixture.

It is a well-known fact that the exhaust valve should close after dead
center and that a certain amount of lag should be given to opening of
the inlet. The lag given the closing of the exhaust valve should not be
as great as that given the closing of the inlet valve. Assuming that the
excess pressure of the exhaust will equal the depression during
aspiration, the time necessary to complete the emptying of the cylinder
will be proportional to the volume of the gas within it. At the end of
the suction stroke the volume of gas contained in the cylinder is equal
to the cylindrical volume plus the space of the combustion chamber. At
the end of the exhaust stroke the volume is but that of the dead space,
and from one-third to one-fifth its volume before compression. While it
is natural to assume that this excess of burned gas will escape faster
than the fresh gas will enter the cylinder, it will be seen that if the
inlet valve were allowed to lag twenty degrees, the exhaust valve lag
need not be more than five degrees, providing that the capacity of the
combustion chamber was such that the gases occupied one-quarter of their
former volume.

It is evident that no absolute rule can be given, as back pressure will
vary with the design of the valve passages, the manifolds, and the
construction of the muffler. The more direct the opening, the sooner the
valve can be closed and the better the cylinder cleared. Ten degrees
represent an appreciable angle of the crank, and the time required for
the crank to cover this angular motion is not inconsiderable and an
important quantity of the exhaust may escape, but the piston is very
close to the dead center after the distance has been covered.

Before the inlet valve opens there should be a certain depression in the
cylinder, and considerable lag may be allowed before the depression is
appreciable. So far as the volume of fresh gas introduced during the
admission stroke is concerned, this is determined by the displacement of
the piston between the point where the inlet valve opens and the point
of closing, assuming that sufficient gas has been inspired so that an
equilibrium of pressure has been established between the interior of the
cylinder and the outer air. The point of inlet opening varies with
different motors. It would appear that a fair amount of lag would be
fifteen degrees past top center for the inlet opening, as a certain
depression will exist in the cylinder, assuming that the exhaust valve
has closed five or ten degrees after center, and at the same time the
piston has not gone down far enough on its stroke to materially decrease
the amount of gas which will be taken into the cylinder.

CLOSING THE INLET VALVE

As in the case with the other points of opening and closing, there is a
wide diversity of practice as relates to closing the inlet valve. Some
of the designers close this exactly at bottom center, but this practice
cannot be commended, as there is a considerable portion of time, at
least ten or fifteen degrees angular motion of the crank, before the
piston will commence to travel to any extent on its compression stroke.
The gases rushing into the cylinder have considerable velocity, and
unless an equilibrium is obtained between the pressure inside and that
of the atmosphere outside, they will continue to rush into the cylinder
even after the piston ceases to exert any suction effect.

For this reason, if the valve is closed exactly on center, a full charge
may not be inspired into the cylinder, though if the time of closing is
delayed, this momentum or inertia of the gas will be enough to insure
that a maximum charge is taken into the cylinder. The writer considers
that nothing will be gained if the valve is allowed to remain open
longer than twenty degrees, and an analysis of practice in this respect
would seem to confirm this opinion. From that point in the crank
movement the piston travel increases and the compressive effect is
appreciable, and it would appear that a considerable proportion of the
charge might be exhausted into the manifold and carburetor if the valve
were allowed to remain open beyond a point corresponding to twenty
degrees angular movement of the crank.

TIME OF IGNITION

In this country engineers unite in providing a variable time of
ignition, though abroad some difference of opinion is noted on this
point. The practice of advancing the time of ignition, when affected
electrically, was severely condemned by early makers, these maintaining
that it was necessary because of insufficient heat and volume of the
spark, and it was thought that advancing ignition was injurious. The
engineers of to-day appreciate the fact that the heat of the electric
spark, especially when from a mechanical generator of electrical energy,
is the only means by which we can obtain practically instantaneous
explosion, as required by the operation of motors at high speeds, and
for the combustion of large volumes of gas.

[Illustration: Fig. 108.--Diagrams Explaining Valve and Ignition Timing
of Hall-Scott Aviation Engine.]

It is apparent that a motor with a fixed point of ignition is not as
desirable, in every way, as one in which the ignition can be advanced to
best meet different requirements, and the writer does not readily
perceive any advantage outside of simplicity of control in establishing
a fixed point of ignition. In fact, there seems to be some difference of
opinion among those designers who favor fixed ignition, and in one case
this is located forty-three degrees ahead of center, and in another
motor the point is fixed at twenty degrees, so that it may be said that
this will vary as much as one hundred per cent. in various forms. This
point will vary with different methods of ignition, as well as the
location of the spark-plug or igniter. For the sake of simplicity, most
airplane engines use set spark; if an advancing and retarding mechanism
is fitted, it is only to facilitate starting, as the spark is kept
advanced while in flight, and control is by throttle alone.

[Illustration: Fig. 109.--Timing Diagram of Typical Six-Cylinder
Engine.]

It is obvious by consideration of the foregoing that there can be no
arbitrary rules established for timing, because of the many conditions
which determine the best times for opening and closing the valves. It is
customary to try various settings when a new motor is designed until the
most satisfactory points are determined, and the setting which will be
very suitable for one motor is not always right for one of different
design. The timing diagram shown at Fig. 108 applies to the Hall-Scott
engine, and may be considered typical. It should be easily followed in
view of the very complete explanation given in preceding pages. Another
six-cylinder engine diagram is shown at Fig. 109, and an eight-cylinder
timing diagram is shown at Fig. 110. In timing automobile engines no
trouble is experienced, because timing marks are always indicated on
the engine fly-wheel register with an indicating trammel on the
crank-case. To time an airplane engine accurately, as is necessary to
test for a suspected cam-shaft defect, a timing disc of aluminum is
attached to the crank-shaft which has the timing marks indicated
thereon. If the disc is made 10 or 12 inches in diameter, it may be
divided into degrees without difficulty.

[Illustration: Fig. 110.--Timing Diagram of Typical Eight-Cylinder V
Engine.]

HOW AN ENGINE IS TIMED

In timing a motor from the marks on the timing disc rim it is necessary
to regulate the valves of but one cylinder at a time. Assuming that the
disc is revolving in the direction of engine rotation, and that the
firing order of the cylinders is 1-3-4-2, the operation of timing would
be carried on as follows: The crank-shaft would be revolved until the
line marked "Exhaust opens 1 and 4" registered with the trammel on the
motor bed. At this point the exhaust-valve of either cylinder No. 1 or
No. 4 should begin to open. This can be easily determined by noting
which of these cylinders holds the compressed charge ready for ignition.
Assuming that the spark has occurred in cylinder No. 1, then when the
fly-wheel is turned from the position to that in which the line marked
"Exhaust opens 1 and 4" coincides with the trammel point, the
valve-plunger under the exhaust-valve of cylinder No. 1 should be
adjusted in such a way that there is no clearance between it and the
valve stem. Further movement of the wheel in the same direction should
produce a lift of the exhaust valve. The disc is turned about two
hundred and twenty-five degrees, or a little less than three-quarters of
a revolution; then the line marked "Exhaust closes 1 and 4" will
register with the trammel point. At this period the valve-plunger and
the valve-stem should separate and a certain amount of clearance obtain
between them. The next cylinder to time would be No. 3. The crank-shaft
is rotated until mark "Exhaust opens 2 and 3" comes in line with the
trammel. At this point the exhaust valve of cylinder No. 3 should be
just about opening. The closing is determined by rotating the shaft
until the line "Exhaust closes 2 and 3" comes under the trammel.

This operation is carried on with all the cylinders, it being well to
remember that but one cylinder is working at a time and that a
half-revolution of the fly-wheel corresponds to a full working stroke of
all the cylinders, and that while one is exhausting the others are
respectively taking in a new charge, compressing and exploding. For
instance, if cylinder No. 1 has just completed its power-stroke, the
piston in cylinder No. 3 has reached the point where the gas may be
ignited to advantage. The piston of cylinder No. 4, which is next to
fire, is at the bottom of its stroke and will have inspired a charge,
while cylinder No. 2, which is the last to fire, will have just finished
expelling a charge of burned gas, and will be starting the intake
stroke. This timing relates to a four-cylinder engine in order to
simplify the explanation. The timing instructions given apply only to
the conventional motor types. Rotary cylinder engines, especially the
Gnome "monosoupape," have a distinctive valve timing on account of the
peculiarities of design.

GNOME "MONOSOUPAPE" VALVE TIMING

In the present design of the Gnome motor, a cycle of operations somewhat
different from that employed in the ordinary four-cycle engine is made
use of, says a writer in "The Automobile," in describing the action of
this power-plant. This cycle does away with the need for the usual inlet
valve and makes the engine operable with only a single valve, hence the
name _monosoupape_, or "single-valve." The cycle is as follows: A charge
being compressed in the outer end of the cylinder or combustion chamber,
it is ignited by a spark produced by the spark-plug located in the side
of this chamber, and the burning charge expands as the piston moves down
in the cylinder while the latter revolves around the crank-shaft. When
the piston is about half-way down on the power stroke, the exhaust
valve, which is located in the center of the cylinder-head, is
mechanically opened, and during the following upstroke of the piston the
burnt gases are expelled from the cylinder through the exhaust valve
directly into the atmosphere.

Instead of closing at the end of the exhaust stroke, or a few degrees
thereafter, the exhaust valve is held open for about two-thirds of the
following inlet stroke of the piston, with the result that fresh air is
drawn through the exhaust valve into the cylinder. When the cylinder is
still 65 degrees from the end of the inlet half-revolution, the exhaust
valve closes. As no more air can get into the cylinder, and as the
piston continues to move inwardly, it is obvious that a partial vacuum
is formed.

When the cylinder approaches within 20 degrees of the end of the inlet
half-revolution a series of small inlet ports all around the
circumference of the cylinder wall is uncovered by the top edge of the
piston, whereby the combustion chamber is placed in communication with
the crank chamber. As the pressure in the crank chamber is substantially
atmospheric and that in the combustion chamber is below atmospheric,
there results a suction effect which causes the air from the crank
chamber to flow into the combustion chamber. The air in the crank
chamber is heavily charged with gasoline vapor, which is due to the fact
that a spray nozzle connected with the gasoline supply tank is located
inside the chamber. The proportion of gasoline vapor in the air in the
crank chamber is several times as great as in the ordinary combustible
mixture drawn from a carburetor into the cylinder. This extra-rich
mixture is diluted in the combustion chamber with the air which entered
it through the exhaust valve during the first part of the inlet stroke,
thus forming a mixture of the proper proportion for complete combustion.

The inlet ports in the cylinder wall remain open until 20 degrees of
the compression half-revolution has been completed, and from that moment
to near the end of the compression stroke the gases are compressed in
the cylinder. Near the end of the stroke ignition takes place and this
completes the cycle.

The exact timing of the different phases of the cycle is shown in the
diagram at Fig. 111. It will be seen that ignition occurs substantially
20 degrees ahead of the outer dead center, and expansion of the burning
gases continues until 85 degrees past the outer dead center, when the
piston is a little past half-stroke. Then the exhaust-valve opens and
remains open for somewhat more than a complete revolution of the
cylinders, or, to be exact, for 390 degrees of cylinder travel, until
115 degrees past the top dead center on the second revolution. Then for
45 degrees of travel the charge within the cylinder is expanded,
whereupon the inlet ports are uncovered and remain open for 40 degrees
of cylinder travel, 20 degrees on each side of the inward dead center
position.

SPRINGLESS VALVES

Springless valves are the latest development on French racing car
engines, and it is possible that the positively-operated types will be
introduced on aviation engines also. Two makes of positively-actuated
valves are shown at Fig. 112. The positive-valve motor differs from the
conventional form by having no necessity for valve-springs, as a cam not
only assures the opening of the valve, but also causes it to return to
the valve-seat. In this respect it is much like the sleeve-valve motor,
where the uncovering of the ports is absolutely positive. The cars
equipped with these valves were a success in long-distance auto races.
Claims made for this type of valve mechanism include the possibility of
a higher number of revolutions and consequently greater engine power.
With the spring-controlled, single-cam operated valve a point is reached
where the spring is not capable of returning the valve to its seat
before the cam has again begun its opening movement. It is possible to
extend the limits considerably by using a light valve on a strong
spring, but the valve still remains a limiting factor in the speed of
the motor.

[Illustration: Fig. 111.--Timing Diagram Showing Peculiar Valve Timing
of Gnome "Monosoupape" Rotary Motor.]

A part sectional view through a cylinder of an engine designed by G.
Michaux is shown at Fig. 112, A. There are two valves per cylinder,
inclined at about ten degrees from the vertical. The valve-stems are of
large diameter, as owing to positive control, there is no necessity of
lightening this part in an unusual degree. A single overhead cam-shaft
has eight pairs of cams, which are shown in detail at B. For each valve
there is a three-armed rocker, one arm of which is connected to the stem
of the valve and the two others are in contact respectively with the
opening and closing cams. The connection to the end of the valve-stem is
made by a short connecting link, which is screwed on to the end of the
valve-stem and locked in position. This allows some adjustment to be
made between the valves and the actuating rocker. It will be evident
that one cam and one rocker arm produce the opening of the valve and
that the corresponding rocker arm and cam result in the closing of the
valve. If the opening cam has the usual convex profile, the closing cam
has a correspondingly concave profile. It will be noticed that a light
valve-spring is shown in drawing. This is provided to give a final
seating to its valve after it has been closed by the cam. This is not
absolutely necessary, as an engine has been run successfully without
these springs. The whole mechanism is contained within an overhead
aluminum cover.

[Illustration: Fig. 112.--Two Methods of Operating Valves by Positive
Cam Mechanism Which Closes as Well as Opens Them.]

The positive-valve system used on the De Lage motor is shown at D. In
this the valves are actuated as shown in sectional views D and E. The
valve system is unique in that four valves are provided per cylinder,
two for exhaust and two for intake. The valves are mounted side by side,
as shown at E, so the double actuator member may be operated by a single
set of cams. The valve-operating member consists of a yoke having guide
bars at the top and bottom. The actuating cam works inside of this yoke.
The usual form of cam acts on the lower portion of the yoke to open the
valve, while the concave cam acts on the upper part to close the valves.
In this design provision is made for expansion of the valve-stems due to
heat, and these are not positively connected to the actuating member. As
shown at E, the valves are held against the seat by short coil springs
at the upper end of the stem. These are very stiff and are only intended
to provide for expansion. A slight space is left between the top of the
valve-stem and the portion of the operating member that bears against
them when the regular profile cam exerts its pressure on the bottom of
the valve-operating mechanism. Another novelty in this motor design is
that the cam-shafts and the valve-operating members are carried in
casing attached above the motor by housing supports in the form of small
steel pillars. The overhead cam-shafts are operated by means of bevel
gearing.

FOUR VALVES PER CYLINDER

[Illustration: Fig. 113.--Diagram Comparing Two Large Valves and Four
Small Ones of Practically the Same Area. Note How Easily Small Valves
are Installed to Open Directly Into the Cylinder.]

Mention has been previously made of the sixteen-valve four-cylinder
Duesenberg motor and its great power output for the piston displacement.
This is made possible by the superior volumetric efficiency of a motor
provided with four valves in each cylinder instead of but two. This
principle was thoroughly tried out in racing automobile motors, and is
especially valuable in permitting of greater speed and power output from
simple four- and six-cylinder engines. On eight- and twelve-cylinder
types, it is doubtful if the resulting complication due to using a very
large number of valves would be worth while. When extremely large valves
are used, as shown in diagram at Fig. 113, it is difficult to have them
open directly into the cylinder, and pockets are sometimes necessary. A
large valve would weigh more than two smaller valves having an area
slightly larger in the aggregate; it would require a stiffer valve
spring on account of its greater weight. A certain amount of metal in
the valve-head is necessary to prevent warping; therefore, the inertia
forces will be greater in the large valve than in the two smaller
valves. As a greater port area is obtained by the use of two valves,
the gases will be drawn into the cylinder or expelled faster than with a
lesser area. Even if the areas are practically the same as in the
diagram at Fig. 113, the smaller valves may have a greater lift without
imposing greater stresses on the valve-operating mechanism and quicker
gas intake and exhaust obtained. The smaller valves are not affected by
heat as much as larger ones are. The quicker gas movements made
possible, as well as reduction of inertia forces, permits of higher
rotative speed, and, consequently, greater power output for a given
piston displacement. The drawings at Fig. 114 show a sixteen-valve motor
of the four-cylinder type that has been designed for automobile racing
purposes, and it is apparent that very slight modifications would make
it suitable for aviation purposes. Part of the efficiency is due to the
reduction of bearing friction by the use of ball bearings, but the
multiple-valve feature is primarily responsible for the excellent
performance.

[Illustration: Fig. 114.--Sectional Views of Sixteen-Valve Four-Cylinder
Automobile Racing Engine That May Have Possibilities for Aviation
Service.]

[Illustration: Fig. 115.--Front View of Curtiss OX-3 Aviation Motor,
Showing Unconventional Valve Action by Concentric Push Rod and Pull
Tube.]

CHAPTER IX

Constructional Details of Pistons--Aluminum Cylinders and
Pistons--Piston Ring Construction--Leak Proof Piston Rings--
Keeping Oil Out of Combustion Chamber--Connecting Rod Forms--
Connecting Rods for Vee Engines--Cam-Shaft and Crank-Shaft
Designs--Ball Bearing Crank-Shafts--Engine Base Construction.

CONSTRUCTIONAL DETAILS OF PISTONS

The piston is one of the most important parts of the gasoline motor
inasmuch as it is the reciprocating member that receives the impact of
the explosion and which transforms the power obtained by the combustion
of gas to mechanical motion by means of the connecting rod to which it
is attached. The piston is one of the simplest elements of the motor,
and it is one component which does not vary much in form in different
types of motors. The piston is a cylindrical member provided with a
series of grooves in which packing rings are placed on the outside and
two bosses which serve to hold the wrist pin in its interior. It is
usually made of cast iron or aluminum, though in some motors where
extreme lightness is desired, such as those used for aëronautic work, it
may be made of steel. The use of the more resisting material enables the
engineer to use lighter sections where it is important that the weight
of this member be kept as low as possible consistent with strength.

[Illustration: Fig. 116.--Forms of Pistons Commonly Employed in Gasoline
Engines. A--Dome Head Piston and Three Packing Rings. B--Flat Top Form
Almost Universally Used. C--Concave Piston Utilized in Knight Motors and
Some Having Overhead Valves. D--Two-Cycle Engine Member with Deflector
Plate Cast Integrally. E--Differential of Two-Diameter Piston Used in
Some Engines Operating on Two-Cycle Principle.]

A number of piston types are shown at Fig. 116. That at A has a round
top and is provided with four split packing rings and two oil grooves. A
piston of this type is generally employed in motors where the combustion
chamber is large and where it is desired to obtain a higher degree of
compression than would be possible with a flat top piston. This
construction is also stronger because of the arched piston top. The most
common form of piston is that shown at B, and it differs from that
previously described only in that it has a flat top. The piston outlined
in section at C is a type used on some of the sleeve-valve motors of the
Knight pattern, and has a concave head instead of the convex form shown
at A. The design shown at D in side and plan views is the conventional
form employed in two-cycle engines. The deflector plate on the top of
the cylinder is cast integral and is utilized to prevent the incoming
fresh gases from flowing directly over the piston top and out of the
exhaust port, which is usually opposite the inlet opening. On these
types of two-cycle engines where a two-diameter cylinder is employed,
the piston shown at E is used. This is known as a "differential
piston," and has an enlarged portion at its lower end which fits the
pumping cylinder. The usual form of deflector plate is provided at the
top of the piston and one may consider it as two pistons in one.

[Illustration: Fig. 117.--Typical Methods of Piston Pin Retention
Generally Used in Engines of American Design. A--Single Set Screw and
Lock Nut. B--Set Screw and Check Nut Fitting Groove in Wrist Pin. C,
D--Two Locking Screws Passing Into Interior of Hollow Wrist Pin.
E--Split Ring Holds Pin in Place. F--Use of Taper Expanding Plugs
Outlined. G--Spring Pressed Plunger Type. H--Piston Pin Pinned to
Connecting Rod. I--Wrist Pin Clamped in Connecting Rod Small End by
Bolt.]

[Illustration: Fig. 118.--Typical Piston and Connecting Rod Assembly.]

[Illustration: Fig. 119.--Parts of Sturtevant Aviation Engine.
A--Cylinder Head Showing Valves. B--Connecting Rod. C--Piston and
Rings.]

One of the important conditions in piston design is the method of
securing the wrist pin which is used to connect the piston to the upper
end of the connecting rod. Various methods have been devised to keep the
pin in place, the most common of these being shown at Fig. 117. The
wrist pin should be retained by some positive means which is not liable
to become loose under the vibratory stresses which obtain at this point.
If the wrist pin was free to move it would work out of the bosses
enough so that the end would bear against the cylinder wall. As it is
usually made of steel, which is a harder material than cast iron used in
cylinder construction, the rubbing action would tend to cut a groove in
the cylinder wall which would make for loss of power because it would
permit escape of gas. The wrist pin member is a simple cylindrical
element that fits the bosses closely, and it may be either hollow or
solid stock. A typical piston and connecting rod assembly which shows a
piston in section also is given at Fig. 118. The piston of the
Sturtevant aëronautical motor is shown at Fig. 119, the aluminum piston
of the Thomas airplane motor with piston rings in place is shown at Fig.
120. A good view of the wrist pin and connecting rod are also given. The
iron piston of the Gnome "Monosoupape" airplane engine and the
unconventional connecting rod assembly are clearly depicted at Fig 121.

[Illustration: Fig. 120.--Aluminum Piston and Light But Strong Steel
Connecting Rod and Wrist Pin of Thomas Aviation Engine.]

The method of retention shown at A is the simplest and consists of a set
screw having a projecting portion passing into the wrist pin and
holding it in place. The screw is kept from turning or loosening by
means of a check nut. The method outlined at B is similar to that shown
at A, except that the wrist pin is solid and the point of the set screw
engages an annular groove turned in the pin for its reception. A very
positive method is shown at C. Here the retention screws pass into the
wrist pin and are then locked by a piece of steel wire which passes
through suitable holes in the ends. The method outlined at D is
sometimes employed, and it varies from that shown at C only in that the
locking wire, which is made of spring steel, is passed through the heads
of the locking screws. Some designers machine a large groove around the
piston at such a point that when the wrist pin is put in place a large
packing ring may be sprung in the groove and utilized to hold the wrist
pin in place.

[Illustration: Fig. 121.--Cast Iron Piston of "Monosoupape" Gnome Engine
Installed On One of the Short Connecting Rods.]

The system shown at F is not so widely used as the simpler methods,
because it is more costly and does not offer any greater security when
the parts are new than the simple lock shown at A. In this a hollow
wrist pin is used, having a tapered thread cut at each end. The wrist
pin is slotted at three or four points, for a distance equal to the
length of the boss, and when taper expansion plugs are screwed in place
the ends of the wrist pin are expanded against the bosses. This method
has the advantage of providing a certain degree of adjustment if the
wrist pin should loosen up after it has been in use for some time. The
taper plugs would be screwed in deeper and the ends of the wrist pin
expanded proportionately to take up the loss motion. The method shown at
G is an ingenious one. One of the piston bosses is provided with a
projection which is drilled out to receive a plunger. The wrist pin is
provided with a hole of sufficient size to receive the plunger, which is
kept in place by means of a spring in back of it. This makes a very
positive lock and one that can be easily loosened when it is desired to
remove the wrist pin. To unlock, a piece of fine rod is thrust into the
hole at the bottom of the boss which pushes the plunger back against the
spring until the wrist pin can be pushed out of the piston.

Some engineers think it advisable to oscillate the wrist pin in the
piston bosses, instead of in the connecting rod small end. It is argued
that this construction gives more bearing surface at the wrist pin and
also provides for more strength because of the longer bosses that can be
used. When this system is followed the piston pin is held in place by
locking it to the connecting rod by some means. At H the simplest method
is outlined. This consisted of driving a taper pin through both rod and
wrist pin and then preventing it from backing out by putting a split
cotter through the small end of the tapered locking pin. Another method,
which is depicted at I, consists of clamping the wrist pin by means of a
suitable bolt which brings the slit connecting rod end together as
shown.

ALUMINUM FOR CYLINDERS AND PISTONS

Aluminum pistons outlined at Fig. 122, have replaced cast iron members
in many airplane engines, as these weigh about one-third as much as the
cast iron forms of the same size, while the reduction in the inertia
forces has made it possible to increase the engine speed without
correspondingly stressing the connecting rods, crank-shaft and engine
bearings.

[Illustration: Fig. 122.--Types of Aluminum Pistons Used In Aviation
Engines.]

Aluminum has not only been used for pistons, but a number of motors will
be built for the coming season that will use aluminum cylinder block
castings as well. Of course, the aluminum alloy is too soft to be used
as a bearing for the piston, and it will not withstand the hammering
action of the valve. This makes the use of cast iron or steel imperative
in all motors. When used in connection with an aluminum cylinder block
the cast iron pieces are placed in the mould so that they act as
cylinder liners and valve seats, and the molten metal is poured around
them when the cylinder is cast. It is said that this construction
results in an intimate bond between the cast iron and the surrounding
aluminum metal. Steel liners may also be pressed into the aluminum
cylinders after these are bored out to receive them. Aluminum has for a
number of years been used in many motor car parts. Alloys have been
developed that have greater strength than cast iron and that are not so
brittle. Its use for manifolds and engine crank and gear cases has been
general for a number of years.

At first thought it would seem as though aluminum would be entirely
unsuited for use in those portions of internal combustion engines
exposed to the heat of the explosion, on account of the low melting
point of that metal and its disadvantageous quality of suddenly
"wilting" when a critical point in the temperature is reached. Those who
hesitated to use aluminum on account of this defect lost sight of the
great heat conductivity of that metal, which is considerably more than
that of cast iron. It was found in early experiments with aluminum
pistons that this quality of quick radiation meant that aluminum pistons
remained considerably cooler than cast iron ones in service, which was
attested to by the reduced formation of carbon deposit thereon. The use
of aluminum makes possible a marked reduction in power plant weight. A
small four-cylinder engine which was not particularly heavy even with
cast iron cylinders was found to weigh 100 pounds less when the cylinder
block, pistons, and upper half of the crank-case had been made of
aluminum instead of cast iron. Aluminum motors are no longer an
experiment, as a considerable number of these have been in use on cars
during the past year without the owners of the cars being apprised of
the fact. Absolutely no complaint was made in any case of the aluminum
motor and it was demonstrated, in addition to the saving in weight, that
the motors cost no more to assemble and cooled much more efficiently
than the cast iron form. One of the drawbacks to the use of aluminum is
its growing scarcity, which results in making it a "near precious"
metal.

PISTON RING CONSTRUCTION

As all pistons must be free to move up and down in the cylinder with
minimum friction, they must be less in diameter than the bore of the
cylinder. The amount of freedom or clearance provided varies with the
construction of the engine and the material the piston is made of, as
well as its size, but it is usual to provide from .005 to .010 of an
inch to compensate for the expansion of the piston due to heat and also
to leave sufficient clearance for the introduction of lubricant between
the working surfaces. Obviously, if the piston were not provided with
packing rings, this amount of clearance would enable a portion of the
gases evolved when the charge is exploded to escape by it into the
engine crank-case. The packing members or piston rings, as they are
called, are split rings of cast iron, which are sprung into suitable
grooves machined on the exterior of the piston, three or four of these
being the usual number supplied. These have sufficient elasticity so
that they bear tightly against the cylinder wall and thus make a
gas-tight joint. Owing to the limited amount of surface in contact with
the cylinder wall and the elasticity of the split rings the amount of
friction resulting from the contact of properly fitted rings and the
cylinder is not of enough moment to cause any damage and the piston is
free to slide up and down in the cylinder bore.

[Illustration: Fig. 123.--Types of Piston Rings and Ring Joints.
A--Concentric Ring. B--Eccentrically Machined Form. C--Lap Joint Ring.
D--Butt Joint, Seldom Used. E--Diagonal Cut Member, a Popular Form.]

These rings are made in two forms, as outlined at Fig. 123. The design
shown at A is termed a "concentric ring," because the inner circle is
concentric with the outer one and the ring is of uniform thickness at
all points. The ring shown at B is called an "eccentric ring," and it is
thicker at one part than at others. It has theoretical advantages in
that it will make a tighter joint than the other form, as it is claimed
its expansion due to heat is more uniform. The piston rings must be
split in order that they may be sprung in place in the grooves, and also
to insure that they will have sufficient elasticity to take the form of
the cylinder at the different points in their travel. If the cylinder
bore varies by small amounts the rings will spring out at the points
where the bore is larger than standard, and spring in at those portions
where it is smaller than standard.

It is important that the joint should be as nearly gas-tight as
possible, because if it were not a portion of the gases would escape
through the slots in the piston rings. The joint shown at C is termed a
"lap joint," because the ends of the ring are cut in such a manner that
they overlap. This is the approved joint. The butt joint shown at D is
seldom used and is a very poor form, the only advantage being its
cheapness. The diagonal cut shown at E is a compromise between the very
good form shown at C and the poor joint depicted at D. It is also widely
used, though most constructors prefer the lap joint, because it does not
permit the leakage of gas as much as the other two types.

There seems to be some difference of opinion relative to the best piston
ring type--some favoring the eccentric pattern, others the concentric
form. The concentric ring has advantages from the lubricating engineer's
point of view; as stated by the Platt & Washburn Company in their
text-book on engine lubrication, the smaller clearance behind the ring
possible with the ring of uniform section is advantageous.

Fig. 124, A, shows a concentric piston ring in its groove. Since the
ring itself is concentric with the groove, very small clearance between
the back of the ring and the bottom of its groove may be allowed. Small
clearance leaves less space for the accumulation of oil and carbon
deposits. The gasket effect of this ring is uniform throughout the
entire length of its edges, which is its marked advantage over the
eccentric ring. This type of piston ring rarely burns fast in its
groove. There are a large number of different concentric rings
manufactured of different designs and of different efficiency.

[Illustration: Fig. 124.--Diagrams Showing Advantages of Concentric
Piston Rings.]

Figs. 124, B and 124, C show eccentric rings assembled in the ring
groove. It will be noted that there is a large space between the thin
ends of this ring and the bottom of the groove. This empty space fills
up with oil which in the case of the upper ring frequently is
carbonized, restricting the action of the ring and nullifying its
usefulness. The edges of the thin ends are not sufficiently wide to
prevent rapid escape of gases past them. In a practical way this leakage
means loss of compression and noticeable drop in power. When new and
properly fitted, very little difference can be noted between the
tightness of eccentric and concentric rings. Nevertheless, after several
months' use, a more rapid leakage will always occur past the eccentric
than past the concentric. If continuous trouble with the carbonization
of cylinders, smoking and sooting of spark-plugs is experienced, it is
a sure indication that mechanical defects exist in the engine, assuming
of course, that a suitable oil has been used. Such trouble can be
greatly lessened, if not entirely eliminated, by the application of
concentric rings (lap joint), of any good make, properly fitted into the
grooves of the piston. Too much emphasis cannot be put upon this point.
If the oil used in the engine is of the correct viscosity, and serious
carbon deposit, smoking, etc., still result, the only certain remedy
then is to have the cylinders rebored and fitted with properly designed,
oversized pistons and piston rings.

LEAK-PROOF PISTON RINGS

In order to reduce the compression loss and leakage of gas by the
ordinary simple form of diagonal or lap joint one-piece piston ring a
number of compound rings have been devised and are offered by their
makers to use in making replacements. The leading forms are shown at
Fig. 125. That shown at A is known as the "Statite" and consists of
three rings, one carried inside while the other two are carried on the
outside. The ring shown at B is a double ring and is known as the
McCadden. This is composed of two thin concentric lap joint rings so
disposed relative to each other that the opening in the inner ring comes
opposite to the opening in the outer ring.

The form shown at C is known as the "Leektite," and is a single ring
provided with a peculiar form of lap and dove tail joint. The ring shown
at D is known as the "Dunham" and is of the double concentric type being
composed of two rings with lap joints which are welded together at a
point opposite the joint so that there is no passage by which the gas
can escape. The Burd high compression ring is shown at E. The joints of
these rings are sealed by means of an H-shaped coupler of bronze which
closes the opening. The ring ends are made with tongues which interlock
with the coupling. The ring shown at F is called the "Evertite" and is
a three-piece ring composed of three members as shown in the sectional
view below the ring. The main part or inner ring has a circumferential
channel in which the two outer rings lock, the resulting cross-section
being rectangular just the same as that of a regular pattern ring. All
three rings are diagonally split and the joints are spaced equally and
the distances maintained by small pins. This results in each joint being
sealed by the solid portion of the other rings.

[Illustration: Fig. 125.--Leak-Proof and Other Compound Piston Rings.]

The use of a number of light steel rings instead of one wide ring in the
groove is found on a number of automobile power plants, but as far as
known, this construction is not used in airplane power plants. It is
contended that where a number of light rings is employed a more flexible
packing means is obtained and the possibility of leakage is reduced.
Rings of this design are made of square section steel wire and are given
a spring temper. Owing to the limited width the diagonal cut joint is
generally employed instead of the lap joint which is so popular on wider
rings.

KEEPING OIL OUT OF COMBUSTION CHAMBERS

An examination of the engine design that is economical in oil
consumption discloses the use of tight piston rings, large centrifugal
rings on the crank-shaft where it passes through the case, ample cooling
fins in the pistons, vents between the crank-case chamber and the valve
enclosures, etc. Briefly put, cooling of the oil in this engine has been
properly cared for and leakage reduced to a minimum. To be specific
regarding details of design: Oil surplus can be kept out of the
explosion chambers by leaving the lower edge of the piston skirt sharp
and by the use of a shallow groove (C), Fig. 126, just below the lower
piston ring. Small holes are bored through the piston walls at the base
of this groove and communicate with the crank-case. The similarity of
the sharp edges of piston skirt (D) and piston ring to a carpenter's
plane bit, makes their operation plain.

[Illustration: Fig. 126.--Sectional View of Engine Showing Means of
Preventing Oil Leakage By Piston Rings.]

The cooling of oil in the sump (A) can be accomplished most effectively
by radiating fins on its outer surface. The lower crank-case should be
fully exposed to the outer air. A settling basin for sediment (B) should
be provided having a cubic content not less than one-tenth of the total
oil capacity as outlined at Fig. 126. The depth of this basin should be
at least 2-1/2 inches, and its walls vertical, as shown, to reduce the
mixing of sediment with the oil in circulation. The inlet opening to the
oil pump should be near the top of the sediment basin in order to
prevent the entrance into the pump with the oil of any solid matter or
water condensed from the products of combustion. This sediment basin
should be drained after every five to seven hours air service of an
airplane engine. Concerning filtering screens there is little to be
said, save that their areas should be ample and the mesh coarse enough
(one-sixteenth of an inch) to offer no serious resistance to the free
flow of cold or heavy oil through them; otherwise the oil in the
crank-case may build up above them to an undesirable level. The
necessary frequency of draining and flushing out the oil sump differs
greatly with the age (condition) of the engine and the suitability of
the oil used. In broad terms, the oil sump of a new engine should be
thoroughly drained and flushed with kerosene at the end of the first
200 miles, next at the end of 500 miles and thereafter every 1,000
miles. While these instructions apply specifically to automobile motors,
it is very good practice to change the oil in airplane engines
frequently. In many cases, the best results have been secured when the
oil supply is completely replenished every five hours that the engine is
in operation.

CONNECTING ROD FORMS

The connecting rod is the simple member that joins the piston to the
crank-shaft and which transmits the power imparted to the piston by the
explosion so that it may be usefully applied. It transforms the
reciprocating movement of the piston to a rotary motion at the
crank-shaft. A typical connecting rod and its wrist pin are shown at
Fig. 120. It will be seen that it has two bearings, one at either end.
The small end is bored out to receive the wrist pin which joins it to
the piston, while the large end has a hole of sufficient size to go on
the crank-pin. The airplane and automobile engine connecting rod is
invariably a steel forging, though in marine engines it is sometimes
made a steel or high tensile strength bronze casting. In all cases it is
desirable to have softer metals than the crank-shaft and wrist pin at
the bearing point, and for this reason the connecting rod is usually
provided with bushings of anti-friction or white metal at the lower end,
and bronze at the upper. The upper end of the connecting rod may be one
piece, because the wrist pin can be introduced after it is in place
between the bosses of the piston. The lower bearing must be made in two
parts in most cases, because the crank-shaft cannot be passed through
the bearing owing to its irregular form. The rods of the Gnome engine
are all one piece types, as shown at Fig. 127, owing to the construction
of the "mother" rod which receives the crank-pins. The complete
connecting rod assembly is shown in Fig. 121, also at A, Fig. 127. The
"mother" rod, with one of the other rods in place and one about to be
inserted, is shown at Fig. 127, B. The built-up crank-shaft which makes
this construction feasible is shown at Fig. 127, C.

[Illustration: Fig. 127.--Connecting Rod and Crank-Shaft Construction of
Gnome "Monosoupape" Engine.]

Some of the various designs of connecting rods that have been used are
shown at Fig. 128. That at A is a simple form often employed in
single-cylinder motors, having built-up crank-shafts. Both ends of the
connecting rod are bushed with a one-piece bearing, as it can be
assembled in place before the crank-shaft assembly is built up. A
built-up crank-shaft such as this type of connecting rod would be used
with is shown at Fig. 106. The pattern shown at B is one that has been
used to some extent on heavy work, and is known as the "marine type." It
is made in three pieces, the main portion being a steel forging having a
flanged lower end to which the bronze boxes are secured by bolts. The
modified marine type depicted at C is the form that has received the
widest application in automobile and aviation engine construction. It
consists of two pieces, the main member being a steel drop forging
having the wrist-pin bearing and the upper crank-pin bearing formed
integral, while the lower crank-pin bearing member is a separate forging
secured to the connecting rod by bolts. In this construction bushings of
anti-friction metal are used at the lower end, and a bronze bushing is
forced into the upper- or wrist-pin end. The rod shown at D has also
been widely used. It is similar in construction to the form shown at C,
except that the upper end is split in order to permit of a degree of
adjustment of the wrist-pin bushing, and the lower bearing cap is a
hinged member which is retained by one bolt instead of two. When it is
desired to assemble it on the crank-shaft the lower cap is swung to one
side and brought back into place when the connecting rod has been
properly located. Sometimes the lower bearing member is split diagonally
instead of horizontally, such a construction being outlined at E.

[Illustration: Fig. 128.--Connecting Rod Types Summarized.
A--Single Connecting Rod Made in One Piece, Usually Fitted in Small
Single-Cylinder Engines Having Built-Up Crank-Shafts. B--Marine Type, a
Popular Form on Heavy Engines. C--Conventional Automobile Type, a
Modified Marine Form. D--Type Having Hinged Lower Cap and Split Wrist
Pin Bushing. E--Connecting Rod Having Diagonally Divided Big End.
F--Ball-Bearing Rod. G--Sections Showing Structural Shapes Commonly
Employed in Connecting Rod Construction.]

In a number of instances, instead of plain bushed bearings anti-friction
forms using ball or rollers have been used at the lower end. A
ball-bearing connecting rod is shown at F. The big end may be made in
one piece, because if it is possible to get the ball bearing on the
crank-pins it will be easy to put the connecting rod in place. Ball
bearings are not used very often on connecting rod big ends because of
difficulty of installation, though when applied properly they give
satisfactory service and reduce friction to a minimum. One of the
advantages of the ball bearing is that it requires no adjustment,
whereas the plain bushings depicted in the other connecting rods must be
taken up from time to time to compensate for wear.

This can be done in forms shown at B, C, D, and E by bringing the lower
bearing caps closer to the upper one and scraping out the brasses to fit
the shaft. A number of liners or shims of thin brass or copper stock,
varying from .002 inch to .005 inch, are sometimes interposed between
the halves of the bearings when it is first fitted to the crank-pin. As
the brasses wear the shims may be removed and the portions of the
bearings brought close enough together to take up any lost motion that
may exist, though in some motors no shims are provided and depreciation
can be remedied only by installing new brasses and scraping to fit.

[Illustration: Fig. 129.--Double Connecting Rod Assembly For Use On
Single Crank-Pin of Vee Engine.]

The various structural shapes in which connecting rods are formed are
shown in section at G. Of these the I section is most widely used in
airplane engines, because it is strong and a very easy shape to form by
the drop-forging process or to machine out of the solid bar when extra
good steel is used. Where extreme lightness is desired, as in small
high-speed motors used for cycle propulsion, the section shown at the
extreme left is often used. If the rod is a cast member as in some
marine engines, the cross, hollow cylinder, or U sections are sometimes
used. If the sections shown at the right are employed, advantage is
often taken of the opportunity for passing lubricant through the center
of the hollow round section on vertical motors or at the bottom of the U
section, which would be used on a horizontal cylinder power plant.

[Illustration: Fig. 130.--Another Type of Double Connecting Rod for Vee
Engines.]

Connecting rods of Vee engines are made in two distinct styles. The
forked or "scissors" joint rod assembly is employed when the cylinders
are placed directly opposite each other. The "blade" rod, as shown at
Fig. 129, fits between the lower ends of the forked rod, which oscillate
on the bearing which encircles the crank-pin. The lower end of the
"blade" rod is usually attached to the bearing brasses, the ends of the
"forked" rod move on the outer surfaces of the brasses. Another form of
rod devised for use under these conditions is shown at Fig. 130 and
installed in an aviation engine at Fig. 132. In this construction the
shorter rod is attached to a boss on the master rod by a short pin to
form a hinge and to permit the short rod to oscillate as the conditions
dictate. This form of rod can be easily adjusted when the bearing
depreciates, a procedure that is difficult with the forked type rod. The
best practice, in the writer's opinion, is to stagger the cylinders and
use side-by-side rods as is done in the Curtiss engine. Each rod may be
fitted independently of the other and perfect compensation for wear of
the big ends is possible.

[Illustration: Fig. 131.--Part Sectional View of Wisconsin Aviation
Engine, Showing Four-Bearing Crank-Shaft, Overhead Cam-Shaft, and Method
of Combining Cylinders in Pairs.]

[Illustration: Fig. 132.--Part Sectional View of Renault Twelve-Cylinder
Water-Cooled Engine, Showing Connecting Rod Construction and Other
Important Internal Parts.]

CAM-SHAFT AND CRANK-SHAFT DESIGN

Before going extensively into the subject of crank-shaft construction it
will be well to consider cam-shaft design, which is properly a part of
the valve system and which has been considered in connection with the
other elements which have to do directly with cylinder construction to
some extent. Cam-shafts are usually simple members carried at the base
of the cylinder in the engine case of Vee type motors by suitable
bearings and having the cams employed to lift the valves attached at
intervals. A typical cam-shaft design is shown at Fig. 133. Two main
methods of cam-shaft construction are followed--that in which the cams
are separate members, keyed and pinned to the shaft, and the other where
the cams are formed integral, the latter being the most suitable for
airplane engine requirements.

[Illustration: Fig. 133.--Typical Cam-Shaft, with Valve Lifting Cams and
Gears to Operate Auxiliary Devices Forged Integrally.]

The cam-shafts shown at Figs. 133 and 134, B, are of the latter type, as
the cams are machined integrally. In this case not only the cams but
also the gears used in driving the auxiliary shafts are forged integral.
This is a more expensive construction, because of the high initial cost
of forging dies as well as the greater expense of machining. It has the
advantage over the other form in which the cams are keyed in place in
that it is stronger, and as the cams are a part of the shaft they can
never become loose, as might be possible where they are separately
formed and assembled on a simple shaft.

[Illustration: Fig. 134.--Important Parts of Duesenberg Aviation Engine.
A--Three Main Bearing Crank-Shaft. B--Cam-Shaft with Integral Cams.
C--Piston and Connecting Rod Assembly. D--Valve Rocker Group. E--Piston.
F--Main Bearing Brasses.]

The importance of the crank-shaft has been previously considered, and
some of its forms have been shown in views of the motors presented in
earlier portions of this work. The crank-shaft is one of the parts
subjected to the greatest strain and extreme care is needed in its
construction and design, because practically the entire duty of
transmitting the power generated by the motor to the gearset devolves
upon it. Crank-shafts are usually made of high tensile strength steel of
special composition. They may be made in four ways, the most common
being from a drop or machine forging which is formed approximately to
the shape of the finished shaft and in rare instances (experimental
motors only) they may be steel castings. Sometimes they are made from
machine forgings, where considerably more machine work is necessary than
would be the case where the shaft is formed between dies. Some engineers
favor blocking the shaft out of a solid slab of metal and then machining
this rough blank to form. In some radial-cylinder motors of the Gnome
and Le Rhone type the crank-shafts are built up of two pieces, held
together by taper fastenings or bolts.

[Illustration: Fig. 135.--Showing Method of Making Crank-Shaft. A--The
Rough Steel Forging Before Machining. B--The Finished Six-Throw,
Seven-Bearing Crank-Shaft.]

The form of the shaft depends on the number of cylinders and the form
has material influence on the method of construction. For instance, a
four-cylinder crank-shaft could be made by either of the methods
outlined. On the other hand, a three- or six-cylinder shaft is best made
by the machine forging process, because if drop forged or cut from the
blank it will have to be heated and the crank throws bent around so that
the pins will lie in three planes one hundred and twenty degrees apart,
while the other types described need no further attention, as the
crank-pins lie in planes one hundred and eighty degrees apart. This can
be better understood by referring to Fig. 135, which shows a
six-cylinder shaft in the rough and finished stages. At A the
appearance of the machine forging before any of the material is removed
is shown, while at B the appearance of the finished crank-shaft is
clearly depicted. The built-up crank-shaft is seldom used on
multiple-cylinder motors, except in some cases where the crank-shafts
revolve on ball bearings as in some automobile racing engines.

[Illustration: Fig. 136.--Showing Form of Crank-Shaft for Twin-Cylinder
Opposed Power Plant.]

[Illustration: Fig. 137.--Crank-Shaft of Thomas-Morse Eight-Cylinder Vee
Engine.]

Crank-shaft form will vary with a number of cylinders and it is possible
to use a number of different arrangements of crank-pins and bearings for
the same number of cylinders. The simplest form of crank-shaft is that
used on simple radial cylinder motors as it would consist of but one
crank-pin, two webs, and the crank-shaft. As the number of cylinders
increase in Vee motors as a general rule more crank-pins are used. The
crank-shaft that would be used on a two-cylinder opposed motor is shown
at Fig. 136. This has two throws and the crank-pins are spaced 180
degrees apart. The bearings are exceptionally long. Four-cylinder
crank-shafts may have two, three or five main bearings and three or four
crank-pins. In some forms of two-bearing crank-shafts, such as used when
four-cylinders are cast in a block, or unit casting, two of the pistons
are attached to one common crank-pin, so that in reality the crank-shaft
has but three crank-pins. A typical three bearing, four-cylinder
crank-shaft is shown at Fig. 134, A. The same type can be used for an
eight-cylinder Vee engine, except for the greater length of crank-pins
to permit of side by side rods as shown at Fig. 137. Six cylinder
vertical tandem and twelve-cylinder Vee engine crank-shafts usually have
four or seven main bearings depending upon the disposition of the
crank-pins and arrangement of cylinders. At Fig. 138, A, the bottom
view of a twelve-cylinder engine with bottom half of crank case removed
is given. This illustrates clearly the arrangement of main bearings when
the crank-shaft is supported on four journals. The crank-shaft shown at
Fig. 138, B, is a twelve-cylinder seven-bearing type.

[Illustration: Fig. 138.--Crank-Case and Crank-Shaft Construction for
Twelve-Cylinder Motors. A--Duesenberg. B--Curtiss.]

[Illustration: Fig. 139.--Counterbalanced Crank-Shafts Reduce Engine
Vibration and Permit of Higher Rotative Speeds.]

In some automobile engines, extremely good results have been secured in
obtaining steady running with minimum vibration by counterbalancing the
crank-shafts as outlined at Fig. 139. The shaft at A is a type suitable
for a high speed four-cylinder vertical or an eight-cylinder Vee type.
That at B is for a six-cylinder vertical or a twelve-cylinder V with
scissors joint rods. If counterbalancing crank-shafts helps in an
automobile engine, it should have advantages of some moment in airplane
engines, even though the crank-shaft weight is greater.

BALL-BEARING CRANK-SHAFTS

While crank-shafts are usually supported in plain journals there seems
to be a growing tendency of late to use anti-friction bearings of the
ball type for their support. This is especially noticeable on block
motors where but two main bearings are utilized. When ball bearings are
selected with proper relation to the load which obtains they will give
very satisfactory service. They permit the crank-shaft to turn with
minimum friction, and if properly selected will never need adjustment.
The front end is supported by a bearing which is clamped in such a
manner that it will take a certain amount of load in a direction
parallel to the axis of the shaft, while the rear end is so supported
that the outer race of the bearing has a certain amount of axial freedom
or "float." The inner race or cone of each bearing is firmly clamped
against shoulders on the crank-shaft. At the front end of the
crank-shaft timing gear and a suitable check nut are used, while at the
back end the bearing is clamped by a threaded retention member between
the fly-wheel and a shoulder on the crank-shaft. The fly-wheel is held
in place by a taper and key retention. The ball bearings are carried in
a light housing of bronze or malleable iron, which in turn are held in
the crank-case by bolts. The Renault engine uses ball bearings at front
and rear ends of the crank-shaft, but has plain bearings around
intermediate crank-shaft journals. The rotary engines of the Gnome, Le
Rhone and Clerget forms would not be practical if ball bearings were not
used as the bearing friction and consequent depreciation would be very
high.

ENGINE-BASE CONSTRUCTION

One of the important parts of the power plant is the substantial casing
or bed member, which is employed to support the cylinders and
crank-shaft and which is attached directly to the fuselage engine
supporting members. This will vary widely in form, but as a general
thing it is an approximately cylindrical member which may be divided
either vertically or horizontally in two or more parts. Airplane engine
crank-cases are usually made of aluminum, a material which has about the
same strength as cast iron, but which only weighs a third as much. In
rare cases cast iron is employed, but is not favored by most engineers
because of its brittle nature, great weight and low resistance to
tensile stresses. Where exceptional strength is needed alloys of bronze
may be used, and in some cases where engines are produced in large
quantities a portion of the crank-case may be a sheet steel or aluminum
stamping.

[Illustration: Fig. 140.--View of Thomas 135 Horse-Power Aeromotor,
Model 8, Showing Conventional Method of Crank-Case Construction.]

[Illustration: Fig. 141.--Views of Upper Half of Thomas Aeromotor
Crank-Case.]

Crank-cases are always large enough to permit the crank-shaft and parts
attached to it to turn inside and obviously its length is determined by
the number of cylinders and their disposition. The crank-case of the
radial cylinder or double-opposed cylinder engine would be substantially
the same in length. That of a four-cylinder will vary in length with
the method of casting the cylinder. When the four-cylinders are cast in
one unit and a two-bearing crank-shaft is used, the crank-case is a very
compact and short member. When a three-bearing crank-shaft is utilized
and the cylinders are cast in pairs, the engine base is longer than it
would be to support a block casting, but is shorter than one designed to
sustain individual cylinder castings and a five-bearing crank-shaft. It
is now common construction to cast an oil container integral with the
bottom of the engine base and to draw the lubricating oil from it by
means of a pump, as shown at Fig. 140. The arms by which the motor is
supported in the fuselage are substantial-ribbed members cast
integrally with the upper half.

[Illustration: Fig. 142.--Method of Constructing Eight-Cylinder Vee
Engine, Possible if Aluminum Cylinder and Crank-Case Castings are Used.]

[Illustration: Fig. 143.--Simple and Compact Crank-Case, Possible When
Radial Cylinder Engine Design is Followed.]

The approved method of crank-case construction favored by the majority
of engineers is shown at the top of Fig. 141, bottom side up. The upper
half not only forms a bed for the cylinder but is used to hold the
crank-shaft as well. In the illustration, the three-bearing boxes form
part of the case, while the lower brasses are in the form of separately
cast caps retained by suitable bolts. In the construction outlined the
bottom part of the case serves merely as an oil container and a
protection for the interior mechanism of the motor. The cylinders are
held down by means of studs screwed into the crank-case top, as shown at
Fig. 141, lower view. If the aluminum cylinder motor has any future, the
method of construction outlined at Fig. 142, which has been used in cast
iron for an automobile motor, might be used for an eight-cylinder Vee
engine for airplane use. The simplicity of the crank-case needed for a
revolving cylinder motor and its small weight can be well understood by
examination of the illustration at Fig. 143, which shows the engine
crank-case for the nine-cylinder "Monosoupape" Gnome engine. This
consists of two accurately machined forgings held together by bolts as
clearly indicated.

CHAPTER X

The proper installation of the airplane power plant is more important
than is generally supposed, as while these engines are usually well
balanced and run with little vibration, it is necessary that they be
securely anchored and that various connections to the auxiliary parts be
carefully made in order to prevent breakage from vibration and that
attendant risk of motor stoppage while in the air. The type of motor to
be installed determines the method of installation to be followed. As a
general rule six-cylinder vertical engine and eight-cylinder Vee type
are mounted in substantially the same way. The radial, fixed cylinder
forms and the radial, rotary cylinder Gnome and Le Rhone rotary types
require an entirely different method of mounting. Some unconventional
mountings have been devised, notably that shown at Fig. 144, which is a
six-cylinder German engine that is installed in just the opposite way to
that commonly followed. The inverted cylinder construction is not
generally followed because even with pressure feed, dry crank-case type
lubricating system there is considerable danger of over-lubrication and
of oil collecting and carbonizing in the combustion chamber and gumming
up the valve action much quicker than would be the case if the engine
was operated in the conventional upright position. The reason for
mounting an engine in this way is to obtain a lower center of gravity
and also to make for more perfect streamlining of the front end of the
fuselage in some cases. It is rather doubtful if this slight advantage
will compensate for the disadvantages introduced by this unusual
construction. It is not used to any extent now but is presented merely
to show one of the possible systems of installing an airplane engine.

[Illustration: Fig. 144.--Unconventional Mounting of German Inverted
Cylinder Motor.]

[Illustration: Fig. 145.--How Curtiss Model OX-2 Motor is Installed in
Fuselage of Curtiss Tractor Biplane. Note Similarity of Mounting to
Automobile Power Plant.]

In a number of airplanes of the tractor-biplane type the power plant
installation is not very much different than that which is found in
automobile practice. The illustration at Fig. 145 is a very clear
representation of the method of mounting the Curtiss eight-cylinder 90
H. P. or model OX-2 engine in the fuselage of the Curtiss JN-4 tractor
biplane which is so generally used in the United States as a training
machine. It will be observed that the fuel tank is mounted under a cowl
directly behind the motor and that it feeds the carburetor by means of
a flexible fuel pipe. As the tank is mounted higher than the
carburetor, it will feed that member by gravity. The radiator is mounted
at the front end of the fuselage and connected to the water piping on
the motor by the usual rubber hose connections. An oil pan is placed
under the engine and the top is covered with a hood just as in motor car
practice. The panels of aluminum are attached to the sides of the
fuselage and are supplied with doors which open and provide access to
the carburetor, oil-gauge and other parts of the motor requiring
inspection. The complete installation with the power plant enclosed is
given at Fig. 146, and in this it will be observed that the exhaust
pipes are connected to discharge members that lead the gases above the
top plane. In the engine shown at Fig. 145 the exhaust flows directly
into the air at the sides of the machine through short pipes bolted to
the exhaust gas outlet ports. The installation of the radiator just
back of the tractor screw insures that adequate cooling will be obtained
because of the rapid air flow due to the propeller slip stream.

[Illustration: Fig. 146.--Latest Model of Curtiss JN-4 Training Machine,
Showing Thorough Enclosure of Power Plant and Method of Disposing of the
Exhaust Gases.]

INSTALLATION OF CURTISS OX-2 ENGINE

[Illustration: Fig. 147.--Front View of L. W. F. Tractor Biplane
Fuselage, Showing Method of Installing Thomas Aeromotor and Method of
Disposing of Exhaust Gases.]

The following instructions are given in the Curtiss Instruction Book for
installing the OX-2 engine and preparing it for flights, and taken in
connection with the very clear illustration presented no difficulty
should be experienced in understanding the proper installation, and
mounting of this power plant. The bearers or beds should be 2 inches
wide by 3 inches deep, preferably of laminated hard wood, and placed
11-5/8 inches apart. They must be well braced. The six arms of the base
of the motor are drilled for 3/8-inch bolts, and none but this size
should he used.

1. _Anchoring the Motor._ Put the bolts in from the bottom, with a large
washer under the head of each so the head cannot cut into the wood. On
every bolt use a castellated nut and a cotter pin, or an ordinary nut
and a lock washer, so the bolt will not work loose. Always set motor in
place and fasten before attaching any auxiliary apparatus, such as
carburetor, etc.

2. _Inspecting the Ignition-Switch Wires._ The wires leading from the
ignition switch must be properly connected--one end to the motor body
for ground, and the other end to the post on the breaker box of the
magneto.

3. _Filling the Radiator._ Be sure that the water from the radiator
fills the cylinder jackets. Pockets of air may remain in the cylinder
jackets even though the radiator may appear full. Turn the motor over a
few times by hand after filling the radiator, and then add more water if
the radiator will take it. The air pockets, if allowed to remain, may
cause overheating and develop serious trouble when the motor is running.

4. _Filling the Oil Reservoir._ Oil is admitted into the crank-case
through the breather tube at the rear. It is well to strain all oil put
into the crank-case. In filling the oil reservoir be sure to turn the
handle on the oil sight-gauge till it is at right angles with the gauge.
The oil sight-gauge is on the side of the lower half of the crank-case.
Put in about 3 gallons of the best obtainable oil, Mobile B recommended.
It is important to remember that the very best oil is none too good.

5. _Oiling Exposed Moving Parts._ Oil all rocker-arm bearings before
each flight. A little oil should be applied where the push rods pass
through the stirrup straps.

6. _Filling the Gasoline Tanks._ Be certain that all connections in the
gasoline system are tight.

7. _Turning on the Gasoline._ Open the cock leading from the gasoline
tank to the carburetor.

8. _Charging the Cylinders._ With the ignition switch OFF, prime the
motor by squirting a little gasoline in each exhaust port and then turn
the propeller backward two revolutions. Never open the exhaust valve by
operating the rocker-arm by hand, as the push-rod is liable to come out
of its socket in the cam follower and bend the rocker-arm when the motor
turns over.

9. _Starting the Motor by Hand._ Always retard the spark part way, to
prevent back-firing, by pulling forward the wire attached to the breaker
box. Failure to so retard the spark in starting may result in serious
injury to the operator. Turn on the ignition switch with throttle partly
open; give a quick, strong pull down and outward on the starting crank
or propeller. As soon as the motor is started advance the spark by
releasing the retard wire.

10. _Oil Circulation._ Let the motor run at low speed for a few minutes
in order to establish oil circulation in all bearings. With all parts
functioning properly, the throttle may be opened gradually for warming
up before flight.

STANDARD S.A.E. ENGINE BED DIMENSIONS

The Society of Automotive Engineers have made efforts to standardize
dimensions of bed timbers for supporting power plant in an aeroplane.
Owing to the great difference in length no standardization is thought
possible in this regard. The dimensions recommended are as follows:

Distance between timbers 12 in. 14 in. 16 in.
Width of bed timbers 1-1/2 in. 1-3/4 in. 2 in.
Distance between centers of bolts 13-1/2 in. 15-3/4 in. 18 in.

It will be evident that if any standard of this nature were adopted by
engine builders that the designers of fuselage could easily arrange
their bed timbers to conform to these dimensions, whereas it would be
difficult to have them adhere to any standard longitudinal dimensions
which are much more easily varied in fuselages than the transverse
dimensions are. It, however, should be possible to standardize the
longitudinal positions of the holding down bolts as the engine designer
would still be able to allow himself considerable space fore-and-aft of
the bolts.

[Illustration: Fig. 148.--End Elevation of Hall-Scott A-7 Four-Cylinder
Motor, with Installation Dimensions.]

HALL-SCOTT ENGINE INSTALLATION

[Illustration: Fig. 149.--Plan and Side Elevation of Hall-Scott A-7
Four-Cylinder Airplane Engine, with Installation Dimensions.]

The very thorough manner in which installation diagrams are prepared by
the leading engine makers leaves nothing to the imagination. The
dimensions of the Hall-Scott four-cylinder airplane engine are given
clearly in our inch measurements with the metric equivalents at Figs.
148 and 149, the former showing a vertical elevation while the latter
has a plan view and side elevation. The installation of this engine in
airplanes is clearly shown at Figs. 150 and 151, the former having the
radiator installed at the front of the motor and having all exhaust
pipes joined to one common discharge funnel, which deflects the gas over
the top plane while the latter has the radiator placed vertically above
the motor at the back end and has a direct exhaust gas discharge to the
air.

[Illustration: Fig. 150.

CENSORED]

[Illustration: Fig. 151.

CENSORED]

The dimensions of the six-cylinder Hall-Scott motor which is known as
the type A-5 125 H. P. are given at Fig. 152, which is an end sectional
elevation, and at Fig. 153, which is a plan view. The dimensions are
given both in inch sizes and the metric equivalents. The appearance of
a Hall-Scott six-cylinder engine installed in a fuselage is given at
Fig. 154, while a diagram showing the location of the engine and the
various pipes leading to the auxiliary groups is outlined at Fig. 155.
The following instructions for installing the Hall-Scott power plant
are reproduced from the instruction book issued by the maker.
Operating instructions which are given should enable any good mechanic
to make a proper installation and to keep the engine in good running
condition.

[Illustration: Fig. 152.

CENSORED]

FUEL SYSTEM INSTALLATION

[Illustration: Fig. 153.--Plan View of Hall-Scott Type A-5 125
Horse-Power Airplane Engine, Showing Installation Dimensions.]

Gasoline giving the best results with this equipment is as follows:
Gravity 58-62 deg. Baume A. Initial boiling point--Richmond method--102°
Fahr. Sulphur .014. Calorimetric bomb test 20610 B. T. U. per pound. If
the gasoline tank is placed in the fuselage below the level of the
carburetor, a hand pump must be used to maintain air pressure in gas
tank to force the gasoline to the carburetor. After starting the engine
the small auxiliary air pump upon the engine will maintain sufficient
pressure. A-7a and A-5a engines are furnished with a new type auxiliary
air pump. This should be frequently oiled and care taken so no grit or
sand will enter which might lodge between the valve and its seat, which
would make it fail to operate properly. An air relief valve is furnished
with each engine. It should be screwed into the gas tank and properly
regulated to maintain the pressure required. This is done by screwing
the ratchet on top either up or down. If two tanks are used in a plane
one should be installed in each tank. All air pump lines should be
carefully gone over quite frequently to ascertain if they are tight.
Check valves have to be placed in these lines. In some cases the
gasoline tank is placed above the engine, allowing it to drain by
gravity to the carburetor. When using this system there should be a drop
of not less than two feet from the lowest portion of the gasoline tank
to the upper part of the carburetor float chamber. Even this height
might not be sufficient to maintain the proper volume of gasoline to the
carburetor at high speeds. Air pressure is advised upon all tanks to
insure the proper supply of gasoline. When using gravity feed without
air pressure be sure to vent the tank to allow circulation of air. If
gravity tank is used and the engine runs satisfactorily at low speeds
but cuts out at high speeds the trouble is undoubtedly due to
insufficient height of the tank above the carburetor. The tank should be
raised or air pressure system used.

[Illustration: Fig. 154.--Three-Quarter View of Hall-Scott Type A-5 125
Horse-Power Six-Cylinder Engine, with One of the Side Radiators Removed
to Show Installation in Standard Fuselage.]

[Illustration: Fig. 155.--Diagram Showing Proper Installation of
Hall-Scott Type A-5 125 Horse-Power Engine with Pressure Feed Fuel
Supply System.]

IGNITION SWITCHES

Two "DIXIE" switches are furnished with each engine. Both of these
should be installed in the pilot's seat, one controlling the R. H., and
the other the L. H. magneto. By shorting either one or the other it can
be quickly determined if both magnetos, with their respective
spark-plugs, are working correctly. Care should be taken not to use
spark-plugs having _special extensions or long protruding points_. Plugs
giving best results are extremely small with short points.

WATER SYSTEMS

A temperature gauge should be installed in the water pipe, coming
directly from the cylinder nearest the propeller (note illustration
above). This instrument installed in the radiator cap has not always
given satisfactory results. This is especially noticeable when the water
in the radiator becomes low, not allowing it to touch the bulb on the
moto-meter. For ordinary running, it should not indicate over 150
degrees Fahr. In climbing tests, however, a temperature of 160 degrees
Fahr. can be maintained without any ill effects upon the engine. In case
the engine becomes overheated, the indicator will register above 180
degrees Fahr., in which case it should be stopped immediately.
Overheating is most generally caused by retarded spark, excessive carbon
in the cylinders, insufficient lubrication, improperly timed valves,
lack of water, clogging of water system in any way which would obstruct
the free circulation of the water.

Overheating will cause the engine to knock, with possible damaging
results. Suction pipes should be made out of thin tubing, and run within
a quarter or an eighth of an inch of each other, so that when a hose is
placed over the two, it will not be possible to suck together. This is
often the case when a long rubber hose is used, which causes
overheating. Radiators should be flushed out and cleaned thoroughly
quite often. A dirty radiator may cause overheating.

When filling the radiator it is very important to remove the plug on top
of the water pump until water appears. This is to avoid air pockets
being formed in the circulating system, which might not only heat up the
engine, but cause considerable damage. All water pump hoses and
connections should be tightly taped and shellacked after the engine is
properly installed in the plane. The greatest care should be taken when
making engine installation _not_ to use smaller inside diameter hose
connection than water pump suction end casting. One inch and a quarter
inside diameter should be used on A-7 and A-5 motors, while nothing less
than one inch and a half inside diameter hose or tubing on all A-7a and
A-5a engines. It is further important to have light spun tubing, void of
any sharp turns, leads from pump to radiator and cylinder water outlet
to radiator. In other words, the water circulation through the engine
must be as little restricted as possible. Be sure no light hose is used,
that will often suck together when engine is started. To thoroughly
drain the water from the entire system, open the drain cock at the
lowest side of the water pump.

PREPARATIONS TO START ENGINE

Always replenish gasoline tanks through a strainer which is clean. This
strainer must catch all water and other impurities in the gasoline. Pour
at least three gallons of fresh oil into the lower crank-case. Oil all
rocker arms through oilers upon rocker arm housing caps. Be sure
radiators are filled within one inch of the top.

After all the parts are oiled, and the tanks filled, the following must
be looked after before starting: See if crank-shaft flange is tight on
shaft. See if propeller bolts are tight and evenly drawn up. See if
propeller bolts are wired. See if propeller is trued up to within 1/8".

Every four days the magnetos should be oiled if the engine is in daily
use.

Every month all cylinder hold-down nuts should be gone over to ascertain
if they are tight. (Be sure to recotter nuts.)

See if magnetos are bolted on tight and wired.

See if magneto cables are in good condition.

See if rocker arm tappets have a .020" clearance from valve stem when
valve is seated.

See if tappet clamp screws are tight and cottered.

See if all gasoline, oil, water pipes and connections are in perfect
condition.

Air on gas line should be tested for leaks.

Pump at least three pounds air pressure into gasoline tank.

After making sure that above rules have been observed, test compression
of cylinders by turning propeller.

"DO NOT FORGET TO SHORT BOTH MAGNETOS"

Be sure all compression release and priming cocks do not leak
compression. If they do, replace same with a new one immediately, as
this might cause premature firing.

Open priming cocks and squirt some gasoline into each.

Close cocks.

Open compression release cocks.

Open throttle slightly.

If using Berling magnetos they should be three-quarters advanced.

If all the foregoing directions have been carefully followed, the engine
is ready for starting.

In cranking engine either by starting crank, or propeller, it is
essential to throw it over compression quickly.

Immediately upon starting, close compression release cocks.

When engine is running, advance magnetos.

After it has warmed up, short one magneto and then the other, to be sure
both magnetos and spark-plugs are firing properly. If there is a miss,
the fouled plug must be located and cleaned. There is a possibility that
the jets in the carburetor are stopped up. If this is the case, do not
attempt to clean same with any sharp instrument. If this is done, it
might change the opening in the jets, thus spoiling the adjustment. Jets
and nozzles should be blown out with air or steam.

An open intake or exhaust valve, which might have become sluggish or
stuck from carbon, might cause trouble. Be sure to remedy this at once
by using a little coal-oil or kerosene on same, working the valve by
hand until it becomes free. We recommend using graphite on valve stems
mixed with oil to guard against sticking or undue wear.

INSTALLING ROTARY AND RADIAL CYLINDER ENGINES

[Illustration: Fig. 156.--Diagram Defining Installation of Gnome
"Monosoupape" Motor in Tractor Biplane. Note Necessary Piping for Fuel,
Oil, and Air Lines.]

When rotary engines are installed simple steel stamping or "spiders,"
are attached to the fuselage to hold the fixed crank-shaft. Inasmuch as
the motor projects clear of the fuselage proper there is plenty of room
back of the front spider plate to install the auxiliary parts such as
the oil pump, air pump and ignition magneto and also the fuel and oil
containers. The diagram given at Fig. 156 shows how a Gnome
"monosoupape" engine is installed on the anchorage plates and it also
outlines clearly the piping necessary to convey the oil and fuel and
also the air-piping needed to put pressure on both fuel and oil tanks to
insure positive supply of these liquids which may be carried in tanks
placed lower than the motor in some installations. The diagram given at
Figs. 157 and 158 shows other mountings of Gnome engines and are
self-explanatory. The simple mounting possible when the Anzani
ten-cylinder radial fixed type engine is used given at Fig. 159. The
front end of the fuselage is provided with a substantial pressed steel
plate having members projecting from it which may be bolted to the
longerons. The bolts that hold the two halves of the crank-case together
project through the steel plate and hold the engine securely to the
front end of the fuselage.

[Illustration: Fig. 157.--Showing Two Methods of Placing Propeller on
Gnome Rotary Motor.]

PRACTICAL HINTS TO LOCATE ENGINE TROUBLES

[Illustration: Fig. 158.--How Gnome Rotary Motor May Be Attached to
Airplane Fuselage Members.]

One who is not thoroughly familiar with engine construction will seldom
locate troubles by haphazard experimenting and it is only by a
systematic search that the cause can be discovered and the defects
eliminated. In this chapter the writer proposes to outline some of the
most common power-plant troubles and to give sufficient advice to enable
those who are not thoroughly informed to locate them by a logical
process of elimination. The internal-combustion motor, which is the
power plant of all gasoline automobiles as well as airplanes, is
composed of a number of distinct groups, which in turn include distinct
components. These various appliances are so closely related to each
other that defective action of any one may interrupt the operation of
the entire power plant. Some of the auxiliary groups are more necessary
than others and the power plant will continue to operate for a time even
after the failure of some important parts of some of the auxiliary
groups. The gasoline engine in itself is a complete mechanism, but it
is evident that it cannot deliver any power without some means of
supplying gas to the cylinders and igniting the compressed gas charge
after it has been compressed in the cylinders. From this it is patent
that the ignition and carburetion systems are just as essential parts of
the power plant as the piston, connecting rod, or cylinder of the motor.
The failure of either the carburetor or igniting means to function
properly will be immediately apparent by faulty action of the power
plant.

[Illustration: Fig. 159.--How Anzani Ten-Cylinder Radial Engine is
Installed to Plate Securely Attached to Front End of Tractor Airplane
Fuselage.]

To insure that the motor will continue to operate it is necessary to
keep it from overheating by some form of cooling system and to supply
oil to the moving parts to reduce friction. The cooling and lubrication
groups are not so important as carburetion and ignition, as the engine
would run for a limited period of time even should the cooling system
fail or the oil supply cease. It would only be a few moments, however,
before the engine would overheat if the cooling system was at fault, and
the parts seize if the lubricating system should fail. Any derangement
in the carburetor or ignition mechanism would manifest itself at once
because the engine operation would be affected, but a defect in the
cooling or oiling system would not be noticed so readily.

The careful aviator will always inspect the motor mechanism before
starting on a trip of any consequence, and if inspection is carefully
carried out and loose parts tightened it is seldom that irregular
operation will be found due to actual breakage of any of the components
of the mechanism. Deterioration due to natural causes matures slowly,
and sufficient warning is always given when parts begin to wear so
satisfactory repairs may be promptly made before serious derangement or
failure is manifested.

A TYPICAL ENGINE STOPPAGE ANALYZED

Before describing the points that may fail in the various auxiliary
systems it will be well to assume a typical case of engine failure and
show the process of locating the trouble in a systematic manner by
indicating the various steps which are in logical order and which could
reasonably be followed. In any case of engine failure the ignition
system, motor compression, and carburetor should be tested first. If the
ignition system is functioning properly one should determine the amount
of compression in all cylinders and if this is satisfactory the
carbureting group should be tested. If the ignition system is working
properly and there is a decided resistance in the cylinders when the
propeller is turned, proving that there is good compression, one may
suspect the carburetor.

[Illustration: Fig. 160.--Side Elevation of Thomas 135 Horse-Power
Airplane Engine, Giving Important Dimensions.]

If the carburetor appears to be in good condition, the trouble may be
caused by the ignition being out of time, which condition is possible
when the magneto timing gear or coupling is attached to the armature
shaft by a taper and nut retention instead of the more positive key or
taper-pin fastening. It is possible that the inlet manifold may be
broken or perforated, that the exhaust valve is stuck on its seat
because of a broken or bent stem, broken or loose cam, or failure of the
cam-shaft drive because the teeth are stripped from the engine shaft or
cam-shaft gears; or because the key or other fastening on either gear
has failed, allowing that member to turn independently of the shaft to
which it normally is attached. The gasoline feed pipe may be clogged or
broken, the fuel supply may be depleted, or the shut-off cock in the
gasoline line may have jarred closed. The gasoline filter may be filled
with dirt or water which prevents passage of the fuel.

[Illustration: Fig. 161.--Front Elevation of Thomas-Morse 135
Horse-Power Aeromotor, Showing Main Dimensions.]

The defects outlined above, except the failure of the gasoline supply,
are very rare, and if the container is found to contain fuel and the
pipe line to be clear to the carburetor, it is safe to assume the
vaporizing device is at fault. If fuel continually runs out of the
mixing chamber the carburetor is said to be flooded. This condition
results from failure of the shut-off needle to seat properly or from a
punctured hollow metal float or a gasoline-soaked cork float. It is
possible that not enough gasoline is present in the float chamber. If
the passage controlled by the float-needle valve is clogged or if the
float was badly out of adjustment, this contingency would be probable.
When the carburetor is examined, if the gasoline level appears to be at
the proper height, one may suspect that a particle of lint, or dust, or
fine scale, or rust from the gasoline tank has clogged the bore of the
jet in the mixing chamber.

If the ignition system and carburetor appear to be in good working
order, and the hand crank shows that there is no compression in one or
more of the cylinders, it means some defect in the valve system. If the
engine is a multiple-cylinder type and one finds poor compression in all
of the cylinders it may be due to the rare defect of improper valve
timing. This may be caused by a gear having altered its position on the
cam-shaft or crank-shaft, because of a sheared key or pin having
permitted the gear to turn about half of a revolution and then having
caught and held the gear in place by a broken or jagged end so that
cam-shaft would turn, but the valves open at the wrong time. If but one
of the cylinders is at fault and the rest appear to have good
compression the trouble may be due to a defective condition either
inside or outside of that cylinder. The external parts may be inspected
easily, so the following should be looked for: a broken valve, a warped
valve-head, broken valve-springs, sticking or bent valve-stems, dirt
under valve-seat, leak at valve-chamber cap or spark-plug gasket.
Defective priming cock, cracked cylinder head (rarely occurs), leak
through cracked spark-plug insulation, valve-plunger stuck in the
guide, lack of clearance between valve-stem end and top of plunger
caused by loose adjusting screw which has worked up and kept the valve
from seating. The faulty compression may be due to defects inside the
motor. The piston-head may be cracked (rarely occurs), piston rings may
be broken, the slots in the piston rings may be in line, the rings may
have lost their elasticity or have become gummed in the grooves of the
piston, or the piston and cylinder walls may be badly scored by a loose
wrist pin or by defective lubrication. If the motor is a type with a
separate head it is possible the gasket or packing between the cylinder
and combustion chamber may leak, either admitting water to the cylinder
or allowing compression to escape.

[Illustration: Fig. 162.--Front and Side Elevations of Sturtevant
Airplane Engine, Giving Principal Dimensions to Facilitate
Installation.]

CONDITIONS THAT CAUSE FAILURE OF IGNITION SYSTEM

If the first test of the motor had showed that the compression was as it
should be and that there were no serious mechanical defects and there
was plenty of gasoline at the carburetor, this would have demonstrated
that the ignition system was not functioning properly. If a battery is
employed to supply current the first step is to take the spark-plugs out
of the cylinders and test the system by turning over the engine by hand.
If there is no spark in any of the plugs, this may be considered a
positive indication that there is a broken main current lead from the
battery, a defective ground connection, a loose battery terminal, or a
broken connector. If none of these conditions are present, it is safe to
say that the battery is no longer capable of delivering current. While
magneto ignition is generally used on airplane engines, there is apt to
be some development of battery ignition, especially on engines equipped
with electric self-starters which are now being experimented with. The
spark-plugs may be short circuited by cracked insulation or carbon and
oil deposits around the electrode. The secondary wires may be broken or
have defective insulation which permits the current to ground to some
metal part of the fuselage or motor. The electrodes of the spark-plug
may be too far apart to permit a spark to overcome the resistance of the
compressed gas, even if a spark jumps the air space, when the plug is
laid on the cylinder.

If magnetos are fitted as is usually the case at present and a spark is
obtained between the points of the plug and that device or the wire
leading to it from the magneto is in proper condition, the trouble is
probably caused by the magneto being out of time. This may result if the
driving gear is loose on the armature-shaft or crank-shaft, and is a
rare occurrence. If no spark is produced at the plugs the secondary wire
may be broken, the ground wire may make contact with some metallic
portion of the chassis before it reaches the switch, the carbon
collecting brushes may be broken or not making contact, the contact
points of the make-and-break device may be out of adjustment, the wiring
may be attached to wrong terminals, the distributor filled with metallic
particles, carbon, dust or oil accumulations, the distributor contacts
may not be making proper connection because of wear and there may be a
more serious derangement, such as a burned out secondary winding or a
punctured condenser.

If the motor runs intermittently, _i.e._, starts and runs only a few
revolutions, aside from the conditions previously outlined, defective
operation may be due to seizing between parts because of insufficient
oil or deficient cooling, too much oil in the crank-case which fouls the
cylinder after the crank-shaft has revolved a few turns, and
derangements in the ignition or carburetion systems that may be easily
remedied. There are a number of defective conditions which may exist in
the ignition group, that will result in "skipping" or irregular
operation and the following points should be considered first: weak
source of current due to worn out dry cells or discharged storage
batteries; weak magnets in magneto, or defective contacts at magneto;
dirt in magneto distributor or poor contact at collecting brushes. Dirty
or cracked insulator at spark-plug will cause short circuit and can
only be detected by careful examination. The following points should
also be checked over when the plug is inspected: Excessive space between
electrodes, points too close together, loose central electrodes, or
loose point on plug body, soot or oil particles between electrodes, or
on the surface of the insulator, cracked insulator, oil or water on
outside of insulator. Short circuits in the condenser or internal wiring
of induction coils or magnetos, which are fortunately not common, can
seldom be remedied except at the factory where these devices were made.
If an engine stops suddenly and the defect is in the ignition system the
trouble is usually never more serious than a broken or loose wire. This
may be easily located by inspecting the wiring at the terminals.
Irregular operation or misfiring is harder to locate because the trouble
can only be found after the many possible defective conditions have been
checked over, one by one.

COMMON DEFECTS IN FUEL SYSTEMS

Defective carburetion often causes misfiring or irregular operation. The
common derangement of the components of the fuel system that are common
enough to warrant suspicion and the best methods for their location
follows: First, disconnect the feed pipe from the carburetor and see if
the gasoline flows freely from the tank. If the stream coming out of the
pipe is not the full size of the orifice it is an indication that the
pipe is clogged with dirt or that there is an accumulation of rust,
scale, or lint in the strainer screens of the filter. It is also
possible that the fuel shut-off valve may be wholly or partly closed. If
the gasoline flows by gravity the liquid may be air bound in the tank,
while if a pressure-feed system is utilized the tank may leak so that it
does not retain pressure; the check valve retaining the pressure may be
defective or the pipe conveying the air or gas under pressure to the
tank may be clogged.

If the gasoline flows from the pipe in a steady stream the carburetor
demands examination. There may be dirt or water in the float chamber,
which will constrict the passage between the float chamber and the spray
nozzle, or a particle of foreign matter may have entered the nozzle and
stopped up the fine holes therein. The float may bind on its guide, the
needle valve regulating the gasoline-inlet opening in bowl may stick to
its seat. Any of the conditions mentioned would cut down the gasoline
supply and the engine would not receive sufficient quantities of gas.
The air-valve spring may be weak or the air valve broken. The
gasoline-adjusting needle may be loose and jar out of adjustment, or the
air-valve spring-adjusting nuts may be such a poor fit on the stem that
adjustments will not be retained. These instructions apply only to
carburetors having air valves and mixture regulating means which are
used only in rare instances in airplane work. Air may leak in through
the manifold, due to a porous casting, or leaky joints in a built up
form and dilute the mixture. The air-intake dust screen may be so
clogged with dirt and lint that not enough air will pass through the
mesh. Water or sediment in the gasoline will cause misfiring because the
fuel feed varies when the water or dirt constricts the standpipe bore.

It is possible that the carburetor may be out of adjustment. If clouds
of black smoke are emitted at the exhaust pipe it is positive indication
that too much gasoline is being supplied the mixture and the supply
should be cut down by screwing in the needle valve on types where this
method of regulation is provided, and by making sure that the fuel level
is at the proper height, or that the proper nozzle is used in those
forms where the spray nozzle has no means of adjustment. If the mixture
contains too much air there will be a pronounced popping back in the
carburetor. This may be overcome by screwing in the air-valve adjustment
so the spring tension is increased or by slightly opening up the
gasoline-supply regulation needle. When a carburetor is properly
adjusted and the mixture delivered the cylinder burns properly, the
exhaust gas will be clean and free from the objectionable odor present
when gasoline is burned in excess.

The character of combustion may be judged by the color of the flame
which issues from it when the engine is running with an open throttle
after nightfall. If the flame is red, it indicates too much gasoline. If
yellowish, it shows an excess of air, while a properly proportioned
mixture will be evidenced by a pronounced blue flame, such as given by a
gas-stove burner.

The Duplex Model O. D. Zenith carburetor used upon most of the six- and
eight-cylinder airplane engines consists of a single float chamber, and
a single air intake, joined to two separate and distinct spray nozzles,
venturi and idling adjustments. It is to be noted that as the carburetor
barrels are arranged side by side, both valves are mounted on the same
shaft, and work in unison through a single operating lever. It is not
necessary to alter their position. In order to make the engine idle
well, it is essential that the ignition, especially the spark-plugs,
should be in good condition. The gaskets between carburetor and
manifold, and between manifold and cylinders should be absolutely
air-tight. The adjustment for low speed on the carburetor is made by
turning in or out the two knurled screws, placed one on each side of the
float chamber. After starting the engine and allowing it to become
thoroughly warmed, one side of the carburetor should be adjusted so that
the three cylinders it affects fire properly at low speed. The other
side should be adjusted in the same manner until all six cylinders fire
perfectly at low speed. As the adjustment is changed on the knurled
screw a difference in the idling of the engine should be noticed. If the
engine begins to run evenly or speeds up it shows that the mixture
becomes right in its proportion.

Be sure the butterfly throttle is closed as far as possible by screwing
out the stop screw which regulates the closed position for idling. Care
should be taken to have the butterfly held firmly against this stop
screw at all times while idling engine. If three cylinders seem to run
irregularly after changing the position of the butterfly, still another
adjustment may have to be made with the knurled screw. Unscrewing this
makes the mixture leaner. Screwing in closes off some of the air supply
to the idling jet, making it richer. After one side has been made to
idle satisfactorily repeat the same procedure with the opposite three
cylinders. In other words, each side should be idled independently to
about the same speed.

Remember that the main jet and compensating jet have no appreciable
effect on the idling of the engine. The idling mixture is drawn directly
through the opening determined by the knurled screw and enters the
carburetor barrel through the small hole at the edge of each butterfly.
This is called the priming hole and is only effective during idling.
Beyond that point the suction is transferred to the main jet and
compensator, which controls the power of the engine beyond the idling
position of the throttle.

DEFECTS IN OILING SYSTEMS

While troubles existing in the ignition or carburetion groups are
usually denoted by imperfect operation of the motor, such as lost power,
and misfiring, derangements of the lubrication or cooling systems are
usually evident by overheating, diminution in engine capacity, or noisy
operation. Overheating may be caused by poor carburetion as much as by
deficient cooling or insufficient oiling. When the oiling group is not
functioning as it should the friction between the motor parts produces
heat. If the cooling system is in proper condition, as will be evidenced
by the condition of the water in the radiator, and the carburetion group
appears to be in good condition, the overheating is probably caused by
some defect in the oiling system.

The conditions that most commonly result in poor lubrication are:
Insufficient oil in the engine crank-case or sump, broken or clogged oil
pipes, screen at filter filled with lint or dirt, broken oil pump, or
defective oil-pump drive. The supply of oil may be reduced by a
defective inlet or discharge-check valve at the mechanical oiler or worn
pumps. A clogged oil passage or pipe leading to an important bearing
point will cause trouble because the oil cannot get between the working
surfaces. It is well to remember that much of the trouble caused by
defective oiling may be prevented by using only the best grades of
lubricant, and even if all parts of the oil system are working properly,
oils of poor quality will cause friction and overheating.

DEFECTS IN COOLING SYSTEMS OUTLINED

Cooling systems are very simple and are not liable to give trouble as a
rule if the radiator is kept full of clean water and the circulation is
not impeded. When overheating is due to defective cooling the most
common troubles are those that impede water circulation. If the radiator
is clogged or the piping of water jackets filled with rust or sediment
the speed of water circulation will be slow, which will also be the case
if the water pump or its driving means fail. Any scale or sediment in
the water jackets or in the piping or radiator passages will reduce the
heat conductivity of the metal exposed to the air, and the water will
not be cooled as quickly as though the scale was not present.

The rubber hose often used in making the flexible connections demanded
between the radiator and water manifolds of the engine may deteriorate
inside and particles of rubber hang down that will reduce the area of
the passage. The grease from the grease cups mounted on the pump-shaft
bearing to lubricate that member often finds its way into the water
system and rots the inner walls of the rubber hose, this resulting in
strips of the partly decomposed rubber lining hanging down and
restricting the passage. The cooling system is prone to overheat after
antifreezing solutions of which calcium chloride forms a part have been
used. This is due to the formation of crystals of salt in the radiator
passages or water jackets, and these crystals can only be dissolved by
suitable chemical means, or removed by scraping when the construction
permits.

Overheating is often caused by some condition in the fuel system that
produces too rich or too lean mixture. Excess gasoline may be supplied
if any of the following conditions are present: Bore of spray nozzle or
standpipe too large, auxiliary air-valve spring too tight, gasoline
level too high, loose regulating valve, fuel-soaked cork float,
punctured sheet-metal float, dirt under float control shut-off valve or
insufficient air supply because of a clogged air screen. If pressure
feed is utilized there may be too much pressure in the tank, or the
float controlled mechanism operating the shut-off in the float bowl of
the carburetor may not act quickly enough.

SOME CAUSES OF NOISY OPERATION

There are a number of power-plant derangements which give positive
indication because of noisy operation. Any knocking or rattling sounds
are usually produced by wear in connecting rods or main bearings of the
engine, though sometimes a sharp metallic knock, which is very much the
same as that produced by a loose bearing, is due to carbon deposits in
the cylinder heads, or premature ignition due to advanced spark-time
lever. Squeaking sounds invariably indicate dry bearings, and whenever
such a sound is heard it should be immediately located and oil applied
to the parts thus denoting their dry condition. Whistling or blowing
sounds are produced by leaks, either in the engine itself or in the gas
manifolds. A sharp whistle denotes the escape of gas under pressure and
is usually caused by a defective packing or gasket that seals a portion
of the combustion chamber or that is used for a joint as the exhaust
manifold. A blowing sound indicates a leaky packing in crank-case.
Grinding noises in the motor are usually caused by the timing gears and
will obtain if these gears are dry or if they have become worn. Whenever
a loud knocking sound is heard careful inspection should be made to
locate the cause of the trouble. Much harm may be done in a few minutes
if the engine is run with loose connecting rod or bearings that would be
prevented by taking up the wear or looseness between the parts by some
means of adjustment.

BRIEF SUMMARY OF HINTS FOR STARTING ENGINE

First make sure that all cylinders have compression. To ascertain this,
open pet cocks of all cylinders except the one to be tested, crank over
motor and see that a strong opposition to cranking is met with once in
two revolutions. If motor has no pet cocks, crank and notice that
oppositions are met at equal distances, two to every revolution of the
starting crank in a four-cylinder motor. If compression is lacking,
examine the parts of the cylinder or cylinders at fault in the following
order, trying to start the motor whenever any one fault is found and
remedied. See that the valve push rods or rocker arms do not touch valve
stems for more than approximately 1/2 revolution in every 2 revolutions,
and that there is not more than .010 to .020 inch clearance between them
depending on the make of the motor. Make sure that the exhaust valve
seats. To determine this examine the spring and see that it is connected
to the valve stem properly. Take out valve and see that there is no
obstruction, such as carbon, on its seat. See that valve works freely in
its guide. Examine inlet valve in same manner. Listen for hissing sound
while cranking motor for leaks at other places.

Make sure that a spark occurs in each cylinder as follows: If magneto or
magneto and battery with non-vibrating coil is used: Disconnect wire
from spark-plug, hold end about 1/8 inch from cylinder or terminal of
spark-plug. Have motor cranked briskly and see if spark occurs. Examine
adjustment of interrupter points. See that wires are placed correctly
and not short circuited. Take out spark-plug and lay it on the cylinder,
being careful that base of plug only touches the cylinder and that
ignition wire is connected. Have motor cranked briskly and see if spark
occurs. Check timing of magneto and see that all brushes are making
contact.

See if there is gasoline in the carburetor. See that there is gasoline
in the tank. Examine valve at tank. Prime carburetor and see that spray
nozzle passage is clear. Be sure throttle is open. Prime cylinders by
putting about a teaspoonful of gasoline in through pet cock or
spark-plug opening. Adjust carburetor if necessary.

LOCATION OF ENGINE TROUBLES MADE EASY

The following tabulation has been prepared and originated by the writer
to outline in a simple manner the various troubles and derangements that
interfere with efficient internal-combustion engine action. The parts
and their functions are practically the same in all gas or gasoline
engines of the four-cycle type, and the general instructions given apply
just as well to all hydro-carbon engines, even if the parts differ in
form materially. The essential components are clearly indicated in the
many part sectional drawings in this book so they may be easily
recognized. The various defects that may materialize are tabulated in a
manner that makes for ready reference, and the various defective
conditions are found opposite the part affected, and under a heading
that denotes the main trouble to which the others are contributing
causes. The various symptoms denoting the individual troubles outlined
are given to facilitate their recognition in a positive manner.

Brief note is also made of the remedies for the restoration of the
defective part or condition. It is apparent that a table of this
character is intended merely as a guide, and it is a compilation of
practically all the known troubles that may materialize in gas-engine
operation. While most of the defects outlined are common enough to
warrant suspicion, they will never exist in an engine all at the same
time, and it will be necessary to make a systematic search for such of
those as exist.

To use the list advantageously, it is necessary to know one main trouble
easily recognized. For example, if the power plant is noisy, look for
the possible troubles under the head of Noisy Operation; if it lacks
capacity, the derangement will undoubtedly be found under the head of
Lost Power. It is assumed in all cases that the trouble exists in the
power plant or its components, and not in the auxiliary members of the
ignition, carburetion, lubrication, or cooling systems. The novice and
student will readily recognize the parts of the average aviation engine
by referring to the very complete and clearly lettered illustrations of
mechanism given in many parts of this treatise.

LOST POWER AND OVERHEATING

NOISY OPERATION OF POWER PLANT

"SKIPPING" OR IRREGULAR OPERATION

IGNITION SYSTEM TROUBLES ONLY

_Motor Will Not Start or Starts Hard_

Loose Battery Terminal.
Magneto Ground Wire Shorted.
Magneto Defective (No Spark at Plugs).
Broken Spark Plug Insulation.
Carbon Deposits or Oil Between Plug Points.
Spark-Plug Points Too Near Together or Far Apart.
Wrong Cables to Plugs.
Short Circuited Secondary Cable.
Broken Secondary Cable.
Dry Battery Weak. }
Storage Battery Discharged. } Battery Systems
Poor Contact at Timer. } Only.
Timer Points Dirty. }
Poor Contact at Switch. }
Primary Wires Broken, or Short Circuited. } Battery and
Battery Grounded in Metal Container. } Coil Ignition
Battery Connectors Broken or Loose. } System Only.
Timer Points Out of Adjustment. }
Defects in Induction Coil. }
Ignition Timing Wrong, Spark Too Late or Too Early.
Defective Platinum Points in Breaker Box (Magneto).
Points Not Separating.
Broken Contact Maker Spring.
No Contact at Secondary Collector Brush.
Platinum Contact Points Burnt or Pitted.
Contact Breaker Bell Crank Stuck.
Fiber Bushing in Bell Crank Swollen.
Short Circuiting Spring Always in Contact.
Dirt or Water in Magneto Casing.
Oil in Contact Breaker.
Oil Soaked Brush and Collector Ring.
Distributor Filled with Carbon Particles.

_Motor Stops Without Warning_

Broken Magneto Carbon Brush.
Broken Lead Wire.
Broken Ground Wire.
Battery Ignition Systems.
Water on High Tension Magneto Terminal.
Main Secondary Cable Burnt Through by Hot Exhaust
Pipe (Transformer Coil, Magneto Systems).
Particle of Carbon Between Spark Plug Points.
Magneto Short Circuited by Ground Wire.
Magneto Out of Time, Due to Slipping Drive.
Water or Oil in Safety Spark Gap (Multi-cylinder Magneto).
Magneto Contact Breaker or Timer Stuck in Retard
Position.
Worn Fiber Block in Magneto Contact Breaker.
Binding Fiber Bushing in Contact Breaker Bell Crank.
Spark Advance Rod or Wire Broken.
Contact Breaker Parts Stuck.

_Motor Runs Irregularly or Misfires_

Loose Wiring or Terminals.
Broken Spark-Plug Insulator.
Spark-Plug Points Sooted or Oily.
Wrong Spark Gap at Plug Points.
Leaking Secondary Cable.
Prematurely Grounded Primary Wire.
Batteries Running Down (Battery Ignition only).
Poor Adjustment of Contact Points at Timer.
Wire Broken Inside of Insulation.
Loose Platinum Points in Magneto.
Weak Contact Spring.
Broken Collector Brush.
Dirt in Magneto Distributor Casing or Contact Breaker.
Worn Fiber Block or Cam Plate in Magneto.
Worn Cam or Contact Roll in Timer (Battery System
only).
Dirty Oil in Timer.
Sticking Coil Vibrators.
Coil Vibrator Points Pitted.
Oil Soaked Magneto Winding.
Punctured Magneto or Coil Winding.
Distributor Contact Segments Rough.
Sulphated Storage Battery Terminals.
Weak Magnets in Magneto.
Poor Contact at Magneto Contact Breaker Points.

DEFECTS IN ELECTRICAL SYSTEM COMPONENTS

To further simplify the location of electrical system faults it is
thought desirable to outline the defects that can be present in the
various parts of the individual devices comprising the ignition system.
If an airplane engine is provided with magneto ignition solely, as most
engines are at the present time, no attention need be paid to such items
as storage or dry batteries, timer or induction coil. There seems to be
some development in the direction of battery ignition so it has been
considered desirable to include components of these systems as well as
the almost universally used magneto group. Spark-plugs, wiring and
switches are needed with either system.

SPARK-PLUGS

DEFECT TROUBLE CAUSED REMEDY
Insulation cracked. Plug inoperative. New insulation.
Insulation oil soaked. Cylinder misfires. Clean.
Carbon deposits. Short circuited spark. Remove.
Insulator loose. Cylinder misfires. Tighten.
Gasket broken. Gas leaks by. New gasket.
Electrode loose on shell. Cylinder misfires. Tighten.
Wire loose in insulator. Cylinder misfires. Tighten.
Air gap too close. Short circuits spark. Set correctly.
Air gap too wide. Spark will not jump. Set points 1/32"
apart.
Loose terminal. Cylinder may misfire. Tighten.
Plug loose in cylinder. Gas leaks. Tighten.
Mica insulation oil soaked. Short circuits spark. Replace.

MAGNETO

DEFECT TROUBLE CAUSED REMEDY
Dirty oil in distributor. Engine misfires. Clean.
Metal dust in distributor. Engine misfires. Clean.
Brushes not making contact. Current cannot pass. Strengthen
spring.
Distributor segments worn. Engine misfires. Secure even
bearing.
Collecting brush broken. Engine misfires. New brush.
Distributing brush broken. Engine misfires. New brush.
Oil soaked winding. Engine misfires. Clean.
Magnets loose on pole Engine misfires. Tighten screws.
pieces.
Armature rubs. Engine misfires. Repair bearings.
Bearings worn. Noisy. Replace.
Magnets weak. Weak spark. Recharge.
Contact breaker points Engine misfires. Clean.
pitted.
Breaker points out of Engine misfires. Reset.
adjustment.
Defective winding (rare). No spark. Replace.
Punctured condenser (rare). Weak or no spark. Replace.
Driving gear loose. Noise. Tighten.
Magneto armature out of Spark will not fire Retime.
time. charge.
Magneto loose on base. Misfiring and noisy. Tighten.
Contact breaker cam worn. Misfiring. Replace.
Fibre shoe or rolls worn Misfiring. Replace.
(Bosch).
Fibre bushing binding in Misfiring. Ream slightly.
contact lever (Bosch).
Contact lever return spring No spark. Replace.
broken.
Contact lever return spring Misfiring. Replace.
weak.
Ground wire grounded. No spark. Insulate.
Ground wire broken. Engine will not stop. Connect up.
Safety spark gap dirty. No spark. Clean.
Fused metal in spark gap. No spark. Remove.
Safety spark gap points too Misfiring. Set properly.
close.
Loose distributor terminals. Misfiring. Tighten.
Contact breaker sticks. No spark control. Remove and clean
bearings.
Magneto switch short- No spark. Insulate.
circuited.
Magneto switch open circuit. No engine stop. Restore contact.

STORAGE BATTERY

DEFECT TROUBLE CAUSED REMEDY
Electrolyte low. Weak current. Replenish with
distilled water.
Loose terminals. Misfiring. Tighten.
Sulphated terminals. Misfiring. Clean thoroughly
and coat with
vaseline.
Battery discharged. Misfiring or no spark. New charge.
Electrolyte weak. Weak current. Bring to proper
specific gravity.
Plates sulphated. Poor capacity. Special slow charge.
Sediment or mud in bottom. Weak current. Clean out.
Active material loose in Poor capacity. New plates.
grids.
Moisture or acid on top of Shorts terminals. Remove.
cells.
Plugged vent cap. Buckles cell jars. Make vent hole.
Cracked vent cap. Acid spills out. New cap.
Cracked cell jar. Electrolyte runs out. New jar.

DRY CELL BATTERY

DEFECT TROUBLE CAUSED REMEDY
Broken wires. No current. New wires.
Loose terminals. Misfiring. Tighten.
Weak cell (7 amperes or Misfiring. New cells.
less).
Cells in contact. Short circuit. Separate and
insulate.
Water in battery box. Short circuit. Dry out.

TIMER

DEFECT TROUBLE CAUSED REMEDY
Contact segments worn or Misfiring. Grind down
pitted. smooth.
Platinum points pitted. Misfiring. Smooth with oil
stone.
Dirty oil or metal dust in Misfiring. Clean out.
interior.
Worn bearing. Misfiring. Replace.
Loose terminals. Misfiring. Tighten.
Worn revolving contact Misfiring. Replace.
brush.
Out of time. Irregular spark. Reset.

INDUCTION COIL

DEFECT TROUBLE CAUSED REMEDY
Loose terminals. Misfiring. Tighten.
Broken connections. No spark. Make new joints.
Vibrators out of adjustment. Misfiring. Readjust.
Vibrator points pitted. Misfiring. Clean.
Defective condenser } rare. No spark. Send to maker
Defective winding } for repairs.
Poor contact at switch. Misfiring. Tighten.
Broken internal wiring. No spark. Replace.
Poor coil unit. One cylinder affected. Replace.

WIRING

DEFECT TROUBLE CAUSED REMEDY
Loose terminals anywhere. Misfiring. Tighten.
Broken plug wire. One cylinder will not Replace.
fire.
Broken timer wire. One coil will not buzz. Replace.
Broken main battery wire. } No spark. Replace.
Broken battery ground wire.}
Broken magneto ground wire. Engine will not stop. Replace.
Chafed insulation anywhere.} Misfiring. Insulate.
Short circuit anywhere. }

CARBURETION SYSTEM FAULTS SUMMARIZED

_Motor Starts Hard or Will Not Start_

No Gasoline in Tank.
No Gasoline in Carburetor Float Chamber.
Tank Shut-Off Closed.
Clogged Filter Screen.
Fuel Supply Pipe Clogged.
Gasoline Level Too Low.
Gasoline Level Too High (Flooding).
Bent or Stuck Float Lever.
Loose or Defective Inlet Manifold.
Not Enough Gasoline at Jet.
Cylinders Flooded with Gas.
Fuel Soaked Cork Float (Causes Flooding).
Water in Carburetor Spray Nozzle.
Dirt in Float Chamber.
Gas Mixture Too Lean.
Carburetor Frozen (Winter Only).

_Motor Stops In Flight_

Gasoline Shut-Off Valve Jarred Closed.
Gasoline Supply Pipe Clogged.
No Gasoline in Tank.
Spray Nozzle Stopped Up.
Water in Spray Nozzle.
Particles of Carbon Between Spark-Plug Points.
Magneto Short Circuited by Ground in Wire.
Air Lock in Gasoline Pipe.
Broken Air Line or Leaky Tank (Pressure Feed System Only).
Fuel Supply Pipe Partially Clogged.
Air Vent in Tank Filler Cap Stopped Up (Gravity and Vacuum Feed
System).
Float Needle Valve Stuck.
Water or Dirt in Spray Nozzle.
Mixture Adjusting Needle Jarred Loose (Rotary Motors Only).

_Motor Races, Will Not Throttle Down_

Air Leak in Inlet Piping.
Air Leak Through Inlet Valve Guides.
Control Rods Broken.
Defective Induction Pipe Joints.
Leaky Carburetor Flange Packing.
Throttle Not Closing.
Poor Slow Speed Adjustment (Zenith Carburetor).

_Motor Misfires_

Carburetor Float Chamber Getting Dry.
Water or Dirt in Gasoline.
Poor Gasoline Adjustment (Rotary Motors).
Not Enough Gasoline in Float Chamber.
Too Much Gasoline, Carburetor Flooding.
Incorrect Jet or Choke (Zenith Carburetor).
Broken Cylinder Head Packing Between Cylinders.

_Noisy Operation_

Popping or Blowing Back in Carburetor.
Incorrectly Timed Inlet Valves.
Inlet Valve Not Seating.
Defective Inlet Valve Spring.
Dirt Under Inlet Valve Seat.
Not Enough Gasoline (Open Needle Valve).
Muffler or Manifold Explosions.
Mixture Not Exploding Regularly.
Exhaust Valve Sticking.
Dirt Under Exhaust Valve Seat.

CHAPTER XI

Tools for Adjusting and Erecting--Forms of Wrenches--Use and
Care of Files--Split Pin Removal and Installation--Complete
Chisel Set--Drilling Machines--Drills, Reamers, Taps and Dies--
Measuring Tools--Micrometer Calipers and Their Use--Typical Tool
Outfits--Special Hall-Scott Tools--Overhauling Airplane Engines
--Taking Engine Down--Defects in Cylinders--Carbon Deposits,
Cause and Prevention--Use of Carbon Scrapers--Burning Out Carbon
with Oxygen--Repairing Scored Cylinders--Valve Removal and
Inspection--Reseating and Truing Valves--Valve Grinding
Processes--Depreciation in Valve Operating System--Piston
Troubles--Piston Ring Manipulation--Fitting Piston Rings--
Wrist-Pin Wear--Inspection and Refitting of Engine Bearings--
Scraping Brasses to Fit--Fitting Connecting Rods--Testing for
Bearing Parallelism--Cam-Shafts and Timing Gears--Precautions in
Reassembling Parts.

TOOLS FOR ADJUSTING AND ERECTING

[Illustration: Fig. 163.--Practical Hand Tools Useful in Dismantling and
Repairing Airplane Engines.]

A very complete outfit of small tools, some of which are furnished as
part of the tool equipment of various engines are shown in group at Fig.
163. This group includes all of the tools necessary to complete a very
practical kit and it is not unusual for the mechanic who is continually
dismantling and erecting engines to possess even a larger assortment
than indicated. The small bench vise provided is a useful auxiliary that
can be clamped to any convenient bench or table or even fuselage
longeron in an emergency and should have jaws at least three inches wide
and capable of opening four or five inches. It is especially useful in
that it will save trips to the bench vises, as it has adequate capacity
to handle practically any of the small parts that need to be worked on
when making repairs. A blow torch, tinner's snips and soldering copper
are very useful in sheet metal work and in making any repairs requiring
the use of solder. The torch can be used in any operation requiring a
source of heat. The large box wrench shown under the vise is used for
removing large special nuts and sometimes has one end of the proper size
to fit the valve chamber cap. The piston ring removers are easily made
from thin strips of sheet metal securely brazed or soldered to a light
wire handle. These are used in sets of three for removing and applying
piston rings in a manner to be indicated. The uses of the wrenches,
screw drivers, and pliers shown are known to all and the variety
outlined should be sufficient for all ordinary work of restoration. The
wrench equipment is very complete, including a set of open end
S-wrenches to fit all standard bolts, a spanner wrench, socket or box
wrenches for bolts that are inaccessible with the ordinary type,
adjustable end wrenches, a thin monkey wrench of medium size, a bicycle
wrench for handling small nuts and bolts, a Stillson wrench for pipe and
a large adjustable monkey wrench for the stubborn fastenings of large
size.

Four different types of pliers are shown, one being a parallel jaw type
with size cutting attachment, while the other illustrated near it is a
combination parallel jaw type adapted for use on round work as well as
in handling flat stock. The most popular form of pliers is the
combination pattern shown beneath the socket wrench set. This is made of
substantial drop forgings having a hinged joint that can be set so that
a very wide opening at the jaws is possible. These can be used on round
work and for wire cutting as well as for handling flat work. Round nose
pliers are very useful also.

A very complete set of files, including square, half round, mill, flat
bastard, three-cornered and rat tail are also necessary. A hacksaw frame
and a number of saws, some with fine teeth for tubing and others with
coarser teeth for bar or solid stock will be found almost indispensable.
A complete punch and chisel set should be provided, samples of which are
shown in the group while the complete outfit is outlined in another
illustration. A number of different forms and sizes of chisels are
necessary, as one type is not suitable for all classes of work. The
adjustable end wrenches can be used in many places where a monkey wrench
cannot be fitted and where it will be difficult to use a wrench having a
fixed opening. The Stillson pipe wrench is useful in turning studs,
round rods, and pipes that cannot be turned by any other means. A
complete shop kit must necessarily include various sizes for Stillson
and monkey wrenches, as no one size can be expected to handle the wide
range of work the engine repairman must cope with. Three sizes of each
form of wrench can be used, one, a 6 inch, is as small as is needed
while, a 12 inch tool will handle almost any piece of pipe or nut used
in engine construction.

Three or four sizes of hammers should be provided, according to
individual requirement, these being small riveting, medium and
heavyweight machinist's hammers. A very practical tool of this nature
for the repair shop can be used as a hammer, screw driver or pry iron.
It is known as the "Spartan" hammer and is a tool steel drop forging in
one piece having the working surfaces properly hardened and tempered
while the metal is distributed so as to give a good balance to the head
and a comfortable grip to the handle. The hammer head provides a
positive and comfortable T-handle when the tool is used as a screw
driver or "tommy" bar. Machinist's hammers are provided with three types
of heads, these being of various weights. The form most commonly used is
termed the "ball pein" on account of the shape of the portion used for
riveting. The straight pein is just the same as the cross pein, except
that in the latter the straight portion is at right angles to the hammer
handle, while in the former it is parallel to that member.

FORMS OF WRENCHES

Wrenches have been made in infinite variety and there are a score or
more patterns of different types of adjustable socket and off-set
wrenches. The various wrench types that differ from the more
conventional monkey wrenches or those of the Stillson pattern are shown
at Fig. 164. The "perfect handle" is a drop forged open end form
provided with a wooden handle similar to that used on a monkey wrench in
order to provide a better grip for the hand. The "Saxon" wrench is a
double alligator form, so called because the jaws are in the form of a
V-groove having one side of the V plain, while the other is serrated in
order to secure a tight grip on round objects. In the form shown, two
jaws of varying sizes are provided, one for large work, the other to
handle the smaller rods. One of the novel features in connection with
this wrench is the provision of a triple die block in the centre of the
handle which is provided with three most commonly used of the standard
threads including 5/16-inch-18, 3/8-inch-16, and 1/2-inch-13. This is
useful in cleaning up burred threads on bolts before they are replaced,
as burring is unavoidable if it has been necessary to drive them out
with a hammer. The "Lakeside" wrench has an adjustable pawl engaging
with one of a series of notches by which the opening may be held in any
desired position.

[Illustration: Fig. 164.--Wrenches are Offered in Many Forms.]

Ever since the socket wrench was invented it has been a popular form
because it can be used in many places where the ordinary open end or
monkey wrench cannot be applied owing to lack of room for the head of
the wrench. A typical set which has been made to fit in a very small
space is shown at D. It consists of a handle, which is nickel-plated and
highly polished, a long extension bar, a universal joint and a number of
case hardened cold drawn steel sockets to fit all commonly used standard
nuts and bolt heads. Two screw-driver bits, one small and the other
large to fit the handle, and a long socket to fit spark-plugs are also
included in this outfit. The universal joint permits one to remove nuts
in a position that would be inaccessible to any other form of wrench, as
it enables the socket to be turned even if the handle is at one side of
an intervening obstruction.

The "Pick-up" wrench, shown at E, is used for spark-plugs and the upper
end of the socket is provided with a series of grooves into which a
suitable blade carried by the handle can be dropped. The handle is
pivoted to the top of the socket in such a way that the blades may be
picked up out of the grooves by lifting on the end of the handle and
dropped in again when the handle is swung around to the proper point to
get another hold on the socket. The "Miller" wrench shown at F, is a
combination socket and open end type, made especially for use with
spark-plugs. Both the open end and the socket are convenient. The
"Handy" set shown at G, consists of a number of thin stamped wrenches of
steel held together in a group by a simple clamp fitting, which enables
either end of any one of the four double wrenches to be brought into
play according to the size of the nut to be turned. The "Cronk" wrench
shown at H, is a simple stamping having an alligator opening at one end
and a stepped opening capable of handling four different sizes of
standard nuts or bolt heads at the other. Such wrenches are very cheap
and are worth many times their small cost, especially for fitting nuts
where there is not sufficient room to admit the more conventional
pattern. The "Starrett" wrench set, which is shown at I, consists of a
ratchet handle together with an extension bar and universal joint, a
spark-plug socket, a drilling attachment which takes standard square
shank drills from 1/8-inch to 1/2-inch in diameter, a double ended
screw-driver bit and several adjustments to go with the drilling
attachment. Twenty-eight assorted cold drawn steel sockets similar in
design to those shown at D, to fit all standard sizes of square and
hexagonal headed nuts are also included. The reversible ratchet handle,
which may be slipped over the extension bar or the universal joint and
which is also adapted to take the squared end of any one of the sockets
is exceptionally useful in permitting, as it does, the instant release
of pressure when it is desired to swing the handle back to get another
hold on the nut. The socket wrench sets are usually supplied in hard
wood cases or in leather bags so that they may be kept together and
protected against loss or damage. With a properly selected socket wrench
set, either of the ratchet handle or T-handle form, any nut on the
engine may be reached and end wrenches will not be necessary.

USE AND CARE OF FILES

Mention has been previously made of the importance of providing a
complete set of files and suitable handles. These should be in various
grades or degrees of fineness and three of each kind should be provided.
In the flat and half round files three grades are necessary, one with
coarse teeth for roughing, and others with medium and fine teeth for the
finishing cuts. The round or rat tail file is necessary in filing out
small holes, the half round for finishing the interior of large ones.
Half round files are also well adapted for finishing surfaces of
peculiar contour, such as the inside of bearing boxes, connecting rod
and main bearing caps, etc. Square files are useful in finishing keyways
or cleaning out burred splines, while the triangular section or
three-cornered file is of value in cleaning out burred threads and
sharp corners. Flat files are used on all plane surfaces.

[Illustration: Fig. 165.--Illustrating Use and Care of Files.]

The file brush shown at Fig. 165, A, consists of a large number of wire
bristles attached to a substantial wood back having a handle of
convenient form so that the bristles may be drawn through the
interstices between the teeth of the file to remove dirt and grease. If
the teeth are filled with pieces of soft metal, such as solder or
babbitt, it may be necessary to remove this accumulation with a piece of
sheet metal as indicated at Fig. 165, B. The method of holding a file
for working on plain surfaces when it is fitted with the regular form of
wooden handle is shown at C, while two types of handles enabling the
mechanic to use the flat file on plain surfaces of such size that the
handle type indicated at C, could not be used on account of interfering
with the surface finished are shown at D. The method of using a file
when surfaces are finished by draw filing is shown at E. This differs
from the usual method of filing and is only used when surfaces are to be
polished and very little metal removed.

SPLIT PIN REMOVAL AND INSERTION

One of the most widely used of the locking means to prevent nuts or
bolts from becoming loose is the simple split pin, sometimes called a
"cotter pin." These can be handled very easily if the special pliers
shown at Fig. 166, A, are used. They have a curved jaw that permits of
grasping the pin firmly and inserting it in the hole ready to receive
it. It is not easy to insert these split pins by other means because the
ends are usually spread out and it is hard to enter the pin in the hole.
With the cotter pin pliers the ends may be brought close together and as
the plier jaws are small the pin may be easily pushed in place. Another
use of this plier, also indicated, is to bend over the ends of the split
pin in order to prevent it from falling out. To remove these pins a
simple curved lever, as shown at Fig. 166, B, is used. This has one end
tapering to a point and is intended to be inserted in the eye of the
cotter pin, the purchase offered by the handle permitting of ready
removal of the pin after the ends have been closed by the cotter pin
pliers.

COMPLETE CHISEL SET

[Illustration: Fig. 166.--Outlining Use of Cotter Pin Pliers, Spring
Winder, and Showing Practical Outfit of Chisels.]

A complete chisel set suitable for repair shop use is also shown at Fig.
166. The type at C is known as a "cape" chisel and has a narrow cutting
point and is intended to chip keyways, remove metal out of corners and
for all other work where the broad cutting edge chisel, shown at D,
cannot be used. The form with the wide cutting edge is used in chipping,
cutting sheet metal, etc. At E, a round nose chisel used in making oil
ways is outlined, while a similar tool having a pointed cutting edge and
often used for the same purpose is shown at F. The centre punch depicted
at G, is very useful for marking parts either for identification or for
drilling. In addition to the chisels shown, a number of solid punches
or drifts resembling very much that shown at E, except that the point is
blunt should be provided to drive out taper pins, bolts, rivets, and
other fastenings of this nature. These should be provided in the common
sizes. A complete set of real value would start at 1/8-inch and increase
by increments of 1/32-inch up to 1/2-inch. A simple spring winder is
shown at Fig. 166, H, this making it possible for the repairman to wind
coil springs, either on the lathe or in the vise. It will handle a
number of different sizes of wire and can be set to space the coils as
desired.

DRILLING MACHINES

[Illustration: Fig. 167.--Forms of Hand Operated Drilling Machines.]

Drilling machines may be of two kinds, hand or power operated. For
drilling small holes in metal it is necessary to run the drill fast,
therefore the drill chuck is usually driven by gearing in order to
produce high drill speed without turning the handle too fast. A small
hand drill is shown at Fig. 167, A. As will be observed, the chuck
spindle is driven by a small bevel pinion, which in turn, is operated by
a large bevel gear turned by a crank. The gear ratio is such that one
turn of the handle will turn the chuck five or six revolutions. A drill
of this design is not suited for drills any larger than one-quarter
inch. For use with drills ranging from one-eighth to three-eighths, or
even half-inch the hand drill presses shown at C and D are used. These
have a pad at the upper end by which pressure may be exerted with the
chest in order to feed the drill into the work, and for this reason they
are termed "breast drills." The form at C has compound gearing, the
drill chuck being driven by the usual form of bevel pinion in mesh with
a larger bevel gear at one end of a countershaft. A small helical spur
pinion at the other end of this countershaft receives its motion from a
larger gear turned by the hand crank. This arrangement of gearing
permits of high spindle speed without the use of large gears, as would
be necessary if but two were used. The form at D gives two speeds, one
for use with small drills is obtained by engaging the lower bevel pinion
with the chuck spindle and driving it by the large ring gear. The slow
speed is obtained by shifting the clutch so that the top bevel pinion
drives the drill chuck. As this meshes with a gear but slightly larger
in diameter, a slow speed of the drill chuck is possible. Breast drills
are provided with a handle screwed into the side of the frame, these
are used to steady the drill press. For drilling extremely large holes
which are beyond the capacity of the usual form of drill press the
ratchet form shown at B, may be used or the bit brace outlined at E. The
drills used with either of these have square shanks, whereas those used
in the drill presses have round shanks. The bit brace is also used
widely in wood work and the form shown is provided with a ratchet by
which the bit chuck may be turned through only a portion of a revolution
in either direction if desired.

DRILLS, REAMERS, TAPS AND DIES

In addition to the larger machine tools and the simple hand tools
previously described, an essential item of equipment of any engine or
plane repair shop, even in cases where the ordinary machine tools are
not provided, is a complete outfit of drills, reamers, and threading
tools. Drills are of two general classes, the flat and the twist drills.
The flat drill has an angle between cutting edges of about 110 degrees
and is usually made from special steel commercially known as drill rod.

A flat drill cannot be fed into the work very fast because it removes
metal by a scraping, rather than a cutting process. The twist drill in
its simplest form is cylindrical throughout the entire length and has
spiral flutes which are ground off at the end to form the cutting lip
and which also serve to carry the metal chips out of the holes. The
simplest form of twist drill used is shown at Fig. 168, C, and is known
as a "chuck" drill, because it must be placed in a suitable chuck to
turn it. A twist drill removes metal by cutting and it is not necessary
to use a heavy feed as the drill will tend to feed itself into the work.

[Illustration: Fig. 168.--Forms of Drills Used in Hand and Power
Drilling Machines.]

Larger drills than 3/4-inch are usually made with a tapered shank as
shown at Fig. 168, B. At the end of the taper a tongue is formed which
engages with a suitable opening in the collet, as the piece used to
support the drill is called. The object of this tongue is to relieve
the tapered portion of the drill from the stress of driving by
frictional contact alone, as this would not turn the drill positively
and the resulting slippage would wear the socket, this depreciation
changing the taper and making it unfit for other drills. The tongue is
usually proportioned so it is adequate to drive the drill under any
condition. A small keyway is provided in the collet into which a
tapering key of flat stock may be driven against the end of the tongue
to drive the drill from the spindle. A standard taper for drill shanks
generally accepted by the machine trade is known as the Morse and is a
taper of five-eighths of an inch to the foot. The Brown and Sharp form
tapers six-tenths of an inch to the foot. Care must be taken, therefore,
when purchasing drills and collets, to make sure that the tapers
coincide, as no attempt should be made to run a Morse taper in a Brown
and Sharp collet, or vice versa.

Sometimes cylindrical drills have straight flutes, as outlined at Fig.
168, A. Such drills are used with soft metals and are of value when the
drill is to pass entirely through the work. The trouble with a drill
with spiral flutes is that it will tend to draw itself through as the
cutting lips break through. This catching of the drill may break it or
move the work from its position. With a straight flute drill the cutting
action is practically the same as with the flat drill shown at Fig. 168,
E and F.

If a drill is employed in boring holes through close-grained, tough
metals, as wrought or malleable iron and steel, the operation will be
facilitated by lubricating the drill with plenty of lard oil or a
solution of soda and water. Either of these materials will effectually
remove the heat caused by the friction of the metal removed against the
lips of the drill, and the danger of heating the drill to a temperature
that will soften it by drawing the temper is minimized. In drilling
large or deep holes it is good practice to apply the lubricating medium
directly at the drill point. Special drills of the form shown at Fig.
168, B, having a spiral oil tube running in a suitably formed channel,
provides communication between the point of the drill and a suitable
receiving hole on a drilled shank. The oil is supplied by a pump and its
pressure not only promotes positive circulation and removal of heat, but
also assists in keeping the hole free of chips. In drilling steel or
wrought iron, lard oil applied to the point of the drill will facilitate
the drilling, but this material should never be used with either brass
or cast iron.

The sizes to be provided depend upon the nature of the work and the
amount of money that can be invested in drills. It is common practice to
provide a set of drills, such as shown at Fig. 169, which are carried in
a suitable metal stand, these being known as number drills on account
of conforming to the wire gauge standards. Number drills do not usually
run higher than 5/16 inch in diameter. Beyond this point drills are
usually sold by the diameter. A set of chuck drills, ranging from 3/8 to
3/4 inch, advancing by 1/32 inch, and a set of Morse taper shank drills
ranging from 3/4 to 1-1/4 inches, by increments of 1/16 inch, will be
all that is needed for the most pretentious repair shop, as it is
cheaper to bore holes larger than 1-1/4 inches with a boring tool than
it is to carry a number of large drills in stock that would be used very
seldom, perhaps not enough to justify their cost.

[Illustration: Fig. 169.--Useful Set of Number Drills, Showing Stand for
Keeping These in an Orderly Manner.]

In grinding drills, care must be taken to have the lips of the same
length, so that they will form the same angle with the axis. If one lip
is longer than the other, as shown in the flat drill at Fig. 168, E, the
hole will be larger than the drill size, and all the work of cutting
will come upon the longest lip. The drill ends should be symmetrical, as
shown at Fig. 168, F.

[Illustration: Fig. 170.--Illustrating Standard Forms of Hand and
Machine Reamers.]

It is considered very difficult to drill a hole to an exact diameter,
but for the most work a variation of a few thousandths of an inch is of
no great moment. Where accuracy is necessary, holes must be reamed out
to the required size. In reaming, a hole is drilled about 1/32 inch
smaller than is required, and is enlarged with a cutting tool known as
the reamer. Reamers are usually of the fluted form shown at Fig. 170, A.
Tools of this nature are not designed to remove considerable amounts of
metal, but are intended to augment the diameter of the drill hole by
only a small fraction of an inch. Reamers are tapered slightly at the
point in order that they will enter the hole easily, but the greater
portion of the fluted part is straight, all cutting edges being
parallel. Hand reamers are made in either the straight or taper forms,
that at A, Fig. 170, being straight, while B has tapering flutes. They
are intended to be turned by a wrench similar to that employed in
turning a tap, as shown at Fig. 172, C. The reamer shown at Fig. 170,
C, is a hand reamer. The form at D has spiral flutes similar to a twist
drill, and as it is provided with a taper shank it is intended to be
turned by power through the medium of a suitable collet.

As the solid reamers must become reduced in size when sharpened, various
forms of inserted blade reamers have been designed. One of these is
shown at E, and as the cutting surfaces become reduced in diameter it is
possible to replace the worn blades with others of proper size.
Expanding reamers are of the form shown at F. These have a bolt passing
through that fits into a tapering hole in the interior of the split
reamer portion of the tool. If the hole is to be enlarged a few
thousandths of an inch, it is possible to draw up on the nut just above
the squared end of the shank, and by drawing the tapering wedge farther
into the reamer body, the cutting portion will be expanded and will cut
a larger hole.

Reamers must be very carefully sharpened or there will be a tendency
toward chattering with a consequent production of a rough surface. There
are several methods of preventing this chattering, one being to separate
the cutting edges by irregular spaces, while the most common method, and
that to be preferred on machine reamers, is to use spiral flutes, as
shown at Fig. 170, D. Special taper reamers are made to conform to the
various taper pin sizes which are sometimes used in holding parts
together in an engine. A taper of 1/16 inch per foot is intended for
holes where a pin, once driven in, is to remain in place. When it is
desired that the pin be driven out, the taper is made steeper, generally
1/4 inch per foot, which is the standard taper used on taper pins.

[Illustration: Fig. 171.--Tools for Thread Cutting.]

When threads are to be cut in a small hole, it will be apparent that it
will be difficult to perform this operation economically on a lathe,
therefore when internal threading is called for, a simple device known
as a "tap" is used. There are many styles of taps, all conforming to
different standards. Some are for metric or foreign threads, some
conform to the American standards, while others are used for pipe and
tubing. Hand taps are the form most used in repair shops, these being
outlined at Fig. 171, A and B. They are usually sold in sets of three,
known respectively as taper, plug, and bottoming. The taper tap is the
one first put into the hole, and is then followed by the plug tap which
cuts the threads deeper. If it is imperative that the thread should be
full size clear to the bottom of the hole, the third tap of the set,
which is straight-sided, is used. It would be difficult to start a
bottoming tap into a hole because it would be larger in diameter at its
point than the hole. The taper tap, as shown at A, Fig. 171, has a
portion of the cutting lands ground away at the point in order that it
will enter the hole. The manipulation of a tap is not hard, as it does
not need to be forced into the work, as the thread will draw it into
the hole as the tap is turned. The tapering of a tap is done so that no
one thread is called upon to remove all of the metal, as for about half
way up the length of the tap each succeeding thread is cut a little
larger by the cutting edge until the full thread enters the hole. Care
must be taken to always enter a tap straight in order to have the thread
at correct angles to the surface.

In cutting external threads on small rods or on small pieces, such as
bolts and studs, it is not always economical to do this work in the
lathe, especially in repair work. Dies are used to cut threads on pieces
that are to be placed in tapped holes that have been threaded by the
corresponding size of tap. Dies for small work are often made solid, as
shown at Fig. 171, C, but solid dies are usually limited to sizes below
1/2 inch. Sometimes the solid die is cylindrical in shape, with a slot
through one side which enables one to obtain a slight degree of
adjustment by squeezing the slotted portion together. Large dies, or the
sizes over 1/2 inch, are usually made in two pieces in order that the
halves may be closed up or brought nearer together. The advantage of
this form of die is that either of the two pieces may be easily
sharpened, and as it may be adjusted very easily the thread may be cut
by easy stages. For example, the die may be adjusted to cut large, which
will produce a shallow thread that will act as an accurate guide when
the die is closed up and a deeper thread cut.

[Illustration: Fig. 172.--Showing Holder Designs for One- and Two-Piece
Thread Cutting Dies.]

A common form of die holder for an adjustable die is shown at Fig. 172,
A. As will be apparent, it consists of a central body portion having
guide members to keep the die pieces from falling out and levers at each
end in order to permit the operator to exert sufficient force to remove
the metal. The method of adjusting the depth of thread with a clamp
screw when a two-piece die is employed is also clearly outlined. The
diestock shown at B is used for the smaller dies of the one-piece
pattern, having a slot in order that they may be closed up slightly by
the clamp screw. The reverse side of the diestock shown at B is outlined
below it, and the guide pieces, which may be easily moved in or out,
according to the size of the piece to be threaded by means of
eccentrically disposed semi-circular slots in the adjustment plate, are
shown. These movable guide members have small pins let into their
surface which engage the slots, and they may be moved in or out, as
desired, according to the position of the adjusting plate. The use of
the guide pieces makes for accurate positioning or centering of the rod
to be threaded. Dies are usually sold in sets, and are commonly
furnished as a portion of a complete outfit such as outlined at Fig.
173. That shown has two sizes of diestock, a tap wrench, eight assorted
dies, eight assorted taps, and a small screw driver for adjusting the
die. An automobile repair shop should be provided with three different
sets of taps and dies, as three different standards for the bolts and
nuts are used in fastening automobile components. These are the
American, metric (used on foreign engines), and the S. A. E. standard
threads. A set of pipe dies and taps will also be found useful.

[Illustration: Fig. 173.--Useful Outfit of Taps and Dies for the Engine
Repair Shop.]

MEASURING TOOLS

The tool outfit of the machinist or the mechanic who aspires to do
machine work must include a number of measuring tools which are not
needed by the floor man or one who merely assembles and takes apart the
finished pieces. The machinist who must convert raw material into
finished products requires a number of measuring tools, some of which
are used for taking only approximate measurements, such as calipers and
scales, while others are intended to take very accurate measurements,
such as the Vernier and the micrometer. A number of common forms of
calipers are shown at Fig. 174. These are known as inside or outside
calipers, depending upon the measurements they are intended to take.
That at A is an inside caliper, consisting of two legs, A and D, and a
gauging piece, B, which can be locked to leg A, or released from that
member by the screw, C. The object of this construction is to permit of
measurements being taken at the bottom of a two diameter hole, where the
point to be measured is of larger diameter than the portion of the hole
through which the calipers entered. It will be apparent that the legs A
and D must be brought close together to pass through the smaller holes.
This may be done without losing the setting, as the guide bar B will
remain in one position as determined by the size of the hole to be
measured, while the leg A may be swung in to clear the obstruction as
the calipers are lifted out. When it is desired to ascertain the
measurements the leg A is pushed back into place into the slotted
portion of the guide B, and locked by the clamp screw C. A tool of this
form is known as an internal transfer caliper.

[Illustration: Fig. 174.--Common Forms of Inside and Outside Calipers.]

The form of caliper shown at B is an outside caliper. Those at C and D
are special forms for inside and outside work, the former being used,
if desired, as a divider, while the latter may be employed for measuring
the walls of tubing. The calipers at E are simple forms, having a
friction joint to distinguish them from the spring calipers shown at B,
C and D. In order to permit of ready adjustment of a spring caliper, a
split nut as shown at G is sometimes used. A solid nut caliper can only
be adjusted by screwing the nut in or out on the screw, which may be a
tedious process if the caliper is to be set from one extreme to the
other several times in succession. With a slip nut as shown at G it is
possible to slip it from one end of the thread to the other without
turning it, and of locking it in place at any desired point by simply
allowing the caliper leg to come in contact with it. The method of
adjusting a spring caliper is shown at Fig. 174, H.

Among the most common of the machinist's tools are those used for linear
measurements. The usual forms are shown in group, Fig. 175. The most
common tool, which is widely known, is the carpenter's folding two-foot
rule or the yardstick. While these are very convenient for taking
measurements where great accuracy is not required, the machinist must
work much more accurately than the carpenter, and the standard steel
scale which is shown at D, is a popular tool for the machinist. The
steel scale is in reality a graduated straight edge and forms an
important part of various measuring tools. These are made of high grade
steel and vary from 1 to 48 inches in length. They are carefully
hardened in order to preserve the graduations, and all surfaces and
edges are accurately ground to insure absolute parallelism. The
graduations on the high grade scales are produced with a special device
known as a dividing engine, but on cheaper scales, etching suffices to
provide a fairly accurate graduation. The steel scales may be very thin
and flexible, or may be about an eighth of an inch thick on the
twelve-inch size, which is that commonly used with combination squares,
protractors and other tools of that nature. The repairman's scale
should be graduated both with the English system, in which the inches
are divided into eighths, sixteenths, thirty-secondths and
sixty-fourths, and also in the metric system, divided into millimeters
and centimeters. Some machinists use scales graduated in tenths,
twentieths, fiftieths and hundredths. This is not as good a system of
graduation as the more conventional one first described.

[Illustration: Fig. 175.--Measuring Appliances for the Machinist and
Floor Man.]

Some steel scales are provided with a slot or groove cut the entire
length on one side and about the center of the scales. This permits the
attachment of various fittings such as the protractor head, which
enables the machinist to measure angles, or in addition the heads
convert the scale into a square or a tool permitting the accurate
bisecting of pieces of circular section. Two scales are sometimes joined
together to form a right angle, such as shown at Fig. 175, C. This is
known as a square and is very valuable in ascertaining the truth of
vertical pieces that are supposed to form a right angle with a base
piece.

The Vernier is a device for reading finer divisions on a scale than
those into which the scale is divided. Sixty-fourths of an inch are
about the finest division that can be read accurately with the naked
eye. When fine work is necessary a Vernier is employed. This consists
essentially of two rules so graduated that the true scale has each inch
divided into ten equal parts, the upper or Vernier portion has ten
divisions occupying the same space as nine of the divisions of the true
scale. It is evident, therefore, that one of the divisions of the
Vernier is equal to nine-tenths of one of those on the true scale. If
the Vernier scale is moved to the right so that the graduations marked
"1" shall coincide, it will have moved one-tenth of a division on the
scale or one-hundredth of an inch. When the graduations numbered 5
coincide the Vernier will have moved five-hundredths of an inch; when
the lines marked 0 and 10 coincide, the Vernier will have moved
nine-hundredths of an inch, and when 10 on the Vernier comes opposite 10
on the scales, the upper rule will have moved ten-hundredths of an inch,
or the whole of one division on the scale. By this means the scale,
though it may be graduated only to tenths of an inch, may be accurately
set at points with positions expressed in hundredths of an inch. When
graduated to read in thousandths, the true scale is divided into fifty
parts and the Vernier into twenty parts. Each division of the Vernier
is therefore equal to nineteen-twentieths of one of the true scale. If
the Vernier be moved so the lines of the first division coincide, it
will have moved one-twentieth of one-fiftieth, or .001 inch. The Vernier
principle can be readily grasped by studying the section of the Vernier
scale and true scale shown at Fig. 176, A.

[Illustration: Fig. 176.--At Left, Special Form of Vernier Caliper for
Measuring Gear Teeth; at Right, Micrometer for Accurate Internal
Measurements.]

The caliper scale which is shown at Fig. 175, A, permits of taking the
over-all dimension of any parts that will go between the jaws. This
scale can be adjusted very accurately by means of a fine thread screw
attached to a movable jaw and the divisions may be divided by eye into
two parts if one sixty-fourth is the smallest of the divisions. A line
is indicated on the movable jaw and coincides with the graduations on
the scale. As will be apparent, if the line does not coincide exactly
with one of the graduations it will be at some point between the lines
and the true measurement may be approximated without trouble.

A group of various other measuring tools of value to the machinist is
shown at Fig. 177. The small scale at A is termed a "center gauge,"
because it can be used to test the truth of the taper of either a male
or female lathe center. The two smaller nicks, or v's, indicate the
shape of a standard thread, and may be used as a guide for grinding the
point of a thread-cutting tool. The cross level which is shown at B is
of marked utility in erecting, as it will indicate absolutely if the
piece it is used to test is level. It will indicate if the piece is
level along its width as well as its length.

[Illustration: Fig. 177.--Measuring Appliances of Value in Airplane
Repair Work.]

A very simple attachment for use with a scale that enables the machinist
to scribe lines along the length of a cylindrical piece is shown at Fig.
177, C. These are merely small wedge-shaped clamps having an angular
face to rest upon the bars. The thread pitch gauge which is shown at
Fig. 177, D, is an excellent pocket tool for the mechanic, as it is
often necessary to determine without loss of time the pitch of the
thread on a bolt or in a nut. This consists of a number of leaves having
serrations on one edge corresponding to the standard thread it is to be
used in measuring. The tool shown gives all pitches up to 48 threads per
inch. The leaves may be folded in out of the way when not in use, and
their shape admits of their being used in any position without the
remainder of the set interfering with the one in use. The fine pitch
gauges have slim, tapering leaves of the correct shape to be used in
finding the pitch of small nuts. As the tool is round when the leaves
are folded back out of the way, it is an excellent pocket tool, as there
are no sharp corners to wear out the pocket. Practical application of a
Vernier having measuring heads of special form for measuring gear teeth
is shown at Fig. 176, A. As the action of this tool has been previously
explained, it will not be necessary to describe it further.

MICROMETER CALIPERS AND THEIR USE

Where great accuracy is necessary in taking measurements the micrometer
caliper, which in the simple form will measure easily .001 inch
(one-thousandth part of an inch) and when fitted with a Vernier that
will measure .0001 inch (one ten-thousandth part of an inch), is used.
The micrometer may be of the caliper form for measuring outside
diameters or it may be of the form shown at Fig. 176, B, for measuring
internal diameters. The operation of both forms is identical except that
the internal micrometer is placed inside of the bore to be measured
while the external form is used just the same as a caliper. The form
outlined will measure from one and one-half to six and a half inches as
extension points are provided to increase the range of the instrument.
The screw has a movement of one-half inch and a hardened anvil is placed
in the end of the thimble in order to prevent undue wear at that point.
The extension points or rods are accurately made in standard lengths and
are screwed into the body of the instrument instead of being pushed in,
this insuring firmness and accuracy. Two forms of micrometers for
external measurements are shown at Fig. 178. The top one is graduated
to read in thousandths of an inch, while the lower one is graduated to
indicate hundredths of a millimeter. The mechanical principle involved
in the construction of a micrometer is that of a screw free to move in a
fixed nut. An opening to receive the work to be measured is provided by
the backward movement of the thimble which turns the screw and the size
of the opening is indicated by the graduations on the barrel.

[Illustration: Fig. 178.--Standard Forms of Micrometer Caliper for
External Measurements.]

The article to be measured is placed between the anvil and spindle, the
frame being held stationary while the thimble is revolved by the thumb
and finger. The pitch of the screw thread on the concealed part of the
spindle is 40 to an inch. One complete revolution of the spindle,
therefore, moves it longitudinally one-fortieth, or twenty-five
thousandths of an inch. As will be evident from the development of the
scale on the barrel of the inch micrometer, the sleeve is marked with
forty lines to the inch, each of these lines indicating twenty-five
thousandths. The thimble has a beveled edge which is graduated into
twenty-five parts. When the instrument is closed the graduation on the
beveled edge of the thimble marked 0 should correspond to the 0 line on
the barrel. If the micrometer is rotated one full turn the opening
between the spindle and anvil will be .025 inch. If the thimble is
turned only one graduation, or one twenty-fifth of a revolution, the
opening between the spindle and anvil will be increased only by .001
inch (one-thousandth of an inch).

As many of the dimensions of the airplane parts, especially of those of
foreign manufacture or such parts as ball and roller bearings, are based
on the metric system, the competent repairman should possess both inch
and metric micrometers in order to avoid continual reference to a table
of metric equivalents. With a metric micrometer there are fifty
graduations on the barrel, these representing .01 of a millimeter, or
approximately .004 inch. One full turn of the barrel means an increase
of half a millimeter, or .50 mm. (fifty one-hundredths). As it takes two
turns to augment the space between the anvil and the stem by increments
of one millimeter, it will be evident that it would not be difficult to
divide the spaces on the metric micrometer thimble in halves by the eye,
and thus the average workman can measure to .0002 inch plus or minus
without difficulty. As set in the illustration, the metric micrometers
show a space of 13.5 mm., or about one millimeter more than half an
inch. The inch micrometer shown is set to five-tenths or five hundred
one-thousandths or one-half inch. A little study of the foregoing matter
will make it easy to understand the action of either the inch or metric
micrometer.

Both of the micrometers shown have a small knurled knob at the end of
the barrel. This controls the ratchet stop, which is a device that
permits a ratchet to slip by a pawl when more than a certain amount of
pressure is applied, thereby preventing the measuring spindle from
turning further and perhaps springing the instrument. A simple rule that
can be easily memorized for reading the inch micrometer is to multiply
the number of vertical divisions on the sleeve by 25 and add to that the
number of divisions on the bevel of the thimble reading from the zero to
the line which coincides with the horizontal line on the sleeve. For
example: if there are ten divisions visible on the sleeve, multiply this
number by 25, then add the number of divisions shown on the bevel of the
thimble, which is 10. The micrometer is therefore opened 10 × 25 equals
250 plus 10 equals 260 thousandths.

Micrometers are made in many sizes, ranging from those having a maximum
opening of one inch to special large forms that will measure forty or
more inches. While it is not to be expected that the repairman will have
use for the big sizes, if a caliper having a maximum opening of six
inches is provided with a number of extension rods enabling one to
measure smaller objects, practically all of the measuring needed in
repairing engine parts can be made accurately. Two or three smaller
micrometers having a maximum range of two or three inches will also be
found valuable, as most of the measurements will be made with these
tools which will be much easier to handle than the larger sizes.

TYPICAL TOOL OUTFITS

The equipment of tools necessary for repairing airplane engines depends
entirely upon the type of the power plant and while the common hand
tools can be used on all forms, the work is always facilitated by having
special tools adapted for reaching the nuts and screws that would be
hard to reach otherwise. Special spanners and socket wrenches are very
desirable. Then again, the nature of the work to be performed must be
taken into consideration. Rebuilding or overhauling an engine calls for
considerably more tools than are furnished for making field repairs or
minor adjustments. A complete set of tools supplied to men working on
Curtiss OX-2 engines and JN-4 training biplanes is shown at Fig. 179.
The tools are placed in a special box provided with a hinged cover and
are arranged in the systematic manner outlined. The various tools and
supplies shown are: A, hacksaw blades; B, special socket wrenches for
engine bolts and nuts; C, ball pein hammers, four sizes; D, five
assorted sizes of screw drivers ranging from very long for heavy work to
short and small for fine work; E, seven pairs of pliers including
combination in three sizes, two pairs of cutting pliers and one round
nose; F, two split pin extractors and spreaders; G, wrench set including
three adjustable monkey wrenches, one Stillson or pipe wrench, five
sizes adjustable end wrenches and ten double end S wrenches; H, set of
files, including flat, three cornered and half round; I, file brush; J,
chisel and drift pin; K, three small punches or drifts; L, hacksaw
frame; M, soldering copper; N, special spanners for propeller retaining
nuts; O, special spanners; P, socket wrenches, long handle; Q, long
handle, stiff bristle brushes for cleaning motor; R, gasoline blow
torch; S, hand drill; T, spools of safety wire; U, flash lamp; V,
special puller and castle wrenches; W, oil can; X, large adjustable
monkey wrench; Y, washer and gasket cutter; Z, ball of heavy twine. In
addition to the tools, various supplies, such as soldering acid, solder,
shellac, valve grinding compound, bolts and nuts, split pins, washers,
wood screws, etc., are provided.

[Illustration: Fig. 179.--Special Tools for Maintaining Curtiss OX-2
Motor Used in Curtiss JN-4 Training Biplane.]

SPECIAL HALL-SCOTT TOOLS

NO. TOOL DIRECTIONS FOR USE
1 Engine hoisting hook, 6-cylinder Hook under cam-shaft housing,
when hoisting engine.
2 Engine hoisting hook, 4-cylinder Hook under cam-shaft housing,
when hoisting engine.
3 Water plug wrench For use on water plugs on top
and end of cylinders.
4 Vertical shaft flange puller For pulling lower pinion shaft
flange from shaft. (Used on A-5
and A-7 engines only.)
5 Oil gun For general lubrication use.
6 Magneto gear puller For pulling magneto gears from
magneto shaft.
7 Socket wrench, 1/4" A.L.A.M. For use on bolts and nuts on
crank cases.
8 Socket wrench, 1/4" A.L.A.M For use on crank cases and
magneto gear housings.
9 Socket wrench, 1/4" A.L.A.M. For use on magneto gear
housings.
10 Socket wrench, 3/8" standard For bolts and nuts which fasten
magnetos to crank-case.
11 Socket wrench, 1/4" A.L.A.M. For use on magneto gear
housings.
12 Vertical shaft gear puller For removing water pump and
magneto drive gear.
13 Brace and facing cutter For facing lugs on cylinders for
cylinder hold down stud washers.
14 Handle for brace Use with brace.
15 Valve grinding brace For grinding in valves.
16 Socket wrench base, 3/8" A.L.A.M. For thrust bearing cap screws.
17 Brace and facing cutter, 5/16" For facing lugs on rocker arm
A.L.A.M. covers.
18 Valve grinding screw driver For grinding in valves.
19 Valve spring tool For putting on and taking off
valve springs.
20 Block-valve spring tool For use with valve spring tool.
21 Socket wrench, 5/8" A.L.A.M. For main bearing nuts.
22 Socket wrench, 1/4" A.L.A.M. For use on cam-shaft housing.
23 Socket wrench, 5/16" A.L.A.M. For cam-shaft housing hold down
stud nuts.
24 Socket wrench, 1/2" A.L.A.M. For cylinder hold down stud
nuts.
25 Socket wrench, 5/16" A.L.A.M. For carburetor and water pump
bolts and nuts.
26 Socket wrench, 5/16" A.L.A.M. For carburetor and water pump
bolts and nuts.
27 Socket wrench For use on carburetor jets.
28 Magneto screw driver For general magneto use.
29 Brass bar, 1" diameter × 7" long For driving piston pins from
pistons.
30 Hack saw For general use.
31 Oil can For cam-shaft housing
lubrication.
32 Gasoline or distillate can For priming or other use.
33 Oil can For magneto gear lubrication.
34 Shellac can For rubber hose connections and
gaskets.
35 Magneto cleaner For use on magnetos.
36 Clamps For holding cylinder hold down
studs, when fitting main
bearings.
37 Piston guards For use in pistons, when out of
engine, to protect them.
38 Screw driver For general use.
39 Vertical shaft clamps For clamping vertical shaft
flanges, when timing engine.
40 Thrust adjusting nut wrench For adjusting propeller thrust
bearing.
41 Stuffing box spanner wrench For adjusting stuffing box nut
on vertical shaft.
42 Water pump spanner wrench For adjusting water pump
stuffing nut.
43 Wrench For use on cylinder relief cocks
and cylinder priming cocks.
44 Hose clamp wrench For use on hose clamps.
45 Scraper For cleaning piston ring grooves
on pistons.
46 Crank-shaft nut wrench For adjusting crank-shaft nut.
47 Spark-plug wrench For putting in and taking out
spark-plugs in cylinders.
48 Timing disc (single disc) For use on crank-shaft to time
engine.
Specify type motor disc should be made for. If double disc is
required, specify the two types of motors the disc is to be made
for. Double disc.
49 Main bearing scraper For scraping in bearings.
50 Cylinder carbon scraper For removing carbon from heads
of cylinders.
51 Valve seating tool For seating valves in cylinder
heads.
52 Scraper, small For general bearing use.
53 Scraper, large For general bearing use.
54 Crank-shaft flange puller For pulling crank-shaft flange
from crank-shaft.
55 Piston and connecting rod racks.
56 Main bearing stud nuts and shim
rack.
57 Main bearing board rack.
58 Rocker arm and cover rack.

The special tools and fixtures recommended by the Hall-Scott Company for
work on their engines are clearly shown at Fig. 180. All tools are
numbered and their uses may be clearly understood by reference to the
illustration and explanatory list given on pages 410 and 411.

OVERHAULING AIRPLANE ENGINES

After an airplane engine has been in use for a period ranging from 60 to
80 hours, depending upon the type, it is necessary to give it a thorough
overhauling before it is returned to service. To do this properly, the
engine is removed from the fuselage and placed on a special supporting
stand, such as shown at Fig. 181, so it can be placed in any position
and completely dismantled. With a stand of this kind it is as easy to
work on the bottom of the engine as on the top and every part can be
instantly reached. The crank-case shown in place in illustration is in a
very convenient position for scraping in the crank-shaft bearings.

[Illustration: Fig. 180.--Special Tools and Appliances to Facilitate
Overhauling Work on Hall-Scott Airplane Engines.]

In order to look over the parts of an engine and to restore the worn or
defective components it is necessary to take the engine entirely apart,
as it is only when the power plant is thoroughly dismantled that the
parts can be inspected or measured to determine defects or wear. If one
is not familiar with the engine to be inspected, even though the work is
done by a repairman of experience, it will be found of value to take
certain precautions when dismantling the engine in order to insure that
all parts will be replaced in the same position they occupied before
removal. There are a number of ways of identifying the parts, one of the
simplest and surest being to mark them with steel numbers or letters or
with a series of center punch marks in order to retain the proper
relation when reassembling. This is of special importance in connection
with dismantling multiple cylinder engines as it is vital that pistons,
piston rings, connecting rods, valves, and other cylinder parts be
always replaced in the same cylinder from which they were removed,
because it is uncommon to find equal depreciation in all cylinders. Some
repairmen use small shipping tags to identify the pieces. This can be
criticised because the tags may become detached and lost and the
identity of the piece mistaken. If the repairing is being done in a shop
where other engines of the same make are being worked on, the repairman
should be provided with a large chest fitted with a lock and key in
which all of the smaller parts, such as rods, bolts and nuts, valves,
gears, valve springs, cam-shafts, etc., may be stored to prevent the
possibility of confusion with similar members of other engines. All
parts should be thoroughly cleaned with gasoline or in the potash kettle
as removed, and wiped clean and dry. This is necessary to show wear
which will be evidenced by easily identified indications in cases where
the machine has been used for a time, but in others, the deterioration
can only be detected by delicate measuring instruments.

[Illustration: Fig. 181.--Special Stand to Make Motor Overhauling Work
Easier.]

In taking down a motor the smaller parts and fittings such as
spark-plugs, manifolds and wiring should be removed first. Then the more
important members such as cylinders may be removed from the crank-case
to give access to the interior and make possible the examination of the
pistons, rings and connecting rods. After the cylinders are removed the
next operation is to disconnect the connecting rods from the crank-shaft
and to remove them and the pistons attached as a unit. Then the
crank-case is dismembered, in most cases by removing the bottom half or
oil sump, thus exposing the main bearings and crank-shaft. The first
operation is the removal of the inlet and exhaust manifolds. In some
cases the manifolds are cored integral with the cylinder head casting
and it is merely necessary to remove a short pipe leading from the
carburetor to one inlet opening and the exhaust pipe from the outlet
opening common to all cylinders. In order to remove the carburetor it is
necessary to shut off the gasoline supply at the tank and to remove the
pipe coupling at the float chamber. It is also necessary to disconnect
the throttle operating rod. After the cylinders are removed and before
taking the crank-case apart it is well to remove the water pump and
magneto. The wiring on most engines of modern development is carried in
conduits and usually releasing two or three minor fastenings will permit
one to take off the plug wiring as a unit. The wire should be
disconnected from both spark-plugs and magneto distributor before its
removal. When the cylinders are removed, the pistons, piston rings, and
connecting rods are clearly exposed and their condition may be readily
noticed.

Before disturbing the arrangement of the timing gears, it is important
that these be marked so that they will be replaced in exactly the same
relation as intended by the engine designer. If the gears are properly
marked the valve timing and magneto setting will be undisturbed when the
parts are replaced after overhauling. With the cylinders off, it is
possible to ascertain if there is any undue wear present in the
connecting rod bearings at either the wrist pin or crank-pin ends and
also to form some idea of the amount of carbon deposits on the piston
top and back of the piston rings. Any wear of the timing gears can also
be determined. The removal of the bottom plate of the engine enables the
repairman to see if the main bearings are worn unduly. Often bearings
may be taken up sufficiently to eliminate all looseness. In other cases
they may be worn enough so that careful refitting will be necessary.
Where the crank-case is divided horizontally into two portions, the
upper one serving as an engine base to which the cylinders and in fact
all important working parts are attached, the lower portion performs the
functions of an oil container and cover for the internal mechanism. This
is the construction generally followed.

DEFECTS IN CYLINDERS

After the cylinders have been removed and stripped of all fittings, they
should be thoroughly cleaned and then carefully examined for defects.
The interior or bore should be looked at with a view of finding score
marks, grooves, cuts or scratches in the interior, because there are
many faults that may be ascribed to depreciation at this point. The
cylinder bore may be worn out of round, which can only be determined by
measuring with an internal caliper or dial indicator even if the
cylinder bore shows no sign of wear. The flange at the bottom of the
cylinder by which it is held to the engine base may be cracked. The
water jacket wall may have opened up due to freezing of the jacket
water at some time or other or it may be filled with scale and sediment
due to the use of impure cooling water. The valve seat may be scored or
pitted, while the threads holding the valve chamber cap may be worn so
that the cap will not be a tight fit. The detachable head construction
makes it possible to remove that member and obtain ready access to the
piston tops for scraping out carbon without taking the main cylinder
portion from the crank-case. When the valves need grinding the head may
be removed and carried to the bench where the work may be performed with
absolute assurance that none of the valve grinding compound will
penetrate into the interior of the cylinder as is sometimes unavoidable
with the I-head cylinder. If the cylinder should be scored, the water
jacket and combustion head may be saved and a new cylinder casting
purchased at considerably less cost than that of the complete unit
cylinder.

The detachable head construction has only recently been applied on
airplane engines, though it was one of the earliest forms of automobile
engine construction. In the early days it was difficult to procure
gaskets or packings that would be both gas and water tight. The sheet
asbestos commonly used was too soft and blew out readily. Besides a new
gasket had to be made every time the cylinder head was removed. Woven
wire and asbestos packings impregnated with rubber, red lead, graphite
and other filling materials were more satisfactory than the soft sheet
asbestos, but were prone to burn out if the water supply became low.
Materials such as sheet copper or brass proved to be too hard to form a
sufficiently yielding packing medium that would allow for the inevitable
slight inaccuracies in machining the cylinder head and cylinder. The
invention of the copper-asbestos gasket, which is composed of two sheets
of very thin, soft copper bound together by a thin edging of the same
material and having a piece of sheet asbestos interposed solved this
problem. Copper-asbestos packings form an effective seal against leakage
of water and a positive retention means for keeping the explosion
pressure in the cylinder. The great advantage of the detachable head is
that it permits of very easy inspection of the piston tops and
combustion chamber and ready removal of carbon deposits.

CARBON DEPOSITS, THEIR CAUSE AND PREVENTION

Most authorities agree that carbon is the result of imperfect combustion
of the fuel and air mixture as well as the use of lubricating oils of
improper flash point. Lubricating oils that work by the piston rings may
become decomposed by the great heat in the combustion chamber, but at
the same time one cannot blame the lubricating oil for all of the carbon
deposits. There is little reason to suspect that pure petroleum oil of
proper body will deposit excessive amounts of carbon, though if the oil
is mixed with castor oil, which is of vegetable origin, there would be
much carbon left in the interior of the combustion chamber. Fuel
mixtures that are too rich in gasoline also produce these undesirable
accumulations.

A very interesting chemical analysis of a sample of carbon scraped from
the interior of a motor vehicle engine shows that ordinarily the
lubricant is not as much to blame as is commonly supposed. The analysis
was as follows:

Oil 14.3%
Other combustible matter 17.9
Sand, clay, etc. 24.8
Iron oxide 24.5
Carbonate of lime 8.9
Other constituents 9.6

It is extremely probable that the above could be divided into two
general classes, these being approximately 32.2% oil and combustible
matter and a much larger proportion, or 67.8% of earthy matter. The
presence of such a large percentage of earthy matter is undoubtedly due
to the impurities in the air, such as road dust which has been sucked
in through the carburetor. The fact that over 17% of the matter which is
combustible was not of an oily nature lends strong support to this view.
There would not be the amount of earthy material present in the carbon
deposits of an airplane engine as above stated because the air is almost
free from dust at the high altitudes planes are usually flown. One could
expect to find more combustible and less earthy matter and the carbon
would be softer and more easily removed. It is very good practice to
provide a screen on the air intake to reduce the amounts of dust sucked
in with the air as well as observing the proper precautions relative to
supplying the proper quantities of air to the mixture and of not using
any more oil than is needed to insure proper lubrication of the internal
mechanism.

USE OF CARBON SCRAPERS

It is not unusual for one to hear an aviator complain that the engine he
operates is not as responsive as it was when new after he has run it but
relatively few hours. There does not seem to be anything actually wrong
with the engine, yet it does not respond readily to the throttle and is
apt to overheat. While these symptoms denote a rundown condition of the
mechanism, the trouble is often due to nothing more serious than
accumulations of carbon. The remedy is the removal of this matter out of
place. The surest way of cleaning the inside of the motor thoroughly is
to remove the cylinders, if these members are cast integrally with the
head or of removing the head member if that is a separate casting, to
expose all parts.

In certain forms of cylinders, especially those of the L form, it is
possible to introduce simple scrapers down through the valve chamber cap
holes and through the spark-plug hole if this component is placed in the
cylinder in some position that communicates directly to the interior of
the cylinder or to the piston top. No claim can be made for originality
or novelty of this process as is has been used for many years on large
stationary engines. The first step is to dismantle the inlet and exhaust
piping and remove the valve caps and valves, although if the deposit is
not extremely hard or present in large quantities one can often
manipulate the scrapers in the valve cap openings without removing
either the piping or the valves. Commencing with the first cylinder, the
crank-shaft is turned till the piston is at the top of its stroke, then
the scraper may be inserted, and the operation of removing the carbon
started by drawing the tool toward the opening. As this is similar to a
small hoe, the cutting edge will loosen some of the carbon and will draw
it toward the opening. A swab is made of a piece of cloth or waste
fastened at the end of a wire and well soaked in kerosene to clean out
the cylinder.

When available, an electric motor with a length of flexible shaft and a
small circular cleaning brush having wire bristles can be used in the
interior of the engine. The electric motor need not be over one-eighth
horse-power running 1,200 to 1,600 R. P. M., and the wire brush must, of
course, be of such size that it can be easily inserted through the valve
chamber cap. The flexible shaft permits one to reach nearly all parts of
the cylinder interior without difficulty and the spreading out and
flattening of the brush insures that considerable surface will be
covered by that member.

BURNING OUT CARBON WITH OXYGEN

A process of recent development that gives very good results in removing
carbon without disassembling the motor depends on the process of burning
out that material by supplying oxygen to support the combustion and to
make it energetic. A number of concerns are already offering apparatus
to accomplish this work, and in fact any shop using an autogenous
welding outfit may use the oxygen tank and reducing valve in connection
with a simple special torch for burning the carbon. Results have
demonstrated that there is little danger of damaging the motor parts,
and that the cost of oxygen and labor is much lower than the old method
of removing the cylinders and scraping the carbon out, as well as being
very much quicker than the alternative process of using carbon solvent.
The only drawback to this system is that there is no absolute insurance
that every particle of carbon will be removed, as small protruding
particles may be left at points that the flame does not reach and cause
pre-ignition and consequent pounding, even after the oxygen treatment.
It is generally known that carbon will burn in the presence of oxygen,
which supports combustion of all materials, and this process takes
advantage of this fact and causes the gas to be injected into the
combustion chamber over a flame obtained by a match or wax taper.

[Illustration: Fig. 182.--Showing Where Carbon Deposits Collect in
Engine Combustion Chamber, and How to Burn Them Out with the Aid of
Oxygen. A--Special Torch. B--Torch Coupled to Oxygen Tank. C--Torch in
Use.]

It is suggested by those favoring this process that the night before the
oxygen is to be used the engine be given a conventional kerosene
treatment. A half tumbler full of this liquid or of denatured alcohol is
to be poured into each cylinder and permitted to remain there over
night. As a precaution against fire, the gasoline is shut off from the
carburetor before the torch is inserted in the cylinder and the motor
started so that the gasoline in the pipe and carburetor float chamber
will be consumed. Work is done on one cylinder at a time. A note of
caution was recently sounded by a prominent spark-plug manufacturer
recommending that the igniter member be removed from the cylinder in
order not to injure it by the heat developed. The outfits on the market
consist of a special torch having a trigger controlled valve and a
length of flexible tubing such as shown at Fig. 182, A, and a regulating
valve and oxygen tank as shown at B. The gauge should be made to
register about twelve pounds pressure.

The method of operation is very simple and is outlined at C. The burner
tube is placed in the cylinder and the trigger valve is opened and the
oxygen permitted to circulate in the combustion chamber. A lighted match
or wax taper is dropped in the chamber and the injector tube is moved
around as much as possible so as to cover a large area. The carbon takes
fire and burns briskly in the presence of the oxygen. The combustion of
the carbon is accompanied by sparks and sometimes by flame if the
deposit is of an oily nature. Once the carbon begins to burn the
combustion continues without interruption as long as the oxygen flows
into the cylinder. Full instructions accompany each outfit and the
amount of pressure for which the regulator should be set depends upon
the design of the torch and the amount of oxygen contained in the
storage tank.

REPAIRING SCORED CYLINDERS

If the engine has been run at any time without adequate lubrication, one
or more of the cylinders may be found to have vertical scratches running
up and down the cylinder walls. The depth of these will vary according
to the amount of time the cylinder was without lubrication, and if the
grooves are very deep the only remedy is to purchase a new member. Of
course, if sufficient stock is available in the cylinder walls, the
cylinders may be rebored and new pistons which are oversize, _i.e._,
larger than standard, may be fitted. Where the scratches are not deep
they may be ground out with a high speed emery wheel or lapped out if
that type of machine is not available. Wrist pins have been known to
come loose, especially when these are retained by set screws that are
not properly locked, and as wrist-pins are usually of hardened steel it
will be evident that the sharp edge of that member can act as a cutting
tool and make a pronounced groove in the cylinder. Cylinder grinding is
a job that requires skilled mechanics, but may be accomplished on any
lathe fitted with an internal grinding attachment. While automobile
engine cylinders usually have sufficient wall thickness to stand
reboring, those of airplane engines seldom have sufficient metal to
permit of enlarging the bore very much by a boring tool. A few
thousandths of an inch may be ground out without danger, however. An
airplane engine cylinder with deep grooves must be scrapped as a general
rule.

Where the grooves in the cylinder are not deep or where it has warped
enough so the rings do not bear equally at all parts of the cylinder
bore, it is possible to obtain a fairly accurate degree of finish by a
lapping process in which an old piston is coated with a mixture of fine
emery and oil and is reciprocated up and down in the cylinder as well as
turned at the same time. This may be easily done by using a dummy
connecting rod having only a wrist pin end boss, and of such size at the
other end so that it can be held in the chuck of a drill press. The
cylinder casting is firmly clamped on the drill press table by suitable
clamping blocks, and a wooden block is placed in the combustion chamber
to provide a stop for the piston at its lower extreme position. The back
gears are put in and the drill chuck is revolved slowly. All the while
that the piston is turning the drill chuck should be raised up and down
by the hand feed lever, as the best results are obtained when the
lapping member is given a combination of rotary and reciprocating
motion.

VALVE REMOVAL AND INSPECTION

One of the most important parts of the gasoline engine and one that
requires frequent inspection and refitting to keep in condition, is the
mushroom or poppet valve that controls the inlet and exhaust gas flow.
In overhauling it is essential that these valves be removed from their
seatings and examined carefully for various defects which will be
enumerated at proper time. The problem that concerns us now is the best
method of removing the valve. These are held against the seating in the
cylinder by a coil spring which exerts its pressure on the cylinder
casting at the upper end and against a suitable collar held by a key at
the lower end of the valve stem. In order to remove the valve it is
necessary to first compress the spring by raising the collar and pulling
the retaining key out of the valve stem. Many forms of valve spring
lifters have been designed to permit ready removal of the valves.

When the cylinder is of the valve in-the-head form, the method of valve
removal will depend entirely upon the system of cylinder construction
followed. In the Sturtevant cylinder design it is possible to remove the
head from the cylinder castings and the valve springs may be easily
compressed by any suitable means when the cylinder head is placed on the
work bench where it can be easily worked on. The usual method is to
place the head on a soft cloth with the valves bearing against the
bench. The valve springs may then be easily pushed down with a simple
forked lever and the valve stem key removed to release the valve spring
collar. In the Curtiss OX-2 (see Fig. 182-1/2) and Hall-Scott engines it
is not possible to remove the valves without taking the cylinder off
the crank-case, because the valve seats are machined directly in the
cylinder head and the valve domes are cast integrally with the cylinder.
This means that if the valves need grinding the cylinder must be removed
from the engine base to provide access to the valve heads which are
inside of that member, and which cannot be reached from the outside as
is true of the L-cylinder construction. In the Curtiss VX engines, the
valves are carried in detachable cages which may be removed when the
valves need attention.

[Illustration: Fig. 182-1/2.--Part Sectional View, Showing Valve
Arrangement in Cylinder of Curtiss OX-2 Aviation Engine.]

RESEATING AND TRUING VALVES

Much has been said relative to valve grinding, and despite the mass of
information given in the trade prints it is rather amusing to watch the
average repairman or the engine user who prides himself on maintaining
his own motor performing this essential operation. The common mistakes
are attempting to seat a badly grooved or pitted valve head on an
equally bad seat, which is an almost hopeless job, and of using coarse
emery and bearing down with all one's weight on the grinding tool with
the hope of quickly wearing away the rough surfaces. The use of improper
abrasive material is a fertile cause of failure to obtain a satisfactory
seating. Valve grinding is not a difficult operation if certain
precautions are taken before undertaking the work. The most important of
these is to ascertain if the valve head or seat is badly scored or
pitted. If such is found to be the case no ordinary amount of grinding
will serve to restore the surfaces. In this event the best thing to do
is to remove the valve from its seating and to smooth down both the
valve head and the seat in the cylinder before attempt is made to fit
them together by grinding. Another important precaution is to make sure
that the valve stem is straight, and that the head is not warped out of
shape.

[Illustration: Fig. 183.--Tools for Restoring Valve Head and Seats.]

A number of simple tools is available at the present time for reseating
valves, these being outlined at Fig. 183. That shown at A is a simple
fixture for facing off the valve head. The stem is supported by suitable
bearings carried by the body or shank of the tool, and the head is
turned against an angularly disposed cutter which is set for the proper
valve seat angle. The valve head is turned by a screw-driver, the amount
of stock removed from the head depending upon the location of the
adjusting screw. Care must be taken not to remove too much metal, only
enough being taken off to remove the most of the roughness. Valves are
made in two standard tapers, the angle being either 45 or 60 degrees. It
is imperative that the cutter blade be set correctly in order that the
bevel is not changed. A set of valve truing and valve-seat reaming
cutters is shown at Fig. 183, B. This is adaptable to various size valve
heads, as the cutter blade D may be moved to correspond to the size of
the valve head being trued up. These cutter blades are made of tool
steel and have a bevel at each end, one at 45 degrees, the other at 60
degrees. The valve seat reamer shown at G will take any one of the heads
shown at F. It will also take any one of the guide bars shown at H. The
function of the guide bars is to fit the valve stem bearing in order to
locate the reamer accurately and to insure that the valve seat is
machined concentrically with its normal center. Another form of valve
seat reamer and a special wrench used to turn it is shown at C. The
valve head truer shown at Fig. 183, D, is intended to be placed in a
vise and is adaptable to a variety of valve head sizes. The smaller
valves merely fit deeper in the conical depression. The cutter blade is
adjustable and the valve stem is supported by a simple self-centering
bearing. In operation it is intended that the valve stem, which
protrudes through the lower portion of the guide bearing, shall be
turned by a drill press or bit stock while the valve head is set against
the cutter by pressure of a pad carried at the end of a feed screw which
is supported by a hinged bridge member. This can be swung out of place
as indicated to permit placing the valve head against the cutter or
removing it.

As the sizes of valve heads and stems vary considerably a "Universal"
valve head truing tool must have some simple means of centering the
valve stem in order to insure concentric machining of the valve head. A
valve head truer which employs an ingenious method of guiding the valve
stem is shown at Fig. 183, E. The device consists of a body portion, B,
provided with an external thread at the top on which the cutter head, A,
is screwed. A number of steel balls, C, are carried in the grooves which
may be altered in size by the adjustment nut, F, which screws in the
bottom of the body portion, B. As the nut F is screwed in against the
spacer member E, the V-grooves are reduced in size and the steel balls,
C, are pressed out in contact with the valve stem. As the circle or
annulus is filled with balls in both upper and lower portions the stem
may be readily turned because it is virtually supported by ball bearing
guides. When a larger valve stem is to be supported, the adjusting nut
F, is screwed out which increases the size of the grooves and permits
the balls, C, to spread out and allow the larger stem to be inserted.

VALVE GRINDING PROCESSES

Mention has been previously made of the importance of truing both valve
head and seat before attempt is made to refit the parts by grinding.
After smoothing the valve seat the next step is to find some way of
turning the valve. Valve heads are usually provided with a screw-driver
slot passing through the boss at the top of the valve or with two
drilled holes to take a forked grinding tool. A combination grinding
tool has been devised which may be used when either the two drilled
holes or the slotted head form of valve is to be rotated. This consists
of a special form of screw driver having an enlarged boss just above the
blade, this boss serving to support a U-shape piece which can be
securely held in operative position by the clamp screw or which can be
turned out of the way if the screw driver blade is to be used.

As it is desirable to turn the valve through a portion of a revolution
and back again rather than turning it always in the same direction, a
number of special tools has been designed to make this oscillating
motion possible without trouble. A simple valve grinding tool is shown
at Fig. 184, C. This consists of a screw-driver blade mounted in a
handle in such a way that the end may turn freely in the handle. A
pinion is securely fastened to the screw-driver blade shank, and is
adapted to fit a race provided with a wood handle and guided by a bent
bearing member securely fastened to the screw-driver handle. As the rack
is pushed back and forth the pinion must be turned first in one
direction and then in the other.

[Illustration: Fig. 184.--Tools and Processes Utilized in Valve
Grinding.]

A valve grinding tool patterned largely after a breast drill is shown at
Fig. 184, D. This is worked in such a manner that a continuous rotation
of the operating crank will result in an oscillating movement of the
chuck carrying the screw-driver blade. The bevel pinions which are used
to turn the chuck are normally free unless clutched to the chuck stem by
the sliding sleeve which must turn with the chuck stem and which carries
clutching members at each end to engage similar members on the bevel
pinions and lock these to the chuck stem, one at a time. The bevel gear
carries a cam-piece which moves the clutch sleeve back and forth as it
revolves. This means that the pinion giving forward motion of the chuck
is clutched to the chuck spindle for a portion of a revolution of the
gear and clutch sleeve is moved back by the cam and clutched to the
pinion giving a reverse motion of the chuck during the remainder of the
main drive gear revolution.

It sometimes happens that the adjusting screw on the valve lift plunger
or the valve lift plunger itself when L head cylinders are used does not
permit the valve head to rest against the seat. It will be apparent that
unless a definite space exists between the end of the valve stem and the
valve lift plunger that grinding will be of little avail because the
valve head will not bear properly against the abrasive material smeared
on the valve seat.

The usual methods of valve grinding are clearly outlined at Fig. 184.
The view at the left shows the method of turning the valve by an
ordinary screw driver and also shows a valve head at A, having both the
drilled holes and the screw-driver slot for turning the member and two
special forms of fork-end valve grinding tools. In the sectional view
shown at the right, the use of the light spring between the valve head
and the bottom of the valve chamber to lift the valve head from the seat
whenever pressure on the grinding tool is released is clearly indicated.
It will be noted also that a ball of waste or cloth is interposed in the
passage between the valve chamber and the cylinder interior to prevent
the abrasive material from passing into the cylinder from the valve
chamber. When a bitstock is used, instead of being given a true rotary
motion the chuck is merely oscillated through the greater part of the
circle and back again. It is necessary to lift the valve from its seat
frequently as the grinding operation continues; this is to provide an
even distribution of the abrasive material placed between the valve head
and its seat. Only sufficient pressure is given to the bitstock to
overcome the uplift of the spring and to insure that the valve will be
held against the seat. Where the spring is not used it is possible to
raise the valve from time to time with the hand which is placed under
the valve stem to raise it as the grinding is carried on. It is not
always possible to lift the valve in this manner when the cylinders are
in place on the engine base owing to the space between the valve lift
plunger and the end of the valve stem. In this event the use of the
spring as shown in sectional view will be desirable.

The abrasive generally used is a paste made of medium or fine emery and
lard oil or kerosene. This is used until the surfaces are comparatively
smooth, after which the final polish or finish is given with a paste of
flour emery, grindstone dust, crocus, or ground glass and oil. An
erroneous impression prevails in some quarters that the valve head
surface and the seating must have a mirror-like polish. While this is
not necessary it is essential that the seat in the cylinder and the
bevel surface of the head be smooth and free from pits or scratches at
the completion of the operation. All traces of the emery and oil should
be thoroughly washed out of the valve chamber with gasoline before the
valve mechanism is assembled and in fact it is advisable to remove the
old grinding compound at regular intervals, wash the seat thoroughly and
supply fresh material as the process is in progress.

The truth of seatings may be tested by taking some Prussian blue pigment
and spreading a thin film of it over the valve seat. The valve is
dropped in place and is given about one-eighth turn with a little
pressure on the tool. If the seating is good both valve head and seat
will be covered uniformly with color. If high spots exist, the heavy
deposit of color will show these while the low spots will be made
evident because of the lack of pigment. The grinding process should be
continued until the test shows an even bearing of the valve head at all
points of the cylinder seating. When the valves are held in cages it is
possible to catch the cage in a vise and to turn the valve in any of the
ways indicated. It is much easier to clean off the emery and oil and
there is absolutely no danger of getting the abrasive material in the
cylinder if the construction is such that the valve cage or cylinder
head member carrying the valve can be removed from the cylinder. When
valves are held in cages, the tightness of the seat may be tested by
partially filling the cage with gasoline and noticing how much liquid
oozes out around the valve head. The degree of moisture present
indicates the efficacy of the grinding process.

The valves of Curtiss OX-2 cylinders are easily ground in by using a
simple fixture or tool and working from the top of the cylinder instead
of from the inside. A tube having a bore just large enough to go over
the valve stem is provided with a wooden handle or taped at one end and
a hole of the same size as that drilled through the valve stem is put in
at the other. To use, the open end of the tube is pushed over the valve
stem and a split pin pushed through the tube and stem. The valve may be
easily manipulated and ground in place by oscillating in the customary
manner.

DEPRECIATION IN VALVE OPERATING SYSTEMS

There are a number of points to be watched in the valve operating system
because valve timing may be seriously interfered with if there is much
lost motion at the various bearing points in the valve lift mechanism.
The two conventional methods of opening valves are shown at Fig. 185.
That at A is the type employed when the valve cages are mounted directly
in the head, while the form at B is the system used when the valves are
located in a pocket or extension of the cylinder casting as is the case
if an L, or T-head cylinder is used. It will be evident that there are
several points where depreciation may take place. The simplest form is
that shown at B, and even on this there are five points where lost
motion may be noted. The periphery of the valve opening cam or roller
may be worn, though this is not likely unless the roller or cam has
been inadvertently left soft. The pin which acts as a bearing for the
roller may become worn, this occurring quite often. Looseness may
materialize between the bearing surfaces of the valve lift plunger and
the plunger guide casting, and there may also be excessive clearance
between the top of the plunger and the valve stem.

[Illustration: Fig. 185.--Outlining Points in Valve Operating Mechanism
Where Depreciation is Apt to Exist.]

On the form shown at A, there are several parts added to those indicated
at B. A walking beam or rocker lever is necessary to transform the
upward motion of the tappet rod to a downward motion of the valve stem.
The pin on which this member fulcrums may wear as will also the other
pin acting as a hinge or bearing for the yoke end of the tappet rod. It
will be apparent that if slight play existed at each of the points
mentioned it might result in a serious diminution of valve opening.
Suppose, for example, that there were .005-inch lost motion at each of
three bearing points, the total lost motion would be .015-inch or
sufficient to produce noisy action of the valve mechanism. When valve
plungers of the adjustable form, such as shown at B, are used, the
hardened bolt head in contact with the end of the valve stem may become
hollowed out on account of the hammering action at that point. It is
imperative that the top of this member be ground off true and the
clearance between the valve stem and plunger properly adjusted. If the
plunger is a non-adjustable type it will be necessary to lengthen the
valve stem by some means in order to reduce the excessive clearance. The
only remedy for wear at the various hinges and bearing pins is to bore
the holes out slightly larger and to fit new hardened steel pins of
larger diameter. Depreciation between the valve plunger guide and the
valve plunger is usually remedied by fitting new plunger guides in place
of the worn ones. If there is sufficient stock in the plunger guide
casting as is sometimes the case when these members are not separable
from the cylinder casting, the guide may be bored out and bushed with a
light bronze bushing.

A common cause of irregular engine operation is due to a sticking valve.
This may be owing to a bent valve stem, a weak or broken valve spring or
an accumulation of burnt or gummed oil between the valve stem and the
valve stem guide. In order to prevent this the valve stem must be
smoothed with fine emery cloth and no burrs or shoulders allowed to
remain on it, and the stem must also be straight and at right angles to
the valve head. If the spring is weak it may be strengthened in some
cases by stretching it out after annealing so that a larger space will
exist between the coils and re-hardening. Obviously if a spring is
broken the only remedy is replacement of the defective member.

Mention has been made of wear in the valve stem guide and its influence
on engine action. When these members are an integral part of the
cylinder the only method of compensating for this wear is to drill the
guide out and fit a bushing, which may be made of steel tube.

In some engines, especially those of recent development, the valve stem
guide is driven or screwed into the cylinder casting and is a separate
member which may be removed when worn and replaced with a new one. When
the guides become enlarged to such a point that considerable play exists
between them and the valve stems, they may be easily knocked out or
unscrewed.

PISTON TROUBLES

If an engine has been entirely dismantled it is very easy to examine the
pistons for deterioration. While it is important that the piston be a
good fit in the cylinder it is mainly upon the piston rings that
compression depends. The piston should fit the cylinder with but little
looseness, the usual practice being to have the piston about .001-inch
smaller than the bore for each inch of piston diameter at the point
where the least heat is present or at the bottom of the piston. It is
necessary to allow more than this at the top of the piston owing to its
expansion due to the direct heat of the explosion. The clearance is
usually graduated and a piston that would be .005-inch smaller than the
cylinder bore at the bottom would be about .0065-inch at the middle and
.0075-inch at the top. If much more play than this is evidenced the
piston will "slap" in the cylinder and the piston will be worn at the
ends more than in the center. Aluminum or alloy pistons require more
clearance than cast iron ones do, usually 1.50 times as much. Pistons
sometimes warp out of shape and are not truly cylindrical. This results
in the high spots rubbing on the cylinder while the low spots will be
blackened where a certain amount of gas has leaked by.

Mention has been previously made of the necessity of reboring or
regrinding a cylinder that has become scored or scratched and which
allows the gas to leak by the piston rings. When the cylinder is ground
out, it is necessary to use a larger piston to conform to the enlarged
cylinder bore. Most manufacturers are prepared to furnish over-size
pistons, there being four standard over-size dimensions adopted by the
S. A. E. for rebored cylinders. These are .010-inch, .020-inch,
.030-inch, and .040-inch larger than the original bore.

The piston rings should be taken out of the piston grooves and all
carbon deposits removed from the inside of the ring and the bottom of
the groove. It is important to take this deposit out because it prevents
the rings from performing their proper functions by reducing the ring
elasticity, and if the deposit is allowed to accumulate it may
eventually result in sticking and binding of the ring, this producing
excessive friction or loss of compression. When the rings are removed
they should be tested to see if they retain their elasticity and it is
also well to see that the small pins in some pistons which keep the
rings from turning around so the joints will not come in line are still
in place. If no pins are found there is no cause for alarm because these
dowels are not always used. When fitted, they are utilized with rings
having a butt joint or diagonal cut as the superior gas retaining
qualities of the lap or step joint render the pins unnecessary.

If gas has been blowing by the ring or if these members have not been
fitting the cylinder properly the points where the gas passed will be
evidenced by burnt, brown or roughened portions of the polished surface
of the pistons and rings. The point where this discoloration will be
noticed more often is at the thin end of an eccentric ring, the
discoloration being present for about 1/2-inch or 3/4-inch each side of
the slot. It may be possible that the rings were not true when first
put in. This made it possible for the gas to leak by in small amounts
initially which increased due to continued pressure until quite a large
area for gas escape had been created.

PISTON RING MANIPULATION

Removing piston rings without breaking them is a difficult operation if
the proper means are not taken, but is a comparatively simple one when
the trick is known. The tools required are very simple, being three
strips of thin steel about one-quarter inch wide and four or five inches
long and a pair of spreading tongs made up of one-quarter inch diameter
keystock tied in the center with a copper wire to form a hinge. The
construction is such that when the hand is closed and the handles
brought together the other end of the expander spreads out, an action
just opposite to that of the conventional pliers. The method of using
the tongs and the metal strips is clearly indicated at Fig. 186. At A
the ring expander is shown spreading the ends of the rings sufficiently
to insert the pieces of sheet metal between one of the rings and the
piston. Grasp the ring as shown at B, pressing with the thumbs on the
top of the piston and the ring will slide off easily, the thin metal
strips acting as guide members to prevent the ring from catching in the
other piston grooves. Usually no difficulty is experienced in removing
the top or bottom rings, as these members may be easily expanded and
worked off directly without the use of a metal strip. When removing the
intermediate rings, however, the metal strips will be found very useful.
These are usually made by the repairman by grinding the teeth from old
hacksaw blades and rounding the edges and corners in order to reduce the
liability of cutting the fingers. By the use of the three metal strips a
ring is removed without breaking or distorting it and practically no
time is consumed in the operation.

FITTING PISTON RINGS

Before installing new rings, they should be carefully fitted to the
grooves to which they are applied. The tools required are a large piece
of fine emery cloth, a thin, flat file, a small vise with copper or
leaden jaw clips, and a smooth hard surface such as that afforded by the
top of a surface plate or a well planed piece of hard wood. After making
sure that all deposits of burnt oil and carbon have been removed from
the piston grooves, three rings are selected, one for each groove. The
ring is turned all around its circumference into the groove it is to
fit, which can be done without springing it over the piston as the
outside edge of the ring may be used to test the width of the groove
just as well as the inside edge. The ring should be a fair fit and while
free to move circumferentially there should be no appreciable up and
down motion. If the ring is a tight fit it should be laid edge down upon
the piece of emery cloth which is placed on the surface plate and
carefully rubbed down until it fits the groove it is to occupy. It is
advisable to fit each piston ring individually and to mark them in some
way to insure that they will be placed in the groove to which they are
fitted.

The repairman next turns his attention to fitting the ring in the
cylinder itself. The ring should be pushed into the cylinder at least
two inches up from the bottom and endeavor should be made to have the
lower edge of the ring parallel with the bottom of the cylinder. If the
ring is not of correct diameter, but is slightly larger than the
cylinder bore, this condition will be evident by the angular slots of
the rings being out of line or by difficulty in inserting the ring if it
is a lap joint form. If such is the case the ring is removed from the
cylinder and placed in the vise between soft metal jaw clips. Sufficient
metal is removed with a fine file from the edges of the ring at the slot
until the edges come into line and a slight space exists between them
when the ring is placed into the cylinder. It is important that this
space be left between the ends, for if this is not done when the ring
becomes heated the expansion of metal may cause the ends to abut and the
ring to jam in the cylinder.

[Illustration: Fig. 186.--Method of Removing Piston Rings, and Simple
Clamp to Facilitate Insertion of Rings in Cylinder.]

It is necessary to use more than ordinary caution in replacing the rings
on the piston because they are usually made of cast iron, a metal that
is very fragile and liable to break because of its brittleness. Special
care should be taken in replacing new rings as these members are more
apt to break than old ones. This is probably accounted for by the
heating action on used rings which tends to anneal the metal as well as
making it less springy. The bottom ring should be placed in position
first which is easily accomplished by springing the ring open enough to
pass on the piston and then sliding it into place in the lower groove
which on some types of engines is below the wrist pin, whereas in others
all grooves are above that member. The other members are put in by a
reversal of the process outlined at Fig. 186, A and B. It is not always
necessary to use the guiding strips of metal when replacing rings as it
is often possible, by putting the rings on the piston a little askew and
maneuvering them to pass the grooves without springing the ring into
them. The top ring should be the last one placed in position.

Before placing pistons in the cylinder one should make sure that the
slots in the piston rings are spaced equidistant on the piston, and if
pins are used to keep the ring from turning one should be careful to
make sure that these pins fit into their holes in the ring and that they
are not under the ring at any point. Practically all cylinders are
chamfered at the lower end to make insertion of piston rings easier. The
operation of putting on a cylinder casting over a piston really requires
two pairs of hands, one to manipulate the cylinder, the other person to
close the rings as they enter the cylinder. This may be done very easily
by a simple clamp member made of sheet brass or iron and used to close
the ring as indicated at Fig. 186, C. It is apparent that the clamp must
be adjusted to each individual ring and that the split portion of the
clamp must coincide with the split portion of the ring. The cylinder
should be well oiled before any attempt is made to install the pistons.
The engine should be run with more than the ordinary amount of lubricant
for several hours after new piston rings have been inserted. On first
starting the engine, one may be disappointed in that the compression is
even less than that obtained with the old rings. This condition will
soon be remedied as the rings become polished and adapt themselves to
the contour of the cylinder.

WRIST PIN WEAR

While wrist pins are usually made of very tough steel, case hardened
with the object of wearing out an easily renewable bronze bushing in the
upper end of the connecting rod rather than the wrist pin it sometimes
happens that these members will be worn so that even the replacement of
a new bushing in the connecting rod will not reduce the lost motion and
attendant noise due to a loose wrist pin. The only remedy is to fit new
wrist pins to the piston. Where the connecting rod is clamped to the
wrist pin and that member oscillates in the piston bosses the wear will
usually be indicated on bronze bushings which are pressed into the
piston bosses. These are easily renewed and after running a reamer
through them of the proper size no difficulty should be experienced in
replacing either the old or a new wrist pin depending upon the condition
of that member. If no bushings are provided, as in alloy pistons, the
bosses can sometimes be bored out and thin bushings inserted, though
this is not always possible. The alternative is to ream out the bosses
and upper end of rod a trifle larger after holes are trued up and fit
oversize wrist pins.

INSPECTION AND REFITTING OF ENGINE BEARINGS

While the engine is dismantled one has an excellent opportunity to
examine the various bearing points in the engine crank-case to ascertain
if any looseness exists due to depreciation of the bearing surfaces. As
will be evident, both main crank-shaft bearings and the lower end of the
connecting rods may be easily examined for deterioration. With the rods
in place, it is not difficult to feel the amount of lost motion by
grasping the connecting rod firmly with the hand and moving it up and
down. After the connecting rods have been removed and the propeller hub
taken off the crank-shaft to permit of ready handling, any looseness in
the main bearing may be detected by lifting up on either the front or
rear end of the crank-shaft and observing if there is any lost motion
between the shaft journal and the main bearing caps. It is not necessary
to take an engine entirely apart to examine the main bearings, as in
most forms these may be readily reached by removing the sump. The
symptoms of worn main bearings are not hard to identify. If an engine
knocks regardless of speed or spark-lever position, and the trouble is
not due to carbon deposits in the combustion chamber, one may reasonably
surmise that the main bearings have become loose or that lost motion may
exist at the connecting rod big ends, and possibly at the wrist pins.
The main journals of any well resigned engine are usually proportioned
with ample surface and will not wear unduly unless lubrication has been
neglected. The connecting rod bearings wear quicker than the main
bearings owing to being subjected to a greater unit stress, and it may
be necessary to take these up.

ADJUSTING MAIN BEARINGS

[Illustration: Fig. 187.--Tools and Processes Used in Refitting Engine
Bearings.]

When the bearings are not worn enough to require refitting the lost
motion can often be eliminated by removing one or more of the thin shims
or liners ordinarily used to separate the bearing caps from the seat.
These are shown at Fig. 187, A. Care must be taken that an even number
of shims of the same thickness are removed from each side of the
journal. If there is considerable lost motion after one or two shims
have been removed, it will be advisable to take out more shims and to
scrape the bearing to a fit before the bearing cap is tightened up. It
may be necessary to clean up the crank-shaft journals as these may be
scored due to not having received clean oil or having had bearings seize
upon them. It is not difficult to true up the crank-pins or main
journals if the score marks are not deep. A fine file and emery cloth
may be used, or a lapping tool such as depicted at Fig. 187, B. The
latter is preferable because the file and emery cloth will only tend to
smooth the surface while the lap will have the effect of restoring the
crank to proper contour.

A lapping tool may be easily made, as shown at B, the blocks being of
lead or hard wood. As the width of these are about half that of the
crank-pin the tool may be worked from side to side as it is rotated. An
abrasive paste composed of fine emery powder and oil is placed between
the blocks, and the blocks are firmly clamped to the crank-pin. As the
lead blocks bed down, the wing nut should be tightened to insure that
the abrasive will be held with some degree of pressure against the
shaft. A liberal supply of new abrading material is placed between the
lapping blocks and crank-shaft from time to time and the old mixture
cleaned off with gasoline. It is necessary to maintain a side to side
movement of the lapping tool in order to have the process affect the
whole width of the crank-pin equally. The lapping is continued until a
smooth surface is obtained. If a crank-pin is worn out of true to any
extent the only method of restoring it is to have it ground down to
proper circular form by a competent mechanic having the necessary
machine tools to carry on the work accurately. A crank-pin truing tool
that may be worked by hand is shown at Fig. 187, K.

After the crank-shaft is trued the next operation is to fit it to the
main bearings or rather to scrape these members to fit the shaft
journal. In order to bring the brasses closer together, it may be
necessary to remove a little metal from the edges of the caps to
compensate for the lost motion. A very simple way of doing this is shown
at Fig. 187, D. A piece of medium emery cloth is rested on the surface
plate and the box or brass is pushed back and forth over that member by
hand, the amount of pressure and rapidity of movement being determined
by the amount of metal it is necessary to remove. This is better than
filing, because the edges will be flat and there will be no tendency
for the bearing caps to rock when placed against the bearing seat. It is
important to take enough off the edges of the boxes to insure that they
will grip the crank tightly. The outer diameter must be checked with a
pair of calipers during this operation to make sure that the surfaces
remain parallel. Otherwise, the bearing brasses will only grip at one
end and with such insufficient support they will quickly work loose,
both in the bearing seat and bearing cap.

SCRAPING BRASSES TO FIT

To insure that the bearing brasses will be a good fit on the trued-up
crank-pins or crank-shaft journals, they must be scraped to fit the
various crank-shaft journals. The process of scraping, while a tedious
one, is not difficult, requiring only patience and some degree of care
to do a good job. The surface of the crank-pin is smeared with Prussian
blue pigment which is spread evenly over the entire surface. The
bearings are then clamped together in the usual manner with the proper
bolts, and the crank-shaft revolved several times to indicate the high
spots on the bearing cap. At the start of the process of scraping in,
the bearing may seat only at a few points as shown at Fig. 187, G.
Continued scraping will bring the bearing surface as indicated at H,
which is a considerable improvement, while the process may be considered
complete when the brass indicates a bearing all over as at I. The high
spots are indicated by blue, as where the shaft does not bear on the
bearing there is no color. The high spots are removed by means of a
scraping tool of the form shown at Fig. 187, F, which is easily made
from a worn-out file. These are forged to shape and ground hollow as
indicated in the section, and are kept properly sharpened by frequent
rubbing on an ordinary oil stone. To scrape properly, the edge of the
scraper must be very keen. The straight and curved half-round scrapers,
shown at M and N, are used for bearings. The three-cornered scraper,
outlined at O, is also used on curved surfaces, and is of value in
rounding off the sharp corners. The straight or curved half-round type
works well on soft-bearing metals, such as babbitt, or white brass, but
on yellow brass or bronze it cuts very slowly, and as soon as the edge
becomes dull considerable pressure is needed to remove any metal, this
calling for frequent sharpening.

When correcting errors on flat or curved surfaces by hand-scraping, it
is desirable, of course, to obtain an evenly spotted bearing with as
little scraping as possible. When the part to be scraped is first
applied to the surface-plate, or to a journal in the case of a bearing,
three or four "high" spots may be indicated by the marking material. The
time required to reduce these high spots and obtain a bearing that is
distributed over the entire surface depends largely upon the way the
scraping is started. If the first bearing marks indicate a decided rise
in the surface, much time can be saved by scraping larger areas than are
covered by the bearing marks; this is especially true of large shaft and
engine bearings, etc. An experienced workman will not only remove the
heavy marks, but also reduce a larger area; then, when the bearing is
tested again, the marks will generally be distributed somewhat. If the
heavy marks which usually appear at first are simply removed by light
scraping, these "point bearings" are gradually enlarged, but a much
longer time will be required to distribute them.

The number of times the bearing must be applied to the journal for
testing is important, especially when the box or bearing is large and
not easily handled. The time required to distribute the bearing marks
evenly depends largely upon one's judgment in "reading" these marks. In
the early stages of the scraping operation, the marks should be used
partly as a guide for showing the high areas, and instead of merely
scraping the marked spot the surface surrounding it should also be
reduced, unless it is evident that the unevenness is local. The idea
should be to obtain first a few large but generally distributed marks;
then an evenly and finely spotted surface can be produced quite easily.

In fitting brasses when these are of the removable type, two methods may
be used. The upper half of the engine base may be inverted on a suitable
bench or stand and the boxes fitted by placing the crank-shaft in
position, clamping down one bearing cap at a time and fitting each
bearing in succession until they bed equally. From that time on the
bearings should be fitted at the same time so the shaft will be parallel
with the bottom of the cylinders. Considerable time and handling of the
heavy crank-shaft may be saved if a preliminary fitting of the bearing
brasses is made by clamping them together with a carpenter's wood clamp
as shown at Fig. 187, J, and leaving the crank-shaft attached to the
bench as shown at C. The brasses are revolved around the crank-shaft
journal and are scraped to fit wherever high spots are indicated until
they begin to seat fairly. When the brasses assume a finished appearance
the final scraping should be carried on with all bearings in place and
revolving the crank-shaft to determine the area of the seating. When the
brasses are properly fitted they will not only show a full bearing
surface, but the shaft will not turn unduly hard if revolved with a
moderate amount of leverage.

Bearings of white metal or babbitt can be fitted tighter than those of
bronze, and care must be observed in supplying lubricant as considerably
more than the usual amount is needed until the bearings are run in by
several hours of test block work. Before the scraping process is started
it is well to chisel an oil groove in the bearing as shown at Fig. 187,
L. Grooves are very helpful in insuring uniform distribution of oil over
the entire width of bearing and at the same time act as reservoirs to
retain a supply of oil. The tool used is a round-nosed chisel, the
effort being made to cut the grooves of uniform depth and having smooth
sides. Care should be taken not to cut the grooves too deeply, as this
will seriously reduce the strength of the bearing bushing. The shape of
the groove ordinarily provided is clearly shown at Fig. 187, G, and it
will be observed that the grooves do not extend clear to the edge of the
bearing, but stop about a quarter of an inch from that point. The hole
through which the oil is supplied to the bearing is usually drilled in
such a way that it will communicate with the groove.

The tool shown at Fig. 187, K, is of recent development, and is known as
a "crank-shaft equalizer." This is a hand-operated turning tool,
carrying cutters which are intended to smooth down scored crank-pins
without using a lathe. The feed may be adjusted by suitable screws and
the device may be fitted to crank-pins and shaft-journals of different
diameters by other adjusting screws. This device is not hard to operate,
being merely clamped around the crank-shaft in the same manner as the
lapping tool previously described, and after it has been properly
adjusted it is turned around by the levers provided for the purpose, the
continuous rotary motion removing the metal just as a lathe tool would.

FITTING CONNECTING RODS

In the marine type rod, which is the form generally used in airplane
engines, one or two bolts are employed at each side and the cap must be
removed entirely before the bearing can be taken off of the crank-pin.
The tightness of the brasses around the crank-pin can never be
determined solely by the adjustment of the bolts, as while it is
important that these should be drawn up as tightly as possible, the
bearing should fit the shaft without undue binding, even if the brasses
must be scraped to insure a proper fit. As is true of the main bearings,
the marine form of connecting rod in some engines has a number of liners
or shims interposed between the top and lower portions of the rod end,
and these may be reduced in number when necessary to bring the brasses
closer together. The general tendency in airplane engines is to
eliminate shims in either the main or connecting rod bearings, and when
wear is noticed the boxes or liners are removed and new ones supplied.
The brasses are held in the connecting rod and cap by brass rivets and
are generally attached in the main bearing by small brass machine
screws. The form of box generally favored is a brass sand casting rich
in copper to secure good heat conductivity which forms a backing for a
thin layer of white brass, babbitt or similar anti-friction metal.

[Illustration: Fig. 188.--Showing Points to Observe When Fitting
Connecting Rod Brasses.]

In fitting new brasses there are two conditions to be avoided, these
being outlined at Fig. 188, B and C. In the case shown at C the light
edges of the bushings are in contact, but the connecting rod and its cap
do not meet. When the retaining nuts are tightened the entire strain is
taken on the comparatively small area of the edges of the bushings which
are not strong enough to withstand the strains existing and which
flatten out quickly, permitting the bearing to run loose. In the example
outlined at B the edges of the brasses do not touch when the connecting
rod cap is drawn in place. This is not good practice, because the
brasses soon become loose in their retaining member. In the case
outlined it is necessary to file off the faces of the rod and cap until
these meet, and to insure contact of the edges of the brasses as well.
In event of the brasses coming together before the cap and rod make
contact, as shown at C, the bearing halves should be reduced at the
edges until both the caps and brasses meet against each other or the
surfaces of the liners as shown at A.

SPRUNG CAM-SHAFT

If the cam-shaft is sprung or twisted it will alter the valve timing to
such an extent that the smoothness of operation of the engine will be
materially affected. If this condition is suspected the cam-shaft may be
swung on lathe centers and turned to see if it runs out and can be
straightened in any of the usual form of shaft-straightening machines.
The shaft may be twisted without being sprung. This can only be
determined by supporting one end of the shaft in an index head and the
other end on a milling machine center. The cams are then checked to see
that they are separated by the proper degree of angularity. This process
is one that requires a thorough knowledge of the valve timing of the
engine in question, and is best done at the factory where the engine was
made. The timing gears should also be examined to see if the teeth are
worn enough so that considerable back lash or lost motion exists between
them. This is especially important where worm or spiral gears are used.
A worn timing gear not only produces noise, but it will cause the time
of opening and closing of the engine valves to vary materially.

PRECAUTIONS IN REASSEMBLING PARTS

When all of the essential components of a power plant have been
carefully looked over and cleaned and all defects eliminated, either by
adjustment or replacement of worn portions, the motor should be
reassembled, taking care to have the parts occupy just the same
relative positions they did before the motor was dismantled. As each
part is added to the assemblage care should be taken to insure adequate
lubrication of all new points of bearing by squirting liberal quantities
of cylinder oil upon them with a hand oil can or syringe provided for
the purpose. In adjusting the crank-shaft bearings, tighten them one at
a time and revolve the shafts each time one of the bearing caps is set
up to insure that the newly adjusted bearing does not have undue
friction. All retaining keys and pins must be positively placed and it
is good practice to cover such a part with lubricant before replacing it
because it will not only drive in easier, but the part may be removed
more easily if necessary at some future time. If not oiled, rust
collects around it.

When a piece is held by more than one bolt or screw, especially if it is
a casting of brittle material such as cast iron or aluminum, the
fastening bolts should be tightened uniformly. If one bolt is tightened
more than the rest it is liable to spring the casting enough to break
it. Spring washers, check nuts, split pins or other locking means should
always be provided, especially on parts which are in motion or subjected
to heavy loads.

Before placing the cylinder over the piston it is imperative that the
slots in the piston rings are spaced equidistant and that the piston is
copiously oiled before the cylinder is slipped over it. When
reassembling the inlet and exhaust manifolds it is well to use only
perfect packings or gaskets and to avoid the use of those that seem to
have hardened up or flattened out too much in service. If it is
necessary to use new gaskets it is imperative to employ these at all
joints on a manifold, because if old and new gaskets are used together
the new ones are apt to keep the manifold from bedding properly upon the
used ones. It is well to coat the threads of all bolts and screws
subjected to heat, such as cylinder head and exhaust manifold retaining
bolts, with a mixture of graphite and oil. Those that enter the water
jacket should be covered with white or red lead or pipe thread
compound. Gaskets will hold better if coated with shellac before the
manifold or other parts are placed over them. The shellac fills any
irregularities in the joint and assists materially in preventing leakage
after the joint is made up and the coating has a chance to set.

Before assembling on the shaft, it is necessary to fit the bearings by
scraping, the same instructions given for restoring the contour of the
main bearings applying just as well in this case. It is apparent that if
the crank-pins are not round no amount of scraping will insure a true
bearing. A point to observe is to make sure that the heads of the bolts
are imbedded solidly in their proper position, and that they are not
raised by any burrs or particles of dirt under the head which will
flatten out after the engine has been run for a time and allow the bolts
to slack off. Similarly, care should be taken that there is no foreign
matter under the brasses and the box in which they seat. To guard
against this the bolts should be struck with a hammer several times
after they are tightened up, and the connecting rod can be hit sharply
several times under the cap with a wooden mallet or lead hammer. It is
important to pin the brasses in place to prevent movement, as
lubrication may be interfered with if the bushing turns round and breaks
the correct register between the oil hole in the cap and brasses.

Care should be taken in screwing on the retaining nuts to insure that
they will remain in place and not slack off. Spring washers should not
be used on either connecting rod ends or main bearing nuts, because
these sometimes snap in two pieces and leave the nut slack. The best
method of locking is to use well-fitting split pins and castellated
nuts.

TESTING BEARING PARALLELISM

It is not possible to give other than general directions regarding the
proper degree of tightening for a connecting rod bearing, but as a guide
to correct adjustment it may be said that if the connecting rod cap is
tightened sufficiently so the connecting rod will just about fall over
from a vertical position due to the piston weight when the bolts are
fully tightened up, the adjustment will be nearly correct. As previously
stated, babbitt or white metal bearings can be set up more tightly than
bronze, as the metal is softer and any high spots will soon be leveled
down with the running of the engine. It is important that care be taken
to preserve parallelism of the wrist-pins and crank-shafts while
scraping in bearings. This can be determined in two ways. That shown at
Fig. 189, A, is used when the parts are not in the engine assembly and
when the connecting rod bearing is being fitted to a mandrel or arbor
the same size as the crank-pin. The arbor, which is finished very smooth
and of uniform diameter, is placed in two V blocks, which in turn are
supported by a level surface plate. An adjustable height gauge may be
tried, first at one side of the wrist-pin which is placed at the upper
end of the connecting rod, then at the other, and any variation will be
easily determined by the degree of tilting of the rod. This test may be
made with the wrist-pin alone, or if the piston is in place, a straight
edge or spirit level may be employed. The spirit level will readily show
any inclination while the straight edge is used in connection with the
height gauge as indicated. Of course, the surface plate must be
absolutely level when tests are made.

When the connecting rods are being fitted with the crank-shaft in place
in crank-case, and that member secured in the frame, a steel square may
be used as it is reasonable to assume that the wrist-pin, and
consequently the piston it carries, should observe a true relation with
the top of the engine base. If the piston side is at right angles with
the top of the engine base it is reasonable to assume that the wrist-pin
and crank-pin are parallel. If the piston is canted to one side or the
other, it will indicate that the brasses have been scraped tapering,
which would mean considerable heating and undue friction if the piston
is installed in the cylinder on account of the pressure against one
portion of the cylinder wall. If the degree of canting is not too great,
the connecting rods may be sprung very slightly to straighten up the
piston, but this is a makeshift that is not advised. The height gauge
method shown above may be used instead of the steel square, if desired,
because the top of the crank-case is planed or milled true and should be
parallel with the center line of the crank-shaft.

[Illustration: Fig. 189.--Methods of Testing to Insure Parallelism of
Bearings After Fitting.]

CAM-SHAFTS AND TIMING GEARS

Knocking sounds are also evident if the cam-shaft is loose in its
bearings, and also if the cams or timing gears are loose on the shaft.
The cam-shaft is usually supported by solid bearings of the removable
bushing type, having no compensation for depreciation. If these bearings
wear the only remedy is replacement with new ones. In the older makes of
cars it was general practice to machine the cams separately and to
secure these to the cam-shaft by means of taper pins or keys. These
members sometimes loosened and caused noise. In the event of the cams
being loose, care should be taken to use new keys or taper pins, as the
case may be. If the fastening used was a pin, the hole through the
cam-shaft will invariably be slightly oval from wear. In order to insure
a tight job, the holes in cam and shaft must be reamed with the next
larger size of standard taper reamer and a larger pin driven in. Another
point to watch is the method of retaining the cam-shaft gear in place.
On some engines the gear is fastened to a flange on the cam-shaft by
retaining screws. These are not apt to become loose, but where reliance
is placed on a key the cam-shaft gear may often be loose on its
supporting member. The only remedy is to enlarge the key slot in both
gear and shaft and to fit a larger retaining key.

CHAPTER XII

Aviation Engine Types--Division in Classes--Anzani Engines--
Canton and Unné Engine--Construction of Gnome Engines--
"Monosoupape" Gnome--German "Gnome" Type--Le Rhone Engine--
Renault Air-Cooled Engine--Simplex Model "A" Hispano-Suiza--
Curtiss Aviation Motors--Thomas-Morse Model 88 Engine--
Duesenberg Engine--Aeromarine Six-Cylinder--Wisconsin Aviation
Engines--Hall-Scott Engines--Mercedes Motor--Benz Motor--
Austro-Daimler--Sunbeam-Coatalen.

AVIATION ENGINE TYPES

Inasmuch as numerous forms of airplane engines have been devised, it
would require a volume of considerable size to describe even the most
important developments of recent years. As considerable explanatory
matter has been given in preceding chapters and the principles involved
in internal combustion engine operation considered in detail, a
relatively brief review of the features of some of the most successful
airplane motors should suffice to give the reader a complete enough
understanding of the art so all types of engines can be readily
recognized and the advantages and disadvantages of each type understood,
as well as defining the constructional features enough so the methods of
locating and repairing the common engine and auxiliary system troubles
will be fully grasped.

Aviation engines can be divided into three main classes. One of the
earliest attempts to devise distinctive power plant designs for aircraft
involved the construction of engines utilizing a radial arrangement of
the cylinders or a star-wise disposition. Among the engines of this
class may be mentioned the Anzani, R. E. P. and the Salmson or Canton
and Unné forms. The two former are air-cooled, the latter design is
water-cooled. Engines of this type have been built in cylinder numbers
ranging from three to twenty. While the simple forms were popular in the
early days of aviation engine development, they have been succeeded by
the more conventional arrangements which now form the largest class. The
reason for the adoption of a star-wise arrangement of cylinders has been
previously considered. Smoothness of running can only be obtained by
using a considerable number of cylinders. The fundamental reason for the
adoption of the star-wise disposition is that a better distribution of
stress is obtained by having all of the pistons acting on the same
crank-pin so that the crank-throw and pin are continuously under maximum
stress. Some difficulty has been experienced in lubricating the lower
cylinders in some forms of six cylinder, rotary crank, radial engines
but these have been largely overcome so they are not as serious in
practice as a theoretical consideration would indicate.

Another class of engines developed to meet aviation requirements is a
complete departure from the preceding class, though when the engines are
at rest, it is difficult to differentiate between them. This class
includes engines having a star-wise disposition of the cylinders but the
cylinders themselves and the crank-case rotate and the crank-shaft
remains stationary. The important rotary engines are the Gnome, the Le
Rhone and the Clerget. By far the most important classification is that
including engines which retain the approved design of the types of power
plants that have been so widely utilized in automobiles and which have
but slight modifications to increase reliability and mechanical strength
and produce a reduction in weight. This class includes the vertical
engines such as the Duesenberg and Hall-Scott four-cylinder; the
Wisconsin, Aeromarine, Mercedes, Benz, and Hall-Scott six-cylinder
vertical engines and the numerous eight- and twelve-cylinder Vee designs
such as the Curtiss, Renault, Thomas-Morse, Sturtevant, Sunbeam, and
others.

ANZANI ENGINES

The attention of the mechanical world was first directed to the great
possibilities of mechanical flight when Bleriot crossed the English
Channel in July, 1909, in a monoplane of his own design and
construction, having the power furnished by a small three-cylinder
air-cooled engine rated at about 24 horse-power and having cylinders
4.13 inches bore and 5.12 inches stroke, stated to develop the power at
about 1600 R.P.M. and weighing 145 pounds. The arrangement of this early
Anzani engine is shown at Fig. 190, and it will be apparent that in the
main, the lines worked out in motorcycle practice were followed to a
large extent. The crank-case was of the usual vertically divided
pattern, the cylinders and heads being cast in one piece and held to the
crank-case by stud bolts passing through substantial flanges at the
cylinder base. In order to utilize but a single crank-pin for the three
cylinders it was necessary to use two forked rods and one rod of the
conventional type. The arrangement shown at Fig. 190, called for the use
of counter-balanced flywheels which were built up in connection with
shafts and a crank-pin to form what corresponds to the usual crank-shaft
assembly.

[Illustration: Fig. 190.--Views Outlining Construction of Three-Cylinder
Anzani Aviation Motor.]

The inlet valves were of the automatic type so that a very simple valve
mechanism consisting only of the exhaust valve push rods was provided.
One of the difficulties of this arrangement of cylinders was that the
impulses are not evenly spaced. For instance, in the forms where the
cylinders were placed 60 degrees apart the space between the firing of
the first cylinder and that next in order was 120 degrees crank-shaft
rotation, after which there was an interval of 300 degrees before the
last cylinder to fire delivered its power stroke. In order to increase
the power given by the simple three-cylinder air-cooled engine a
six-cylinder water-cooled type, as shown at Figs. 191 and 192, was
devised. This was practically the same in action as the three-cylinder
except that a double throw crank-shaft was used and while the
explosions were not evenly spaced the number of explosions obtained
resulted in fairly uniform application of power.

[Illustration: Fig. 190a.--Illustrations Depicting Wrong and Right
Methods of "Swinging the Stick" to Start Airplane Engine. At Top, Poor
Position to Get Full Throw and Get Out of the Way. Below, Correct
Position to Get Quick Turn Over of Crank-Shaft and Spring Away from
Propeller.]

[Illustration: Fig. 191.--The Anzani Six-Cylinder Water-Cooled Aviation
Engine.]

[Illustration: Fig. 192.--Sectional View of Anzani Six-Cylinder
Water-Cooled Aviation Engine.]

The latest design of three-cylinder Anzani engine, which is used to some
extent for school machines, is shown at Fig. 193. In this, the
three-cylinders are symmetrically arranged about the crank-case or 120
degrees apart. The balance is greatly improved by this arrangement and
the power strokes occur at equal intervals of 240 degrees of crank-shaft
rotation. This method of construction is known as the Y design. By
grouping two of these engines together, as outlined at Fig. 194, which
gives an internal view, and at Fig. 195, which shows the sectional view,
and using the ordinary form of double throw crank-shaft with crank-pins
separated by 180 degrees, a six-cylinder radial engine is produced which
runs very quietly and furnishes a steady output of power. The
peculiarity of the construction of this engine is in the method of
grouping the connecting rod about the common crank-pin without using
forked rods or the "Mother rod" system employed in the Gnome engines. In
the Anzani the method followed is to provide each connecting rod big end
with a shoe which consists of a portion of a hollow cylinder held
against the crank-pin by split clamping rings. The dimensions of these
shoes are so proportioned that the two adjacent connecting rods of a
group of three will not come into contact even when the connecting rods
are at the minimum relative angle. The three shoes of each group rest
upon a bronze sleeve which is in halves and which surrounds the
crank-pin and rotates relatively to it once in each crank-shaft
revolution. The collars, which are of tough bronze, resist the inertia
forces while the direct pressure of the explosions is transmitted
directly to the crank-pin bushing by the shoes at the big end of the
connecting rod. The same method of construction, modified to some
extent, is used in the Le Rhone rotary cylinder engine.

[Illustration: Fig. 193.--Three-Cylinder Anzani Air-Cooled Y-Form
Engine.]

[Illustration: Fig. 194.--Anzani Fixed Crank-Case Engine of the
Six-Cylinder Form Utilizes Air Cooling Successfully.]

Both cylinders and pistons of the Anzani engines are of cast iron, the
cylinders being provided with a liberal number of cooling flanges which
are cast integrally. A series of auxiliary exhaust ports is drilled near
the base of each cylinder so that a portion of the exhaust gases will
flow out of the cylinder when the piston reaches the end of its power
stroke. This reduces the temperature of the gases passing around the
exhaust valves and prevents warping of these members. Another
distinctive feature of this engine design is the method of attaching the
Zenith carburetor to an annular chamber surrounding the rear portion of
the crank-case from which the intake pipes leading to the intake valves
radiate. The magneto is the usual six-cylinder form having the armature
geared to revolve at one and one-half times crank-shaft speed.

[Illustration: Fig. 195.--Sectional View Showing Internal Parts of
Six-Cylinder Anzani Engine, with Starwise Disposition of Cylinders.]

[Illustration: Fig. 196.--The Anzani Ten-Cylinder Aviation Engine at
the Left, and the Twenty-Cylinder Fixed Type at the Right.]

The Anzani aviation engines are also made in ten- and twenty-cylinder
forms as shown at Fig. 196. It will be apparent that in the
ten-cylinder form explosions will occur every 72 degrees of crank-shaft
rotation, while in the twenty-cylinder, 200 horse-power engine at any
instant five of the cylinders are always working and explosions are
occurring every 36 degrees of crank-shaft rotation. On the
twenty-cylinder engine, two carburetors are used and two magnetos,
which are driven at two and one-half times crank-shaft speed. The
general cylinder and valve construction is practically the same, as in
the simpler engines.

[Illustration: Fig. 197.--Application of R. E. P. Five-Cylinder
Fan-Shape Air-Cooled Motor to Early Monoplane.]

CANTON AND UNNÉ ENGINE

This engine, which has been devised specially for aviation service, is
generally known as the "Salmson" and is manufactured in both France and
Great Britain. It is a nine-cylinder water-cooled radial engine, the
nine cylinders being symmetrically disposed around the crank-shaft while
the nine connecting rods all operate on a common crank-pin in somewhat
the same manner as the rods in the Gnome motor. The crank-shaft of the
Salmson engine is not a fixed one and inasmuch as the cylinders do not
rotate about the crank-shaft it is necessary for that member to revolve
as in the conventional engine. The stout hollow steel crank-shaft is in
two pieces and has a single throw. The crank-shaft is built up somewhat
the same as that of the Gnome engine. Ball bearings are used throughout
this engine as will be evident by inspecting the sectional view given at
Fig. 199. The nine steel connecting rods are machined all over and are
fitted at each end with bronze bushings, the distance between the
bearing centers being about 3.25 times crank length. The method of
connecting up the rods to the crank-pin is one of the characteristic
features of this design. No "mother" rod as supplied in the Gnome engine
is used in this type inasmuch as the steel cage or connecting rod
carrier is fitted with symmetrically disposed big end retaining pins.
Inasmuch as the carrier is mounted on ball bearings some means must be
provided of regulating the motion of the carrier as if no means were
provided the resulting motion of the pistons would be irregular.

[Illustration: Fig. 198.--The Canton and Unné Nine-Cylinder Water-Cooled
Radial Engine.]

The method by which the piston strokes are made to occur at precise
intervals involves a somewhat lengthy and detailed technical
explanation. It is sufficient to say that an epicyclic train of gears,
one of which is rigidly attached to the crank-case so it cannot rotate
is used, while other gears make a connection between the fixed gear and
with another gear which is exactly the same size as the fixed gear
attached to the crank-case and which is formed integrally with the
connecting rod carrier. The action of the gearing is such that the cage
carrying the big end retaining pins does not rotate independently of
the crank-shaft, though, of course, the crank-shaft or rather crank-pin
bearings must turn inside of the big end carrier cage.

[Illustration: Fig. 199.--Sectional View Showing Construction of Canton
and Unné Water-Cooled Radial Cylinder Engine.]

Cylinders of this engine are of nickel steel machined all over and carry
water-jackets of spun copper which are attached to the cylinders by
brazing. The water jackets are corrugated to permit the cylinder to
expand freely. The ignition is similar to that of the fixed crank
rotating cylinder engine. An ordinary magneto of the two spark type
driven at 1-3/4 times crank-shaft speed is sufficient to ignite the
seven-cylinder form, while in the nine-cylinder engines the ignition
magneto is of the "shield" type giving four sparks per revolution. The
magneto is driven at 1-1/9 times crank-shaft speed. Nickel steel valves
are used and are carried in castings or cages which screw into bosses in
the cylinder head. Each valve is cam operated through a tappet, push rod
and rocker arm, seven cams being used on a seven-cylinder engine and
nine cams on the nine-cylinder. One cam serves to open both valves as in
its rotation it lifts the tappets in succession and so operates the
exhaust and inlet valves respectively. This method of operation involves
the same period of intake and exhaust. In normal engine practice the
inlet valve opens 12 degrees late and closes 20 degrees late. The
exhaust opens 45 degrees early and closes 6 degrees late. This means
about 188 degrees in the case of inlet valve and 231 degrees crank-shaft
travel for exhaust valves. In the Salmson engine, the exhaust closes and
the inlet opens at the outer dead center and the exhaust opens and the
inlet closes at about the inner dead center. This engine is also made in
a fourteen-cylinder 200 B. H. P. design which is composed of two groups
of seven-cylinders, and it has been made in an eighteen-cylinder design
of 600 horse-power. The nine-cylinder 130 horse-power has a cylinder
bore of 4.73 inches and a stroke of 5.52 inches. Its normal speed of
rotation is 1250 R. P. M. Owing to the radial arrangement of the
cylinders, the weight is but 4-1/4 pounds per B. H. P.

CONSTRUCTION OF EARLY GNOME MOTOR

It cannot be denied that for a time one of the most widely used of
aeroplane motors was the seven-cylinder revolving air-cooled Gnome, made
in France. For a total weight of 167 pounds this motor developed 45 to
47 horse-power at 1,000 revolutions, being equal to 3.35 pounds per
horse-power, and has proved its reliability by securing many
long-distance and endurance records. The same engineers have produced
a nine-cylinder and by combining two single engines a fourteen-cylinder
revolving Gnome, having a nominal rating of 100 horse-power, with which
world's speed records were broken. A still more powerful engine has been
made with eighteen-cylinders. The nine-cylinder "monosoupape" delivers
100 horse-power at 1200 R. P. M., the engine of double that number of
cylinders is rated at about 180 horse-power.

[Illustration: Fig. 200.--Sectional View Outlining Construction of Early
Type Gnome Valve-in-Piston Type Motor.]

Except in the number of cylinders and a few mechanical details the
fourteen-cylinder motor is identical with the seven-cylinder one; fully
three-quarters of the parts used by the assemblers would do just as well
for one motor as for the other. Owing to the greater power demands of
the modern airplane the smaller sizes of Gnome engines are not used as
much as they were except for school machines. There is very little in
this motor that is common to the standard type of vertical motorcar
engine. The cylinders are mounted radially round a circular crank-case;
the crank-shaft is fixed, and the entire mass of cylinders and
crank-case revolves around it as outlined at Fig. 200. The explosive
mixture and the lubricating oil are admitted through the fixed hollow
crank-shaft, passed into the explosion chamber through an automatic
intake valve in the piston head in the early pattern, and the spent
gases exhausted through a mechanically operated valve in the cylinder
head. The course of the gases is practically a radial one. A peculiarity
of the construction of the motor is that nickel steel is used
throughout. Aluminum is employed for the two oil pump housings; the
single compression ring known as the "obdurator" for each piston is made
of brass; there are three or four brass bushes; gun metal is employed
for certain pins--the rest is machined out of chrome nickel steel. The
crank-case is practically a steel hoop, the depth depending on whether
it has to receive seven-or fourteen-cylinders; it has seven or fourteen
holes bored as illustrated on its circumference. When fourteen or
eighteen cylinders are used the holes are bored in two distinct planes,
and offset in relation one to the other.

The cylinders of the small engine which have a bore of 4-3/10 inches and
a stroke of 4-7/10 inches, are machined out of the solid bar of steel
until the thickness of the walls is only 1.5 millimeters--.05905 inch,
or practically 1/16 inch. Each one has twenty-two fins which gradually
taper down as the region of greatest pressure is departed from. In
addition to carrying away heat, the fins assist in strengthening the
walls of the cylinder. The barrel of the cylinder is slipped into the
hole bored for it on the circumference of the crank-case and secured by
a locking member in the nature of a stout compression ring, sprung onto
a groove on the base of the cylinder within the crank chamber. On each
lateral face of the crank chamber are seven holes, drilled right through
the chamber parallel with the crank-shaft. Each one of these holes
receives a stout locking-pin of such a diameter that it presses against
the split rings of two adjacent cylinders; in addition each cylinder is
fitted with a key-way. This construction is not always followed, some of
the early Gnome engines using the same system of cylinder retention as
used on the latest "monosoupape" pattern.

The exhaust valve is mounted in the cylinder head, Fig. 201, its seating
being screwed in by means of a special box spanner. On the
fourteen-cylinder model the valve is operated directly by an overhead
rocker arm with a gun metal rocker at its extremity coming in contact
with the extremity of the valve stem. As in standard motor car practice,
the valve is opened under the lift of the vertical push rod, actuated by
the cam. The distinctive feature is the use of a four-blade leaf spring
with a forked end encircling the valve stems and pressing against a
collar on its extremity. On the seven-cylinder model the movement is
reversed, the valve being opened on the downward pull of the push rod,
this lifting the outer extremity of the main rocker arm, which tips a
secondary and smaller rocker arm in direct contact with the extremity
of the valve stem. The springs are the same in each case. The two types
are compared at A and B, Fig. 202.

[Illustration: Fig. 201.--Sectional View of Early Type Gnome Cylinder
and Piston Showing Construction and Application of Inlet and Exhaust
Valves.]

The pistons, like the cylinders, are machined out of the solid bar of
nickel steel, and have a portion of their wall cut away, so that the two
adjacent ones will not come together at the extremity of their stroke.
The head of the piston is slightly reduced in diameter and is provided
with a groove into which is fitted a very light L-section brass split
ring; back of this ring and carried within the groove is sprung a light
steel compression ring, serving to keep the brass ring in expansion. As
already mentioned, the intake valves are automatic, and are mounted in
the head of the piston as outlined at Fig. 202, C. The valve seating is
in halves, the lower portion being made to receive the wrist-pin and
connecting rod, and the upper portion, carrying the valve, being screwed
into it. The spring is composed of four flat blades, with the hollowed
stem of the automatic valve passing through their center and their two
extremities attached to small levers calculated to give balance against
centrifugal force. The springs are naturally within the piston, and are
lubricated by splash from the crank chamber. They are of a delicate
construction, for it is necessary that they shall be accurately balanced
so as to have no tendency to fly open under the action of centrifugal
force. The intake valve is withdrawn by the use of special tools through
the cylinder head, the exhaust valve being first dismounted.

[Illustration: Fig. 202.--Details of Old Style Gnome Motor Inlet and
Exhaust Valve Construction and Operation.]

The fourteen-cylinder motor shown at Fig. 203, has a two-throw
crank-shaft with the throws placed at 180 degrees, each one receiving
seven connecting rods. The parts are the same as for the seven-cylinder
motor, the larger one consisting of two groups placed side by side. For
each group of seven-cylinders there is one main connecting rod, together
with six auxiliary rods. The main connecting rod, which, like the
others, is of H section, has machined with it two L-section rings bored
with six holes--51-1/2 degrees apart to take the six other connecting
rods. The cage of the main connecting rod carries two ball races, one on
either side, fitting onto the crank-pin and receiving the thrust of the
seven connecting rods. The auxiliary connecting rods are secured in
position in each case by a hollow steel pin passing through the two
rings. It is evident that there is a slightly greater angularity for the
six shorter rods, known as auxiliary connecting rods, than for the
longer main rods; this does not appear to have any influence on the
running of the motor.

[Illustration: Fig. 203.--The Gnome Fourteen-Cylinder 100 Horse-Power
Aviation Engine.]

Coming to the manner in which the earliest design exhaust valves are
operated on the old style motor, this at first sight appears to be one
of the most complicated parts of the motor, probably because it is one
in which standard practice is most widely departed from. Within the
cylindrical casing bolted to the rear face of the crank-case are seven,
thin flat-faced steel rings, forming female cams. Across a diameter of
each ring is a pair of projecting rods fitting in brass guides and
having their extremities terminating in a knuckle eye receiving the
adjustable push rods operating the overhead rocker arms of the exhaust
valve. The guides are not all in the same plane, the difference being
equal to the thickness of the steel rings, the total thickness being
practically 2 inches. Within the female cams is a group of seven male
cams of the same total thickness as the former and rotating within them.
As the boss of the male cam comes into contact with the flattened
portion of the ring forming the female cam, the arm is pushed outward
and the exhaust valve opened through the medium of the push-rod and
overhead rocker. This construction was afterwards changed to seven male
cams and simple valve operating plunger and roller cam followers as
shown at Fig. 204.

On the face of the crank-case of the fourteen-cylinder motor opposite to
the valve mechanism is a bolted-on end plate, carrying a pinion for
driving the two magnetos and the two oil pumps, and having bolted to it
the distributor for the high-tension current. Each group of
seven-cylinders has its own magneto and lubricating pump. The two
magnetos and the two pumps are mounted on the fixed platform carrying
the stationary crank-shaft, being driven by the pinion on the revolving
crank chamber. The magnetos are geared up in the proportion of 4 to 7.
Mounted on the end plate back of the driving pinion are the two
high-tension distributor plates, each one with seven brass segments let
into it and connection made to the plugs by means of plain brass wire.
The wire passes through a hole in the plug and is then wrapped round
itself, giving a loose connection.

[Illustration: Fig. 204.--Cam and Cam-Gear Case of the Gnome
Seven-Cylinder Revolving Engine.]

[Illustration: Fig. 205.--Diagrams Showing Why An Odd Number of
Cylinders is Best for Rotary Cylinder Motors.]

A good many people doubtless wonder why rotary engines are usually
provided with an odd number of cylinders in preference to an even
number. It is a matter of even torque, as can easily be understood from
the accompanying diagram. Fig. 205, A, represents a six-cylinder rotary
engine, the radial lines indicating the cylinders. It is possible to
fire the charges in two ways, firstly, in rotation, 1, 2, 3, 4, 5, 6,
thus having six impulses in one revolution and none in the next; or
alternately, 1, 3, 5, 2, 4, 6, in which case the engine will have turned
through an equal number of degrees between impulses 1 and 3, and 3 and
5, but a greater number between 5 and 2, even again between 2 and 4, 4
and 6, and a less number between 6 and 1, as will be clearly seen on
reference to the diagram. Turning to Fig. 205, B, which represents a
seven-cylinder engine. If the cylinders fire alternately it is obvious
that the engine turns through an equal number of degrees between each
impulse, thus, 1, 3, 5, 7, 2, 4, 6, 1, 3, etc. Thus supposing the engine
to be revolving, the explosion takes place as each alternate cylinder
passes, for instance, the point 1 on the diagram, and the ignition is
actually operated in this way by a single contact.

[Illustration: Fig. 206.--Simple Carburetor Used On Early Gnome Engines
Attached to Fixed Crank-Shaft End.]

The crank-shaft of the Gnome, as already explained, is fixed and hollow.
For the seven- and nine-cylinder motors it has a single throw, and for
the fourteen- and eighteen-cylinder models has two throws at 180
degrees. It is of the built-up type, this being necessary on account of
the distinctive mounting of the connecting rods. The carburetor shown at
Fig. 206 is mounted at one end of the stationary crank-shaft, and the
mixture is drawn in through a valve in the piston as already explained.
There is neither float chamber nor jet. In many of the tests made at the
factory it is said the motor will run with the extremity of the gasoline
pipe pushed into the hollow crank-shaft, speed being regulated entirely
by increasing or decreasing the flow through the shut-off valve in the
base of the tank. Even under these conditions the motor has been
throttled down to run at 350 revolutions without misfiring. Its normal
speed is 1,000 to 1,200 revolutions a minute. Castor oil is used for
lubricating the engine, the oil being injected into the hollow
crank-shaft through slight-feed fittings by a mechanically operated pump
which is clearly shown in sectional diagrams at Fig. 207.

[Illustration: Fig. 207.--Sectional Views of the Gnome Oil Pump.]

The Gnome is a considerable consumer of lubricant, the makers' estimate
being 7 pints an hour for the 100 horse-power motor; but in practice
this is largely exceeded. The gasoline consumption is given as 300 to
350 grammes per horse-power. The total weight of the fourteen-cylinder
motor is 220 pounds without fuel or lubricating oil. Its full power is
developed at 1,200 revolutions, and at this speed about 9 horse-power is
lost in overcoming air resistance to cylinder rotation.

[Illustration: Fig. 208.--Simplified Diagram Showing Gnome Motor Magneto
Ignition System.]

While the Gnome engine has many advantages, on the other hand, the head
resistance offered by a motor of this type is considerable; there is a
large waste of lubricating oil due to the centrifugal force which tends
to throw the oil away from the cylinders; the gyroscopic effect of the
rotary motor is detrimental to the best working of the aeroplane, and
moreover it requires about seven per cent. of the total power developed
by the motor to drive the revolving cylinders around the shaft. Of
necessity, the compression of this type of motor is rather low, and an
additional disadvantage manifests itself in the fact that there is as
yet no satisfactory way of muffling the rotary type of motor.

GNOME "MONOSOUPAPE" TYPE

The latest type of Gnome engine is known as the "monosoupape" type
because but one valve is used in the cylinder head, the inlet valve in
the piston being dispensed with on account of the trouble caused by that
member on earlier engines. The construction of this latest type follows
the lines established in the earlier designs to some extent and it
differs only in the method of charging. The very rich mixture of gas and
air is forced into the crank-case through the jet inside the
crank-shaft, and enters the cylinder when the piston is at its lowest
position, through the half-round openings in the guiding flange and the
small holes or ports machined in the cylinder and clearly shown at Fig.
210. The returning piston covers the port, and the gas is compressed and
fired in the usual way. The exhaust is through a large single valve in
the cylinder head, which gives rise to the name "monosoupape," or
single-valve motor, and this valve also remains open a portion of the
intake stroke to admit air into the cylinder and dilute the rich gas
forced in from the crank-case interior. Aviators who have used the early
form of Gnome say that the inlet valve in the piston type was prone to
catch on fire if any valve defect materialized, but the "monosoupape"
pattern is said to be nearly free of this danger. The bore of the 100
horse-power nine-cylinder engine is 110 mm., the piston stroke 150 mm.
Extremely careful machine work and fitting is necessary. In many parts,
tolerances of less than .0004" (four ten thousandths of an inch) are all
that are allowed. This is about one-sixth the thickness of the average
human hair, and in other parts the size must be absolutely standard, no
appreciable variation being allowable. The manufacture of this engine
establishes new mechanical standards of engine production in this
country. Much machine work is needed in producing the finished
components from the bar and forging.

[Illustration: Fig. 209.--The G. V. Gnome "Monosoupape" Nine-Cylinder
Rotary Engine Mounted on Testing Stand.]

[Illustration: Fig. 210.--Sectional View Showing Construction of General
Vehicle Co. "Monosoupape" Gnome Engine.]

The cylinders, for example, are machined from 6 inch solid steel bars,
which are sawed into blanks 11 inches in length and weighing about 97
pounds. The first operation is to drill a 2-1/16 inch hole through the
center of the block. A heavy-duty drilling machine performs this work,
then the block goes to the lathe for further operations. Fig. 211 shows
six stages of the progress of a cylinder, a few of the intermediate
steps being omitted. These give, however, a good idea of the work done.
The turning of the gills, or cooling flanges, is a difficult
proposition, owing to the depth of the cut and the thin metal that forms
the gills. This operation requires the utmost care of tools and the use
of a good lubricant to prevent the metal from tearing as the tools
approach their full depth. These gills are only 0.6 mm., or 0.0237 in.,
thick at the top, tapering to a thickness of 1.4 mm. (0.0553 in.) at the
base, and are 16 mm. (0.632 in.) deep. When the machine work is
completed the cylinder weighs but 5-1/2 pounds.

[Illustration: Fig. 211.--How a Gnome Cylinder is Reduced from Solid
Chunk of Steel Weighing 97 Pounds to Finished Cylinder Weighing 5-1/2
Pounds.]

GNOME FUEL SYSTEM, IGNITION AND LUBRICATION

The following description of the fuel supply, ignition and oiling of the
"monosoupape," or single valve Gnome, is taken from "The Automobile."

Gasoline is fed to the engine by means of air pressure at 5 pounds per
sq. in., which is produced by the air pump on the engine clearly shown
at Fig. 210. A pressure gauge convenient to the operator indicates this
pressure, and a valve enables the operator to control it. No carburetor
is used. The gasoline flows from the tank through a shut-off valve near
the operator and through a tube leading through the hollow crank-shaft
to a spray nozzle located in the crank-case. There is no throttle valve,
and as each cylinder always receives the same amount of air as long as
the atmospheric pressure is the same, the output cannot be varied by
reducing the fuel supply, except within narrow limits. A fuel capacity
of 65 gallons is provided. The fuel consumption is at the rate of 12 U.
S. gallons per hour.

The high-tension magnetos, with double cam or two break per revolution
interrupter, is located on the thrust plate in an inverted position, and
is driven at such a speed as to produce nine sparks for every two
revolutions; that is, at 2-1/4 times engine speed. A Splitdorf magneto
is fitted. There is no distributor on the magneto. The high-tension
collector brush of the magneto is connected to a distributor brush
holder carried in the bearer plate of the engine. The brush in this
brush holder is pressed against a distributor ring of insulating
material molded in position in the web of a gear wheel keyed to the
thrust plate, which gear serves also for starting the engine by hand.
Molded in this ring of insulating material are nine brass contact
sectors, connecting with contact screws at the back side of the gear,
from which bare wires connect to the spark-plugs. The distributor
revolves at engine speed, instead of at half engine speed as on ordinary
engines, and the distributor brush is brought into electrical connection
with each spark-plug every time the piston in the cylinder in which this
spark-plug is located approaches the outer dead center. However, on the
exhaust stroke no spark is being generated in the magneto, hence none is
produced at the spark-plug.

[Illustration: Fig. 212.--The Gnome Engine Cam-Gear Case, a Fine Example
of Accurate Machine Work.]

Ordinarily the engine is started by turning on the propeller, but for
emergency purposes as in seaplanes or for a quick "get away" if landing
inadvertently in enemy territory, a hand starting crank is provided.
This is supported in bearings secured to the pressed steel carriers of
the engine and is provided with a universal joint between the two
supports so as to prevent binding of the crank in the bearings due to
possible distortion of the supports. The gear on this starting crank and
the one on the thrust plate with which it meshes are cut with helical
teeth of such hand that the starting pinion is thrown out of mesh as
soon as the engine picks up its cycle. A coiled spring surrounds part of
the shaft of the starting crank and holds it out of gear when not in
use.

[Illustration: Fig. 213.--G. V. Gnome "Monosoupape," with Cam-Case Cover
Removed to Show Cams and Valve-Operating Plungers with Roller Cam
Followers.]

Lubricating oil is carried in a tank of 25 gallon capacity, and if this
tank has to be placed in a low position it is connected with the
air-pressure line, so that the suction of the oil pump is not depended
upon to get the oil to the pump. From the bottom of the oil tank a pipe
leads to the pump inlet. There are two outlets from the pump, each
entering the hollow crank-shaft, and there is a branch from each outlet
pipe to a circulation indicator convenient to the operator. One of the
oil leads feeds to the housing in the thrust plate containing the two
rear ball bearings, and the other lead feeds through the crank-pin to
the cams, as already explained.

Owing to the effect of centrifugal force and the fact that the oil is
not used over again, the oil consumption of a revolving cylinder engine
is considerably higher than that of a stationary cylinder engine. Fuel
consumption is also somewhat higher, and for this reason the revolving
cylinder engine is not so well suited for types of airplanes designed
for long trips, as the increased weight of supplies required for such
trips, as compared with stationary cylinder type motors, more than
offsets the high weight efficiency of the engine itself. But for short
trips, and especially where high speed is required, as in single seated
scout and battle planes or "avions de chasse," as the French say, the
revolving cylinder engine has the advantage. The oil consumption of the
Gnome engine is as high as 2.4 gallon per hour. Castor oil is used for
lubrication because it is not cut by the gasoline mist present in the
engine interior as an oil of mineral derivation would be.

GERMAN "GNOME" TYPE ENGINE

[Illustration: Fig. 214.--The 50 Horse-Power Rotary Bayerischen Motoren
Gesellschaft Engine, a German Adaptation of the Early Gnome Design.]

A German adaptation of the Gnome design is shown at Fig. 214. This is
known as the Bayerischen Motoren Gesellschaft engine and the type shown
is an early design rated at 50 horse-power. The bore is 110 mm., the
stroke is 120 mm., and it is designed to run at a speed of 1,200 R. P.
M. It is somewhat similar in design to the early Gnome "valve-in-piston"
design except that two valves are carried in the piston top instead of
one. The valve operating arrangement is different also, as a single four
point cam is used to operate the seven exhaust valves. It is driven by
epicyclic gearing, the cam being driven by an internal gear machined
integrally with it, the cam being turned at 7/8 times the engine speed.
Another feature is the method of holding the cylinders on the
crank-case. The cylinder is provided with a flange that registers with a
corresponding member of the same diameter on the crank-case. A U
section, split clamping ring is bolted in place as shown, this holding
both flanges firmly together and keeping the cylinder firmly seated
against the crank-case flange. The "monosoupape" type has also been
copied and has received some application in Germany, but the most
successful German airplanes are powered with six-cylinder vertical
engines such as the Benz and Mercedes.

THE LE RHONE MOTOR

The Le Rhone motor is a radial revolving cylinder engine that has many
of the principles which are incorporated in the Gnome but which are
considered to be an improvement by many foreign aviators. Instead of
having but one valve in the cylinder head, as the latest type
"monosoupape" Gnome has, the Le Rhone has two valves, one for intake and
one for exhaust in each cylinder. By an ingenious rocker arm and tappet
rod arrangement it is possible to operate both valves with a single push
rod. Inlet pipes communicate with the crank-case at one end and direct
the fresh gas to the inlet valve cage at the other. Another peculiarity
in the design is the method of holding the cylinders in place. Instead
of having a vertically divided crank-case as the Gnome engine has and
clamping both halves of the case around the cylinders, the crank-case of
the Le Rhone engine is in the form of a cylinder having nine bosses
provided with threaded openings into which the cylinders are screwed. A
thread is provided at the base of each cylinder and when the cylinder
has been screwed down the proper amount it is prevented from further
rotation about its own axis by a substantial lock nut which screws down
against the threaded boss on the crank-case. The external appearance of
the Le Rhone type motor is clearly shown at Fig. 215, while the general
features of construction are clearly outlined in the sectional views
given at Figs. 216 and 217.

[Illustration: Fig. 215--Nine-Cylinder Revolving Le Rhone Type Aviation
Engine.]

[Illustration: Fig. 216.--Part Sectional Views of Le Rhone Rotary
Cylinder Engine, Showing Method of Cylinder Retention, Valve Operation
and Novel Crank Disc Assembly.]

[Illustration: Fig. 217.--Side Sectional View of Le Rhone Aviation
Engine.]

[Illustration: Fig. 218.--View Showing Le Rhone Valve Action and
Connecting Rod Big End Arrangement.]

The two main peculiarities of this motor are the method of valve
actuation by two large cams and the distinctive crank-shaft and
connecting rod big end construction. The connecting rods are provided
with "feet" or shoes on the end which fit into grooves lined with
bearing metal which are machined into crank discs revolving on ball
bearings and which are held together so that the connecting rod big ends
are sandwiched between them by clamping screws. This construction is a
modification of that used on the Anzani six-cylinder radial engine.
There are three grooves machined in each crank disc and three connecting
rod big ends run in each pair of grooves. The details of this
construction can be readily ascertained by reference to explanatory
diagrams at Figs. 218 and 219, A. Three of the rods which work in the
groove nearest the crank-pin are provided with short shoes as shown at
Fig. 219, B. The short shoes are used on the rods employed in cylinders
number 1, 4, and 7. The set of connecting rods that work in the central
grooves are provided with medium-length shoes and actuate the pistons in
cylinders numbers 3, 6, and 9. The three rods that work in the outside
grooves have still longer shoes and are employed in cylinders numbers 2,
5, and 8. The peculiar profile of the inlet and exhaust cam plates are
shown at C, Fig. 219, while the construction of the wrist-pin, wrist-pin
bushing and piston are clearly outlined at the sectional view at E. The
method of valve actuation is clearly outlined at Fig. 220, which shows
an end section through the cam case and also a partial side elevation
showing one of the valve operating levers which is fulcrumed at a
central point and which has a roller at one end bearing on one cam while
the roller or cam follower at the other end bears on the other cam. The
valve rocker arm actuating rod is, of course, operated by this simple
lever and is attached to it in such a way that it can be pulled down to
depress the inlet valve and pushed up to open the exhaust valve.

[Illustration: Fig. 219.--Diagrams Showing Important Components of Le
Rhone Motor.]

[Illustration: Fig. 220.--How the Cams of the Le Rhone Motor Can Operate
Two Valves with a Single Push Rod.]

A carburetor of peculiar construction is employed in the Le Rhone
engine, this being a very simple type as outlined at Fig. 221. It is
attached to the threaded end of the hollow crank-shaft by a right and
left coupling. The fuel is pumped to the spray nozzle, the opening in
which is controlled by a fuel regulating needle having a long taper
which is lifted out of the jet opening when the air-regulating slide is
moved. The amount of fuel supplied the carburetor is controlled by a
special needle valve fitting which combines a filter screen and which is
shown at B. In regulating the speed of the Le Rhone engine, there are
two possible means of controlling the mixture, one by altering the
position of the air-regulating slide, which also works the metering
needle in the jet, and the other by controlling the amount of fuel
supplied to the spray nozzle through the special fitting provided for
that purpose.

[Illustration: Fig. 221.--The Le Rhone Carburetor at A and Fuel Supply
Regulating Device at B.]

In considering the action of this engine one can refer to Fig. 222. The
crank O. M. is fixed, while the cylinders can turn about the crank-shaft
center O and the piston turns around the crank-pin M, because of the
eccentricity of the centers of rotation the piston will reciprocate in
the cylinders. This distance is at its maximum when the cylinder is
above O and at a minimum when it is above M, and the difference between
these two positions is equal to the stroke, which is twice the distance
of the crank-throw O, M. The explosion pressure resolves itself into the
force F exerted along the line of the connecting rod A, M, and also into
a force N, which tends to make the cylinders rotate around point O in
the direction of the arrow. An odd number of cylinders acting on one
crank-pin is desirable to secure equally spaced explosions, as the basic
action is the same as the Gnome engine.

[Illustration: Fig. 222.--Diagrams Showing Le Rhone Motor Action and
Firing Order.]

The magneto is driven by a gear having 36 teeth attached to crank-case
which meshes with 16-tooth pinion on armature. The magneto turns at 2.25
times crank-case speed. Two cams, one for inlet, one for exhaust, are
mounted on a carrying member and act on nine rocker arms which are
capable of giving a push-and-pull motion to the valve-actuating
rocker-operating rods. A gear driven by the crank-case meshes with a
larger member having internal teeth carried by the cam carrier. Each cam
has five profiles and is mounted in staggered relation to the other.
These give the nine fulcrumed levers the proper motion to open the inlet
and exhaust valves at the proper time. The cams are driven at 45/50 or
9/10 of the motor speed. The cylinder dimensions and timing follows; the
weight can be approximated by figuring 3 pounds per horse-power.

80 H.P. 105 M/M bore 4.20" bore.
140 M/M stroke 5.60" stroke.

110 H.P. 112 M/M bore 4.48" bore.
170 M/M stroke 6.80" stroke.

Timing--Intake valve opening, lag 18°} 18°}
Intake valve closing, lag 35°} 35°}
Exhaust valve opening, lead 55°} 110 H.P. 45°} 80 H.P.
Exhaust valve closing, lag 5°} 5°}
Ignition time advance 26°} 26°}

[Illustration: Fig. 223.--Diagram Showing Positions of Piston in Le
Rhone Rotary Cylinder Motor.]

THE RENAULT AIR-COOLED VEE ENGINE

[Illustration: Fig. 224.--Diagrams Showing Valve Timing of Le Rhone
Aviation Engine.]

[Illustration: Fig. 225.--Diagrams Showing How Cylinder Cooling is
Effected in Renault Vee Engines.]

Air-cooled stationary engines are rarely used in airplanes, but the
Renault Frères of France have for several years manufactured a complete
series of such engines of the general design shown at Fig. 225, ranging
from a low-powered one developed eight or nine years ago and rated at
40 and 50 horse-power, to later eight-cylinder models rated at 70
horse-power and a twelve-cylinder, or twin six, rated at 90 horse-power.
The cylinders are of cast iron and are furnished with numerous cooling
ribs which are cast integrally. The cylinder heads are separate
castings and are attached to the cylinder as in early motorcycle engine
practice, and serve to hold the cylinder in place on the aluminum alloy
crank-case by a cruciform yoke and four long hold-down bolts (Fig. 226).
The pistons are of cast steel and utilize piston rings of cast iron. The
valves are situated on the inner side of the cylinder head, the
arrangement being unconventional in that the exhaust valves are placed
above the inlet. The inlet valves seat in an extension of the combustion
head and are actuated by direct push rod and cam in the usual manner
while an overhead gear in which rockers are operated by push rods is
needed to actuate the exhaust valves. The valve action is clearly shown
in Figs. 226 and 227. The air stream by which the cylinders are cooled
is produced by a centrifugal or blower type fan of relatively large
diameter which is mounted on the end of a crank-shaft and the air blast
is delivered from this blower into an enclosed space between the
cylinder from which it escapes only after passing over the cooling fins.
In spite of the fact that considerable prejudice exists against
air-cooling fixed cylinder engines, the Renault has given very good
service in both England and France.

[Illustration: Fig. 226.--End Sectional View of Renault Air-Cooled
Aviation Engine.]

[Illustration: Fig. 227.--Side Sectional View of Renault Twelve-Cylinder
Air-Cooled Aviation Engine Crank-Case, Showing Use of Plain and Ball
Bearings for Crank-Shaft Support.]

As will be seen by the sectional view at Fig. 227, the steel crank-shaft
is carried in a combination of plain bearings inside the crank-case and
by ball bearings at the ends. Owing to air cooling, special precautions
are taken with the lubrication system, though the lubrication is not
forced or under high pressure. An oil pump of the gear-wheel type
delivers oil from the sump at the bottom of the crank-case to a chamber
above, from which the oil flows by gravity along suitable channels to
the various main bearings. It flows from the bearings into hollow rings
fastened to the crank-webs, and the oil thrown from the whirling
connecting rod big ends bathes the internal parts in an oil mist. In the
eight-cylinder designs ignition is effected by a magneto giving four
sparks per revolution and is accordingly driven at engine speed. In the
twelve-cylinder machine two magnetos of the ordinary revolving armature
or two-spark type, each supplying six cylinders, are fitted as outlined
at Fig. 228. The carburetor is a float feed form. Warm air is supplied
for Winter and damp weather by air pipes surrounding the exhaust pipes.
The normal speed of the Renault engine is 1,800 R. P. M., but as the
propeller is mounted upon an extension of the cam-shaft the normal
propeller speed is but half that of the engine, which makes it possible
to use a propeller of large diameter and high efficiency. Owing to the
air cooling, but low compression may be used, this being about 60 pounds
per square inch, which, of course, lowers the mean effective pressure
and makes the engine less efficient than water-cooled forms where it is
possible to use compression pressure of 100 or more pounds per square
inch. The 70 horse-power engine has cylinders with a bore of 3.78 inches
and a stroke of 5.52 inches. Its weight is given as 396 pounds, when in
running order, which figures 5.7 pounds per horse-power. The same
cylinder size is used on the twelve-cylinder 100 horse-power and the
stroke is the same. This engine in running order weighs 638 pounds,
which figures approximately 6.4 pounds per B. H. P.

[Illustration: Fig. 228.--End View of Renault Twelve-Cylinder Engine
Crank-Case, Showing Magneto Mounting.]

[Illustration: Fig. 229.--Diagram Outlining Renault Twelve-Cylinder
Engine Ignition System.]

SIMPLEX MODEL "A" HISPANO-SUIZA

The Model A is of the water-cooled four-cycle Vee type, with eight
cylinders, 4.7245 inch bore by 5.1182 inch stroke, piston displacement
718 cubic inches. At sea-level it develops 150 horse-power at 1,450 R.
P. M. It can be run successfully at much higher speeds, depending on
propeller design and gearing, developing proportionately increased
power. The weight, including carburetor, two magnetos, propeller hub,
starting magneto and crank, but without radiator, water or oil or
exhaust pipes, is 445 pounds. Average fuel consumption is .5 pound per
horse-power hour and the oil consumption at 1,450 R. P. M. is three
quarts per hour. The external appearance is shown at Fig. 230.

Four cylinders are contained in each block, which is of built-up
construction; the water jackets and valve ports are cast aluminum and
the individual cylinders heat-treated steel forgings threaded into the
bored holes of the aluminum castings. Each block after assembly is given
a number of protective coats of enamel, both inside and out, baked on.
Coats on the inside are applied under pressure. The pistons are aluminum
castings, ribbed. Connecting rods are tubular, of the forked type. One
rod bears directly on the crank-pin; the other rod has a bearing on the
outside of the one first mentioned.

The crank-shaft is of the five-bearing type, very short, stiff in
design, bored for lightness and for the oiling system. The crank-shaft
extension is tapered for the French standard propeller hub, which is
keyed and locked to the shaft. This makes possible instant change of
propellers. The case is in two halves divided on the center line of the
crank-shaft, the bearings being fitted between the upper and lower
sections. The lower half is deep, providing a large oil reservoir and
stiffening the engine. The upper half is simple and provides magneto
supports on extension ledges of the two main faces. The valves are of
large diameter with hollow stems, working in cast iron bushings. They
are directly operated by a single hollow cam-shaft located over the
valves. The cam-shafts are driven from the crank-shaft by vertical
shafts and bevel gears. The cam-shafts, cams and heads of the valve
stems are all enclosed in oil-tight removable housings of cast aluminum.

[Illustration: Fig. 230.--The Simplex Model A Hispano-Suiza Aviation
Engine, a Very Successful Form.]

Oiling is by a positive pressure system. The oil is taken through a
filter and steel tubes cast in the case to main bearings, through
crank-shaft to crank-pins. The fourth main bearing is also provided with
an oil lead from the system and through tubes running up the end of each
cylinder block, oil is provided for the cam-shafts, cams and bearings.
The surplus oil escapes through the end of the cam-shaft where the
driving gears are mounted, and with the oil that has gathered in the top
casing, descends through the drive shaft and gears to the sump.

Ignition is by two eight-cylinder magnetos firing two spark-plugs per
cylinder. The magnetos are driven from each of the two vertical shafts
by small bevel pinions meshing in bevel gears. The carburetor is mounted
between the two cylinder blocks and feeds the two blocks through
aluminum manifolds which are partly water-jacketed. The engine can be
equipped with a geared hand crank-starting device.

STURTEVANT MODEL 5A 140 HORSE-POWER ENGINE

These motors are of the eight-cylinder "V" type, four-stroke cycle,
water-cooled, having a bore of 4 inches and a stroke of 5-1/2 inches,
equivalent to 102 mm. × 140 mm. The normal operating speed of the
crank-shaft is 2,000 R. P. M. The propeller shaft is driven through
reducing gears which can be furnished in different gear ratios. The
standard ratio is 5:3, allowing a propeller speed of 1,200 R. P. M.

The construction of the motor is such as to permit of the application of
a direct drive. The change from the direct drive to gear drive, or vice
versa, can be accomplished in approximately one hour.

The cylinders are cast in pairs from an aluminum alloy and are provided
with steel sleeves, carefully fitted into each cylinder. A perfect
contact is secured between cylinder and sleeve; at the same time a
sleeve can be replaced without injury to the cylinder proper. No
difficulties due to expansion occur on account of the rapid transmission
of heat and the fact that the sleeve is always at higher temperature
than the cylinder. A moulded copper asbestos gasket is placed between
the cylinder and the head, permitting the cooling water to circulate
freely and at the same time insuring a tight joint. The cylinder heads
are cast in pairs from an aluminum alloy and contain ample water
passages for circulation of cooling water over the entire head. Trouble
due to hot valves is thereby eliminated, a most important consideration
in the operation of an aeroplane motor. The water jacket of the head
corresponds to the water jacket of the cylinders and large openings in
both allow the unobstructed circulation of the cooling water. The
cylinder heads and cylinders are both held to the base by six long
bolts. The valves are located in the cylinder heads and are mechanically
operated. The valves and valve springs are especially accessible and of
such size as to permit high volumetric efficiency. The valves are
constructed of hardened tungsten steel, the heads and stems being made
from one piece. The valve rocker arms located on the top of the cylinder
are provided with adjusting screws. A check nut enables the adjusting
screw to be securely locked in position, once the correct clearance has
been determined. The rocker arm bearings are adequately lubricated by a
compression grease cup. Cam-rollers are interposed between the cams and
the push rods in order to reduce the side thrust on the push rods.

A system of double springs is employed which greatly reduces the stress
on each spring and insures utmost reliability. A spring of extremely
large diameter returns the valve; a second spring located at the
cylinder base handles the push rod linkage. These springs, which operate
under low stress, are made from the best of steel and are given a
special double heat treatment. The pistons are made from a special
aluminum alloy; are deeply ribbed in the head for cooling and strength
and provided with two piston rings. These pistons are exceedingly light
weight in order to minimize vibration and prevent wear on the bearings.
The piston pin is made of chrome nickel steel, bored hollow and
hardened. It is allowed to turn, both in piston and connecting rod. The
piston rings are of special design, developed after years of
experimenting in aeronautical engines.

The connecting rods are of "H" section, machined all over from forgings
of a special air-hardening chrome nickel steel which, after being heat
treated has a tensile strength of 280,000 pounds per square inch. They
are consequently very strong and yet unusually light, and being machined
all over are of absolutely uniform section, which gives as nearly
perfect balance as can be obtained. The big ends are lined with white
metal and the small ends are bushed with phosphor bronze. The connecting
rods are all alike and take their bearings side by side on the
crank-pin, the cylinders being offset to permit of this arrangement. The
crank-shaft is machined from the highest grade chrome nickel steel, heat
treated in order to obtain the best properties of this material. It is
2-1/4 inches in diameter (57 mm.) and bored hollow throughout, insuring
maximum strength with minimum weight. It is carried in three large,
bronze-backed white metal bearings. A new method of producing these
bearings insures a perfect bond between the two metals and eliminates
breakage.

The base is cast from an aluminum alloy. Great strength and rigidity is
combined with light weight. The sides extend considerably below the
center line of the crank-shaft, providing an extremely deep section. At
all highly stressed points, deep ribs are provided to distribute the
load evenly and eliminate bending. The lower half of the base is of cast
aluminum alloy of extreme lightness. This collects the lubricating oil
and acts as a small reservoir for same. An oil-filtering screen of large
area covers the entire surface of the sump. The propeller shaft is
carried on two large annular ball bearings driven from the crank-shaft
by hardened chrome nickel steel spur gears. These gears are contained
within an oil-tight casing integral with the base on the opposite end
from the timing gears. A ball-thrust bearing is provided on the
propeller shaft to take the thrust of a propeller or tractor, as the
case may be. In case of the direct drive a stub shaft is fastened direct
to the crank-shaft and is fitted with a double thrust bearing.

The cam-shaft is contained within the upper half of the base between the
two groups of cylinders, and is supported in six bronze bearings. It is
bored hollow throughout and the cams are formed integral with the shaft
and ground to the proper shape and finish. An important development in
the shape of cams has resulted in a maintained increase of power at high
speeds. The gears operating the cam-shaft, magneto, oil and water pumps
are contained within an oil-tight casing and operate in a bath of oil.

Lubrication is of the complete forced circulating system, the oil being
supplied to every bearing under high pressure by a rotary pump of large
capacity. This is operated by gears from the crank-shaft. The oil
passages from the pump to the main bearings are cast integral with the
base, the hollow crank-shaft forming a passage through the connecting
rod bearings and the hollow cam-shaft distributing the oil to the
cam-shaft bearings. The entire surface of the lower half of the base is
covered with a fine mesh screen through which the oil passes before
reaching the pump. Approximately one gallon of oil is contained within
the base and this is continually circulated through an external tank by
a secondary pump operated by an eccentric on the cam-shaft. This also
draws fresh oil from the external tank which can be made of any desired
capacity.

SPECIFICATIONS--MODEL 5A TYPE 8

Horse-power rating, 140 at 2,000 R. P. M.
Bore, 4 inches = 102 mm.
Stroke, 5-1/2 inches = 140 mm.
Number of cylinders, 8.
Arrangement of cylinders, "V."
Cooling, water. Circulation by centrifugal pump.
Cycle, four stroke.
Ignition (double), 2 Bosch or Splitdorf magnetos.
Carburetor, Zenith duplex. Water jacket manifold.
Oiling system, complete forced. Circulating gear pump.
Normal crank-shaft speed, 2,000 R. P. M.
Propeller shaft, 3/5 crank-shaft speed at normal, 1,200 R. P. M.
Stated power at 30" barometer, 140 B. H. P.
Stated weight with all accessories but without water, gasoline or oil,
514 pounds = 234 kilos.
Weight per B. H. P., 3.7 pounds = 1.68 kilos.
Stated weight with all accessories with water, 550 pounds = 250 kilos.
Weight per B. H. P. with water, 3.95 pounds = 1.79 kilos.

THE CURTISS AVIATION MOTORS

The Curtiss OX motor has eight cylinders, 4-inch bore, 5-inch stroke,
delivers 90 horse-power at 1,400 turns, and the weight turns out at 4.17
pounds per horse-power. This motor has cast iron cylinders with monel
metal jackets, overhead inclined valves operated by means of two rocker
arms, push-and-pull rods from the central cam-shaft located in the
crank-case. The cam and push rod design is extremely ingenious and the
whole valve construction turns out very light. This motor is an
evolution from the early Curtiss type motor which was used by Glenn
Curtiss when he won the Gordon Bennett Cup at Rheims. A slightly larger
edition of this type motor is the OXX-5, as shown at Figs. 231 and 232,
which has cylinders 4-1/4 inches by 5 inches, delivers 100 horse-power
at 1,400 turns and has the same fuel and oil consumption as the OX type
motor, namely, .60 pound of fuel per brake horse-power hour and .03
pound of lubricating oil per brake horse-power hour.

[Illustration: Fig. 231.--The Curtiss OXX-5 Aviation Engine is an
Eight-Cylinder Type Largely Used on Training Machines.]

The Curtiss Company have developed in the last two years a larger-sized
motor now known as the V-2, which was originally rated at 160
horse-power and which has since been refined and improved so that the
motor gives 220 horse-power at 1,400 turns, with a fuel consumption of
52/100 of a pound per brake horse-power hour and an oil consumption of
.02 of a pound per brake horse-power hour. This larger motor has a
weight of 3.45 pounds per horse-power and is now said to be giving very
satisfactory service. The V-2 motor has drawn steel cylinders, with a
bore of 5 inches and a stroke of 7 inches, with a steel water jacket top
and a monel metal cylindrical jacket, both of which are brazed on to the
cylinder barrel itself. Both these motors use side by side connecting
rods and fully forced lubrication. The cam-shafts act as a gallery from
which the oil is distributed to the cam-shaft bearings, the main
crank-shaft bearings, and the gearing. Here again we find extremely
short rods, which, as before mentioned, enables the height and the
consequent weight of construction to be very much reduced. For ordinary
flying at altitudes of 5,000 to 6,000 feet, the motors are sent out with
an aluminum liner, bolted between the cylinder and the crank-case in
order to give a compression ratio which does not result in pre-ignition
at a low altitude. For high flying, however, these aluminum liners are
taken out and the compression volume is decreased to about 18.6 per
cent. of the total volume.

[Illustration: Fig. 232.--Top and Bottom Views of the Curtiss OXX-5 100
Horse-Power Aviation Engine.]

The Curtiss Aeroplane Company announces that it has recently built, and
is offering, a twelve-cylinder 5" × 7" motor, which was designed for
aeronautical uses primarily. This engine is rated at 250 horse-power,
but it is claimed to develop 300 at 1,400 R. P. M. Weights--Motor, 1,125
pounds; radiator, 120 pounds; cooling water, 100 pounds; propeller, 95
pounds.

Gasoline Consumption per Horse-power Hour, 6/10 pounds.

Oil Consumption per Hour at Maximum Speed--2 pints.

Installation Dimensions--Overall length, 84-5/8 inches; overall width,
34-1/8 inches; overall depth, 40 inches; width at bed, 30-1/2 inches;
height from bed, 21-1/8 inches; depth from bed, 18-1/2 inches.

THOMAS-MORSE MODEL 88 ENGINE

The Thomas-Morse Aircraft Corporation of Ithaca, N. Y., has produced a
new engine, Model 88, bearing a close resemblance to the earlier model.
The main features of that model have been retained; in fact, many parts
are interchangeable in the two engines. Supported by the great
development in the wide use of aluminum, the Thomas engineers have
adopted this material for cylinder construction, which adoption forms
the main departure from previous accepted design.

The marked tendency to-day toward a higher speed of rotation has been
conclusively justified, in the opinion of the Thomas engineers, by the
continued reliable performance of engines with crank-shafts operating at
speeds near 2,000 revolutions per minute, driving the propeller through
suitable gearing at the most efficient speed. High speed demands that
the closest attention be paid to the design of reciprocating and
rotating parts and their adjacent units. Steel of the highest
obtainable tensile strength must be used for connecting rods and piston
pins, that they may be light and yet retain a sufficient factor of
safety. Piston design is likewise subjected to the same strict scrutiny.
At the present day, aluminum alloy pistons operate so satisfactorily
that they may be said to have come to stay.

The statement often made in the past, that the gearing down of an engine
costs more in the weight of reduction gears and propeller shaft than is
warranted by the increase in horse-power, is seldom heard to-day.

The mean effective pressure remaining the same, the brake horse-power of
any engine increases as the speed. That is, an engine delivering 100
brake horse-power at 1,500 revolutions per minute will show 133 brake
horse-power at 2,000 revolutions per minute, an increase of 33 brake
horse-power. To utilize this increase in horse-power, a matter of some
fifteen pounds must be spent in gearing and another fifteen perhaps on
larger valves, bearings, etc. Two per cent. may be assumed lost in the
gears. In other words, the increase in horse-power due to increasing the
speed has been attained at the expense of about one pound per brake
horse-power.

The advantages of the eight-cylinder engine over the six and twelve,
briefly stated, are: lower weight per horse-power, shorter length,
simpler and stiffer crank-shaft, cam-shaft and crank-case, and simpler
and more direct manifold arrangement. As to torque, the eight is
superior to the six, and yet in practice not enough inferior to the
twelve to warrant the addition of four more cylinders. It must, however,
be recognized that the eight is subject to the action of inherent
unbalanced inertia couples, which set up horizontal vibrations,
impossible of total elimination. These vibrations are functions of the
reciprocating weights, which, as already mentioned, are cut down to the
minimum. Vibrations due to the elasticity of crank-case, crank-shaft,
etc., can be and are reduced in the Thomas engine to minor quantities by
ample webbing of the crank-case and judicious use of metal elsewhere.
All things considered, there is actually so little difference to be
discerned between the balance of a properly designed eight-cylinder
engine and that of a six or twelve as to make a discussion of the pros
and cons more one of theory than of practice.

The main criticisms of the L head cylinder engine are that it is less
efficient and heavier. This is granted, as it relates to cylinders
alone. More thorough investigation, however, based on the main
desideratum, weight-power ratio, leads us to other conclusions,
particularly with reference to high speed engines. The valve gear must
not be forgotten. A cylinder cannot be taken completely away from its
component parts and judged, as to its weight value, by itself alone. A
part away from the whole becomes an item unimportant in comparison with
the whole. The valve gear of a high speed engine is a too often
overlooked feature. The stamp of approval has been made by high speed
automobile practice upon the overhead cam-shaft drive, with valves in
the cylinder head operated direct from the cam-shaft or by means of
valve lifters or short rockers.

The overhead cam-shaft mechanism applied to an eight-cylinder engine
calls for two separate cam-shafts carried above and supported by the
cylinders in an oil-tight housing, and driven by a series of spur gears
or bevels from the crank-shaft. It is patent that this valve gearing is
heavy and complicated in comparison with the simple moving valve units
of the L head engine, which are operated from one single cam-shaft,
housed rigidly in the crank-case. The inherently lower volumetric
efficiency of the L head engine is largely overcome by the use of a
properly designed head, large valves and ample gas passages. Again, the
customary use of a dual ignition system gives to the L head a relatively
better opportunity for the advantageous placing of spark-plugs, in order
that better flame propagation and complete combustion may be secured.

[Illustration: Fig. 233.--End View of Thomas-Morse 150 Horse-Power
Aluminum Cylinder Aviation Motor Having Detachable Cylinder Heads.]

The Thomas Model 88 engine is 4-1/8 inch bore and 5-1/2 inch stroke. The
cylinders and cylinder heads are of aluminum, and as steel liners are
used in the cylinders the pistons are also made of aluminum. This engine
is actually lighter than the earlier model of less power. It weighs but
525 pounds, with self-starter. The general features of design can be
readily ascertained by study of the illustrations: Fig. 233, which shows
an end view; Fig. 234, which is a side view, and Fig. 235, which
outlines the reduction gear-case and the propeller shaft supporting
bearings.

[Illustration: Fig. 234.--Side View of Thomas-Morse High Speed 150
Horse-Power Aviation Motor with Geared Down Propeller Drive.]

SIXTEEN-VALVE DUESENBERG ENGINE

[Illustration: Fig. 235.--The Reduction Gear-Case of Thomas-Morse 150
Horse-Power Aviation Motor, Showing Ball Bearing and Propeller Drive
Shaft Gear.]

This engine is a four-cylinder, 4-3/4" × 7", 125 horse-power at 2,100 R.
P. M. of the crank-shaft and 1,210 R. P. M. of the propeller. Motors are
sold on above rating; actual power tests prove this motor capable of
developing 140 horse-power at 2,100 R. P. M. of the motor. The exact
weight with magneto, carburetor, gear reduction and propeller hub, as
illustrated, 509 pounds; without gear reduction, 436 pounds. This motor
has been produced as a power plant weighing 3.5 pounds per horse-power,
yet nothing has been sacrificed in rigidity and strength. At its normal
speed it develops 1 horse-power for every 3.5 cubic inches piston
displacement. Cylinders are semi-steel, with aluminum plates enclosing
water jackets. Pistons specially ribbed and made of Magnalite aluminum
compound. Piston rings are special Duesenberg design, being three-piece
rings. Valves are tungsten steel, 1-15/16" inlets and 2" exhausts, two
of each to each cylinder. Arranged horizontally in the head, allowing
very thorough water-jacketing. Inlet valves in cages. Exhaust valves,
seating directly in the cylinder head, are removable through the inlet
valve holes. Valve stems lubricated by splash in the valve action
covers. Valve rocker arms forged with cap screw and nut at upper end to
adjust clearance. Entirely enclosed by aluminum housing, as is entire
valve mechanism. Connecting rods are tubular, chrome nickel steel, light
and strong. Crank-shaft is one-piece forging, hollow bored, 2-1/2-inch
diameter at main bearings. Connecting rod bearings, 2-1/4-inch diameter,
3 inches long. Front main bearing, 3-1/2 inches long; intermediate main
bearing, 3-1/2 inches long; rear main bearing, 4 inches long. Crank-case
of aluminum, barrel type, oil pan on bottom removable. Hand hole plates
on both sides. Strongly webbed.

The oiling system of this sixteen-valve Duesenberg motor is one of its
vital features. An oil pump located in the base and submerged in oil
forces oil through cored passages to the three main bearings, then
through tubes under each connecting rod into which the rod dips. The oil
is thrown off from these and lubricates every part of the motor. This
constitutes the main oiling system; it is supplemented by a splash
system, there being a trough under each connecting rod into which the
rod slips. The oil is returned to the main supply sump by gravity, where
it is strained and re-used. Either system is in itself sufficient to
operate the motor. A pressure gauge is mounted for observation on a
convenient part of the system. A pressure of approximately 25 pounds is
maintained by the pressure system, which insures efficient lubrication
at all speeds of the motor. The troughs under the connecting rods are so
constructed that no matter what the angle of flight may be, oil is
retained in each individual trough so that each connecting rod can dip
up its supply of oil at each revolution.

AEROMARINE SIX-CYLINDER VERTICAL MOTOR

[Illustration: Fig. 236.--The Six-Cylinder Aeromarine Engine.]

These motors are four-stroke cycle, six-cylinder vertical type, with
cylinder 4-5/16" bore by 5-1/8" stroke. The general appearance of this
motor is shown in illustration at Fig. 236. This engine is rated at
85-90 horse-power. All reciprocating and revolving parts of this motor
are made of the highest grades of steel obtainable as are the studs,
nuts and bolts. The upper and lower parts of crank-case are made of
composition aluminum casting. Lower crank-case is made of high grade
aluminum composition casting and is bolted directly to the upper half.
The oil reservoir in this lower half casting provides sufficient oil
capacity for five hours' continuous running at full power. Increased
capacity can be provided if needed to meet greater endurance
requirements. Oil is forced under pressure to all bearings by means of
high-pressured duplex-geared pumps. One side of this pump delivers oil
under pressure to all the bearings, while the other side draws the oil
from the splash case and delivers it to the main sump. The oil reservoir
is entirely separate from the crank-case chamber. Under no circumstances
will oil flood the cylinder, and the oiling system is not affected in
any way by any angle of flight or position of motor. An oil pressure
gauge is placed on instrument board of machine, which gives at all
times the pressure in oil system, and a sight glass at lower half of
case indicates the amount of oil contained. The oil pump is external on
magneto end of motor, and is very accessible. An external oil strainer
is provided, which is removable in a few minutes' time without the loss
of any oil. All oil from reservoir to the motor passes through this
strainer. Pressure gauge feed is also attached and can be piped to any
part of machine desired.

The cylinders are made of high-grade castings and are machined and
ground accurately to size. Cylinders are bolted to crank-case with
chrome nickel steel studs and nuts which securely lock cylinder to upper
half of crank-case. The main retaining cylinder studs go through
crank-case and support crank-shaft bearings so that crank-shaft and
cylinders are tied together as one unit. Water jackets are of copper,
1/16" thick, electrically deposited. This makes a non-corrosive metal.
Cooling is furnished by a centrifugal pump, which delivers 25 gallons
per minute at 1,400 R. P. M. Pistons are made cast iron, accurately
machined and ground to exact dimensions, which are carefully balanced.
Piston rings are semi-steel rings of Aeromarine special design.

Connecting rods are of chrome nickel steel, H-section. Crank-shaft is
made of chrome nickel steel, machined all over, and cut from solid
billet, and is accurately balanced through the medium of balance weights
being forged integral with crank. It is drilled for lightness and
plugged for force feed lubrication. There are seven main bearings to
crank-shaft. All bearings are of high-grade babbitt, die cast, and are
interchangeable and easily replaced. The main bearings of the
crank-shaft are provided with a single groove to take oil under pressure
from pressure tube which is cast integral with case. Connecting rod
bearings are of the same type. The gudgeon pin is hardened, ground and
secured in connecting rod, and is allowed to work in piston. Cam-shaft
is of steel, with cams forged integral, drilled for lightness and
forced-feed lubrication, and is case-hardened. The bearings of
cam-shaft are of bronze. Magneto, two high-tension Bosch D. U. 6. The
intake manifold for carburetors are aluminum castings and are so
designed that each carburetor feeds three cylinders, thereby insuring
easy flow of vapor at all speeds. Weight, 420 pounds.

[Illustration: Fig. 237.--The Wisconsin Aviation Engine, at Top, as
Viewed from Carburetor Side. Below, the Exhaust Side.]

WISCONSIN AVIATION ENGINES

[Illustration: Fig. 238.--Dimensioned End Elevation of Wisconsin Six
Motor.]

The new six-cylinder Wisconsin aviation engines, one of which is shown
at Fig. 237, are of the vertical type, with cylinders in pairs and
valves in the head. Dimensioned drawings of the six-cylinder vertical
type are given at Figs. 238 and 239. The cylinders are made of aluminum
alloy castings, are bored and machined and then fitted with hardened
steel sleeves about 1/16 inch in thickness. After these sleeves have
been shrunk into the cylinders, they are finished by grinding in place.
Gray iron valve seats are cast into the cylinders. The valve seats and
cylinders, as well as the valve ports, are entirely surrounded by water
jackets. The valves set in the heads at an angle of 25° from the
vertical, are made of tungsten steel and are provided with double
springs, the outer or main spring and the inner or auxiliary spring,
which is used as a precautionary measure to prevent a valve falling into
the cylinder in remote case of a main spring breaking. The cam-shaft is
made of one solid forging, case-hardened. It is carried in an aluminum
housing bolted to the top of the cylinders. This housing is split
horizontally, the upper half carrying the chrome vanadium steel rocker
levers. The lower half has an oil return trough cast integral, into
which the excess oil overflows and then drains back to the crank-case.
Small inspection plates are fitted over the cams and inner ends of the
cam rocker levers. The cam-shaft runs in bronze bearings and the drive
is through vertical shaft and bevel gears.

[Illustration: Fig. 239.--Dimensioned Side Elevation of Wisconsin Six
Motor.]

The crank-case is made of aluminum, the upper half carrying the
bearings for the crank-shaft. The lower half carries the oil sump in
which all of the oil except that circulating through the system at the
time is carried. The crank-shaft is made of chrome vanadium steel of an
elastic limit of 115,000 pounds. The crank-pins and ends of the shaft
are drilled for lightness and the cheeks are also drilled for oil
circulation. The crank-shaft runs in bronze-backed, Fahrig metal-lined
bearings, four in number. A double thrust bearing is also provided, so
that the motor may be used either in a tractor or pusher type of
machine. Outside of the thrust bearing an annular ball bearing is used
to take the radial load of the propeller. The propeller is mounted on a
taper. At the opposite end of the shaft a bevel gear is fitted which
drives the cam-shaft, through a vertical shaft, and also drives the
water and oil pumps and magnetos. All gears are made of chrome vanadium
steel, heat-treated.

The connecting rods are tubular and machined from chrome vanadium steel
forgings. Oil tubes are fitted to the rods which carry the oil up to the
wrist-pins and pistons. The rods complete with bushings weigh 5-1/2
pounds each. The pistons are made of aluminum alloy and are very light
and strong, weighing only 2 pounds 2 ounces each. Two leak-proof rings
are fitted to each piston. The wrist-pins are hollow, of hardened steel,
and are free to turn either in the piston or the rod. A bronze bushing
is fitted in the upper end of the rod, but no bushing is fitted in the
pistons, the hardened steel wrist-pins making an excellent bearing in
the aluminum alloy.

[Illustration: Fig. 240.--Power, Torque and Efficiency Curves of
Wisconsin Aviation Motor.]

The water circulation is by centrifugal pump, which is mounted at the
lower end of the vertical shaft. The water is pumped through brass pipes
to the lower end of the cylinder water jackets and leaves the upper end
of the jackets just above the exhaust valves. The lubricating system is
one of the main features of the engines, being designed to work with the
motor at any angle. The oil is carried in the sump, from where it is
taken by the oil circulating pump through a strainer and forced through
a header, extending the full length of the crank-case, and distributed
to the main bearings. From the main bearings it is forced through the
hollow crank-shaft to the connecting rod big ends and then through
tubes on the rods to wrist-pins and pistons. Another lead takes oil from
the main header to the cam-shaft bearings. The oil forced out of the
ends of the cam-shaft bearings fills pockets under the cams and in the
cam rocker levers. The excess flows back through pipes and through the
train of gears to the crank-case. A strainer is fitted at each end of
the crank-case, through which the oil is drawn by separate pumps and
returned to the sump. Either one of these pumps is large enough to take
care of all of the return oil, so that the operation is perfect whether
the motor is inclined up or down. No splash is used in the crank-case,
the system being a full force feed. An oil level indicator is provided,
showing the amount of oil in the sump at all times. The oil pressure in
these motors is carried at ten pounds, a relief valve being fitted to
hold the pressure constant.

[Illustration: Fig. 241.--Timing Diagram, Wisconsin Aviation Engine.]

Ignition is by two Bosch magnetos, each on a separate set of plugs fired
simultaneously on opposite sides of the cylinders. Should one magneto
fail, the other would still run the engine at only a slight loss in
power. The Zenith double carburetor is used, three cylinders being
supplied by each carburetor. This insures a higher volumetric
efficiency, which means more power, as there is no overlapping of inlet
valves whatever by this arrangement. All parts of these motors are very
accessible. The water and oil pumps, carburetors, magnetos, oil strainer
or other parts can be removed without disturbing other parts. The lower
crank-case can be removed for inspection or adjustment of bearings, as
the crank-shaft and bearing caps are carried by the upper half. The
motor supporting lugs are also part of the upper crank-case.

The six-cylinder motor, without carburetors or magnetos, weighs 547
pounds. With carburetor and magnetos, the weight is 600 pounds. The
weight of cooling water in the motor is 38 pounds. The sump will carry 4
gallons of oil, or about 28 pounds. A radiator can be furnished suitable
for the motor, weighing 50 pounds. This radiator will hold 3 gallons of
water or about 25 pounds. The motor will drive a two-blade, 8 feet
diameter by 6.25 feet pitch Paragon propeller 1400 revolutions per
minute, developing 148 horse-power. The weight of this propeller is 42
pounds. This makes a total weight of motor, complete with propeller,
radiator filled with water, but without lubricating oil, 755 pounds, or
about 5.1 pounds per horse-power for complete power plant. The fuel
consumption is .5 pound per horse-power per hour. The lubricating oil
consumption is .0175 pound per horse-power per hour, or a total of 2.6
pounds per hour at 1400 revolutions per minute. This would make the
weight of fuel and oil, per hour's run at full power at 1400 revolutions
per minute, 76.6 pounds.

PRINCIPAL DIMENSIONS

Following are the principal dimensions of the six-cylinder motor:

Bore 5 inches.
Stroke 6-1/2 inches.
Crank-shaft diameter throughout 2 inches.
Length of crank-pin and main bearings 3-1/2 inches.
Diameter of valves 3 inches (2-3/4 inches clear).
Lift of valves 1/2 inch.
Volume of compression space 22 per cent. of total.
Diameter of wrist-pins 1-3/16 inches.
Firing order 1-4-2-6-3-5.

The horse-power developed at 1200 revolutions per minute is 130, at 1300
revolutions per minute 140, at 1400 revolutions per minute 148. 1400 is
the maximum speed at which it is recommended to run these motors.

TWELVE-CYLINDER ENGINE

A twelve-cylinder V-type engine illustrated, is also being built by this
company, similar in dimensions of cylinders to the six. The principal
differences being in the drive to cam-shaft, which is through spur gears
instead of bevel. A hinged type of connecting rod is used which does not
increase the length of the motor and, at the same time, this
construction provides for ample bearings. A double centrifugal water
pump is provided for this motor, so as to distribute the water uniformly
to both sets of cylinders. Four magnetos are used, two for each set of
six cylinders. The magnetos are very accessibly located on a bracket on
the spur gear cover. The carburetors are located on the outside of the
motors, where they are very accessible, while the exhaust is in the
center of the valley. The crank-shaft on the twelve is 2-1/2 inches in
diameter and the shaft is bored to reduce weight. Dimensioned drawings
of the twelve-cylinder engine are given at Figs. 242 and 243 and should
prove useful for purposes of comparison with other motors.

HALL-SCOTT AVIATION ENGINES

The following specifications of the Hall-Scott "Big Four" engines apply
just as well to the six-cylinder vertical types which are practically
the same in construction except for the structural changes necessary to
accommodate the two extra cylinders. Cylinders are cast separately from
a special mixture of semi-steel, having cylinder head with valve seats
integral. Special attention has been given to the design of the water
jacket around the valves and head, there being two inches of water space
above same. The cylinder is annealed, rough machined, then the inner
cylinder wall and valve seats ground to mirror finish. This adds to the
durability of the cylinder, and diminishes a great deal of the excess
friction.

[Illustration: Fig. 242.--Dimensioned End View of Wisconsin
Twelve-Cylinder Airplane Motor.]

Great care is taken in the casting and machining of these cylinders, to
have the bore and walls concentric with each other. Small ribs are cast
between outer and inner walls to assist cooling as well as to transfer
stresses direct from the explosion to hold-down bolts which run from
steel main bearing caps to top of cylinders. The cylinders are machined
upon the sides so that when assembled on the crank-case with grooved
hold-down washers tightened, they form a solid block, greatly assisting
the rigidity of crank-case.

[Illustration: Fig. 243.--Dimensioned Side Elevation of Wisconsin
Twelve-Cylinder Airplane Motor.]

The connecting rods are very light, being of the I beam type, milled
from a solid Chrome nickel die forging. The caps are held on by two
1/2"-20 thread Chrome nickel through bolts. The rods are first roughed
out, then annealed. Holes are drilled, after which the rods are hardened
and holes ground parallel with each other. The piston end is fitted with
a gun metal bushing, while the crank-pin end carries two bronze serrated
shells, which are tinned and babbitted hot, being broached to harden the
babbitt. Between the cap and rod proper are placed laminated shims for
adjustment. Crank-cases are cast of the best aluminum alloy, hand
scraped and sand blasted inside and out. The lower oil case can be
removed without breaking any connections, so that the connecting rods
and other working parts can readily be inspected. An extremely large
strainer and dirt trap is located in the center and lowest point of the
case, which is easily removed from the outside without disturbing the
oil pump or any working parts. A Zenith carburetor is provided.
Automatic valves and springs are absent, making the adjustment simple
and efficient. This carburetor is not affected by altitude to any
appreciable extent. A Hall-Scott device, covered by U. S. Patent No.
1,078,919, allows the oil to be taken direct from the crank-case and run
around the carburetor manifold, which assists carburetion as well as
reduces crank-case heat. Two waterproof four-cylinder Splitdorf "Dixie"
magnetos are provided. Both magneto interruptors are connected to a rock
shaft integral with the motor, making outside connections unnecessary.
It is worthy of note that with this independent double magneto system,
one complete magneto can become inoperative, and still the motor will
run and continue to give good power.

The pistons as provided in the A-7 engines are cast from a mixture of
steel and gray iron. These are extremely light, yet provided with six
deep ribs under the arch head, greatly aiding the cooling of the piston
as well as strengthening it. The piston pin bosses are located very low
in order to keep the heat from the piston head away from the upper end
of the connecting rod, as well as to arrange them at the point where the
piston fits the cylinder best. Three 1/4" rings are carried. The pistons
as provided in the A-7a engines are cast from aluminum alloy. Four 1/4"
rings are carried. In both piston types a large diameter, heat treated,
Chrome nickel steel wrist-pin is provided, assembled in such a way as to
assist the circular rib between the wrist-pin bosses to keep the piston
from being distorted from the explosions.

The oiling system is known as the high pressure type, oil being forced
to the under side of the main bearings with from 5 to 30 points
pressure. This system is not affected by extreme angles obtained in
flying, or whether the motor is used for push or pull machines. A large
gear pump is located in the lowest point of the oil sump, and being
submerged at all times with oil, does away with troublesome stuffing
boxes and check valves. The oil is first drawn from the strainer in oil
sump to the long jacket around the intake manifold, then forced to the
main distributor pipe in crank-case, which leads to all main bearings. A
bi-pass, located at one end of the distributor pipe, can be regulated to
provide any pressure required, the surplus oil being returned to the
case. A special feature of this system is the dirt, water and sediment
trap, located at the bottom of the oil sump. This can be removed without
disturbing or dismantling the oil pump or any oil pipes. A small oil
pressure gauge is provided, which can be run to the aviator's instrument
board. This registers the oil pressure, and also determines its
circulation.

The cooling of this motor is accomplished by the oil as well as the
water, this being covered by patent No. 1,078,919. This is accomplished
by circulating the oil around a long intake manifold jacket; the
carburetion of gasoline cools this regardless of weather conditions.
Crank-case heat is therefore kept at a minimum. The uniform temperature
of the cylinders is maintained by the use of ingenious internal outlet
pipes, running through the head of each of the six-cylinders, rubber
hose connections being used so that any one of the cylinders may be
removed without disturbing the others. Slots are cut in these pipes so
that cooler water is drawn directly around the exhaust valves. Extra
large water jackets are provided upon the cylinders, two inches of water
space is left above the valves and cylinder head. The water is
circulated by a large centrifugal pump insuring ample circulation at all
speeds.

The crank-shaft is of the five bearing type, being machined from a
special heat treated drop forging of the highest grade nickel steel. The
forging is first drilled, then roughed out. After this the shaft is
straightened, turned down to a grinding size, then ground accurately to
size. The bearing surfaces are of extremely large size, over-size,
considering general practice in the building of high speed engines of
similar bore and stroke. The crank-shaft bearings are 2" in diameter by
1-15/16" long, excepting the rear main bearing, which is 4-3/8" long,
and front main bearing, which is 2-3/16" long. Steel oil scuppers are
pinned and sweated onto the webs of the shaft, which allows of properly
oiling the connecting rod bearings. Two thrust bearings are installed on
the propeller end of the shaft, one for pull and the other for push. The
propeller is driven by the crank-shaft flange, which is securely held in
place upon the shaft by six keys. These drive an outside propeller
flange, the propeller being clamped between them by six through bolts.
The flange is fitted to a long taper on crank-shaft. This enables the
propeller to be removed without disturbing the bolts. Timing gears and
starting ratchets are bolted to a flange turned integral with shaft.

The cam-shaft is of the one piece type, air pump eccentric, and gear
flange being integral. It is made from a low carbon specially heat
treated nickel forging, is first roughed out and drilled entire length;
the cams are then formed, after which it is case hardened and ground to
size. The cam-shaft bearings are extra long, made from Parson's White
Brass. A small clutch is milled in gear end of shaft to drive revolution
indicator. The cam-shaft is enclosed in an aluminum housing bolted
directly on top of all six cylinders, being driven by a vertical shaft
in connection with bevel gears. This shaft, in conjunction with rocker
arms, rollers and other working parts, are oiled by forcing the oil into
end of shaft, using same as a distributor, allowing the surplus supply
to flow back into the crank-case through hollow vertical tube. This
supply oils the magneto and pump gears. Extremely large Tungsten valves,
being one-half the cylinder diameter, are seated in the cylinder heads.
Large diameter oil tempered springs held in tool steel cups, locked with
a key, are provided. The ports are very large and short, being designed
to allow the gases to enter and exhaust with the least possible
resistance. These valves are operated by overhead one piece cam-shaft in
connection with short Chrome nickel rocker arms. These arms have
hardened tool steel rollers on cam end with hardened tool steel
adjusting screws opposite. This construction allows accurate valve
timing at all speeds with least possible weight.

CENSORED

GERMAN AIRPLANE MOTORS

In a paper on "Aviation Motors," presented by E. H. Sherbondy before the
Cleveland section of the S. A. E. in June, 1917, the Mercedes and Benz
airplane motor is discussed in some detail and portions of the
description follow.

[Illustration: Fig. 244.--Side and End Sectional Views of Four-Cylinder
Argus Engine, a German 100 Horse-Power Design Having Bore and Stroke of
140 mm., or 5.60 inches, and Developing Its Power at 1,368 R.P.M.
Weight, 350 Pounds.]

MERCEDES MOTOR

The 150 horse-power six-cylinder Mercedes motor is 140 millimeters bore
and 160 millimeters stroke. The Mercedes company started with
smaller-sized cylinders, namely 100 millimeters bore and 140 millimeters
stroke, six-cylinders. The principal features of the design are forged
steel cylinders with forged steel elbows for gas passages, pressed steel
water jackets, which when welded together forms the cylinder
assembly, the use of inclined overhead valves operated by means of an
overhead cam-shaft through rocker arms which multiply with the motion of
the cam. By the use of steel cylinders, not only is the weight greatly
reduced, but certain freedom from distortion through unequal sections,
leaks and cracks are entirely avoided. The construction is necessarily
very expensive. It is certainly a sound job. In the details of this
construction there are a number of important things, such as finished
gas passages, water-cooled valve guides and a very small mass of metal,
which is water-cooled, surrounding the spark-plug. Of course, it is
necessary to use very high compression in aviation motors in order to
secure high power and economy and owing to the fact that aviation motors
are worked at nearly their maximum, the heat flow through the cylinder,
piston, and valves is many times higher than that encountered in
automobile motors. It has been found necessary to develop special types
of pistons to carry the heat from the center of the head in order to
prevent pre-ignition. In the Mercedes motor the pistons have a drop
forged steel head which includes the piston boss and this head is
screwed into a cast iron skirt which has been machined inside to secure
uniform wall thickness.

CENSORED

[A] Piston Displacement (Cubic Inches)
[B] Weight of Engine with Carburetor and Ignition
[C] Gas Consumption

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Maker's |Number|Bore |Stroke| | | | |
Name | of |(In- |(In- | | | | |
and Model | Cyl. |ches) |ches) | [A] |H.P.|R.P.M.| [B]| [C]
-----------+------+------+------+-------+----+------+----+-----------------
Aeromarine | 6 |4-1/2 |5-1/8 | 449 | 85| 1400 | 440| ...
-----------+------+------+------+-------+----+------+----+-----------------
Aeromarine | 12 |4-5/16|5-1/8 | ... | ...| ... | 750| ...
D-12 | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Curtiss OX | 8 |4 |5 | 502.6 | 90| 1400 | 375| ...
-----------+------+------+------+-------+----+------+----+-----------------
Curtiss | 8 |4-1/4 |5 | 567.5 | 100| 1400 | 423| ...
OXX-2 | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Curtiss V-2| 8 |5 |7 |1100 | 200| 1400 | 690| ...
-----------+------+------+------+-------+----+------+----+-----------------
CENSORED
-----------+------+------+------+-------+----+------+----+-----------------
General Ve-| 9 |4.33 |5.9 | 848 | 100| 1200 | 272|12 gals/hour at
hicle Gnome Mono | | | | | | |rated H.P.
-----------+------+------+------+-------+----+------+----+-----------------
Gyro K | 7 |4-1/2 |6 | ... | 90| 1250| 215|8 gals/hour at
Rotary, Le Rhone Type | | | | | |rated H.P.
-----------+------+------+------+-------+----+------+----+-----------------
Gyro L | 9 |4-1/2 |6 | 859 | 100| 1200| 285|10 gals/hour at
Rotary, Le Rhone Type | | | | | |rated H.P.
-----------+------+------+------+-------+----+------+----+-----------------
Hall-Scott | 4 |5 |7 | 550 | 90-| 1400| 410| ...
A-7 | | | | | 100| | |
-----------+------+------+------+-------+----+------+----+-----------------
Hall-Scott | 6 |5 |7 | 825 | 125| 1300| 592| ...
A-5 | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Hispano- | 8 |4-5/8 |5 | 672 | 154| 1500| 455| ...
Suiza | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Knox Motors| 12 |4-3/4 |7 |1555 | 300| 1800|1425|31.5 gals/hour
Co. | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Maximotor | 6 |4-1/2 |5 | 477 | 85| 1600| 340| ...
A-6 | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Maximotor | 6 |5 |6 | 706.8 | 115| 1600| 385| ...
B-6 | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Maximotor | 8 |4-1/2 |5 | 636 | 115| 1600| 420| ...
A-8 | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Packard 12 | 12 |4 |6 | 903 | 225| 2100| 800| ...
-----------+------+------+------+-------+----+------+----+-----------------
Sturtevant | 8 |4 |5-1/2 | 552.9 | 140| 2000| 580| ...
5 | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Sturtevant | 8 |4 |5-1/2 | ... | 140| 2000| 514|13.75 gals/hour
5-A | | | | | | | |
-----------+------+------+------+-------+----+------+----+-----------------
Thomas 8 | 8 |4 |5-1/2 | 552.9 | 135| 2000| 630| ...
| | | | | | |lbs. with self-starter
-----------+------+------+------+-------+----+------+----+-----------------
Thomas 88 | 8 |4-1/8 |5-1/2 | 552.9 | 150| 2100| 525| ...
| | | | | | |lbs. with self-starter
-----------+------+------+------+-------+----+------+----+-----------------
Wisconsin | 6 |5 |6-1/2 | 765.7 | 140| 1380| 637| ...
-----------+------+------+------+-------+----+------+----+-----------------
Wisconsin | 12 |5 |6-1/2 |1531.4 | 250| 1200| ...| ...
-----------+------+------+------+-------+----+------+----+-----------------

The carburetor used on this 150 horse-power Mercedes motor is precisely
of the same type used on the Twin Six motor. It has two venturi throats,
in the center of which is placed the gasoline spray nozzle of
conventional type, fixed size orifices, immediately above which are
placed two panel type throttles with side outlets. An idling or primary
nozzle is arranged to discharge above the top of the venturi throat. The
carburetor body is of cast aluminum and is water jacketed. It is bolted
directly to air passage passing through the top and bottom half of the
crank-case which passes down through the oil reservoir. The air before
reaching the carburetor proper to some extent has cooled the oil in the
crank chamber and has itself been heated to assist in the vaporization.
The inlet pipes themselves are copper. All the passages between the
venturi throat and the inlet valve have been carefully finished and
polished. The only abnormal thing in the design of this motor is the
short connecting rod which is considerably less than twice the stroke
and would be considered very bad practice in motor car engines. A short
connecting rod, however, possesses two very real virtues in that it cuts
down height of the motor and the piston passes over the bottom dead
center much more slowly than with a long rod.

[Illustration: Fig. 245.--Part Sectional View of 90 Horse-Power Mercedes
Engine, Which is Typical of the Design of Larger Sizes.]

Other features of the design are a very stiff crank-case, both halves of
which are bolted together by means of long through bolts, the
crank-shaft main bearings are seated in the lower half of the case
instead of in the usual caps and no provision is made for taking up the
main bearings. The Mercedes company uses a plunger type of pump having
mechanically operated piston valves and it is driven by means of worm
gearing.

The overhead cam-shaft construction is extremely light. The cam-shaft is
mounted in a nearly cylindrical cast bronze case and is driven by means
of bevel gears from the crank-shaft. The vertical bevel gear shaft
through which the drive is taken from the crank-shaft to the cam-shaft
operates at one and one-half times the crank-shaft speeds and the
reduction to the half-time cam-shaft is secured through a pair of
bevels. On this vertical shaft there is mounted the water pump and a
bevel gear for driving two magnetos. The water pump mounted on this
shaft tends to steady the drive and avoid vibration in the gearing.

The cylinder sizes of six-cylinder aviation motors which have been built
by Mercedes are

Bore Stroke Horse-power
105 mm. 140 mm. 100
120 mm. 140 mm. 135
140 mm. 150 mm. 150
140 mm. 160 mm. 160

The largest of these motors has recently had its horse-power increased
to 176 at 1450 R. P. M. This general design of motor has been the
foundation for a great many other aviation motor designs, some of which
have proved very successful but none of which is equal to the original.
Among the motors which follow more or less closely the scheme of design
and arrangement are the Hall-Scott, the Wisconsin motor, the Renault
water-cooled, the Packard, the Christofferson and the Rolls-Royce. Each
of these motors show considerable variation in detail. The Rolls-Royce
and Renault are the only ones who have used the steel cylinder with the
steel jacket. The Wisconsin motor uses an aluminum cylinder with a
hardened steel liner and cast-iron valve seats. The Christofferson has
somewhat similar design to the Wisconsin with the exception that the
valve seats are threaded into the aluminum jacket and the cylinder head
has a blank end which is secured to the aluminum casting by means of the
valve seat pieces. The Rolls-Royce motors show small differences in
details of design in cylinder head and cam-shaft housing from the
Mercedes on which it has taken out patents, not only abroad but in this
country.

THE BENZ MOTOR

In the Kaiser prize contest for aviation motors a four-cylinder Benz
motor of 130 by 180 mm. won first prize, developing 103 B. H. P. at 1290
R. P. M. The fuel consumption was 210 grams per horse-power hour. Total
weight of the motor was 153 kilograms. The oil consumption was .02 of a
kilogram per horse-power hour. This motor was afterward expanded into a
six-cylinder design and three different sizes were built.

The accompanying table gives some of the details of weight, horse-power,
etc.

Motor type B FD FF
Rated horse-power 85 100 150
Horse-power at 1250 r.p.m 88 108 150
Horse-power at 1350 r.p.m 95 115 160
Bore in millimeters 106 116 130
Stroke in millimeters 150 160 180
Offset of the cylinders in millimeters 18 20 20
Rate of gasoline consumption in grams 240 230 225
Oil consumption in grams per b.h.p. hour 10 10 10
Oil capacity in kilograms 36 4 4-1/2
Water capacity in litres 5-1/2 7-1/2 9-1/2
The weight with water and oil but with
two magnetos, fuel feeder and air pump in
kilograms 170 200 245
The weight of motors, including the water
pump, two magnetos, double ignition, etc. 160 190 230
The weight of the exhaust pipe, complete
in kilograms 4 4.8 5-1/2
The weight of the propeller hub in
kilograms. 3-1/2 4 4

The Benz cylinder is a simple, straightforward design and a very
reliable construction and not particularly difficult to manufacture. The
cylinder is cast of iron without a water jacket but including 45
degrees angle elbows to the valve ports. The cylinders are machined
wherever possible and at other points have been hand filed and scraped,
after which a jacket, which is pressed in two halves, is gas welded by
means of short pipes welded on to the jacket. The bottom and the top of
the cylinders become water galleries, and by this means separate water
pipes with their attendant weight and complication are eliminated.
Rubber rings held in aluminum clamps serve to connect the cylinders
together. The whole construction turns out very neat and light. The
cylinder walls are 4 mm. or 3/16" thick and the combustion chamber is of
cylindrical pancake form and is 140 mm. or 5.60 inch in diameter. The
valve seats are 68 mm. in diameter and the valve port is 62 mm. in
diameter.

The passage joining the port is 57 mm. in diameter. In order to insert
the valves into the cylinder the valve stem is made with two diameters
and the valve has to be cocked to insert it in the guide, which has a
bronze bushing at its upper end to compensate for the smaller valve stem
diameter. The valve stem is 14 mm. or 9/16" in diameter and is reduced
at its upper portion to 9-1/2 mm. The valves are operated through a push
rod and rocker arm construction, which is 7/16" and exceedingly light.
Rocker arm supports are steel studs with enlarged heads to take a double
row ball bearing. A roller is mounted at one end of the rocker arm to
impinge on the end of the valve stem, and the rocker arm has an
adjustable globe stud at the other end. The push rods are light steel
tubes with a wall thickness of 0.75 mm. and have a hardened steel cup at
their upper end to engage the rocker arm globe stud and a hardened steel
globe at their lower end to socket in the roller plunger.

The Benz cam-shaft has a diameter of 26 mm. and is bored straight
through 18 mm. and there is a spiral gear made integrally with the shaft
in about the center of its length for driving the oil pump gear. The cam
faces are 10 mm. wide. There is also, in addition to the intake and
exhaust cams, a set of half compression cams. The shaft is moved
longitudinally in its bearings by means of an eccentric to put these
cams into action. At the fore end of the shaft is a driving gear flange
which is very small in diameter and very thin. The flange is 68 mm. in
diameter and 4 mm. thick and is tapped to take 6 mm. bolts. The total
length of cam-shaft is 1038 mm., and it becomes a regular gun boring job
to drill a hole of this length.

The cam-shaft gear is 140 mm. or 5-1/2 inches outside diameter. It has
fifty-four teeth and the gear face is 15 mm. or 19/32". The flange and
web have an average thickness of 4 mm. or 5/32" and the web is drilled
full of holes interposed between the spur gear mounted on the cam-shaft
and the cam-shaft gear. There is a gear which serves to drive the
magnetos and tachometer, also the air pump. The shaft is made integrally
with this gear and has an eccentric portion against which the air pump
roll plunger impinges.

The seven-bearing crank-shaft is finished all over in a beautiful
manner, and the shaft out of the particular motor we have shows no signs
of wear whatever. The crank-pins are 55 mm. in diameter and 69 mm. long.
Through both the crank-pin and main bearings there is drilled a 28 mm.
hole, and the crank cheeks are plugged with solder. The crank cheeks are
also built to convey the lubricant to the crank-pins. At the fore end of
the crank cheek there is pressed on a spur driving gear. There is
screwed on to the front end of the shaft a piece which forms a bevel
water pump driving gear and the starting dog. At the rear end of the
shaft very close to the propeller hub mounting there is a double thrust
bearing to take the propeller thrust.

Long, shouldered studs are screwed into the top half of the crank-case
portion of the case and pass clean through the bottom half of the case.
The case is very stiff and well ribbed. The three center bearing
diaphragms have double walls. The center one serves as a duct through
which water pipe passes, and those on either side of the center form the
carburetor intake air passages and are enlarged in section at one side
to take the carburetor barrel throttle.

The pistons are of cast iron and carry three concentric rings 1/4 inch
wide on their upper end, which are pinned at the joint. The top of the
piston forms the frustum of the cone and the pistons are 110 mm. in
length. The lower portion of the skirt is machined inside and has a wall
thickness of 1 mm. Riveted to the piston head is a conical diaphragm
which contacts with the piston pin when in place and serves to carry the
heat off the center of the piston.

The oil pump assembly comprises a pair of plunger pumps which draw oil
from a separate outside pump, and constructed integrally with it is a
gear pump which delivers the oil under about 60 pound pressure through a
set of copper pipes in the base to the main bearings. The plunger oil
pump shows great refinement of detail. A worm wheel and two eccentrics
are machined up out of one piece and serve to operate the plungers.

[Illustration: Fig. 246.--Part Sectional Side View and Sectional End
View of Benz 160 Horse-Power Aviation Engine.]

Some interesting details of the 160 horse-power Benz motor, which is
shown at Fig. 246, are reproduced from the "Aerial Age Weekly," and show
how carefully the design has been considered.

Maximum horse-power, 167.5 B. H. P.
Speed at maximum horse-power, 1,500 R. P. M.
Piston speed at maximum horse-power, 1,770 ft. per minute.
Normal horse-power, 160 B. H. P.
Speed at normal horse-power, 1,400 R. P. M.
Piston speed at normal horse-power, 1,656 ft. per minute.
Brake mean pressure at maximum horse-power, 101.2 pound per square
inch.
Brake mean pressure at normal horse-power, 103.4 pound per square
inch.
Specific power cubic inch swept volume per B. H. P., 5.46 cubic inch;
160 B. H. P.
Weight of piston, complete with gudgeon pin, rings, etc., 5.0 pound.
Weight of connecting rod, complete with bearings, 4.99 pound; 1.8
pound reciprocating.
Weight of reciprocating parts per cylinder, 6.8 pound.
Weight of reciprocating parts per square inch of piston area, 0.33
pound.
Outside diameter of inlet valve, 68 mm.; 2.68 inches.
Diameter of inlet valve port (_d_), 61.5 mm.; 2.42 inches.
Maximum lift of inlet valve (_h_), 11 mm.; 0.443 inch.
Area of inlet valve opening ([pi] _d_ _h_), 21.25 square cm.; 3.29
square inches.
Inlet valve opens, degrees on crank, top dead center.
Inlet valve closes, degrees on crank, 60° late; 35 mm. late.
Outside diameter of exhaust valve, 68 mm.; 2.68 inches.
Diameter of exhaust valve port (_d_), 61.5 mm.; 2.42 inches.
Maximum lift of exhaust valve (_h_) 11 mm.; 0.433 inch.
Area of exhaust valve opening ([pi] _d_ _h_), 21.25 square cm.; 3.29
square inches.
Exhaust valve opens, degrees on crank, 60° early; 35 mm. early.
Exhaust valve closes, degrees on crank, 16-1/2° late; 5 mm. late.
Length of connecting rod between centers, 314 mm.; 12.36 inches.
Ratio connecting rod to crank throw, 3.49:1.
Diameter of crank-shaft, 55 mm. outside, 2.165 inches; 28 mm. inside,
1.102 inches.
Diameter of crank-pin, 55 mm. outside, 2.165 inches; 28 mm. inside,
1.102 inches.
Diameter of gudgeon pin, 30 mm. outside, 1.181 inches; 19 mm. inside,
0.708 inch.
Diameter of cam-shaft, 26 mm. outside, 1.023 inches; 18 mm. inside,
0.708 inch.
Number of crank-shaft bearings, 7.
Projected area of crank-pin bearings, 36.85 square cm.; 5.72 square
inches.
Projected area of gudgeon pin bearings, 22.20 square cm.; 3.44 square
inches.
Firing sequence, 1, 5, 3, 6, 2, 4.
Type of magnetos, ZH6 Bosch.
Direction of rotation of magneto from driving end, one clock, one
anti-clock.
Magneto timing, full advance, 30° early (16 mm. early).
Type of carburetors (2) Benz design.
Fuel consumption per hour, normal horse-power, 0.57 pint.
Normal speed of propeller, engine speed, 1,400 R. P. M.

AUSTRO-DAIMLER ENGINE

One of the first very successful European flying engines which was
developed in Europe is the Austro-Daimler, which is shown in end section
in a preceding chapter. The first of these motors had four-cylinders,
120 by 140 millimeters, bore and stroke, with cast iron cylinders,
overhead valves operated by means of a single rocker arm, controlled by
two cams and the valves were closed by a single leaf spring which
oscillates with the rocker arm. The cylinders are cast singly and have
either copper or steel jackets applied to them. The four-cylinder design
was afterwards expanded to the six-cylinder design and still later a
six-cylinder motor of 130 by 175 millimeters was developed. This motor
uses an offset crank-shaft, as does the Benz motor, and the effect of
offset has been discussed earlier on in this treatise. The Benz motor
also uses an offset cam-shaft which improves the valve operation and
changes the valve lift diagram. The lubrication also is different than
any other aviation motor, since individual high pressure metering pumps
are used to deliver fresh oil only to the bearings and cylinders, as was
the custom in automobile practice some ten years ago.

SUNBEAM AVIATION ENGINES

These very successful engines have been developed by Louis Coatalen. At
the opening of the war the largest sized Coatalen motor was 225
horse-power and was of the L-head type having a single cam-shaft for
operating valves and was an evolution from the twelve-cylinder racing
car which the Sunbeam Company had previously built. Since 1914 the
Sunbeam Company have produced engines of six-, eight-, twelve- and
eighteen-cylinders from 150 to 500 horse-power with both iron and
aluminum cylinders. For the last two years all the motors have had
overhead cam-shafts with a separate shaft for operating the intake and
exhaust valves. Cam-shafts are connected through to the crank-shaft by
means of a train of spur gears, all of which are mounted on two double
row ball bearings. In the twin six, 350 horse-power engine, operating at
2100 R. P. M., requires about 4 horse-power to operate the cam-shafts.
This motor gives 362 horse-power at 2100 revolutions and has a fuel
consumption of 51/100 of a pint per brake horse-power hour. The
cylinders are 110 by 160 millimeters. The same design has been expanded
into an eighteen-cylinder which gives 525 horse-power at 2100 turns.
There has also been developed a very successful eight-cylinder motor
rated at 2220 horse-power which has a bore and stroke of 120 by 130
millimeters, weight 450 pounds. This motor is an aluminum block
construction with steel sleeves inserted. Three valves are operated, one
for the inlet and two for the exhaust. One cam-shaft operates the three
valves.

[Illustration: Fig. 247.--At Top, the Sunbeam Overhead Valve 170
Horse-Power Six-Cylinder Engine. Below, Side View of Sunbeam 350
Horse-Power Twelve-Cylinder Vee Engine.]

The modern Sunbeam engines operate with a mean effective pressure of 135
pounds with a compression ratio of 6 to 1 sea level. The connecting rods
are of the articulated type as in the Renault motor and are very short.
The weight of these motors turns out at 2.6 pounds per brake
horse-power, and they are able to go through a 100 hour test without any
trouble of any kind. The lubricating system comprises a dry base and oil
pump for drawing the oil off from the base, whence it is delivered to
the filter and cooling system. It then is pumped by a separate high
pressure gear pump through the entire motor. In these larger European
motors, castor-oil is used largely for lubrication. It is said that
without the use of castor-oil it is impossible to hold full power for
five hours. Coatalen favors aluminum cylinders rather than cast iron.
The series of views in Figs. 247 to 250 inclusive, illustrates the
vertical, narrow type of engine; the V-form; and the broad arrow type
wherein three rows, each of six-cylinders, are set on a common
crank-case. In this water-cooled series the gasoline and oil consumption
are notably low, as is the weight per horse-power.

[Illustration: Fig. 248.--Side View of Eighteen-Cylinder Sunbeam
Coatalen Aircraft Engine Rated at 475 B.H.P.]

[Illustration: Fig. 249.--Sunbeam Eighteen-Cylinder Motor, Viewed from
Pump and Magneto End.]

In the eighteen-cylinder overhead valve Sunbeam-Coatalen aircraft engine
of 475 brake horse-power, there are no fewer than half a dozen magnetos.
Each magneto is inclosed. Two sparks are furnished to each cylinder
from independent magnetos. On this engine there are also no fewer than
six carburetors. Shortness of crank-shaft, and therefore of engine
length, and absence of vibration are achieved by the linking of the
connecting-rods. Those concerned with three-cylinders in the broad arrow
formation work on one crank-pin, the outer rods being linked to the
central master one. In consequence of this arrangement, the piston
travel in the case of the central row of cylinders is 160 mm., while the
stroke of the pistons of the cylinders set on either side is in each
case 168 mm. Inasmuch as each set of six-cylinders is completely
balanced in itself, this difference in stroke does not affect the
balance of the engine as a whole. The duplicate ignition scheme also
applies to the twelve-cylinder 350 brake horse-power Sunbeam-Coatalen
overhead valve aircraft engine type. It is distinguishable,
incidentally, by the passage formed through the center of each induction
pipe for the sparking plug in the center cylinder of each block of
three. In this, as in the eighteen-cylinder and the six-cylinder types,
there are two cam-shafts for each set of cylinders. These cam-shafts are
lubricated by low pressure and are operated through a train of inclosed
spur wheels at the magneto end of the machine. The six-cylinder, 170
brake horse-power vertical type employs the same general principles,
including the detail that each carburetor serves gas to a group of
three-cylinders only. It will be observed that this engine presents
notably little head resistance, being suitable for multi-engined
aircraft.

[Illustration: Fig. 250.--Propeller End of Sunbeam Eighteen-Cylinder 475
B.H.P. Aviation Engine.]

INDICATING METERS FOR AUXILIARY SYSTEMS

[Illustration: Fig. 251.--View of Airplane Cowl Board, Showing the
Various Navigating and Indicating Instruments to Aid the Aviator in
Flight.]

The proper functioning of the power plant and the various groups
comprising it may be readily ascertained at any time by the pilot
because various indicating meters and pressure gauges are provided which
are located on a dash or cowl board in front of the aviator, as shown at
Fig. 251. The speed indicator corresponds to the speedometer of an
automobile and gives an indication of the speed the airplane is making,
which taken in conjunction with the clock will make it possible to
determine the distance covered at a flight. The altimeter, which is an
aneroid barometer, outlines with fair accuracy the height above the
ground at which a plane is flying. These instruments are furnished to
enable the aviator to navigate the airplane when in the air, and if the
machine is to be used for cross-country flying, they may be supplemented
by a compass and a drift set. It will be evident that these are purely
navigating instruments and only indicate the motor condition in an
indirect manner. The best way of keeping track of the motor action is to
watch the tachometer or revolution counter which is driven from the
engine by a flexible shaft. This indicates directly the number of
revolutions the engine is making per minute and, of course, any slowing
up of the engine in normal flights indicates that something is not
functioning as it should. The tachometer operates on the same principle
as the speed indicating device or speedometer used in automobiles except
that the dial is calibrated to show revolutions per minute instead of
miles per hour. At the extreme right of the dash at Fig. 251 the spark
advance and throttle control levers are placed. These, of course,
regulate the motor speed just as they do in an automobile. Next to the
engine speed regulating levers is placed a push button cut-out switch to
cut out the ignition and stop the motor. Three pressure gauges are
placed in a line. The one at the extreme right indicates the pressure of
air on the fuel when a pressure feed system is used. The middle one
shows oil pressure, while that nearest the center of the dash board is
employed to show the air pressure available in the air starting system.
It will be evident that the character of the indicating instruments will
vary with the design of the airplane. If it was provided with an
electrical starter instead of an air system electrical indicating
instruments would have to be provided.

COMPRESSED AIR-STARTING SYSTEMS

Two forms of air-starting systems are in general use, one in which the
crank-shaft is turned by means of an air motor, the other class where
compressed air is admitted to the cylinders proper and the motor turned
over because of the air pressure acting on the engine pistons. A system
known as the "Never-Miss" utilizes a small double-cylinder air pump is
driven from the engine by means of suitable gearing and supplies air to
a substantial container located at some convenient point in the
fuselage. The air is piped from the container to a dash-control valve
and from this member to a peculiar form of air motor mounted near the
crank-shaft. The air motor consists of a piston to which a rack is
fastened which engages a gear mounted on the crank shaft provided with
some form of ratchet clutch to permit it to revolve only in one
direction, and then only when the gear is turning faster than the engine
crank-shaft.

The method of operation is extremely simple, the dash-control valve
admitting air from the supply tank to the top of the pump cylinder. When
in the position shown in cut the air pressure will force the piston and
rack down and set the engine in motion. A variety of air motors are used
and in some the pump and motor may be the same device, means being
provided to change the pump to an air motor when the engine is to be
turned over.

The "Christensen" air starting system is shown at Figs. 252 and 253. An
air pump is driven by the engine, and this supplies air to an air
reservoir or container attached to the fuselage. This container
communicates with the top of an air distributor when a suitable control
valve is open. An air pressure gauge is provided to enable one to
ascertain the air pressure available. The top of each cylinder is
provided with a check valve, through which air can flow only in one
direction, i.e., from the tank to the interior of the cylinder. Under
explosive pressure these check valves close. The function of the
distributor is practically the same as that of an ignition timer, its
purpose being to distribute the air to the cylinders of the engine only
in the proper firing order. All the while that the engine is running and
the car is in motion the air pump is functioning, unless thrown out of
action by an easily manipulated automatic control. When it is desired to
start the engine a starting valve is opened which permits the air to
flow to the top of the distributor, and then through a pipe to the check
valve on top of the cylinder about to explode. As the air is going
through under considerable pressure it will move the piston down just as
the explosion would, and start the engine rotating. The inside of the
distributor rotates and directs a charge of air to the cylinder next to
fire. In this way the engine is given a number of revolutions, and
finally a charge of gas will be ignited and the engine start off on its
cycle of operation. To make starting positive and easier some gasoline
is injected in with the air so an inflammable mixture is present in the
cylinders instead of air only. This ignites easily and the engine starts
off sooner than would otherwise be the case. The air pressure required
varies from 125 to 250 pounds per square inch, depending upon the size
and type of the engine to be set in motion.

[Illustration: Fig. 252.--Parts of Christensen Air Starting System Shown
at A, and Application of Piping and Check Valves to Cylinders of
Thomas-Morse Aeromotor Outlined at B.]

[Illustration: Fig. 253.--Diagrams Showing Installation of Air Starting
System on Thomas-Morse Aviation Motor.]

ELECTRIC STARTING SYSTEMS

Starters utilizing electric motors to turn over the engine have been
recently developed, and when properly made and maintained in an
efficient condition they answer all the requirements of an ideal
starting device. The capacity is very high, as the motor may draw
current from a storage battery and keep the engine turning over for
considerable time on a charge. The objection against their use is that
it requires considerable complicated and costly apparatus which is
difficult to understand and which requires the services of an expert
electrician to repair should it get out of order, though if battery
ignition is used the generator takes the place of the usual ignition
magneto.

In the Delco system the electric current is generated by a combined
motor-generator permanently geared to the engine. When the motor is
running it turns the armature and the motor generator is acting as a
dynamo, only supplying current to a storage battery. On account of the
varying speeds of the generator, which are due to the fluctuation in
engine speed, some form of automatic switch which will disconnect the
generator from the battery at such times that the motor speed is not
sufficiently high to generate a current stronger than that delivered by
the battery is needed. These automatic switches are the only delicate
part of the entire apparatus, and while they require very delicate
adjustment they seem to perform very satisfactorily in practice.

When it is desired to start the engine an electrical connection is
established between the storage battery and the motor-generator unit,
and this acts as a motor and turns the engine over by suitable gearing
which engages the gear teeth cut into a special gear or disc attached to
the engine crank-shaft. When the motor-generator furnishes current for
ignition as well as for starting the motor, the fact that the current
can be used for this work as well as starting justifies to a certain
extent the rather complicated mechanism which forms a complete starting
and ignition system, and which may also be used for lighting if
necessary in night flying.

An electric generator and motor do not complete a self-starting system,
because some reservoir or container for electric current must be
provided. The current from the generator is usually stored in a storage
battery from which it can be made to return to the motor or to the same
armature that produced it. The fundamental units of a self-starting
system, therefore, are a generator to produce the electricity, a storage
battery to serve as a reservoir, and an electric motor to rotate the
motor crank-shaft. Generators are usually driven by enclosed gearing,
though silent chains are used where the center distance between the
motor shaft and generator shaft is too great for the gears. An electric
starter may be directly connected to the gasoline engine, as is the case
where the combined motor-generator replaces the fly-wheel in an
automobile engine. The motor may also drive the engine by means of a
silent chain or by direct gear reduction.

Every electric starter must use a switch of some kind for starting
purposes and most systems include an output regulator and a reverse
current cut-out. The output regulator is a simple device that regulates
the strength of the generator current that is supplied the storage
battery. A reverse current cut-out is a form of check valve that
prevents the storage battery from discharging through the generator.
Brief mention is made of electric starting because such systems will
undoubtedly be incorporated in some future airplane designs. Battery
ignition is already being experimented with.

BATTERY IGNITION SYSTEM PARTS

A battery ignition system in its simplest form consists of a current
producer, usually a set of dry cells or a storage battery, an induction
coil to transform the low tension current to one having sufficient
strength to jump the air gap at the spark-plug, an igniter member
placed in the combustion chamber and a timer or mechanical switch
operated by the engine so that the circuit will be closed only when it
is desired to have a spark take place in the cylinders. Battery ignition
systems may be of two forms, those in which the battery current is
stepped up or intensified to enable it to jump an air gap between the
points of the spark plug, these being called "high tension" systems and
the low tension form (never used on airplane motors) in which the
battery current is not intensified to a great degree and a spark
produced in the cylinder by the action of a mechanical circuit breaker
in the combustion chamber. The low tension system is the simplest
electrically but the more complex mechanically. The high tension system
has the fewest moving parts but numerous electrical devices. At the
present time all airplane engines use high tension ignition systems, the
magneto being the most popular at the present time. The current
distribution and timing devices used with modern battery systems are
practically the same as similar parts of a magneto.

INDEX

PAGE

Action of Four-cycle Engine 38
Action of Le Rhone Rotary Engine 503
Action of Two-cycle Engine 41
Action of Vacuum Feed System 119
Actual Duration of Different Functions 93
Actual Heat Efficiency 62
Adiabatic Diagram 51
Adiabatic Law 50
Adjustment of Bearings 449
Adjustment of Carburetors 151
Aerial Motors, Must be Light 20
Aerial Motors, Operating Conditions of 19
Aerial Motors, Requirements of 19
Aeromarine Six-cylinder Engine 527
Aeronautics, Division in Branches 18
Aerostatics 18
Air-cooled Engine Design 229
Air-cooling Advantages 231
Air-cooling, Direct Method 228
Air-cooling Disadvantages 231
Air-cooling Systems 223
Aircraft, Heavier Than Air 17
Aircraft, Lighter Than Air 18
Aircraft Types, Brief Consideration of 17
Air Needed to Burn Gasoline 113
Airplane Engine, Power Needed 21
Airplane Engines, Overhauling 412
Airplane Engine, How to Time 269
Airplane Engine Lubrication 209
Airplane, How Supported 21
Airplane Motors, German 543
Airplane Motor Types 20
Airplane Motors, Weight of 21
Airplane Power Plant Installation 324
Airplane Types 18
Airplanes, Horse-power Used in 26
Air Pressure Diminution, With Altitude 144
Altitude, How it Affects Mixture 153
Aluminum, Use in Pistons 297
American Aviation Engines, Statistics 546
Anzani Radial Engine Installation 344
Anzani Six-cylinder Star Engine 465
Anzani Six-cylinder Water-cooled Engine 459
Anzani Ten- and Twenty-cylinder Engines 468
Anzani Three-cylinder Engine 459
Anzani Three-cylinder Y Type 462
Argus Engine Construction 545
Armature Windings 168
Atmospheric Conditions, Compensating For 143
Austro-Daimler Engine 557
Aviatics 18
Aviation Engine, Aeromarine 527
Aviation Engine, Anzani Six-cylinder Star 465
Aviation Engine, Canton and Unné 469
Aviation Engine Cooling 219
Aviation Engine, Curtiss 519
Aviation Engine Cylinders 233
Aviation Engine, Early Gnome 472
Aviation Engine, German Gnome Type 495
Aviation Engine, Gnome Monosoupape 486
Aviation Engine, How To Dismantle 415
Aviation Engine, How to Start 460
Aviation Engine, Le Rhone Rotary 495
Aviation Engine Oiling 218
Aviation Engine Parts, Functions of 82
Aviation Engine, Renault Air-cooled 507
Aviation Engine, Stand for Supporting 414
Aviation Engine, Sturtevant 515
Aviation Engine, Thomas-Morse 521
Aviation Engine Types 457
Aviation Engine, Wisconsin 531
Aviation Engines, Anzani Six-cylinder Water-cooled 459
Aviation Engines, Anzani Ten- and Twenty-cylinder 468
Aviation Engines, Anzani Three-cylinder 459
Aviation Engines, Anzani Y Type 462
Aviation Engines, Argus 545
Aviation Engines, Austro-Daimler 557
Aviation Engines, Benz 551
Aviation Engines, Four- and Six-cylinder 88
Aviation Engines, German 543
Aviation Engines, Hall-Scott 539
Aviation Engines, Hispano-Suiza 512
Aviation Engines, Mercedes 543
Aviation Engines, Overhauling 412
Aviation Engines, Principal Parts of 80
Aviation Engines, Starting Systems For 567
Aviation Engines, Sunbeam 558

Balanced Crank-shafts 318
Ball-bearing Crank-shafts 319
Battery Ignition Systems 571
Baverey Compound Nozzle 137
Bearings, Adjustment of 449
Bearing Alignment 453
Bearing Brasses, Fitting 450
Bearing Parallelism, Testing 453
Bearing Scrapers and Their Use 446
Benz Aviation Engines 551
Benz Engine Statistics 551
Berling Magneto 174
Berling Magneto, Adjustment of 180
Berling Magneto Care 180
Berling Magneto Circuits 176
Berling Magneto, Setting 178
Block Castings 234
Blowing Back 269
Bolts, Screwing Down 452
Bore and Stroke Ratio 240
Boyle's Law 49
Brayton Engine 48
Breaker Box, Adjustment of 180
Breast and Hand Drills 387
Burning Out Carbon Deposits 421
Bushings, Cam-shaft, Wear in 456

Calipers, Inside and Outside 398
Cam Followers, Types of 260
Cams for Valve Actuation 259
Cam-shaft Bushings 456
Cam-shaft Design 313
Cam-shaft Drive Methods 261
Cam-shaft Testing 451
Cam-shafts and Timing Gears 456
Canton and Unné Engine 469
Carbon, Burning out with Oxygen 421
Carbon Deposits, Cause of 418
Carbon Removal 419
Carbon Scrapers, How Used 420
Carburetion Principles 112
Carburetion System Troubles 355
Carburetor, Claudel 127
Carburetor, Compound Nozzle Zenith 135
Carburetor, Concentric Float and Jet Type 125
Carburetor, Duplex Zenith 138
Carburetor, Duplex Zenith, Trouble in 357
Carburetor Installation, In Airplanes 148
Carburetor, Le Rhone 501
Carburetor, Master Multiple Jet 133
Carburetor, Schebler 125
Carburetor Troubles, How to Locate 354
Carburetor, Two Stage 131
Carburetor, What it Should Do 114
Carburetors, Float Feed 122
Carburetors, Multiple Nozzle 130
Carburetors, Notes on Adjustment 151
Carburetors, Reversing Position of 149
Carburetors, Spraying 120
Care of Dixie Magneto 188
Castor Oil, for Cylinder Lubrication 205
Castor Oil, Why Used In Gnome Engines 211
Center Gauge 403
Chisels, Forms of 384
Christensen Air Starting System 567
Circuits, Magnetic 161
Classification of Engines 458
Claudel Carburetor 127
Cleaning Distributor 180
Clearances Between Valve Stem and Actuators 261
Combustion Chamber Design 239
Combustion Chambers, Spherical 76
Common Tools, Outfit of 378
Comparing Two-cycle and Four-cycle Types 44
Compound Cam Followers 260
Compound Piston Rings 301
Compressed Air Starting System 565
Compression, Factors Limiting 69
Compression, in Explosive Motors, Value of 68
Compression Pressures, Chart for 72
Compression Temperature 71
Computations for Horse-power Needed 25
Computations for Temperature 52
Concentric Piston Ring 299
Concentric Valves 255
Connecting Rod Alignment, Testing 454
Connecting Rod, Conventional 308
Connecting Rod Forms 305
Connecting Rod, Gnome Engine 305
Connecting Rods, Fitting 449
Connecting Rods for Vee Engines 310
Connecting Rods, Le Rhone 498
Connecting Rods, Master 310
Constant Level Splash System 215
Construction of Dixie Magneto 186
Construction of Pistons 288
Conversion of Heat to Power 58
Cooling by Air 223
Cooling by Positive Water Circulation 224
Cooling, Heat Loss in 66
Cooling System Defects 358
Cooling Systems Used 223
Cooling Systems, Why Needed 219
Cotter Pin Pliers 384
Crank-case, Conventional 320
Crank-case Forms 320
Crank-case, Gnome 323
Crank-shaft, Built Up 315
Crank-shaft Construction 315
Crank-shaft Design 315
Crank-shaft Equalizer 449
Crank-shaft Form 315
Crank-shaft, Gnome Engine 483
Crank-shafts, Balanced 318
Crank-shafts, Ball Bearing 319
Cross Level 403
Crude Petroleum, Distillates of 111
Curtiss Aviation Engines 519
Curtiss Engine Installation 328
Curtiss Engine Repairing Tools 408
Cutting Oil Grooves 448
Cylinder Blocks, Advantages of 237
Cylinder Block, Duesenberg 235
Cylinder Castings, Individual 234
Cylinder Construction 233
Cylinder Faults and Correction 416
Cylinder Form and Crank-shaft Design 238
Cylinder Head Packings 417
Cylinder Head, Removable 239
Cylinder, I Head Form 248
Cylinder, L Head Form 248
Cylinder Oils 206
Cylinder Placing 20
Cylinder Placing in V Motor 99
Cylinder Retention, Gnome 475
Cylinder, T Head Form 248
Cylinders, Cast in Blocks 235
Cylinders, Odd Number in Rotary Engines 482
Cylinders, Repairing Scored 423
Cylinders, Valve Location in 245

Defects in Cylinders 417
Defects in Dry Battery 373
Defects in Fuel System 354
Defects in Induction Coil 373
Defects in Magneto 372
Defects in Storage Battery 372
Defects in Timer 373
Defects in Wiring and Remedies 373
Die Holder 394
Dies for Thread Cutting 395
Diesel Motor Cards 67
Diesel System 144
Direct Air Cooling 228
Dirigible Balloons 18
Dismantling Airplane Engine 415
Distillates of Crude Petroleum 111
Division of Circle in Degrees 268
Dixie Ignition Magneto 184
Dixie Magneto, Care of 188
Draining Oil From Crank-case 214
Drilling Machines 386
Drills, Types and Use 388
Driving Cam-shaft, Methods of 262
Dry Cell Battery, Defects in 373
Duesenberg Sixteen Valve Engine 525
Duesenberg Valve Action 255
Duplex Zenith Carburetor 138

Early Gnome Motor, Construction of 472
Early Ignition Systems 155
Early Types of Gas Engine 28
Early Vaporizer Forms 120
Eccentric Piston Ring 299
Economy, Factors Governing 64
Efficiency, Actual Heat 62
Efficiency, Maximum Theoretical 61
Efficiency, Mechanical 62
Efficiency of Internal Combustion Engine 60
Efficiency, Various Measures of 61
Eight-cylinder Engine 95
Eight-cylinder Timing Diagram 276
Electricity and Magnetism, Relation of 162
Electrical Ignition Best 156
Electric Starting Systems 569
Engine, Advantages of V Type 95
Engine Base Construction 319
Engine Bearings, Adjusting 443
Engine Bearings, Refitting 442
Engine Bed Timbers, Standard 330
Engine, Four-cycle, Action of 38
Engine, Four-cycle, Piston Movements in 40
Engine Functions, Duration of 93
Engine Ignition, Locating Troubles 353
Engine Installation, Gnome 344
Engine Installation, Anzani Radial 344
Engine Installation, Hall-Scott 332
Engine Installation, Rotary 342
Engine Operation, Sequence of 84
Engine Parts and Functions 80
Engine Starts Hard, Ignition Troubles Causing 369
Engine Stoppage, Causes of 347
Engine Temperatures 221
Engine Trouble Charts 369
Engine Troubles, Cooling 358
Engine Troubles, Hints For Locating 345
Engine Troubles, Ignition 353
Engine Troubles, Noisy Operation 359
Engine Troubles, Oiling 357
Engine Troubles Summarized 350
Engine, Two-cycle, Action of 41
Engines, Classification of 458
Engines, Cylinder Arrangement 31-32
Engines, Eight-cylinder V 95
Engines, Four-cylinder Forms 88
Engines, Graphic Comparison of 33-34-35
Engines, Internal Combustion, Types of 30
Engines, Multiple Cylinder, Power Delivery in 91
Engines, Multiple Cylinder, Why Best 83
Engines, Rotary Cylinder 107
Engines, Six-cylinder Forms 88
Engines, Twelve-cylinder 96
Equalizer, Crank-shaft 449
Exhaust Closing 270
Exhaust Valve Design, Early Gnome 475
Exhaust Valve Opening 270
Explosive Gases, Mixtures of 56
Explosive Motors, Inefficiency in 74
Explosive Motors, Why Best 27

Factors Governing Economy 64
Factors Limiting Compression 70
Faults in Ignition 352
Figuring Horse-power Needed 21
Files, Use and Care of 383
First Law of Gases 49
Fitting Bearings By Scraping 447
Fitting Brasses 450
Fitting Connecting Rods 449
Fitting Main Bearings 448
Fitting Piston Rings 439
Float Feed Carburetor Development 124
Float Feed Carburetors 122
Force Feed Oiling System 218
Forked Connecting Rods 310
Four-cycle Engine, Action of 38
Four-cycle Engine, Why Best 45
Fourteen-cylinder Engine 474
Four Valves Per Cylinder 284
Friction, Definition of 302
Fuel Feed By Gravity 116
Fuel Feed by Vacuum Tank 117
Fuel Storage and Supply 116
Fuel Strainers, Types of 141
Fuel Strainers, Utility of 140
Fuel System Faults 354
Fuel System Installation, Hall-Scott 336
Fuel System, Gnome 490
Fuel Utilization Chart 62

Gas Engine, Beau de Rocha's Principles 59
Gas Engine Development 28
Gas Engine, Early Forms of 48
Gas Engine, Inventors of 29
Gas Engine, Theory of 47
Gases, Compression of 49
Gases, First Law of 49
Gases, Second Law of 50
Gaskets, How to Use 452
Gasoline, Air Needed to Burn 113
Gas Engines, Parts of 80
Gas Vacuum Engine, Brown's 28
German Airplane Motors 543
German Gnome Type Engine 495
Gnome Aviation Engine, Early Form 472
Gnome Crank-shaft 483
Gnome Cylinder, Machining 489
Gnome Cylinder Retention 475
Gnome Engine, Fuel, Lubrication and Ignition 490
Gnome Engine, German Type 495
Gnome Engine Installation 344
Gnome Firing Order 482
Gnome Fourteen-cylinder, Engine 474
Gnome Fourteen-cylinder Engine Details 480
Gnome Monosoupape, How to Time 278
Gnome Monosoupape Type Engine 486
Graphic Comparison of Engine Types 33-34-35
Graphic Comparison, Two- and Four-cycle 46
Gravity Feed System 116
Grinding Valves 429

Hall-Scott Aviation Engines 539
Hall-Scott Engine Installation 332
Hall-Scott Engine, Preparations For Starting 341
Hall-Scott Engine Tools 410
Hall-Scott Lubrication System 211
Hall-Scott Statistic Sheet 544
Heat and Its Work 54
Heat in Gas Engine Cylinder 69
Heat Given to Cooling Water 78
Heat Loss, Causes of 74
Heat Loss in Airplane Engine 221
Heat Loss in Wall Cooling 65
High Altitude, How it Affects Power 144
High Tension Magneto 172
Hints For Locating Engine Troubles 345
Hints for Starting Engine 361
Hispano-Suiza Model A Engine 512
Horse-power Needed in Airplane 21
Horse-power Needed, How Figured 22
How An Engine is Timed 277

Ignition, Electric 156
Ignition, Elements of 157
Ignition of Gnome Engine 490
Ignition System, Battery 571
Ignition Systems, Early 155
Ignition System Faults 352
Ignition, Time of 273
Ignition, Two Spark 196
I Head Cylinders 248
Improvements in Gas Engines 29
Indicating Meters, Engine Speed 563
Indicating Meters, Oil and Air Pressure 563
Indicator Cards, How To Read 66
Indicator Cards, Value of 66
Individual Cylinder Castings 234
Induction Coil, Defects in 373
Inefficiency, Causes of 74
Inlet Valve Closing 272
Inlet Valve Opening 270
Installation, Airplane Engine 324
Installation, Curtiss OX-2 Engine 328
Installation, Hall-Scott Engine 332
Installation of Rotary Engines 342
Intake Manifold Construction 143
Intake Manifold Design 142
Internal Combustion Engine, Efficiency of 60, 62
Internal Combustion Engines, Main Types of 30
Inverted Engine Placing 325
Isothermal Diagram 51
Isothermal Law 48

Keeping Oil Out of Combustion Chamber 303
Knight Sleeve Valves 266

Lag and Lead, Explanation of 268
Lapping Crank-pins 445
Lead Given Exhaust Valve 270
Leak Proof Piston Rings 301
Lenoir Engine Action 48
Le Rhone Cams and Valve Actuation 500
Le Rhone Carburetor 501
Le Rhone Connecting Rod Assembly, Distinctive 498
Le Rhone Engine Action 503
Le Rhone Rotary Engine 495
L Head Cylinders 248
Liquid Fuels, Properties of 110
Locating Carburetor Troubles 354
Locating Engine Troubles 350
Locating Ignition Troubles 353
Locating Oiling Troubles 357
Location of Magneto Trouble 181
Losses in Wall Cooling 65
Lost Power and Overheating, Summary of Troubles Causing 363
Lubricants, Derivation of 204
Lubricants, Requirements of 204
Lubricating System Classification 208
Lubricating Systems, Selection of 208
Lubrication By Constant Level Splash System 215
Lubrication By Dry Crank-case Method 218
Lubrication By Force Feed Best 218
Lubrication of Magneto 180
Lubrication System, Gnome 490
Lubrication System, Hall-Scott 211
Lubrication System, Thomas-Morse 210
Lubrication, Theory of 202
Lubrication, Why Necessary 201

Magnetic Circuits 161
Magnetic Influence Defined 158
Magnetic Lines of Force 161
Magnetic Substances 158
Magnetism, Flow Through Armature 166
Magnetism, Fundamentals of 157
Magnetism, Relation to Electricity 162
Magneto, Action of High Tension 173
Magneto Armature Windings 168
Magneto, Basic Principles of 163
Magneto, Berling 174
Magneto, Defects in 372
Magneto Distributor, Cleaning 180
Magneto Ignition Systems 169
Magneto Ignition Wiring 179
Magneto Interrupter, Adjustment of 180
Magneto, Low Voltage 168
Magneto, Lubrication of 180
Magneto Maintenance 180
Magneto, Method of Driving 175
Magneto Parts and Functions 167
Magneto, The Dixie 184
Magneto Timing 179
Magneto, Timing Dixie 188
Magneto, Transformer System 171
Magneto Trouble, Location of 181
Magneto, True High Tension 172
Magneto, Two Spark Dual 177
Magnets, Forms of 160
Magnets, How Produced 162
Magnets, Properties of 159
Main Bearings, Fitting 448
Manifold, Intake 143
Master Multiple Jet Carburetor 133
Master Rod Construction 310
Maximum Theoretical Efficiency 61
Meaning of Piston Speed 241
Measures of Efficiency 61
Measuring Tools 397
Mechanical Efficiency 62
Mercedes Aviation Engine 543
Metering Pin Carburetor, Stewart 128
Micrometer Caliper, Beading 405
Micrometer Calipers, Types and Use 404
Mixture, Effect of Altitude on 153
Mixture, Proportions of 151
Mixture, Starvation of 149
Monosoupape Gnome Engine 486
Mother Bod, Gnome Engine 305
Motor Misfires, Carburetor Faults Causing 374
Motor Misfires, Ignition Troubles Causing 370
Motor Races, Carburetor Faults Causing 374
Motor Starts Hard, Carburetor Faults Causing 374
Motor Stops In Flight, Carburetor Faults 374
Motor Stops Without Warning, Ignition Troubles 370
Multiple Cylinder Engine, Why Best 83
Multiple Nozzle Vaporizers 129
Multiple Valve Advantages 286

Noisy Engine Operation, Causes of 359
Noisy Operation, Carburetor Faults Causing 374
Noisy Operation, Summary of Troubles Causing 365

Offset Cylinders, Reason for 243
Oil Bi-pass, Function of 213
Oil, Draining From Crank-case 214
Oil Grooves, Cutting 448
Oil Pressure in Hall-Scott System 214
Oil Pressure Relief Bi-pass 213
Oiling System Defects 357
Oils for Cylinder Lubrication 206
Oils for Hall-Scott Engine 215
Oils for Lubrication 204
Operating Principles of Engines 37
Oscillating Piston Pin 295
Otto Four-cycle Cards 67
Overhauling Aviation Engines 412
Overhead Cam-shaft Location 252
Overheating, Causes of 359

Panhard Concentric Valves 255
Petroleum, Distillates of 111
Piston, Differential 291
Piston Pin Retention 293
Piston Ring Construction 298
Piston Ring Joints 299
Piston Ring Manipulation 438
Piston Ring Troubles 437
Piston Rings, Compound 301
Piston Rings, Concentric 299
Piston Rings, Eccentric 299
Piston Rings, Fitting 439
Piston Rings, Leak Proof 301
Piston Rings, Replacing 441
Piston Speed in Airplane Engines 241
Piston Speed, Meaning of 241
Piston Troubles and Remedies 436
Pistons, Aluminum 296
Pistons, Details of 288
Pistons for Two-cycle Engines 289
Positive Valve Systems 283
Power, Affected by High Altitude 145
Power Delivery in Multiple Cylinder Engines 91
Power, How Obtained From Heat 58
Power Needed in Airplane Engines 21
Power Used in Airplanes 26
Precautions in Assembling Parts 452
Pressure Relief Fitting 213
Pressures and Temperatures 63
Principles of Carburetion 112
Principles of Magneto Action 163
Properties of Cylinder Oils 207
Properties of Liquid Fuels 110
Pump Circulation Systems 226
Pump Forms 226

Radial Cylinder Arrangement 103
Reading Indicator Cards 67
Reamers, Types and Use 392
Reassembling Parts, Precautions in 451
Removable Cylinder Head 239
Renault Air Cooled Engine 507
Renault Engine Details 508
Repairing Scored Cylinders 423
Requisites for Best Power Effect 59
Reseating and Truing Valves 426
Resistance, Influence of 22
Rotary Cylinder Engines 107
Rotary Engine, Le Rhone 495
Rotary Engines, Castor Oil for 211
Rotary Engines, Installing 342
Rotary Engines, Why Odd Number of Cylinders 109
Rotary Engines, Why Odd Number of Cylinders Is Used 482

S. A. E. Engine Bed Dimensions 330
Salmson Nine-cylinder Engine 470
Schebler Carburetor 125
Scissors Joint Rods 310
Scored Cylinders, Repairing 422
Scrapers, Types of Bearing 446
Scraping Bearings to Fit 447
Second Law of Gases 50
Sequence of Engine Operation 84
Six-cylinder Timing Diagram 275
Sixteen Valve Duesenberg Engine 525
Skipping or Irregular Operation, Causes of 367
Sliding Sleeve Valves 266
Spark Plug Air Gaps, Setting 197
Spark Plug, Design of 193
Spark Plug, Mica 194
Spark Plug, Porcelain 193
Spark Plugs, Defects in 371
Spark Plugs for Two Spark Ignition 197
Spark Plug, Special for Airplane Engine 199
Spark Plug, Standard S. A. E. 195
Spherical Combustion Chambers 76
Splash Lubrication 215
Split Pin Remover 384
Spraying Carburetors 120
Springless Valves 280
Springs, for Valves 263
Spring Winder 384
Sprung Cam-shaft, Testing 451
Stand for Supporting Engine 414
Starting Engine, Hints for 361
Starting Hall-Scott Engine 341
Starting System, Christensen 567
Starting Systems, Compressed Air 565
Starting Systems, Electric 569
Statistics, American Engines 546, 547
Statistic Sheet, Hall-Scott Engines 544
Statistics of Benz Engine 551
Steam Engine, Efficiency of 59
Steam Engine, Why Not Used 27
Steel Scale, Machinists' 399
Stewart Metering Pin Carburetor 128
Storage Battery, Defects in 372
Stroke and Bore Ratio 240
Sturtevant Model 5A Engine 515
Summary of Engine Types 30
Sunbeam Aviation Engines 588
Sunbeam Eighteen-Cylinder Engine 561

Tap and Die Sets 397
Taps for Thread Cutting 394
Tee Head Cylinders 247
Temperature Computations 52
Temperatures and Explosive Pressures 64
Temperatures and Pressures 63
Temperatures, Operating 221
Testing Bearing Parallelism 453
Testing Connecting Rod Alignment 454
Testing Fit of Bearings 446
Testing Sprung Cam-shaft 451
Theory of Gas Engine 47
Theory of Lubrication 203
Thermo-syphon Cooling System 227
Thomas-Morse Aviation Engine 521
Thomas-Morse Lubrication System 210
Thread Pitch Gauge 403
Time of Ignition 273
Timer, Defects in 373
Times of Explosion 56
Timing Dixie Magneto 188
Timing Gears, Effects of Wear 456
Timing Magneto 179
Timing Valves 267
Tool Outfits, Typical 408
Tools for Adjusting and Erecting 378
Tools for Bearing Work 445
Tools for Curtiss Engines 408
Tools for Grinding Valves 430
Tools for Hall-Scott Engines 410, 411
Tools for Measuring 397
Tools for Reseating Valves 426
Trouble in Carburetion System 355
Trouble, Location of Magneto 181
Troubles, Engine, How to Locate 345
Troubles, Ignition 353
Troubles in Oiling System 357
True High Tension Magneto 172
Twelve-Cylinder Engines 96
Two-and Four-Cycle Types, Comparison of 44
Two-Cycle Engine Action 41
Two-Cycle Three-Port Engine 43
Two-Cycle Two-Port Engine 42
Two-Spark Ignition 196
Two-Stage Carburetor 131
Types of Aircraft 17
Types of Internal Combustion Engines 30

Vacuum Fuel Feed, Stewart 119
Value of Compression 69
Value of Indicator Cards 66
Valve Actuation, Le Rhone 500
Valve Design and Construction 256
Valve-Grinding Processes 429
Valve-Lifting Cams 259
Valve-Lifting Plungers 260
Valve Location Practice 245
Valve Operating Means 252
Valve Operating System, Depreciation in 433
Valve Operation 258
Valve Removal and Inspection 424
Valve Seating, How to Test 432
Valve Springs 263
Valve Timing, Exhaust 270
Valve Timing, Gnome Monosoupape 278
Valve Timing, Intake 270
Valve Timing, Lag and Lead 269
Valve Timing Procedure 277
Valve Timing Practice 267
Valves, Electric Welded 258
Valves, Flat and Bevel Seat 257
Valves, Four per Cylinder 284
Valves, How Placed in Cylinder 247
Valves in Cages 249
Valves in Removable Heads 249
Valves, Materials Used for 258
Valves, Reseating 426
Vaporizer, Simple Forms of 120
V Engines, Cylinder Arrangement in 102
Vernier, How Used 401

Wall Cooling, Losses in 65
Water Cooling by Natural Circulation 227
Water Cooling System 224
Weight of Airplane Motors 21
Wiring, Defects in 373
Wiring Magneto Ignition System 179
Wisconsin Engines 531
Wrenches, Forms of 380
Wrist-pin Retention 293
Wrist-pin Retention Locks 295
Wrist-pin Wear and Remedy 442

Zenith Carburetor, Action of 137
Zenith Duplex Carburetor, Troubles in 356
Zenith Carburetor Installation 139

LIST OF ILLUSTRATIONS

Frontispiece. Part Sectional View of Hall-Scott Airplane Motor, Showing
Principal Parts.

Fig. 1. Diagrams Illustrating Computations for Horse-Power Required for
Airplane Flight.

Fig. 2. Plate Showing Heavy, Slow Speed Internal Combustion Engines Used
Only for Stationary Power in Large Installations Giving Weight to
Horse-Power Ratio.

Fig. 3. Various Forms of Internal Combustion Engines Showing Decrease in
Weight to Horse-Power Ratio with Augmenting Speed of Rotation.

Fig. 4. Internal Combustion Engine Types of Extremely Fine Construction
and Refined Design, Showing Great Power Outputs for Very Small Weight, a
Feature Very Much Desired in Airplane Power Plants.

Fig. 5. Outlining First Two Strokes of Piston in Four-Cycle Engine.

Fig. 6. Outlining Second Two Strokes of Piston in Four-Cycle Engine.

Fig. 7. Sectional View of L Head Gasoline Engine Cylinder Showing Piston
Movements During Four-Stroke Cycle.

Fig. 8. Showing Two-port, Two-cycle Engine Operation.

Fig. 9. Defining Three-port, Two-cycle Engine Action.

Fig. 10. Diagrams Contrasting Action of Two- and Four-Cycle Cylinders on
Exhaust and Intake Stroke.

Fig. 11. Diagram Isothermal and Adiabatic Lines.

Fig. 12. Graphic Diagram Showing Approximate Utilization of Fuel Burned
in Internal-Combustion Engine.

Fig. 13. Otto Four-Cycle Card.

Fig. 14. Diesel Motor Card.

Fig. 15. Diagram of Heat in the Gas Engine Cylinder.

Fig. 16. Chart Showing Relation Between Compression Volume and Pressure.

Fig. 17. The Thompson Indicator, an Instrument for Determining
Compressions and Explosion Pressure Values and Recording Them on Chart.

Fig. 18. Spherical Combustion Chamber.

Fig. 19. Enlarged Combustion Chamber.

Fig. 20. Mercedes Aviation Engine Cylinder Section Showing Approximately
Spherical Combustion Chamber and Concave Piston Top.

Fig. 21. Side Sectional View of Typical Airplane Engine, Showing Parts
and Their Relation to Each Other. This Engine is an Aeromarine Design
and Utilizes a Distinctive Concentric Valve Construction.

Fig. 22. Diagrams Illustrating Sequence of Cycles in One- and
Two-Cylinder Engines Showing More Uniform Turning Effort on Crank-Shaft
with Two-Cylinder Motors.

Fig. 23. Diagrams Demonstrating Clearly Advantages which Obtain when
Multiple-Cylinder Motors are Used as Power Plants.

Fig. 24. Showing Three Possible Though Unconventional Arrangements of
Four-Cylinder Engines.

Fig. 25. Diagrams Outlining Advantages of Multiple Cylinder Motors, and
Why They Deliver Power More Evenly Than Single Cylinder Types.

Fig. 26. Diagrams Showing Duration of Events for a Four-Stroke Cycle,
Six-Cylinder Engine.

Fig. 27. Diagram Showing Actual Duration of Different Strokes in
Degrees.

Fig. 28. Another Diagram to Facilitate Understanding Sequence of
Functions in Six-Cylinder Engine.

Fig. 29. Types of Eight-Cylinder Engines Showing the Advantage of the V
Method of Cylinder Placing.

Fig. 30. Curves Showing Torque of Various Engine Types Demonstrate
Graphically Marked Advantage of the Eight-Cylinder Type.

Fig. 31. Diagrams Showing How Increasing Number of Cylinders Makes for
More Uniform Power Application.

Fig. 32. How the Angle Between the Cylinders of an Eight- and
Twelve-Cylinder V Motor Varies.

Fig. 33. The Hall-Scott Four-Cylinder 100 Horse-Power Aviation Motor.

Fig. 34. Two Views of the Duesenberg Sixteen Valve Four-Cylinder
Aviation Motor.

Fig. 35. The Hall-Scott Six-Cylinder Aviation Engine.

Fig. 36. The Curtiss Eight-Cylinder, 200 Horse-Power Aviation Engine.

Fig. 37. The Sturtevant Eight-Cylinder, High Speed Aviation Motor.

Fig. 38. Anzani 40-50 Horse-Power Five-Cylinder Air Cooled Engine.

Fig. 39. Unconventional Six-Cylinder Aircraft Motor of Masson Design.

Fig. 40. The Gnome Fourteen-Cylinder Revolving Motor.

Fig. 41. How Gravity Feed Fuel Tank May Be Mounted Back of Engine and
Secure Short Fuel Line.

Fig. 42. The Stewart Vacuum Fuel Feed Tank.

Fig. 43. Marine-Type Mixing Valve, by which Gasoline is Sprayed into Air
Stream Through Small Opening in Air-Valve Seat.

Fig. 44. Tracing Evolution of Modern Spray Carburetor. A--Early Form
Evolved by Maybach. B.--Phoenix-Daimler Modification of Maybach's
Principle. C--Modern Concentric Float Automatic Compensating Carburetor.

Fig. 45. New Model of Schebler Carburetor With Metering Valve and
Extended Venturi. Note Mechanical Connection Between Air Valve and Fuel
Regulating Needle.

Fig. 46. The Claudel Carburetor.

Fig. 47. The Stewart Metering Pin Carburetor.

Fig. 48. The Ball and Ball Two-Stage Carburetor.

Fig. 49. The Master Carburetor.

Fig. 50. Sectional View of Master Carburetor Showing Parts.

Fig. 51. Sectional View of Zenith Compound Nozzle Compensating
Carburetor.

Fig. 52. Diagrams Explaining Action of Baverey Compound Nozzle Used in
Zenith Carburetor.

Fig. 53. The Zenith Duplex Carburetor for Airplane Motors of the V Type.

Fig. 54. Rear View of Curtiss OX-2 90 Horse-Power Airplane Motor Showing
Carburetor Location and Hot Air Leads.

Fig. 55. Types of Strainers Interposed Between Vaporizer and Gasoline
Tank to Prevent Water or Dirt Passing Into Carbureting Device.

Fig. 56. Chart Showing Diminution of Air Pressure as Altitude Increases.

Fig. 57. Some Simple Experiments to Demonstrate Various Magnetic
Phenomena and Clearly Outline Effects of Magnetism and Various Forms of
Magnets.

Fig. 58. Elementary Form of Magneto Showing Principal Parts Simplified
to Make Method of Current Generation Clear.

Fig. 59. Showing How Strength of Magnetic Influence and of the Currents
Induced in the Windings of Armature Vary with the Rapidity of Changes of
Flow.

Fig. 60. Diagrams Explaining Action of Low Tension Transformer Coil and
True High Tension Magneto Ignition Systems.

Fig. 60A. Side Sectional View of Bosch High-Tension Magneto Shows
Disposition of Parts. End Elevation Depicts Arrangement of Interruptor
and Distributor Mechanism.

Fig. 61. Berling Two-Spark Dual Ignition System.

Fig. 62. Berling Double-Spark Independent System.

Fig. 63. Type DD Berling High Tension Magneto.

Fig. 64. Wiring Diagrams of Berling Magneto Ignition Systems.

Fig. 65. The Berling Magneto Breaker Box Showing Contact Points
Separated and Interruptor Lever on Cam.

Fig. 66. The Dixie Model 60 for Six-Cylinder Airplane Engine Ignition.

Fig. 67. Installation Dimensions of Dixie Model 60 Magneto.

Fig. 68. The Rotating Elements of the Dixie Magneto.

Fig. 69. Suggestions for Adjusting and Dismantling Dixie Magneto.
A--Screw Driver Adjusts Contact Points. B--Distributor Block Removed.
C--Taking off Magnets. D--Showing How Easily Condenser and High Tension
Windings are Removed.

Fig. 69A. Sectional Views Outlining Construction of Dixie Magneto with
Compound Distributor for Eight-Cylinder Engine Ignition.

Fig. 70. Wiring Diagram of Dixie Magneto Installation on Hall-Scott
Six-Cylinder 125 Horse-Power Aeronautic Motor.

Fig. 71. How Magneto Ignition is Installed on Thomas-Morse 135
Horse-Power Motor.

Fig. 72. Spark-Plug Types Showing Construction and Arrangement of Parts.

Fig. 73. Standard Airplane Engine Plug Suggested by S. A. E. Standards
Committee.

Fig. 74. Special Mica Plug for Aviation Engines.

Fig. 75. Showing Use of Magnifying Glass to Demonstrate that Apparently
Smooth Metal Surfaces May Have Minute Irregularities which Produce
Friction.

Fig. 76. Pressure Feed Oiling System of Thomas Aviation Engine Includes
Oil Cooling Means.

Fig. 77. Diagram of Oiling System, Hall-Scott Type A 125 Horse-Power
Engine.

Fig. 78. Sectional View of Typical Motor Showing Parts Needing
Lubrication and Method of Applying Oil by Constant Level Splash System.
Note also Water Jacket and Spaces for Water Circulation.

Fig. 79. Pressure Feed Oil-Supply System of Airplane Power Plants has
Many Good Features.

Fig. 80. Why Pressure Feed System is Best for Eight-Cylinder Vee
Airplane Engines.

Fig. 81. Operating Temperatures of Automobile Engine Parts Useful as a
Guide to Understand Airplane Power Plant Heat.

Fig. 82. Water Cooling of Salmson Seven-Cylinder Radial Airplane Engine.

Fig. 83. How Water Cooling System of Thomas Airplane Engine is Installed
in Fuselage.

Fig. 84. Finned Tube Radiators at the Side of Hall-Scott Airplane Power
Plant Installed in Standard Fuselage.

Fig. 85. Anzani Testing His Five-Cylinder Air Cooled Aviation Motor
Installed in Bleriot Monoplane. Note Exposure of Flanged Cylinders to
Propeller Slip Stream.

Fig. 86. Views of Four-Cylinder Duesenberg Airplane Engine Cylinder
Block.

Fig. 87. Twin-Cylinder Block of Sturtevant Airplane Engine is Cast of
Aluminum, and Has Removable Cylinder Head.

Fig. 88. Aluminum Cylinder Pair Casting of Thomas 150 Horse-Power
Airplane Engine is of the L Head Type.

Fig. 90. Cross Section of Austro-Daimler Engine, Showing Offset Cylinder
Construction. Note Applied Water Jacket and Peculiar Valve Action.

Fig. 91. Diagrams Demonstrating Advantages of Offset Crank-Shaft
Construction.

Fig. 92. Diagram Showing Forms of Cylinder Demanded by Different Valve
Placings. A--T Head Type, Valves on Opposite Sides. B--L Head Cylinder,
Valves Side by Side. C--L Head Cylinder, One Valve in Head, Other in
Pocket. D--Inlet Valve Over Exhaust Member, Both in Side Pocket.
E--Valve-in-the-Head Type with Vertical Valves. F--Inclined Valves
Placed to Open Directly into Combustion Chamber.

Fig. 93. Sectional View of Engine Cylinder Showing Valve and Cage
Installation.

Fig. 94. Diagrams Showing How Gas Enters Cylinder Through Overhead
Valves and Other Types. A--Tee Head Cylinder. B--L Head Cylinder.
C--Overhead Valve.

Fig. 95. Conventional Methods of Operating Internal Combustion Motor
Valves.

Fig. 96. Examples of Direct Valve Actuation by Overhead Cam-Shaft.
A--Mercedes. B--Hall-Scott. C--Wisconsin.

Fig. 97. CENSORED

Fig. 98. CENSORED

Fig. 99. Sectional Views Showing Arrangement of Novel Concentric Valve
Arrangement Devised by Panhard for Aerial Engines.

Fig. 100. Showing Clearance Allowed Between Valve Stem and Valve Stem
Guide to Secure Free Action.

Fig. 101. Forms of Valve-Lifting Cams Generally Employed. A--Cam Profile
for Long Dwell and Quick Lift. B--Typical Inlet Cam Used with Mushroom
Type Follower. C--Average Form of Cam. D--Designed to Give Quick Lift
and Gradual Closing.

Fig. 102. Showing Principal Types of Cam Followers which Have Received
General Application.

Fig. 103. Diagram Showing Proper Clearance to Allow Between Adjusting
Screw and Valve Stems in Hall-Scott Aviation Engines.

Fig. 104. Cam-Shaft of Thomas Airplane Motor Has Cams Forged Integral.
Note Split Cam-Shaft Bearings and Method of Gear Retention.

Fig. 105. Section Through Cylinder of Knight Motor, Showing Important
Parts of Valve Motion.

Fig. 106. Diagrams Showing Knight Sleeve Valve Action.

Fig. 107. Cross Sectional View of Knight Type Eight Cylinder V Engine.

Fig. 108. Diagrams Explaining Valve and Ignition Timing of Hall-Scott
Aviation Engine.

Fig. 109. Timing Diagram of Typical Six-Cylinder Engine.

Fig. 110. Timing Diagram of Typical Eight-Cylinder V Engine.

Fig. 111. Timing Diagram Showing Peculiar Valve Timing of Gnome
"Monosoupape" Rotary Motor.

Fig. 112. Two Methods of Operating Valves by Positive Cam Mechanism
Which Closes as Well as Opens Them.

Fig. 113. Diagram Comparing Two Large Valves and Four Small Ones of
Practically the Same Area. Note How Easily Small Valves are Installed to
Open Directly Into the Cylinder.

Fig. 114. Sectional Views of Sixteen-Valve Four-Cylinder Automobile
Racing Engine That May Have Possibilities for Aviation Service.

Fig. 115. Front View of Curtiss OX-3 Aviation Motor, Showing
Unconventional Valve Action by Concentric Push Rod and Pull Tube.

Fig. 116. Forms of Pistons Commonly Employed in Gasoline Engines.
A--Dome Head Piston and Three Packing Rings. B--Flat Top Form Almost
Universally Used. C--Concave Piston Utilized in Knight Motors and Some
Having Overhead Valves. D--Two-Cycle Engine Member with Deflector Plate
Cast Integrally. E--Differential of Two-Diameter Piston Used in Some
Engines Operating on Two-Cycle Principle.

Fig. 117. Typical Methods of Piston Pin Retention Generally Used in
Engines of American Design. A--Single Set Screw and Lock Nut. B--Set
Screw and Check Nut Fitting Groove in Wrist Pin. C, D--Two Locking
Screws Passing Into Interior of Hollow Wrist Pin. E--Split Ring Holds
Pin in Place. F--Use of Taper Expanding Plugs Outlined. G--Spring
Pressed Plunger Type. H--Piston Pin Pinned to Connecting Rod. I--Wrist
Pin Clamped in Connecting Rod Small End by Bolt.

Fig. 118. Typical Piston and Connecting Rod Assembly.

Fig. 119. Parts of Sturtevant Aviation Engine. A--Cylinder Head Showing
Valves. B--Connecting Rod. C--Piston and Rings.

Fig. 120. Aluminum Piston and Light But Strong Steel Connecting Rod and
Wrist Pin of Thomas Aviation Engine.

Fig. 121. Cast Iron Piston of "Monosoupape" Gnome Engine Installed On
One of the Short Connecting Rods.

Fig. 122. Types of Aluminum Pistons Used In Aviation Engines.

Fig. 123. Types of Piston Rings and Ring Joints. A--Concentric Ring.
B--Eccentrically Machined Form. C--Lap Joint Ring. D--Butt Joint, Seldom
Used. E--Diagonal Cut Member, a Popular Form.

Fig. 124. Diagrams Showing Advantages of Concentric Piston Rings.

Fig. 125. Leak-Proof and Other Compound Piston Rings.

Fig. 126. Sectional View of Engine Showing Means of Preventing Oil
Leakage By Piston Rings.

Fig. 127. Connecting Rod and Crank-Shaft Construction of Gnome
"Monosoupape" Engine.

Fig. 128. Connecting Rod Types Summarized. A--Single Connecting Rod Made
in One Piece, Usually Fitted in Small Single-Cylinder Engines Having
Built-Up Crank-Shafts. B--Marine Type, a Popular Form on Heavy Engines.
C--Conventional Automobile Type, a Modified Marine Form. D--Type Having
Hinged Lower Cap and Split Wrist Pin Bushing. E--Connecting Rod Having
Diagonally Divided Big End. F--Ball-Bearing Rod. G--Sections Showing
Structural Shapes Commonly Employed in Connecting Rod Construction.

Fig. 129. Double Connecting Rod Assembly For Use On Single Crank-Pin of
Vee Engine.

Fig. 130. Another Type of Double Connecting Rod for Vee Engines.

Fig. 131. Part Sectional View of Wisconsin Aviation Engine, Showing
Four-Bearing Crank-Shaft, Overhead Cam-Shaft, and Method of Combining
Cylinders in Pairs.

Fig. 132. Part Sectional View of Renault Twelve-Cylinder Water-Cooled
Engine, Showing Connecting Rod Construction and Other Important Internal
Parts.

Fig. 133. Typical Cam-Shaft, with Valve Lifting Cams and Gears to
Operate Auxiliary Devices Forged Integrally.

Fig. 134. Important Parts of Duesenberg Aviation Engine. A--Three Main
Bearing Crank-Shaft. B--Cam-Shaft with Integral Cams. C--Piston and
Connecting Rod Assembly. D--Valve Rocker Group. E--Piston. F--Main
Bearing Brasses.

Fig. 135. Showing Method of Making Crank-Shaft. A--The Rough Steel
Forging Before Machining. B--The Finished Six-Throw, Seven-Bearing
Crank-Shaft.

Fig. 136. Showing Form of Crank-Shaft for Twin-Cylinder Opposed Power
Plant.

Fig. 137. Crank-Shaft of Thomas-Morse Eight-Cylinder Vee Engine.

Fig. 138. Crank-Case and Crank-Shaft Construction for Twelve-Cylinder
Motors. A--Duesenberg. B--Curtiss.

Fig. 139. Counterbalanced Crank-Shafts Reduce Engine Vibration and
Permit of Higher Rotative Speeds.

Fig. 140. View of Thomas 135 Horse-Power Aeromotor, Model 8, Showing
Conventional Method of Crank-Case Construction.

Fig. 141. Views of Upper Half of Thomas Aeromotor Crank-Case.

Fig. 142. Method of Constructing Eight-Cylinder Vee Engine, Possible if
Aluminum Cylinder and Crank-Case Castings are Used.

Fig. 143. Simple and Compact Crank-Case, Possible When Radial Cylinder
Engine Design is Followed.

Fig. 144. Unconventional Mounting of German Inverted Cylinder Motor.

Fig. 145. How Curtiss Model OX-2 Motor is Installed in Fuselage of
Curtiss Tractor Biplane. Note Similarity of Mounting to Automobile Power
Plant.

Fig. 146. Latest Model of Curtiss JN-4 Training Machine, Showing
Thorough Enclosure of Power Plant and Method of Disposing of the Exhaust
Gases.

Fig. 147. Front View of L. W. F. Tractor Biplane Fuselage, Showing
Method of Installing Thomas Aeromotor and Method of Disposing of Exhaust
Gases.

Fig. 148. End Elevation of Hall-Scott A-7 Four-Cylinder Motor, with
Installation Dimensions.

Fig. 149. Plan and Side Elevation of Hall-Scott A-7 Four-Cylinder
Airplane Engine, with Installation Dimensions.

Fig. 150. CENSORED

Fig. 151. CENSORED

Fig. 152. CENSORED

Fig. 153. Plan View of Hall-Scott Type A-5 125 Horse-Power Airplane
Engine, Showing Installation Dimensions.

Fig. 154. Three-Quarter View of Hall-Scott Type A-5 125 Horse-Power
Six-Cylinder Engine, with One of the Side Radiators Removed to Show
Installation in Standard Fuselage.

Fig. 155. Diagram Showing Proper Installation of Hall-Scott Type A-5 125
Horse-Power Engine with Pressure Feed Fuel Supply System.

Fig. 156. Diagram Defining Installation of Gnome "Monosoupape" Motor in
Tractor Biplane. Note Necessary Piping for Fuel, Oil, and Air Lines.

Fig. 157. Showing Two Methods of Placing Propeller on Gnome Rotary
Motor.

Fig. 158. How Gnome Rotary Motor May Be Attached to Airplane Fuselage
Members.

Fig. 159. How Anzani Ten-Cylinder Radial Engine is Installed to Plate
Securely Attached to Front End of Tractor Airplane Fuselage.

Fig. 160. Side Elevation of Thomas 135 Horse-Power Airplane Engine,
Giving Important Dimensions.

Fig. 161. Front Elevation of Thomas-Morse 135 Horse-Power Aeromotor,
Showing Main Dimensions.

Fig. 162. Front and Side Elevations of Sturtevant Airplane Engine,
Giving Principal Dimensions to Facilitate Installation.

Fig. 163. Practical Hand Tools Useful in Dismantling and Repairing
Airplane Engines.

Fig. 164. Wrenches are Offered in Many Forms.

Fig. 165. Illustrating Use and Care of Files.

Fig. 166. Outlining Use of Cotter Pin Pliers, Spring Winder, and Showing
Practical Outfit of Chisels.

Fig. 167. Forms of Hand Operated Drilling Machines.

Fig. 168. Forms of Drills Used in Hand and Power Drilling Machines.

Fig. 169. Useful Set of Number Drills, Showing Stand for Keeping These
in an Orderly Manner.

Fig. 170. Illustrating Standard Forms of Hand and Machine Reamers.

Fig. 171. Tools for Thread Cutting.

Fig. 172. Showing Holder Designs for One- and Two-Piece Thread Cutting
Dies.

Fig. 173. Useful Outfit of Taps and Dies for the Engine Repair Shop.

Fig. 174. Common Forms of Inside and Outside Calipers.

Fig. 175. Measuring Appliances for the Machinist and Floor Man.

Fig. 176. At Left, Special Form of Vernier Caliper for Measuring Gear
Teeth; at Right, Micrometer for Accurate Internal Measurements.

Fig. 177. Measuring Appliances of Value in Airplane Repair Work.

Fig. 178. Standard Forms of Micrometer Caliper for External
Measurements.

Fig. 179. Special Tools for Maintaining Curtiss OX-2 Motor Used in
Curtiss JN-4 Training Biplane.

Fig. 180. Special Tools and Appliances to Facilitate Overhauling Work on
Hall-Scott Airplane Engines.

Fig. 181. Special Stand to Make Motor Overhauling Work Easier.

Fig. 182. Showing Where Carbon Deposits Collect in Engine Combustion
Chamber, and How to Burn Them Out with the Aid of Oxygen. A--Special
Torch. B--Torch Coupled to Oxygen Tank. C--Torch in Use.

Fig. 1821/2. Part Sectional View, Showing Valve Arrangement in Cylinder
of Curtiss OX-2 Aviation Engine.

Fig. 183. Tools for Restoring Valve Head and Seats.

Fig. 184. Tools and Processes Utilized in Valve Grinding.

Fig. 185. Outlining Points in Valve Operating Mechanism Where
Depreciation is Apt to Exist.

Fig. 186. Method of Removing Piston Rings, and Simple Clamp to
Facilitate Insertion of Rings in Cylinder.

Fig. 187. Tools and Processes Used in Refitting Engine Bearings.

Fig. 188. Showing Points to Observe When Fitting Connecting Rod Brasses.

Fig. 189. Methods of Testing to Insure Parallelism of Bearings After
Fitting.

Fig. 190. Views Outlining Construction of Three-Cylinder Anzani Aviation
Motor.

Fig. 190a. Illustrations Depicting Wrong and Right Methods of "Swinging
the Stick" to Start Airplane Engine. At Top, Poor Position to Get Full
Throw and Get Out of the Way. Below, Correct Position to Get Quick Turn
Over of Crank-Shaft and Spring Away from Propeller.

Fig. 191. The Anzani Six-Cylinder Water-Cooled Aviation Engine.

Fig. 192. Sectional View of Anzani Six-Cylinder Water-Cooled Aviation
Engine.

Fig. 193. Three-Cylinder Anzani Air-Cooled Y-Form Engine.

Fig. 194. Anzani Fixed Crank-Case Engine of the Six-Cylinder Form
Utilizes Air Cooling Successfully.

Fig. 195. Sectional View Showing Internal Parts of Six-Cylinder Anzani
Engine, with Starwise Disposition of Cylinders.

Fig. 196. The Anzani Ten-Cylinder Aviation Engine at the Left, and the
Twenty-Cylinder Fixed Type at the Right.

Fig. 197. Application of R. E. P. Five-Cylinder Fan-Shape Air-Cooled
Motor to Early Monoplane.

Fig. 198. The Canton and Unné Nine-Cylinder Water-Cooled Radial Engine.

Fig. 199. Sectional View Showing Construction of Canton and Unné
Water-Cooled Radial Cylinder Engine.

Fig. 200. Sectional View Outlining Construction of Early Type Gnome
Valve-in-Piston Type Motor.

Fig. 201. Sectional View of Early Type Gnome Cylinder and Piston Showing
Construction and Application of Inlet and Exhaust Valves.

Fig. 202. Details of Old Style Gnome Motor Inlet and Exhaust Valve
Construction and Operation.

Fig. 203. The Gnome Fourteen-Cylinder 100 Horse-Power Aviation Engine.

Fig. 204. Cam and Cam-Gear Case of the Gnome Seven-Cylinder Revolving
Engine.

Fig. 205. Diagrams Showing Why An Odd Number of Cylinders is Best for
Rotary Cylinder Motors.

Fig. 206. Simple Carburetor Used On Early Gnome Engines Attached to
Fixed Crank-Shaft End.

Fig. 207. Sectional Views of the Gnome Oil Pump.

Fig. 208. Simplified Diagram Showing Gnome Motor Magneto Ignition
System.

Fig. 209. The G. V. Gnome "Monosoupape" Nine-Cylinder Rotary Engine
Mounted on Testing Stand.

Fig. 210. Sectional View Showing Construction of General Vehicle Co.
"Monosoupape" Gnome Engine.

Fig. 211. How a Gnome Cylinder is Reduced from Solid Chunk of Steel
Weighing 97 Pounds to Finished Cylinder Weighing 51/2 Pounds.

Fig. 212. The Gnome Engine Cam-Gear Case, a Fine Example of Accurate
Machine Work.

Fig. 213. G. V. Gnome "Monosoupape," with Cam-Case Cover Removed to Show
Cams and Valve-Operating Plungers with Roller Cam Followers.

Fig. 214. The 50 Horse-Power Rotary Bayerischen Motoren Gesellschaft
Engine, a German Adaptation of the Early Gnome Design.

Fig. 215. Nine-Cylinder Revolving Le Rhone Type Aviation Engine.

Fig. 216. Part Sectional Views of Le Rhone Rotary Cylinder Engine,
Showing Method of Cylinder Retention, Valve Operation and Novel Crank
Disc Assembly.

Fig. 217. Side Sectional View of Le Rhone Aviation Engine.

Fig. 218. View Showing Le Rhone Valve Action and Connecting Rod Big End
Arrangement.

Fig. 219. Diagrams Showing Important Components of Le Rhone Motor.

Fig. 220. How the Cams of the Le Rhone Motor Can Operate Two Valves with
a Single Push Rod.

Fig. 221. The Le Rhone Carburetor at A and Fuel Supply Regulating Device
at B.

Fig. 222. Diagrams Showing Le Rhone Motor Action and Firing Order.

Fig. 223. Diagram Showing Positions of Piston in Le Rhone Rotary
Cylinder Motor.

Fig. 224. Diagrams Showing Valve Timing of Le Rhone Aviation Engine.

Fig. 225. Diagrams Showing How Cylinder Cooling is Effected in Renault
Vee Engines.

Fig. 226. End Sectional View of Renault Air-Cooled Aviation Engine.

Fig. 227. Side Sectional View of Renault Twelve-Cylinder Air-Cooled
Aviation Engine Crank-Case, Showing Use of Plain and Ball Bearings for
Crank-Shaft Support.

Fig. 228. End View of Renault Twelve-Cylinder Engine Crank-Case, Showing
Magneto Mounting.

Fig. 229. Diagram Outlining Renault Twelve-Cylinder Engine Ignition
System.

Fig. 230. The Simplex Model A Hispano-Suiza Aviation Engine, a Very
Successful Form.

Fig. 231. The Curtiss OXX-5 Aviation Engine is an Eight-Cylinder Type
Largely Used on Training Machines.

Fig. 232. Top and Bottom Views of the Curtiss OXX-5 100 Horse-Power
Aviation Engine.

Fig. 233. End View of Thomas-Morse 150 Horse-Power Aluminum Cylinder
Aviation Motor Having Detachable Cylinder Heads.

Fig. 234. Side View of Thomas-Morse High Speed 150 Horse-Power Aviation
Motor with Geared Down Propeller Drive.

Fig. 235. The Reduction Gear-Case of Thomas-Morse 150 Horse-Power
Aviation Motor, Showing Ball Bearing and Propeller Drive Shaft Gear.

Fig. 236. The Six-Cylinder Aeromarine Engine.

Fig. 237. The Wisconsin Aviation Engine, at Top, as Viewed from
Carburetor Side. Below, the Exhaust Side.

Fig. 238. Dimensioned End Elevation of Wisconsin Six Motor.

Fig. 239. Dimensioned Side Elevation of Wisconsin Six Motor.

Fig. 240. Power, Torque and Efficiency Curves of Wisconsin Aviation
Motor.

Fig. 241. Timing Diagram, Wisconsin Aviation Engine.

Fig. 242. Dimensioned End View of Wisconsin Twelve-Cylinder Airplane
Motor.

Fig. 243. Dimensioned Side Elevation of Wisconsin Twelve-Cylinder
Airplane Motor.

Fig. 244. Side and End Sectional Views of Four-Cylinder Argus Engine, a
German 100 Horse-Power Design Having Bore and Stroke of 140 mm., or 5.60
inches, and Developing Its Power at 1,368 R.P.M. Weight, 350 Pounds.

Fig. 245. Part Sectional View of 90 Horse-Power Mercedes Engine, Which
is Typical of the Design of Larger Sizes.

Fig. 246. Part Sectional Side View and Sectional End View of Benz 160
Horse-Power Aviation Engine.

Fig. 247. At Top, the Sunbeam Overhead Valve 170 Horse-Power
Six-Cylinder Engine. Below, Side View of Sunbeam 350 Horse-Power
Twelve-Cylinder Vee Engine.

Fig. 248. Side View of Eighteen-Cylinder Sunbeam Coatalen Aircraft
Engine Rated at 475 B.H.P.

Fig. 249. Sunbeam Eighteen-Cylinder Motor, Viewed from Pump and Magneto
End.

Fig. 250. Propeller End of Sunbeam Eighteen-Cylinder 475 B.H.P. Aviation
Engine.

Fig. 251. View of Airplane Cowl Board, Showing the Various Navigating
and Indicating Instruments to Aid the Aviator in Flight.

Fig. 252. Parts of Christensen Air Starting System Shown at A, and
Application of Piping and Check Valves to Cylinders of Thomas-Morse
Aeromotor Outlined at B.

Fig. 253. Diagrams Showing Installation of Air Starting System on
Thomas-Morse Aviation Motor.

CATALOGUE
_Of the_ LATEST _and_ BEST
PRACTICAL _and_ MECHANICAL
BOOKS

_Including Automobile and Aviation Books_

[Illustration]

_Any of these books will be sent prepaid to any part of the world, on
receipt of price. Remit by Draft, Postal Order, Express Order or
Registered Letter_

Published and For Sale By
The Norman W. Henley Publishing Co.,
2 West 45th Street, New York, U.S.A.

INDEX

PAGES
Air Brakes 21, 24
Arithmetic 14, 25, 31
Automobile Books 3, 4, 5, 6
Automobile Charts 6, 7
Automobile Ignition Systems 5
Automobile Lighting 5
Automobile Questions and Answers 4
Automobile Repairing 4
Automobile Starting Systems 5
Automobile Trouble Charts 5, 6
Automobile Welding 5
Aviation 7
Aviation Chart 7
Batteries, Storage 5
Bevel Gear 19
Boiler-Room Chart 9
Brazing 7
Cams 19
Carburetion Trouble Chart 6
Change Gear 19
Charts 6, 7, 8
Coal 22
Coke 9
Combustion 22
Compressed Air 10
Concrete 10, 11, 12
Concrete for Farm Use 11
Concrete for Shop Use 11
Cosmetics 27
Cyclecars 5
Dictionary 12
Dies 12, 13
Drawing 13, 14
Drawing for Plumbers 28
Drop Forging 13
Dynamo Building 14
Electric Bells 14
Electric Switchboards 14, 16
Electric Toy Making 15
Electric Wiring 14, 15, 16
Electricity 14, 15, 16, 17
Encyclopedia 24
E-T Air Brake 24
Every-day Engineering 34
Factory Management 17
Ford Automobile 3
Ford Trouble Chart 6
Formulas and Recipes 29
Fuel 17
Gas Construction 18
Gas Engines 18, 19
Gas Tractor 33
Gearing and Cams 19
Glossary of Aviation Terms 7, 12
Heating 31, 32
Horse-Power Chart 9
Hot-Water Heating 31, 32
House Wiring 15, 17
How to Run an Automobile 3
Hydraulics 5
Ice and Refrigeration 20
Ignition Systems 5
Ignition-Trouble Chart 6
India Rubber 30
Interchangeable Manufacturing 24
Inventions 20
Knots 20
Lathe Work 20
Link Motions 22
Liquid Air 21
Locomotive Boilers 22
Locomotive Breakdowns 22
Locomotive Engineering 21, 22, 23, 24
Machinist Book 24, 25, 26
Magazine, Mechanical 34
Manual Training 26
Marine Engineering 26
Marine Gasoline Engines 19
Mechanical Drawing 13, 14
Mechanical Magazine 34
Mechanical Movements 25
Metal Work 12, 13
Motorcycles 5, 6
Patents 20
Pattern Making 27
Perfumery 27
Perspective 13
Plumbing 28, 29
Producer Gas 19
Punches 13
Questions and Answers on Automobile 4
Questions on Heating 32
Railroad Accidents 23
Railroad Charts 9
Recipe Book 29
Refrigeration 20
Repairing Automobiles 4
Rope Work 20
Rubber 30
Rubber Stamps 30
Saw Filing 30
Saws, Management of 30
Sheet-Metal Works 12, 13
Shop Construction 25
Shop Management 25
Shop Practice 25
Shop Tools 25
Sketching Paper 14
Soldering 7
Splices and Rope Work 20
Steam Engineering 30, 31
Steam Heating 31, 32
Steel 32
Storage Batteries 5
Submarine Chart 9
Switchboards 14, 16
Tapers 21
Telegraphy, Wireless 17
Telephone 16
Thread Cutting 26
Tool Making 24
Toy Making 15
Train Rules 23
Tractive Power Chart 9
Tractor, Gas 33
Turbines 33
Vacuum Heating 32
Valve Setting 22
Ventilation 31
Watch Making 33
Waterproofing 12
Welding with Oxy-acetylene Flame 5, 33
Wireless Telegraphy 17
Wiring 14, 15
Wiring Diagrams 14

Any of these books promptly sent prepaid to any address in the world on
receipt of price.

=HOW TO REMIT=--By Postal Money Order, Express Money Order, Bank Draft
or Registered Letter.

~AUTOMOBILES AND MOTORCYCLES~

=The Modern Gasoline Automobile--Its Design, Construction, and
Operation, 1918 Edition.= By VICTOR W. PAGÉ, M.S.A.E.

This is the most complete, practical and up-to-date treatise on
gasoline automobiles and their component parts ever published.
In the new _revised_ and _enlarged_ 1918 _edition_, all phases
of automobile construction, operation and maintenance are fully
and completely described, and in language anyone can understand.
Every part of all types of automobiles, from light cycle-cars to
heavy motor trucks and tractors, are described in a thorough
manner, not only the automobile, but every item of it;
equipment, accessories, tools needed, supplies and spare parts
necessary for its upkeep, are fully discussed.

_It is clearly and concisely written by an expert familiar with
every branch of the automobile industry and the originator of
the practical system of self-education on technical subjects. It
is a liberal education in the automobile art, useful to all who
motor for either business or pleasure._

Anyone reading the incomparable treatise is in touch with all
improvements that have been made in motor-car construction. All
latest developments, such as high speed aluminum motors and
multiple valve and sleeve-valve engines, are considered in
detail. The latest ignition, carburetor and lubrication practice
is outlined. New forms of change speed gears, and final power
transmission systems, and all latest chassis improvements are
shown and described. This book is used in all leading automobile
schools and is conceded to be the STANDARD TREATISE. The chapter
on Starting and Lighting Systems has been greatly enlarged, and
many automobile engineering features that have long puzzled
laymen are explained so clearly that the underlying principles
can be understood by anyone. This book was first published six
years ago and so much new matter has been added that it is
nearly twice, its original size. The only treatise covering
various forms of war automobiles and recent developments in
motor-truck design as well as pleasure cars. _This book is not
too technical for the layman nor too elementary for the more
expert. It is an incomparable work of reference, for home or
school_. 1,000 6x9 pages, nearly 1,000 illustrations, 12 folding
plates. Cloth bound. Price =$3.00=

WHAT IS SAID OF THIS BOOK:

"It is the best book on the Automobile seen up to date."--J. H.
Pile, Associate Editor _Automobile Trade Journal_.

"Every Automobile Owner has use for a book of this
character."--_The Tradesman_.

"This book is superior to any treatise heretofore published on
the subject."--_The Inventive Age_.

"We know of no other volume that is so complete in all its
departments, and in which the wide field of automobile
construction with its mechanical intricacies is so plainly
handled, both in the text and in the matter of
illustrations."--_The Motorist_.

"The book is very thorough, a careful examination failing to
disclose any point in connection with the automobile, its care
and repair, to have been overlooked."--_Iron Age_.

"Mr. Pagé has done a great work, and benefit to the Automobile
Field."--W. C. Hasford, Mgr. Y. M. C. A. Automobile School,
Boston, Mass.

"It is just the kind of a book a motorist needs if he wants to
understand his car."--_American Thresherman_.

=The Model T Ford Car, Its Construction, Operation and Repair.= By
VICTOR W. PAGÉ, M.S.A.E.

This is a complete instruction book. All parts of the Ford Model
T Car are described and illustrated; the construction is fully
described and operating principles made clear to everyone. Every
Ford owner needs this practical book. You don't have to guess
about the construction or where the trouble is, as it shows how
to take all parts apart and how to locate and fix all faults.
The writer, Mr. Pagé, has operated a Ford car for many years and
writes from actual knowledge. Among the contents are: 1. The
Ford Car: Its Parts and Their Functions. 2. The Engine and
Auxiliary Groups. How the Engine Works--The Fuel Supply
System--The Carburetor--Making the Ignition Spark--Cooling and
Lubrication. 3. Details of Chassis. Change Speed Gear--Power
Transmission--Differential Gear Action--Steering Gear--Front
Axle--Frame and Springs--Brakes. 4. How to Drive and Care for
the Ford. The Control System Explained--Starting the
Motor--Driving the Car--Locating Roadside Troubles--Tire
Repairs--Oiling the Chassis--Winter Care of Car. 5. Systematic
Location of Troubles and Remedies. Faults in Engine--Faults in
Carburetor--Ignition Troubles--Cooling and Lubrication System
Defects--Adjustment of Transmission Gear--General Chassis
Repairs. 95 illustrations, 300 pages, 2 large folding plates.
Price =$1.00=

=How to Run an Automobile.= By VICTOR W. PAGÉ, M.S.A.E.

This treatise gives concise instructions for starting and
running all makes of gasoline automobiles, how to care for them,
and gives distinctive features of control. Describes every step
for shifting gears, controlling engines, etc. Among the chapters
contained are: I.--Automobile Parts and Their Functions.
II.--General Starting and Driving Instructions. III.--Typical
1917 Control Systems. IV.--Care of Automobiles. 178 pages. 72
specially made illustrations. Price =$1.00=

=Automobile Repairing Made Easy.= By VICTOR W. PAGÉ, M.S.A.E.

A comprehensive, practical exposition of every phase of modern
automobile repairing practice. Outlines every process incidental
to motor car restoration. Gives plans for workshop construction,
suggestions for equipment, power needed, machinery and tools
necessary to carry on business successfully. Tells how to
overhaul and repair all parts of all automobiles. Everything is
explained so simply that motorists and students can acquire a
full working knowledge of automobile repairing. This work starts
with the engine, then considers carburetion, ignition, cooling
and lubrication systems. The clutch, change speed gearing and
transmission system are considered in detail. Contains
instructions for repairing all types of axles, steering gears
and other chassis parts. Many tables, short cuts in figuring and
rules of practice are given for the mechanic. Explains fully
valve and magneto timing, "tuning" engines, systematic location
of trouble, repair of ball and roller bearings, shop kinks,
first aid to injured and a multitude of subjects of interest to
all in the garage and repair business. _This book contains
special instructions on electric starting_, _lighting and
ignition systems_, tire _repairing and rebuilding_, _autogenous
welding_, _brazing and soldering_, _heat treatment of steel_,
_latest timing practice_, _eight and twelve-cylinder motors_,
_etc._ 5-3/4x8. Cloth. 1,056 pages, 1,000 illustrations, 11
folding plates. Price =$3.00=

WHAT IS SAID OF THIS BOOK:

"'Automobile Repairing Made Easy' is the best book on the
subject I have ever seen and the only book I ever saw that is of
any value in a garage."--Fred Jeffrey, Martinsburg, Neb. "I wish
to thank you for sending me a copy of 'Automobile Repairing Made
Easy.' I do not think it could be excelled."--S. W. Gisriel,
Director of Instruction, Y. M. C. A., Philadelphia, Pa.

=Questions and Answers Relating to Modern Automobile Construction,
Driving and Repair.= By VICTOR W. PAGÉ, M.S.A.E.

A practical self-instructor for students, mechanics and
motorists, consisting of thirty-seven lessons in the form of
questions and answers, written with special reference to the
requirements of the non-technical reader desiring easily
understood, explanatory matter relating to all branches of
automobiling. The subject-matter is absolutely correct and
explained in simple language. If you can't answer all of the
following questions, you need this work. The answers to these
and over 2,000 more are to be found in its pages. Give the name
of all important parts of an automobile and describe their
functions. Describe action of latest types of kerosene
carburetors. What is the difference between a "double" ignition
system and a "dual" ignition system? Name parts of an induction
coil. How are valves timed? What is an electric motor starter
and how does it work? What are advantages of worm drive gearing?
Name all important types of ball and roller bearings. What is a
"three-quarter" floating axle? What is a two-speed axle? What is
the Vulcan electric gear shift? Name the causes of lost power in
automobiles. Describe all noises due to deranged mechanism and
give causes? How can you adjust a carburetor by the color of the
exhaust gases? What causes "popping" in the carburetor? What
tools and supplies are needed to equip a car? How do you drive
various makes of cars? What is a differential lock and where is
it used? Name different systems of wire wheel construction,
etc., etc. A popular work at a popular price. 5-1/4x7-1/2.
Cloth. 650 pages, 350 illustrations, 3 folding plates. Price
=$1.50=

WHAT IS SAID OF THIS BOOK:

"If you own a car--get this book."--_The Glassworker_.

"Mr. Page has the faculty of making difficult subjects plain and
understandable."--_Bristol Press_.

"We can name no writer better qualified to prepare a book of
instruction on automobiles than Mr. Victor W.
Pagé."--_Scientific American_.

"The best automobile catechism that has appeared."--_Automobile
Topics_.

"There are few men, even with long experience, who will not find
this book useful. Great pains have been taken to make it
accurate. Special recommendation must be given to the
illustrations, which have been made specially for the work. Such
excellent books as this greatly assist in fully understanding
your automobile."--_Engineering News_.

=The Automobilist's Pocket Companion and Expense Record.= Arranged by
VICTOR W. PAGÉ, M.S.A.E.

This book is not only valuable as a convenient cost record but
contains much information of value to motorists. Includes a
condensed digest of auto laws of all States, a lubrication
schedule, hints for care of storage battery and care of tires,
location of road troubles, anti-freezing solutions, horse-power
table, driving hints and many useful tables and recipes of
interest to all motorists. Not a technical book in any sense of
the word, just a collection of practical facts in simple
language for the everyday motorist. Price =$1.00=

=Modern Starting, Lighting and Ignition Systems.= By VICTOR W. PAGÉ,
M.E.

This practical volume has been written with special reference to
the requirements of the non-technical reader desiring easily
understood, explanatory matter, relating to all types of
automobile ignition, starting and lighting systems. It can be
understood by anyone, even without electrical knowledge, because
elementary electrical principles are considered before any
attempt is made to discuss features of the various systems.
These basic principles are clearly stated and illustrated with
simple diagrams. _All the leading systems of starting, lighting
and ignition have been described and illustrated with the
co-operation of the experts employed by the manufacturers._
Wiring diagrams are shown in both technical and non-technical
forms. All symbols are fully explained. It is a comprehensive
review of modern starting and ignition system practice, and
includes a complete exposition of storage battery construction,
care and repair. All types of starting motors, generators,
magnetos, and all ignition or lighting system-units are fully
explained. _Every person in the automobile business needs this
volume._ Among some of the subjects treated are: I.--Elementary
Electricity; Current Production; Flow; Circuits; Measurements;
Definitions; Magnetism; Battery Action; Generator Action.
II.--Battery Ignition Systems. III.--Magneto Ignition Systems.
IV.--Elementary Exposition of Starting System Principles.
V.--Typical Starting and Lighting Systems; Practical
Application; Wiring Diagrams; Auto-lite, Bijur, Delco,
Dyneto-Entz, Gray and Davis, Remy, U. S. L., Westinghouse,
Bosch-Rushmore, Genemotor, North-East, etc. VI.--Locating and
Repairing Troubles in Starting and Lighting Systems.
VII.--Auxiliary. Electric Systems; Gear-shifting by Electricity;
Warning Signals; Electric Brake; Entz-Transmission, Wagner-Saxon
Circuits, Wagner-Studebaker Circuits. 5-1/4x7-1/2. Cloth. 530
pages, 297 illustrations, 3 folding plates. Price =$1.50=

=Automobile Welding With the Oxy-Acetylene Flame.= By M. KEITH DUNHAM.

This is the only complete book on the "why" and "how" of Welding
with the Oxy-Acetylene Flame, and from its pages one can gain
information so that he can weld anything that comes along.

No one can afford to be without this concise book, as it first
explains the apparatus to be used, and then covers in detail the
actual welding of all automobile parts. The welding of aluminum,
cast iron, steel, copper, brass and malleable iron is clearly
explained, as well as the proper way to burn the carbon out of
the combustion head of the motor. Among the contents are:
Chapter I.--Apparatus Knowledge. Chapter II.--Shop Equipment and
Initial Procedure. Chapter III.--Cast Iron. Chapter
IV.--Aluminum. Chapter V.--Steel. Chapter VI.--Malleable Iron,
Copper, Brass, Bronze. Chapter VII.--Carbon Burning and other
Uses of Oxygen and Acetylene. Chapter VIII.--How to Figure Cost
of Welding. 167 pages, fully illustrated. Price =$1.00=

=Storage Batteries Simplified.= By VICTOR W. PAGÉ, M.S.A.E.

A comprehensive treatise devoted entirely to secondary batteries
and their maintenance, repair and use.

This is the most up-to-date book on this subject. Describes
fully the Exide, Edison, Gould, Willard, U. S. L. and other
storage battery forms in the types best suited for automobile,
stationary and marine work. Nothing of importance has been
omitted that the reader should know about the practical
operation and care of storage batteries. No details have been
slighted. The instructions for charging and care have been made
as simple as possible. Brief Synopsis of Chapters: Chapter
I.--Storage Battery Development; Types of Storage Batteries;
Lead Plate Types; The Edison Cell. Chapter II.--Storage Battery
Construction; Plates and Girds; Planté Plates; Fauré Plates;
Non-Lead Plates; Commercial Battery Designs. Chapter
III.--Charging Methods; Rectifiers; Converters; Rheostats; Rules
for Charging. Chapter IV.--Battery Repairs and Maintenance.
Chapter V.--Industrial Application of Storage Batteries;
Glossary of Storage Battery Terms. 208 Pages. Very Fully
Illustrated. Price =$1.50 net=.

=Motorcycles, Side Cars and Cyclecars; their Construction, Management
and Repair.= By VICTOR W. PAGÉ, M.S.A.E.

The only complete work published for the motorcyclist and
cyclecarist. Describes fully all leading types of machines,
their design, construction, maintenance, operation and repair.
This treatise outlines fully the operation of two- and
four-cycle power plants and all ignition, carburetion and
lubrication systems in detail. Describes all representative
types of free engine clutches, variable speed gears and power
transmission systems. Gives complete instructions for operating
and repairing all types. Considers fully electric self-starting
and lighting systems, all types of spring frames and spring
forks and shows leading control methods. For those desiring
technical information a complete series of tables and many
formulæ to assist in designing are included. The work tells how
to figure power needed to climb grades, overcome air resistance
and attain high speeds. It shows how to select gear ratios for
various weights and powers, how to figure braking efficiency
required, gives sizes of belts and chains to transmit power
safely, and shows how to design sprockets, belt pulleys, etc.
This work also includes complete formulæ for figuring
horse-power, shows how dynamometer tests are made, defines
relative efficiency of air and water-cooled engines, plain and
anti-friction bearings and many other data of a practical,
helpful, engineering nature. Remember that you get this
information in addition to the practical description and
instructions which alone are worth several times the price of
the book. 550 pages. 350 specially made illustrations, 5 folding
plates. Cloth. Price =$1.50=

WHAT IS SAID OF THIS BOOK:

"Here is a book that should be in the cycle repairer's
kit."--_American Blacksmith._

"The best way for any rider to thoroughly understand his
machine, is to get a copy of this book; it is worth many times
its price."--_Pacific Motorcyclist._

~AUTOMOBILE AND MOTORCYCLE CHARTS~

=Chart. Location of Gasoline Engine Troubles Made Easy--A Chart Showing
Sectional View of Gasoline Engine.= Compiled by VICTOR W. PAGÉ, M.S.A.E.

It shows clearly all parts of a typical four-cylinder gasoline
engine of the four-cycle type.

It outlines distinctly all parts liable to give trouble and also
details the derangements apt to interfere with smooth engine
operation.

Valuable to students, motorists, mechanics, repairmen,
garagemen, automobile salesmen, chauffeurs, motorboat owners,
motor-truck and tractor drivers, aviators, motor-cyclists, and
all others who have to do with gasoline power plants.

It simplifies location of all engine troubles, and while it will
prove invaluable to the novice, it can be used to advantage by
the more expert. It should be on the walls of every public and
private garage, automobile repair shop, club house or school. It
can be carried in the automobile or pocket with ease, and will
insure against loss of time when engine trouble manifests
itself.

This sectional view of engine is a complete review of all motor
troubles. It is prepared by a practical motorist for all who
motor. More information for the money than ever before offered.
No details omitted. Size 25x38 inches. Securely mailed on
receipt of =25 Cents=

=Chart. Location of Ford Engine Troubles Made Easy.= Compiled by VICTOR
W. PAGÉ, M.S.A.E.

This shows clear sectional views depicting all portions of the
Ford power plant and auxiliary groups. It outlines clearly all
parts of the engine, fuel supply system, ignition group and
cooling system, that are apt to give trouble, detailing all
derangements that are liable to make an engine lose power, start
hard or work irregularly. This chart is valuable to students,
owners, and drivers, as it simplifies location of all engine
faults. Of great advantage as an instructor for the novice, it
can be used equally well by the more expert as a work of
reference and review. It can be carried in the tool-box or
pocket with ease and will save its cost in labor eliminated the
first time engine trouble manifests itself. Prepared with
special reference to the average man's needs and is a practical
review of all motor troubles because it is based on the actual
experience of an automobile engineer-mechanic with the mechanism
the chart describes. It enables the non-technical owner or
operator of a Ford car to locate engine derangements by
systematic search, guided by easily recognized symptoms instead
of by guesswork. It makes the average owner independent of the
roadside repair shop when touring. Must be seen to be
appreciated. Size 25x38 inches. Printed on heavy bond paper.
Price =25 cents=

=Chart. Lubrication of the Motor Car Chassis.= Compiled by VICTOR W.
PAGÉ, M.S.A.E.

This chart presents the plan view of a typical six-cylinder
chassis of standard design and all parts are clearly indicated
that demand oil, also the frequency with which they must be
lubricated and the kind of oil to use. A practical chart for all
interested in motor-car maintenance. Size 24x38 inches. Price
=25 cents=

=Chart. Location of Carburetion Troubles Made Easy.= Compiled by VICTOR
W. PAGÉ, M.S.A.E.

This chart shows all parts of a typical pressure feed fuel
supply system and gives causes of trouble, how to locate defects
and means of remedying them. Size 24x38 inches. Price =25 cents=

=Chart. Location of Ignition System Troubles Made Easy.= Compiled by
VICTOR W. PAGÉ, M.S.A.E.

In this diagram all parts of a typical double ignition system
using battery and magneto current are shown, and suggestions are
given for readily finding ignition troubles and eliminating them
when found. Size 24x38 inches. Price =25 cents=

=Chart. Location of Cooling and Lubrication System Faults.= Compiled by
VICTOR W. PAGÉ, M.S.A.E.

This composite diagram shows a typical automobile power plant
using pump circulated water-cooling system and the most popular
lubrication method. Gives suggestions for curing all overheating
and loss of power faults due to faulty action of the oiling or
cooling group. Size 24x38 inches. Price =25 cents=

=Chart. Motorcycle Troubles Made Easy.= Compiled by VICTOR W PAGÉ,
M.S.A.E.

A chart showing sectional view of a single-cylinder gasoline
engine. This chart simplifies location of all power-plant
troubles. A single-cylinder motor is shown for simplicity. It
outlines distinctly all parts liable to give trouble and also
details the derangements apt to interfere with smooth engine
operation. This chart will prove of value to all who have to do
with the operation, repair or sale of motorcycles. No details
omitted. Size 30x20 inches Price =25 cents=

~AVIATION~

=Aviation Engines, their Design, Construction, Operation and Repair.= By
Lieut. VICTOR W. PAGÉ, Aviation Section, S.C.U.S.R.

A practical work containing valuable instructions for aviation
students, mechanicians, squadron engineering officers and all
interested in the construction and upkeep of airplane power
plants.

The rapidly increasing interest in the study of aviation, and
especially of the highly developed internal combustion engines
that make mechanical flight possible, has created a demand for a
text-book suitable for schools and home study that will clearly
and concisely explain the workings of the various aircraft
engines of foreign and domestic manufacture.

This treatise, written by a recognized authority on all of the
practical aspects of internal combustion engine construction,
maintenance and repair fills the need as no other book does.

The matter is logically arranged; all descriptive matter is
simply expressed and copiously illustrated so that anyone can
understand airplane engine operation and repair even if without
previous mechanical training. This work is invaluable for anyone
desiring to become an aviator or aviation mechanician.

The latest rotary types, such as the Gnome, Monosoupape, and Le
Rhone, are fully explained, as well as the recently developed
Vee and radial types. The subjects of carburetion, ignition,
cooling and lubrication also are covered in a thorough manner.
The chapters on repair and maintenance are distinctive and found
in no other book on this subject.

Invaluable to the student, mechanic and soldier wishing to enter
the aviation service.

Not a technical book, but a practical, easily understood work of
reference for all interested in aeronautical science. 576 octavo
pages. 253 specially made engravings. Price =$3.00 net=

~GLOSSARY OF AVIATION TERMS~

=Termes D'Aviation, English-French, French-English.= Compiled by Lieuts.
VICTOR W. PAGÉ, A.S., S.C.U.S.R., and PAUL MONTARIOL of the French
Flying Corps, on duty on Signal Corps Aviation School, Mineola, L. I.

A complete, well illustrated volume intended to facilitate
conversation between English-speaking and French aviators. A
very valuable book for all who are about to leave for duty
overseas.

Approved for publication by Major W. G. Kilner, S.C., U.S.C.O.
Signal Corps Aviation School. Hazelhurst Field, Mineola, L. I.

This book should be in every Aviator's and Mechanic's Kit for
ready reference. 128 pages. Fully illustrated with detailed
engravings. Price =$1.00=

=Aviation Chart. Location of Airplane Power Plant Troubles Made Easy.=
By Lieut. VICTOR W. PAGÉ, A.S., S.C.U.S.R.

A large chart outlining all parts of a typical airplane power
plant, showing the points where trouble is apt to occur and
suggesting remedies for the common defects. Intended especially
for Aviators and Aviation Mechanics on School and Field Duty.
Price =50 cents=

~BRAZING AND SOLDERING~

=Brazing and Soldering.= By JAMES F. HOBART.

The only book that shows you just how to handle any job of
brazing or soldering that comes along; it tells you what mixture
to use, how to make a furnace if you need one. Full of valuable
kinks. The fifth edition of this book has just been published,
and to it much new matter and a large number of tested formulæ
for all kinds of solders and fluxes have been added.
Illustrated. Price =25 cents=

~CHARTS~

=Aviation Chart. Location of Airplane Power Plant Troubles Made Easy.=
By Lieut. VICTOR W. PAGÉ, A.S., S.C.U.S.R.

A large chart outlining all parts of a typical airplane power
plant, showing the points where trouble is apt to occur and
suggesting remedies for the common defects. Intended especially
for Aviators and Aviation Mechanics on School and Field Duty.
Price =50 cents=

=Gasoline Engine Troubles Made Easy--A Chart Showing Sectional View of
Gasoline Engine.= Compiled by Lieut. VICTOR W. PAGÉ, A.S., S.C.U.S.R.

It shows clearly all parts of a typical four-cylinder gasoline
engine of the four-cycle type. It outlines distinctly all parts
liable to give trouble and also details the derangements apt to
interfere with smooth engine operation.

Valuable to students, motorists, mechanics, repairmen,
garagemen, automobile salesmen, chauffeurs, motor-boat owners,
motor-truck and tractor drivers, aviators, motor-cyclists, and
all others who have to do with gasoline power plants.

It simplifies location of all engine troubles, and while it will
prove invaluable to the novice, it can be used to advantage by
the more expert. It should be on the walls of every public and
private garage, automobile repair shop, club house or school. It
can be carried in the automobile or pocket with ease and will
insure against loss of time when engine trouble manifests
itself.

This sectional view of engine is a complete review of all motor
troubles. It is prepared by a practical motorist for all who
motor. No details omitted. Size 25x38 inches. Price =25 cents=

=Lubrication of the Motor Car Chassis.=

=Location of Carburetion Troubles Made Easy.=

This chart shows all parts of a typical pressure feed fuel
supply system and gives causes of trouble, how to locate defects
and means of remedying them. Size 24x38 inches. Price =25 cents=

=Location of Ignition System Troubles Made Easy.=

In this chart all parts of a typical double ignition system
using battery and magneto current are shown and suggestions are
given for readily finding ignition troubles and eliminating them
when found. Size 24x38 inches. Price =25 cents=

=Location of Cooling and Lubrication System Faults.=

This composite chart shows a typical automobile power plant
using pump circulated water-cooling system and the most popular
lubrication method. Gives suggestions for curing all overheating
and loss of power faults due to faulty action of the oiling or
cooling group. Size 24x38 inches. Price =25 Cents=

=Motorcycle Troubles Made Easy--A Chart Showing Sectional View of
Single-Cylinder Gasoline Engine.= Compiled by VICTOR W. PAGÉ, M.S.A.E.

This chart simplifies location of all power-plant troubles, and
will prove invaluable to all who have to do with the operation,
repair or sale of motorcycles. No details omitted. Size 25x38
inches. Price =25 cents=

=Location of Ford Engine Troubles Made Easy.= Compiled by VICTOR W.
PAGÉ, M.S.A.E.

This shows clear sectional views depicting all portions of the
Ford power plant and auxiliary groups. It outlines clearly all
parts of the engine, fuel supply system, ignition group and
cooling system, that are apt to give trouble, detailing all
derangements that are liable to make an engine lose power, start
hard or work irregularly. This chart is valuable to students,
owners, and drivers, as it simplifies location of all engine
faults. Of great advantage as an instructor for the novice, it
can be used equally well by the more expert as a work of
reference and review. It can be carried in the toolbox or pocket
with ease and will save its cost in labor eliminated the first
time engine trouble manifests itself. Prepared with special
reference to the average man's needs and is a practical review
of all motor troubles because it is based on the actual
experience of an automobile engineer-mechanic with the mechanism
the chart describes. It enables the non-technical owner or
operator of a Ford car to locate engine derangements by
systematic search, guided by easily recognized symptoms instead
of by guesswork. It makes the average owner independent of the
roadside repair shop when touring. Must be seen to be
appreciated. Size 25x38 inches. Printed on heavy bond paper.
Price =25 cents=

=Modern Submarine Chart--with Two Hundred Parts Numbered and Named.=

A cross-section view, showing clearly and distinctly all the
interior of a Submarine of the latest type. You get more
information from this chart, about the construction and
operation of a Submarine, than in any other way. No details
omitted--everything is accurate and to scale. It is absolutely
correct in every detail, having been approved by Naval
Engineers. All the machinery and devices fitted in a modern
Submarine Boat are shown, and to make the engraving more readily
understood all the features are shown in operative form, with
Officers and Men in the act of performing the duties assigned to
them in service conditions. This CHART IS REALLY AN ENCYCLOPEDIA
OF A SUBMARINE. It is educational and worth many times its cost.
Mailed in a Tube for =25 Cents=

=Box Car Chart.=

A chart showing the anatomy of a box car, having every part of
the car numbered and its proper name given in a reference list.
Price =25 Cents=

=Gondola Car Chart.=

A chart showing the anatomy of a gondola car, having every part
of the car numbered and its proper reference name given in a
reference list. Price =25 Cents=

=Passenger-Car Chart.=

A chart showing the anatomy of a passenger-car, having every
part of the car numbered and its proper name given in a
reference list =25 Cents=

=Steel Hopper Bottom Coal Car.=

A chart showing the anatomy of a steel Hopper Bottom Coal Car,
having every part of the car numbered and its proper name given
in a reference list. Price =25 Cents=

=Tractive Power Chart.=

A chart whereby you can find the tractive power or drawbar pull
of any locomotive without making a figure. Shows what cylinders
are equal, how driving wheels and steam pressure affect the
power. What sized engine you need to exert a given drawbar pull
or anything you desire in this line. Price =50 Cents=

=Horse-Power Chart.=

Shows the horse-power of any stationary engine without
calculation. No matter what the cylinder diameter of stroke, the
steam pressure of cut-off, the revolutions, or whether
condensing or non-condensing, it's all there. Easy to use,
accurate, and saves time and calculations. Especially useful to
engineers and designers. Price =50 Cents=

=Boiler Room Chart.= By GEO. L. FOWLER.

A chart--size 14x28 inches--showing in isometric perspective the
mechanisms belonging in a modern boiler room. The various parts
are shown broken or removed, so that the internal construction
is fully illustrated. Each part is given a reference number, and
these, with the corresponding name, are given in a glossary
printed at the sides. This chart is really a dictionary of the
boiler room--the names of more than 200 parts being given. Price
=25 Cents=

~COKE~

=Modern Coking Practice, Including Analysis of Materials and Products.=

By J. E. CHRISTOPHER and T. H. BYROM.

This, the standard work on the subject, has just been revised.
It is a practical work for those engaged in Coke manufacture and
the recovery of By-products. Fully illustrated with folding
plates. It has been the aim of the authors, in preparing this
book, to produce one which shall be of use and benefit to those
who are associated with, or interested in, the modern
developments of the industry. Among the Chapters contained in
Volume I are: Introduction; Classification of Fuels; Impurities
of Coals; Coal Washing; Sampling and Valuation of Coals, etc.;
Power of Fuels; History of Coke Manufacture; Developments in the
Coke Oven Design; Recent Types of Coke Ovens; Mechanical
Appliances at Coke Ovens; Chemical and Physical Examination of
Coke. Volume II covers fully the subject of By-Products. Price,
per volume =$3.00 net=

~COMPRESSED AIR~

=Compressed Air in All Its Applications.= By GARDNER D. HISCOX.

This is the most complete book on the subject of Air that has
ever been issued, and its thirty-five chapters include about
every phase of the subject one can think of. It may be called an
encyclopedia of compressed air. It is written by an expert, who,
in its 665 pages, has dealt with the subject in a comprehensive
manner, no phase of it being omitted. Includes the physical
properties of air from a vacuum to its highest pressure, its
thermodynamics, compression, transmission and uses as a motive
power, in the Operation of Stationary and Portable Machinery, in
Mining, Air Tools, Air Lifts, Pumping of Water, Acids, and Oils;
the Air Blast for Cleaning and Painting the Sand Blast and its
Work, and the Numerous Appliances in which Compressed Air is a
Most Convenient and Economical Transmitter of Power for
Mechanical Work, Railway Propulsion, Refrigeration, and the
Various Uses to which Compressed Air has been applied. Includes
forty-four tables of the physical properties of air, its
compression, expansion, and volumes required for various kinds
of work, and a list of patents on compressed air from 1875 to
date. Over 500 illustrations, 5th Edition, revised and enlarged.

Cloth bound. Price =$5.00=

Half Morocco. Price =$6.50=

~CONCRETE~

=Concrete Workers' Reference Books. A Series of Popular Handbooks for
Concrete Users.= Prepared by A. A. HOUGHTON =50 cents=

_The author, in preparing this Series, has not only treated on
the usual types of construction, but explains and illustrates
molds and systems that are not patented, but which are equal in
value and often superior to those restricted by patents. These
molds are very easily and cheaply constructed and embody
simplicity, rapidity of operation, and the most successful
results in the molded concrete. Each of these books is fully
illustrated, and the subjects are exhaustively treated in plain
English._

=Concrete Wall Forms.= By A. A. HOUGHTON.

A new automatic wall clamp is illustrated with working drawings.
Other types of wall forms, clamps, separators, etc., are also
illustrated and explained. (No. 1 of Series) Price =50 cents=

=Concrete Floors and Sidewalks.= By A. A. HOUGHTON.

The molds for molding squares, hexagonal and many other styles
of mosaic floor and sidewalk blocks are fully illustrated and
explained. (No. 2 of Series) Price =50 cents=

=Practical Concrete Silo Construction.= By A. A. HOUGHTON.

Complete working drawings and specifications are given for
several styles of concrete silos, with illustrations of molds
for monolithic and block silos. The tables, data, and
information presented in this book are of the utmost value in
planning and constructing all forms of concrete silos. (No. 3 of
Series) Price =50 cents=

=Molding Concrete Chimneys, Slate and Hoof Tiles.= By A. A. HOUGHTON.

The manufacture of all types of concrete slate and roof tile is
fully treated. Valuable data on all forms of reinforced concrete
roofs are contained within its pages. The construction of
concrete chimneys by block and monolithic systems is fully
illustrated and described. A number of ornamental designs of
chimney construction with molds are shown in this valuable
treatise. (No. 4 of Series.) Price =50 cents=

=Molding and Curing Ornamental Concrete.= By A. A. HOUGHTON.

The proper proportions of cement and aggregates for various
finishes, also the method of thoroughly mixing and placing in
the molds, are fully treated. An exhaustive treatise on this
subject that every concrete worker will find of daily use and
value. (No. 5 of Series.) Price =50 cents=

=Concrete Monuments, Mausoleums and Burial Vaults.= By A. A. HOUGHTON.

The molding of concrete monuments to imitate the most expensive
cut stone is explained in this treatise with working drawings of
easily built molds. Cutting inscriptions and designs are also
fully treated. (No. 6 of Series.) Price =50 cents=

=Molding Concrete Bathtubs, Aquariums and Natatoriums.= By A. A.
HOUGHTON.

Simple molds and instruction are given for molding many styles
of concrete bathtubs, swimming-pools, etc. These molds are
easily built and permit rapid and successful work. (No. 7 of
Series.) Price =50 cents=

=Concrete Bridges, Culverts and Sewers.= By A. A. HOUGHTON.

A number of ornamental concrete bridges with illustrations of
molds are given. A collapsible center or core for bridges,
culverts and sewers is fully illustrated with detailed
instructions for building. (No. 8 of Series.) Price =50 cents=

=Constructing Concrete Porches.= By A. A. HOUGHTON.

A number of designs with working drawings of molds are fully
explained so any one can easily construct different styles of
ornamental concrete porches without the purchase of expensive
molds. (No. 9 of Series.) Price =50 cents=

=Molding Concrete Flower-Pots, Boxes, Jardinieres, Etc.= By A. A.
HOUGHTON.

The molds for producing many original designs of flower-pots,
urns, flower-boxes, jardinieres, etc., are fully illustrated and
explained, so the worker can easily construct and operate same.
(No. 10 of Series.) Price =50 cents=

=Molding Concrete Fountains and Lawn Ornaments.= By A. A. HOUGHTON.

The molding of a number of designs of lawn seats, curbing,
hitching posts, pergolas, sun dials and other forms of
ornamental concrete for the ornamentation of lawns and gardens,
is fully illustrated and described. (No. 11 of Series.) Price
=50 cents=

=Concrete from Sand Molds.= By A. A. HOUGHTON.

A Practical Work treating on a process which has heretofore been
held as a trade secret by the few who possessed it, and which
will successfully mold every and any class of ornamental
concrete work. The process of molding concrete with sand molds
is of the utmost practical value, possessing the manifold
advantages of a low cost of molds, the ease and rapidity of
operation, perfect details to all ornamental designs, density
and increased strength of the concrete, perfect curing of the
work without attention and the easy removal of the molds
regardless of any undercutting the design may have. 192 pages.
Fully illustrated Price =$2.00=

=Ornamental Concrete without Molds.= By A. A. HOUGHTON.

The process for making ornamental concrete without molds has
long been held as a secret, and now, for the first time, this
process is given to the public. The book reveals the secret and
is the only book published which explains a simple, practical
method whereby the concrete worker is enabled, by employing wood
and metal templates of different designs, to mold or model in
concrete any Cornice, Archivolt, Column, Pedestal, Base Cap, Urn
or Pier in a monolithic form--right upon the job. These may be
molded in units or blocks and then built up to suit the
specifications demanded. This work is fully illustrated, with
detailed engravings. Price =$2.00=

=Concrete for the Farm and in the Shop.= By H. COLIN CAMPBELL, C.E.,
E.M.

"Concrete for the Farm and in the Shop" is a new book from cover
to cover, illustrating and describing in plain, simple language
many of the numerous applications of concrete within the range
of the home worker. Among the subjects treated are: Principles
of Reinforcing; Methods of Protecting Concrete so as to Insure
Proper Hardening; Home-made Mixers; Mixing by Hand and Machine;
Form Construction, Described and Illustrated by Drawings and
Photographs; Construction of Concrete Walls and Fences; Concrete
Fence Posts; Concrete Gate Posts; Corner Posts; Clothes Line
Posts; Grape Arbor Posts; Tanks; Troughs; Cisterns; Hog Wallows;
Feeding Floors and Barnyard Pavements; Foundations; Well Curbs
and Platforms; Indoor Floors; Sidewalks; Steps; Concrete Hotbeds
and Cold Frames; Concrete Slab Roofs; Walls for Buildings;
Repairing Leaks in Tanks and Cisterns; and all topics associated
with these subjects as bearing upon securing the best results
from concrete are dwelt upon at sufficient length in plain
every-day English so that the inexperienced person desiring to
undertake a piece of concrete construction can, by following the
directions set forth in this book, secure 100 per cent. success
every time. A number of convenient and practical tables for
estimating quantities, and some practical examples, are also
given. (5x7.) 149 pages. 51 illustrations. Price =75 cents=

=Popular Handbook for Cement and Concrete Users.= By MYRON H. LEWIS.

This is a concise treatise of the principles and methods
employed in the manufacture and use of cement in all classes of
modern works. The author has brought together in this work all
the salient matter of interest to the user of concrete and its
many diversified products. The matter is presented in logical
and systematic order, clearly written, fully illustrated and
free from involved mathematics. Everything of value to the
concrete user is given, including kinds of cement employed in
construction, concrete architecture, inspection and testing,
waterproofing, coloring and painting, rules, tables, working and
cost data. The book comprises thirty-three chapters, as follow:
Introductory. Kinds of Cement and How They are Made. Properties.
Testing and Requirements of Hydraulic Cement. Concrete and Its
Properties. Sand, Broken Stone and Gravel for Concrete. How to
Proportion the Materials. How to Mix and Place Concrete. Forms
of Concrete Construction. The Architectural and Artistic
Possibilities of Concrete. Concrete Residences. Mortars,
Plasters and Stucco, and How to Use Them. The Artistic Treatment
of Concrete Surfaces. Concrete Building Blocks. The Making of
Ornamental Concrete. Concrete Pipes, Fences, Posts, etc.
Essential Features and Advantages of Reenforced Concrete. How to
Design Reenforced Concrete Beams, Slabs and Columns.
Explanations of the Methods and Principles in Designing
Reenforced Concrete, Beams and Slabs. Systems of Reenforcement
Employed. Reenforced Concrete in Factory and General Building
Construction. Concrete in Foundation Work. Concrete Retaining
Walls, Abutments and Bulkheads. Concrete Arches and Arch
Bridges. Concrete Beam and Girder Bridges. Concrete in Sewerage
and Draining Works. Concrete Tanks, Dams and Reservoirs.
Concrete Sidewalks, Curbs and Pavements. Concrete in Railroad
Construction. The Utility of Concrete on the Farm. The
Waterproofing of Concrete Structures. Grout of Liquid Concrete
and Its Use. Inspection of Concrete Work. Cost of Concrete Work.
Some of the special features of the book are: 1.--The Attention
Paid to the Artistic and Architectural Side of Concrete Work.
2.--The Authoritative Treatment of the Problem of Waterproofing
Concrete. 3.--An Excellent Summary of the Rules to be Followed
in Concrete Construction. 4.--The Valuable Cost Data and Useful
Tables given. A valuable Addition to the Library of Every Cement
and Concrete User. Price =$2.50=

WHAT IS SAID OF THIS BOOK:

"The field of Concrete Construction is well covered and the
matter contained is well within the understanding of any
person."--_Engineering-Contracting._

"Should be on the bookshelves of every contractor, engineer, and
architect in the land."--_National Builder._

=Waterproofing Concrete.= By MYRON H. LEWIS.

Modern Methods of Waterproofing Concrete and Other Structures. A
condensed statement of the Principles, Rules, and Precautions to
be Observed in Waterproofing and Dampproofing Structures and
Structural Materials. Paper binding. Illustrated. Price =50
cents=

~DICTIONARIES~

=Aviation Terms, Termes D'Aviation, English-French, French-English.=
Compiled by Lieuts. VICTOR W. PAGÉ, A.S., S.C.U.S.R., and PAUL
MONTARIOL, of the French Flying Corps, on duty on Signal Corps Aviation
School, Mineola, L. I.

The lists contained are confined to essentials, and special
folding plates are included to show all important airplane
parts. The lists are divided in four sections as follows:
1.--Flying Field Terms. 2.--The Airplane. 3.--The Engine.
4.--Tools and Shop Terms.

A complete, well illustrated volume intended to facilitate
conversation between English-speaking and French aviators. A
very valuable book for all who are about to leave for duty
overseas.

Approved for publication by Major W. G. Kilner, S.C., U.S.C.O.
Signal Corps Aviation School, Hazelhurst Field, Mineola, L. I.
This book should be in every Aviator's and Mechanic's Kit for
ready reference. 128 pages, fully illustrated, with detailed
engravings. Price =$1.00=

=Standard Electrical Dictionary.= By T. O'CONOR SLOANE.

~DIES--METAL WORK~

=Dies: Their Construction and Use for the Modern Working of Sheet
Metals.= By J. V. WOODWORTH.

A most useful book, and one which should be in the hands of all
engaged in the press working of metals; treating on the
Designing, Constructing, and Use of Tools, Fixtures and Devices,
together with the manner in which they should be used in the
Power Press, for the cheap and rapid production of the great
variety of sheet-metal articles now in use. It is designed as a
guide to the production of sheet-metal parts at the minimum of
cost with the maximum of output. The hardening and tempering of
Press tools and the classes of work which may be produced to the
best advantage by the use of dies in the power press are fully
treated. Its 515 illustrations show dies, press fixtures and
sheet-metal working devices, the descriptions of which are so
clear and practical that all metal-working mechanics will be
able to understand how to design, construct and use them. Many
of the dies and press fixtures treated were either constructed
by the author or under his supervision. Others were built by
skilful mechanics and are in use in large sheet-metal
establishments and machine shops. 6th Revised and Enlarged
Edition. Price =$3.00=

=Punches, Dies and Tools for Manufacturing in Presses.= By J. V.
WOODWORTH.

This work is a companion volume to the author's elementary work
entitled "Dies: Their Construction and Use." It does not go into
the details of die-making to the extent of the author's previous
book, but gives a comprehensive review of the field of
operations carried on by presses. A large part of the
information given has been drawn from the author's personal
experience. It might well be termed an Encyclopedia of
Die-Making, Punch-Making, Die-Sinking, Sheet-Metal Working, and
Making of Special Tools, Sub-presses, Devices and Mechanical
Combinations for Punching, Cutting, Bending, Forming, Piercing,
Drawing, Compressing and Assembling Sheet-Metal Parts, and also
Articles of other Materials in Machine Tools. 2d Edition. Price
=$4.00=

=Drop Forging, Die-Sinking and Machine-Forming of Steel.= By J. V.
WOODWORTH.

This is a practical treatise on Modern Shop Practice, Processes,
Methods, Machine Tools, and Details treating on the Hot and Cold
Machine-Forming of Steel and Iron into Finished Shapes: together
with Tools, Dies, and Machinery involved in the manufacture of
Duplicate Forgings and Interchangeable Hot and Cold Pressed
Parts from Bar and Sheet Metal. This book fills a demand of long
standing for information regarding drop-forgings, die-sinking
and machine-forming of steel and the shop practice involved, as
it actually exists in the modern drop-forging shop. The
processes of die-sinking and force-making, which are thoroughly
described and illustrated in this admirable work, are rarely to
be found explained in such a clear and concise manner as is here
set forth. The process of die-sinking relates to the engraving
or sinking of the female or lower dies, such as are used for
drop-forgings, hot and cold machine-forging, swedging, and the
press working of metals. The process of force-making relates to
the engraving or raising of the male or upper dies used in
producing the lower dies for the press-forming and
machine-forging of duplicate parts of metal.

In addition to the arts above mentioned the book contains
explicit information regarding the drop-forging and hardening
plants, designs, conditions, equipment, drop hammers, forging
machines, etc., machine forging, hydraulic forging, autogenous
welding and shop practice. The book contains eleven chapters,
and the information contained in these chapters is just what
will prove most valuable to the forged-metal worker. All
operations described in the work are thoroughly illustrated by
means of perspective half-tones and outline sketches of the
machinery employed. 300 detailed illustrations. Price =$2.50=

~DRAWING--SKETCHING PAPER~

=Practical Perspective.= By RICHARDS and COLVIN.

Shows just how to make all kinds of mechanical drawings in the
only practical perspective isometric. Makes everything plain, so
that any mechanic can understand a sketch or drawing in this
way. Saves time in the drawing room, and mistakes in the shops.
Contains practical examples of various classes of work. 4th
Edition. Price =50 cents=

=Linear Perspective Self-Taught.= By HERMAN T. C. KRAUS.

This work gives the theory and practice of linear perspective,
as used in architectural, engineering and mechanical drawings.
Persons taking up the study of the subject by themselves will be
able, by the use of the instruction given, to readily grasp the
subject, and by reasonable practice become good perspective
draftsmen. The arrangement of the book is good; the plate is on
the left-hand, while the descriptive text follows on the
opposite page, so as to be readily referred to. The drawings are
on sufficiently large scale to show the work clearly and are
plainly figured. There is included a self-explanatory chart
which gives all information necessary for the thorough
understanding of perspective. This chart alone is worth many
times over the price of the book. 2d Revised and Enlarged
Edition. Price =$2.50=

=Self-Taught Mechanical Drawing and Elementary Machine Design.= By F. L.
SYLVESTER, M.E., Draftsman, with additions by ERIK OBERG, associate
editor of "Machinery."

This is a practical treatise on Mechanical Drawing and Machine
Design, comprising the first principles of geometric and
mechanical drawing, workshop mathematics, mechanics, strength of
materials and the calculations and design of machine details.
The author's aim has been to adapt this treatise to the
requirements of the practical mechanic and young draftsman and
to present the matter in as clear and concise a manner as
possible. To meet the demands of this class of students,
practically all the important elements of machine design have
been dealt with, and in addition algebraic formulas have been
explained, and the elements of trigonometry treated in the
manner best suited to the needs of the practical man. The book
is divided into 20 chapters, and in arranging the material,
mechanical drawing, pure and simple, has been taken up first, as
a thorough understanding of the principles of representing
objects facilitates the further study of mechanical subjects.
This is followed by the mathematics necessary for the solution
of the problems in machine design which are presented later, and
a practical introduction to theoretical mechanics and the
strength of materials. The various elements entering into
machine design, such as cams, gears, sprocket-wheels, cone
pulleys, bolts, screws, couplings, clutches, shafting and
fly-wheels, have been treated in such a way as to make possible
the use of the work as a text-book for a continuous course of
study. It is easily comprehended and assimilated even by
students of limited previous training. 330 pages, 215
engravings. Price =$2.00=

=A New Sketching Paper.=

A new specially ruled paper to enable you to make sketches or
drawings in isometric perspective without any figuring or
fussing. It is being used for shop details as well as for
assembly drawings, as it makes one sketch do the work of three,
and no workman can help seeing just what is wanted.

Pads of 40 sheets, 6x9 inches. Price =25 cents=
Pads of 40 sheets, 9x12 inches. Price =50 cents=
40 sheets, 12x18 inches. Price =$1.00=

~ELECTRICITY~

=Arithmetic of Electricity.= By Prof. T. O'CONOR SLOANE.

A practical treatise on electrical calculations of all kinds
reduced to a series of rules, all of the simplest forms, and
involving only ordinary arithmetic; each rule illustrated by one
or more practical problems, with detailed solution of each one.
This book is classed among the most useful works published on
the science of electricity, covering as it does the mathematics
of electricity in a manner that will attract the attention of
those who are not familiar with algebraical formulas. 20th
Edition. 160 pages. Price =$1.00=

=Commutator Construction.= By WM. BAXTER, JR.

The business end of any dynamo or motor of the direct current
type is the commutator. This book goes into the designing,
building, and maintenance of commutators, shows how to locate
troubles and how to remedy them; everyone who fusses with
dynamos needs this. 4th Edition. Price =25 cents=

=Dynamo Building for Amateurs, or How to Construct a Fifty-Watt Dynamo.=
By ARTHUR J. WEED, Member of N. Y. Electrical Society.

A practical treatise showing in detail the construction of a
small dynamo or motor, the entire machine work of which can be
done on a small foot lathe. Dimensioned working drawings are
given for each piece of machine work, and each operation is
clearly described. This machine, when used as a dynamo, has an
output of fifty watts; when used as a motor it will drive a
small drill press or lathe. It can be used to drive a sewing
machine on any and all ordinary work. The book is illustrated
with more than sixty original engravings, showing the actual
construction of the different parts. Among the contents are
chapters on: 1. Fifty-Watt Dynamo. 2. Side Bearing Rods. 3.
Field Punching. 4. Bearings. 5. Commutator. 6. Pulley. 7. Brush
Holders. 8. Connection Board. 9. Armature Shaft. 10. Armature.
11. Armature Winding. 12. Field Winding. 13. Connecting and
starting.

Paper. Price =50 Cents=
Cloth. Price =$1.00=

=Electric Bells.= By M. B. SLEEPER.

A complete treatise for the practical worker in Installing,
Operating and Testing Bell Circuits, Burglar Alarms,
Thermostats, and other apparatus used with Electric Bells.

Both the electrician and the experimenter will find in this book
new material which is essential in their work. Tools, bells,
batteries, unusual circuits, burglar alarms, annunciator
systems, thermostats, circuit breakers, time alarms, and other
apparatus used in bell circuits are described from the
standpoints of their application, construction and repair. The
detailed instruction for building the apparatus will appeal to
the experimenter particularly.

The practical worker will find the chapter on Wiring,
Calculation of Wire Sizes and Magnet Winding, Upkeep of Systems,
and the Location of Faults, of the greatest value in their work.
Among the chapters are: Tools and Materials for Bell Work; How
and Why Bell Work; Batteries for Small Installations; Making
Bells and Push Buttons; Wiring Bell Systems; Construction of
Annunciators and Signals; Burglary Alarms and Auxiliary
Apparatus; More Elaborate Bell Systems; Finding Faults and
Remedying Them. 124 pages, fully illustrated. Price =50 cents=

=Electric Lighting and Heating Pocket Book.= By SYDNEY F. WALKER.

This book puts in convenient form useful information regarding
the apparatus which is likely to be attached to the mains of an
electrical company. Tables of units and equivalents are included
and useful electrical laws and formulas are stated. 438 pages,
300 engravings. Bound in leather. Pocket book form. Price
=$3.00=

=Electric Wiring, Diagrams and Switchboards.= By NEWTON HARRISON, with
additions by THOMAS POPPE.

A thoroughly practical treatise covering the subject of Electric
Wiring in all its branches, deluding explanations and diagrams
which are thoroughly explicit and greatly simplify the subject.
Practical every-day problems in wiring are presented and the
method of obtaining intelligent results clearly shown. Only
arithmetic is used. Ohm's law is given a simple explanation with
reference to wiring for direct and alternating currents. The
fundamental principle of drop of potential in circuits is shown
with its various applications. The simple circuit is developed
with the position of mains, feeders and branches; their
treatment as a part of a wiring plan and their employment in
house wiring clearly illustrated. Some simple facts about
testing are included in connection with the wiring. Molding and
conduit work are given careful consideration; and switchboards
are systematically treated, built up and illustrated, showing
the purpose they serve, for connection with the circuits, and to
shunt and compound wound machines. The simple principles of
switchboard construction, the development of the switchboard,
the connections of the various instruments, including the
lightning arrester, are also plainly set forth.

Alternating current wiring is treated, with explanations of the
power factor, conditions calling for various sizes of wire, and
a simple way of obtaining the sizes for single-phase, two-phase
and three-phase circuits. This is the only complete work issued
showing and telling you what you should know about direct and
alternating current wiring. It is a ready reference. The work is
free from advanced technicalities and mathematics, arithmetic
being used throughout. It is in every respect a handy,
well-written, instructive, comprehensive volume on wiring for
the wireman, foreman, contractor, or electrician. 2nd Revised
Edition. 303 pages, 130 illustrations. Price =$1.50=

=Electric Furnaces and their Industrial Applications.= By J. WRIGHT.

This is a book which will prove of interest to many classes of
people: the manufacturer who desires to know what product can be
manufactured successfully in the electric furnace, the chemist
who wishes to post himself on the electro-chemistry, and the
student of science who merely looks into the subject from
curiosity. New, Revised and Enlarged Edition. 320 pages. Fully
illustrated, cloth. Price =$3.00=

=Electric Toy Making, Dynamo Building, and Electric Motor Construction.=
By Prof. T. O'CONOR SLOANE.

This work treats of the making at home of electrical toys,
electrical apparatus, motors, dynamos, and instruments in
general, and is designed to bring within the reach of young and
old the manufacture of genuine and useful electrical appliances.
The work is especially designed for amateurs and young folks.

Thousands of our young people are daily experimenting, and
busily engaged in making electrical toys and apparatus of
various kinds. The present work is just what is wanted to give
the much needed information in a plain, practical manner, with
illustrations to make easy the carrying out of the work. 20th
Edition. Price =$1.00=

=Practical Electricity.= By Prof. T. O'CONOR SLOANE.

This work of 768 pages was previously known as Sloane's
Electricians' Hand Book, and is intended for the practical
electrician who has to make things go. The entire field of
electricity is covered within its pages. Among some of the
subjects treated are: The Theory of the Electric Current and
Circuit, Electro-Chemistry, Primary Batteries, Storage
Batteries, Generation and Utilization of Electric Powers,
Alternating Current, Armature Winding, Dynamos and Motors, Motor
Generators, Operation of the Central Station Switchboards,
Safety Appliances, Distribution of Electric Light and Power,
Street Mains, Transformers, Arc and Incandescent Lighting,
Electric Measurements, Photometry, Electric Railways, Telephony,
Bell-Wiring, Electric-Plating, Electric Heating, Wireless
Telegraphy, etc. It contains no useless theory; everything is to
the point. It teaches you just what you want to know about
electricity. It is the standard work published on the subject.
Forty-one chapters, 556 engravings. Price =$2.50=

=Electricity Simplified.= By Prof. T. O'CONOR SLOANE.

The object of "Electricity Simplified" is to make the subject as
plain as possible and to show what the modern conception of
electricity is; to show how two plates of different metal,
immersed in acid, can send a message around the globe; to
explain how a bundle of copper wire rotated by a steam engine
can be the agent in lighting our streets; to tell what the volt,
ohm and ampere are, and what high and low tension mean; and to
answer the questions that perpetually arise in the mind in this
age of electricity. 13th Edition. 172 pages. Illustrated. Price
=$1.00=

=House Wiring.= By THOMAS W. POPPE.

This work describes and illustrates the actual installation of
Electric Light Wiring, the manner in which the work should be
done, and the method of doing it. The book can be conveniently
carried in the pocket. It is intended for the Electrician,
Helper and Apprentice. It solves all Wiring Problems and
contains nothing that conflicts with the rulings of the National
Board of Fire Underwriters. It gives just the information
essential to the Successful Wiring of a Building. Among the
subjects treated are: Locating the Meter. Panel-Boards.
Switches. Plug Receptacles. Brackets. Ceiling Fixtures. The
Meter Connections. The Feed Wires. The Steel Armored Cable
System. The Flexible Steel Conduit System. The Ridig Conduit
System. A digest of the National Board of Fire Underwriters'
rules relating to metallic wiring systems. Various switching
arrangements explained and diagrammed. The easiest method of
testing the Three- and Four-way circuits explained. The
grounding of all metallic wiring systems and the reason for
doing so shown and explained. The insulation of the metal parts
of lamp fixtures and the reason for the same described and
illustrated. 125 pages. 2nd Edition, revised and enlarged. Fully
illustrated. Flexible cloth. Price =50 cents=

=How to Become a Successful Electrician.= By Prof. T. O'CONOR SLOANE.

Every young man who wishes to become a successful electrician
should read this book. It tells in simple language the surest
and easiest way to become a successful electrician. The studies
to be followed, methods of work, field of operation and the
requirements of the successful electrician are pointed out and
fully explained. Every young engineer will find this an
excellent stepping stone to more advanced works on electricity
which he must master before success can be attained. Many young
men become discouraged at the very outstart by attempting to
read and study books that are far beyond their comprehension.
This book serves as the connecting link between the rudiments
taught in the public schools and the real study of electricity.
It is interesting from cover to cover. 18th Revised Edition,
just issued. 205 pages. Illustrated. Price =$1.00=

=Management of Dynamos.= By LUMMIS-PATERSON.

A handbook of theory and practice. This work is arranged in
three parts. The first part covers the elementary theory of the
dynamo. The second part, the construction and action of the
different classes of dynamos in common use are described; while
the third part relates to such matters as affect the practical
management and working of dynamos and motors. 4th Edition. 292
pages, 117 illustrations. Price =$1.50=

=Standard Electrical Dictionary.= By T. O'CONOR SLOANE.

An indispensable work to all interested in electrical science.
Suitable alike for the student and professional. A practical
handbook of reference containing definitions of about 5,000
distinct words, terms and phrases. The definitions are terse and
concise and include every term used in electrical science.
Recently issued. An entirely new edition. Should be in the
possession of all who desire to keep abreast with the progress
of this branch of science. In its arrangement and typography the
book is very convenient. The word or term defined is printed in
black-faced type, which readily catches the eye, while the body
of the page is in smaller but distinct type. The definitions are
well worded, and so as to be understood by the non-technical
reader. The general plan seems to be to give an exact, concise
definition, and then amplify and explain in a more popular way.
Synonyms are also given, and references to other words and
phrases are made. A very complete and accurate index of fifty
pages is at the end of the volume; and as this index contains
all synonyms, and as all phrases are indexed in every reasonable
combination of words, reference to the proper place in the body
of the book is readily made. It is difficult to decide how far a
book of this character is to keep the dictionary form, and to
what extent it may assume the encyclopedia form. For some
purposes, concise, exactly worded definitions are needed; for
other purposes, more extended descriptions are required. This
book seeks to satisfy both demands, and does it with
considerable success. 682 pages, 393 illustrations. 12th
Edition. Price =$3.00=

=Storage Batteries Simplified.= By VICTOR W. PAGÉ, M.E.

A complete treatise on storage battery operating principles,
repairs and applications. The greatly increasing application of
storage batteries in modern engineering and mechanical work has
created a demand for a book that will consider this subject
completely and exclusively. This is the most thorough and
authoritative treatise ever published on this subject. It is
written in easily understandable, non-technical language so that
any one may grasp the basic principles of storage battery action
as well as their practical industrial applications. All electric
and gasoline automobiles use storage batteries. Every automobile
repairman, dealer or salesman should have a good knowledge of
maintenance and repair of these important elements of the motor
car mechanism. This book not only tells how to charge, care for
and rebuild storage batteries but also outlines all the
industrial uses. Learn how they run street cars, locomotives and
factory trucks. Get an understanding of the important functions
they perform in submarine boats, isolated lighting plants,
railway switch and signal systems, marine applications, etc.
This book tells how they are used in central station standby
service, for starting automobile motors and in ignition systems.
Every practical use of the modern storage battery is outlined in
this treatise. 320 pages, fully illustrated. Price =$1.50=

=Switchboards.= By WILLIAM BAXTER, JR.

This book appeals to every engineer and electrician who wants to
know the practical side of things. It takes up all sorts and
conditions of dynamos, connections and circuits, and shows by
diagram and illustration just how the switchboard should be
connected. Includes direct and alternating current boards, also
those for arc lighting, incandescent and power circuits. Special
treatment on high voltage boards for power transmission. 2nd
Edition. 190 pages, Illustrated. Price =$1.50=

=Telephone Construction, Installation, Wiring, Operation and
Maintenance.= By W. H. RADCLIFFE and H. C. CUSHING.

This book is intended for the amateur, the wireman, or the
engineer who desires to establish a means of telephonic
communication between the rooms of his home, office, or shop. It
deals only with such things as may be of use to him rather than
with theories.

Gives the principles of construction and operation of both the
Bell and Independent instruments; approved methods of installing
and wiring them; the means of protecting them from lightning and
abnormal currents; their connection together for operation as
series or bridging stations; and rules for their inspection and
maintenance. Line wiring and the wiring and operation of special
telephone systems are also treated. Intricate mathematics are
avoided, and all apparatus, circuits and systems are thoroughly
described. The appendix contains definitions of units and terms
used in the text. Selected wiring tables, which are very
helpful, are also included. Among the subjects treated are
Construction, Operation, and Installation of Telephone
Instruments; Inspection and Maintenance of Telephone
Instruments; Telephone Line Wiring; Testing Telephone Line Wires
and Cables; Wiring and Operation of Special Telephone Systems,
etc. 2nd Edition, Revised and Enlarged. 223 pages, 154
illustrations. Price =$1.00=

=Wireless Telegraphy and Telephony Simply Explained.= By ALFRED P.
MORGAN.

This is undoubtedly one of the most complete and comprehensible
treatises on the subject ever published, and a close study of
its pages will enable one to master all the details of the
wireless transmission of messages. The author has filled a
long-felt want and has succeeded in furnishing a lucid,
comprehensible explanation in simple language of the theory and
practice of wireless telegraphy and telephony.

Among the contents are: Introductory; Wireless Transmission and
Reception--The Aerial System, Earth Connections--The
Transmitting Apparatus, Spark Coils and Transformers,
Condensers, Helixes, Spark Gaps, Anchor Gaps, Aerial
Switches--The Receiving Apparatus, Detectors, etc.--Tuning and
Coupling, Tuning Coils, Loose Couplers, Variable Condensers,
Directive Wave Systems--Miscellaneous Apparatus, Telephone
Receivers, Range of Stations, Static Interference--Wireless
Telephones, Sound and Sound Waves, The Vocal Cords and
Ear--Wireless Telephone, How Sounds Are Changed into Electric
Waves--Wireless Telephones, The Apparatus--Summary. 154 pages,
156 engravings. Price =$1.00=

=Wiring a House.= By HERBERT PRATT.

Shows a house already built; tells just how to start about
wiring it; where to begin; what wire to use; how to run it
according to Insurance Rules; in fact, just the information you
need. Directions apply equally to a shop. 4th Edition. Price =25
cents=

~FACTORY MANAGEMENT, ETC.~

=Modern Machine Shop Construction, Equipment and Management.= By O. E.
PERRIGO, M.E.

The only work published that describes the modern machine shop
or manufacturing plant from the time the grass is growing on the
site intended for it until the finished product is shipped. By a
careful study of its thirty-two chapters the practical man may
economically build, efficiently equip, and successfully manage
the modern machine shop or manufacturing establishment. Just the
book needed by those contemplating the erection of modern shop
buildings, the rebuilding and reorganization of old ones, or the
introduction of modern shop methods, time and cost systems. It
is a book written and illustrated by a practical shop man for
practical shop men who are too busy to read _theories_ and want
_facts_. It is the most complete all-around book of its kind
ever published. It is a practical book for practical men, from
the apprentice in the shop to the president in the office. It
minutely describes and illustrates the most simple and yet the
most efficient time and cost system yet devised. 2nd Revised and
Enlarged Edition, just issued. 384 pages, 219 illustrations.
Price =$5.00=

~FUEL~

=Combustion of Coal and the Prevention of Smoke.= By WM. M. BARR.

This book has been prepared with special reference to the
generation of heat by the combustion of the common fuels found
in the United States, and deals particularly with the conditions
necessary to the economic and smokeless combustion of bituminous
coals in Stationary and Locomotive Steam Boilers.

The presentation of this important subject is systematic and
progressive. The arrangement of the book is in a series of
practical questions to which are appended accurate answers,
which describe in language, free from technicalities, the
several processes involved in the furnace combustion of American
fuels; it clearly states the essential requisites for perfect
combustion, and points out the best methods for furnace
construction for obtaining the greatest quantity of heat from
any given quality of coal. Nearly 350 pages, fully illustrated.
Price =$1.00=

=Smoke Prevention and Fuel Economy.= By BOOTH and KERSHAW.

A complete treatise for all interested in smoke prevention and
combustion, being based on the German work of Ernst Schmatolla,
but it is more than a mere translation of the German treatise,
much being added. The authors show as briefly as possible the
principles of fuel combustion, the methods which have been and
are at present in use, as well as the proper scientific methods
for obtaining all the energy in the coal and burning it without
smoke. Considerable space is also given to the examination of
the waste gases, and several of the representative English and
American mechanical stoker and similar appliances are described.
The losses carried away in the waste gases are thoroughly
analyzed and discussed in the Appendix, and abstracts are also
here given of various patents on combustion apparatus. The book
is complete and contains much of value to all who have charge of
large plants. 194 pages. Illustrated. Price =$2.50=

~GAS ENGINES AND GAS~

=Gas, Gasoline and Oil Engines.= By GARDNER D. HISCOX. Revised by VICTOR
W. PAGÉ, M.E.

Just issued New 1918 Edition, Revised and Enlarged. Every user
of a gas engine needs this book. Simple, instructive and right
up-to-date. The only complete work on the subject. Tells all
about internal combustion engineering, treating exhaustively on
the design, construction and practical application of all forms
of gas, gasoline, kerosene and crude petroleum-oil engines.
Describes minutely all auxiliary systems, such as lubrication,
carburetion and ignition. Considers the theory and management of
all forms of explosive motors for stationary and marine work,
automobiles, aeroplanes and motor-cycles. Includes also Producer
Gas and Its Production. Invaluable instructions for all
students, gas-engine owners, gas-engineers, patent experts,
designers, mechanics, draftsmen and all having to do with the
modern power. Illustrated by over 400 engravings, many specially
made from engineering drawings, all in correct proportion. 650
pages, 435 engravings. Price =$2.50 net=

=The Gasoline Engine on the Farm: Its Operation, Repair and Uses.= By
XENO W. PUTNAM.

This is a practical treatise on the Gasoline and Kerosene Engine
intended for the man who wants to know just how to manage his
engine and how to apply it to all kinds of farm work to the best
advantage.

This book abounds with hints and helps for the farm and
suggestions for the home and house-wife. There is so much of
value in this book that it is impossible to adequately describe
it in such small space. Suffice to say that it is the kind of a
book every farmer will appreciate and every farm home ought to
have. Includes selecting the most suitable engine for farm work,
its most convenient and efficient installation, with chapters on
troubles, their remedies, and how to avoid them. The care and
management of the farm tractor in plowing, harrowing, harvesting
and road grading are fully covered; also plain directions are
given for handling the tractor on the road. Special attention is
given to relieving farm life of its drudgery by applying power
to the disagreeable small tasks which must otherwise be done by
hand. Many home made contrivances for cutting wood, supplying
kitchen, garden, and barn with water, loading, hauling and
unloading hay, delivering grain to the bins or the feed trough
are included; also full directions for making the engine milk
the cows, churn, wash, sweep the house and clean the windows,
etc. Very fully illustrated with drawings of working parts and
cuts showing Stationary, Portable and Tractor Engines doing all
kinds of farm work. All money-making farms utilize power. Learn
how to utilize power by reading the pages of this book. It is an
aid to the result getter, invaluable to the up-to-date farmer,
student, blacksmith, implement dealer and, in fact, all who can
apply practical knowledge of stationary gasoline engines or gas
tractors to advantage. 530 pages. Nearly 180 engravings. Price
=$2.00=

WHAT IS SAID OF THIS BOOK:

"Am much pleased with the book and find it to be very complete
and up-to-date. I will heartily recommend it to students and
farmers whom I think would stand in need of such a work, as I
think it is an exceptionally good one."--_N. S. Gardiner_, Prof.
in Charge, Clemson Agr. College of S. C.; Dept. of Agri. and
Agri. Exp. Station, Clemson College, S. C.

"I feel that Mr. Putnam's book covers the main points which a
farmer should know."--_R. T. Burdick_, Instructor in Agronomy,
University of Vermont, Burlington, Vt.

=Gasoline Engines: Their Operation, Use and Care.= By A. HYATT VERRILL.

The simplest, latest and most comprehensive popular work
published on Gasoline Engines, describing what the Gasoline
Engine is; its construction and operation; how to install it;
how to select it; how to use it and how to remedy troubles
encountered. Intended for Owners, Operators and Users of
Gasoline Motors of all kinds. This work fully describes and
illustrates the various types of Gasoline Engines used in Motor
Boats, Motor Vehicles and Stationary Work. The parts,
accessories and appliances are described with chapters on
ignition, fuel, lubrication, operation and engine troubles.
Special attention is given to the care, operation and repair of
motors, with useful hints and suggestions on emergency repairs
and makeshifts. A complete glossary of technical terms and an
alphabetically arranged table of troubles and their symptoms
form most valuable and unique features of this manual. Nearly
every illustration in the book is original, having been made by
the author. Every page is full of interest and value. A book
which you cannot afford to be without. 275 pages, 152 specially
made engravings. Price =$1.50=

=Gas Engine Construction, or How to Build a Half-horsepower Gas Engine.=
By PARSELL and WEED.

A practical treatise of 300 pages describing the theory and
principles of the action of Gas Engines of various types and the
design and construction of a half-horsepower Gas Engine, with
illustrations of the work in actual progress, together with the
dimensioned working drawings, giving clearly the sizes of the
various details; for the student, the scientific investigator,
and the amateur mechanic. This book treats of the subject more
from the standpoint of practice than that of theory. The
principles of operation of Gas Engines are clearly and simply
described, and then the actual construction of a half-horsepower
engine is taken up, step by step, showing in detail the making
of the Gas Engine. 3rd Edition. 300 pages. Price =$2.50=

=How to Run and Install Two- and Four-Cycle Marine Gasoline Engines.= By
C. VON CULIN.

Revised and enlarged edition just issued. The object of this
little book is to furnish a pocket instructor for the beginner,
the busy man who uses an engine for pleasure or profit, but who
does not have the time or inclination for a technical book, but
simply to thoroughly understand how to properly operate, install
and care for his own engine. The index refers to each trouble,
remedy, and subject alphabetically. Being a quick reference to
find the cause, remedy and prevention for troubles, and to
become an expert with his own engine. Pocket size. Paper
binding. Price =25 cents=

=Modern Gas Engines and Producer Gas Plants.= By R. E. MATHOT.

A guide for the gas engine designer, user, and engineer in the
construction, selection, purchase, installation, operation, and
maintenance of gas engines. More than one book on gas engines
has been written, but not one has thus far even encroached on
the field covered by this book. Above all, Mr. Mathot's work is
a practical guide. Recognizing the need of a volume that would
assist the gas engine user in understanding thoroughly the motor
upon which he depends for power, the author has discussed his
subject without the help of any mathematics and without
elaborate theoretical explanations. Every part of the gas engine
is described in detail, tersely, clearly, with a thorough
understanding of the requirements of the mechanic. Helpful
suggestions as to the purchase of an engine, its installation,
care, and operation, form a most valuable feature of the work.
320 pages, 175 detailed illustrations. Price =$2.50=

=The Modern Gas Tractor.= By VICTOR W. PAGÉ, M. E.

A complete treatise describing all types and sizes of gasoline,
kerosene and oil tractors. Considers design and construction
exhaustively, gives complete instructions for care, operation
and repair, outlines all practical applications on the road and
in the field. The best and latest work on farm tractors and
tractor power plants. A work needed by farmers, students,
blacksmiths, mechanics, salesmen, implement dealers, designers
and engineers. 2nd Edition, Revised. 504 pages, 228
illustrations, 3 folding plates. Price =$2.00=

~GEARING AND CAMS~

=Bevel Gear Tables.= By D. AG. ENGSTROM.

A book that will at once commend itself to mechanics and
draftsmen. Does away with all the trigonometry and fancy
figuring on bevel gears, and makes it easy for anyone to lay
them out or make them just right. There are 36 full-page tables
that show every necessary dimension for all sizes or
combinations you're apt to need. No puzzling, figuring or
guessing. Gives placing distance, all the angles (including
cutting angles), and the correct cutter to use. A copy of this
prepares you for anything in the bevel-gear line. 3rd Edition.
66 pages. Price =$1.00=

=Change Gear Devices.= By OSCAR E. PERRIGO.

A practical book for every designer, draftsman, and mechanic
interested in the invention and development of the devices for
feed changes on the different machines requiring such mechanism.
All the necessary information on this subject is taken up,
analyzed, classified, sifted, and concentrated for the use of
busy men who have not the time to go through the masses of
irrelevant matter with which such a subject is usually
encumbered and select such information as will be useful to
them.

It shows just what has been done, how it has been done, when it
was done, and who did it. It saves time in hunting up patent
records and re-inventing old ideas. 88 pages. 3rd Edition. Price
=$1.00=

=Drafting of Cams.= By LOUIS ROUILLION.

The laying out of cams is a serious problem unless you know how
to go at it right. This puts you on the right road for
practically any kind of cam you are likely to run up against.
3rd Edition. Price =25 Cents=

~HYDRAULICS~

=Hydraulic Engineering.= By GARDNER D. HISCOX.

A treatise on the properties, power, and resources of water for
all purposes. Including the measurement of streams, the flow of
water in pipes or conduits; the horsepower of falling water,
turbine and impact water-wheels, wave motors, centrifugal,
reciprocating and air-lift pumps. With 300 figures and diagrams
and 36 practical tables. All who are interested in water-works
development will find this book a useful one, because it is an
entirely practical treatise upon a subject of present importance
and cannot fail in having a far-reaching influence, and for this
reason should have a place in the working library of every
engineer. Among the subjects treated are: Historical Hydraulics;
Properties of Water; Measurement of the Flow of Streams; Flow
from Sub-surface Orifices and Nozzles; Flow of Water in Pipes;
Siphons of Various Kinds; Dams and Great Storage Reservoirs;
City and Town Water Supply; Wells and Their Reinforcement;
Air-lift Methods of Raising Water; Artesian Wells; Irrigation of
Arid Districts; Water Power; Water Wheels; Pumps and Pumping
Machinery; Reciprocating Pumps; Hydraulic Power Transmission;
Hydraulic Mining; Canals; Ditches; Conduits and Pipe Lines;
Marine Hydraulics; Tidal and Sea Wave Power, etc. 320 pages.
Price =$4.00=

~ICE AND REFRIGERATION~

=Pocketbook of Refrigeration and Ice Making.= By A. J. WALLIS-TAYLOR.

This is one of the latest and most comprehensive reference books
published on the subject of refrigeration and cold storage. It
explains the properties and refrigerating effect of the
different fluids in use, the management of refrigerating
machinery and the construction and insulation of cold rooms with
their required pipe surface for different degrees of cold;
freezing mixtures and non-freezing brines, temperatures of cold
rooms for all kinds of provisions, cold storage charges for all
classes of goods, ice making and storage of ice, data and
memoranda for constant reference by refrigerating engineers,
with nearly one hundred tables containing valuable references to
every fact and condition required in the installment and
operation of a refrigerating plant. New edition just published.
Price =$1.50=

~INVENTIONS--PATENTS~

=Inventors' Manual: How to Make a Patent Pay.=

This is a book designed as a guide to inventors in perfecting
their inventions, taking out their patents and disposing of
them. It is not in any sense a Patent Solicitor's Circular nor a
Patent Broker's Advertisement. No advertisements of any
description appear in the work. It is a book containing a
quarter of a century's experience of a successful inventor,
together with notes based upon the experience of many other
inventors.

Among the subjects treated in this work are: How to Invent. How
to Secure a Good Patent. Value of Good Invention. How to Exhibit
an Invention. How to Interest Capital. How to Estimate the Value
of a Patent. Value of Design Patents. Value of Foreign Patents.
Value of Small Inventions. Advice on Selling Patents. Advice on
the Formation of Stock Companies. Advice on the Formation of
Limited Liability Companies. Advice on Disposing of Old Patents.
Advice as to Patent Attorneys. Advice as to Selling Agents.
Forms of Assignments. License and Contracts. State Laws
Concerning Patent Rights. 1900 Census of the United States by
Counts of Over 10,000 Population. Revised Edition. 120 pages.
Price =$1.00=

~KNOTS~

=Knots, Splices and Rope Work.= By A. HYATT VERRILL.

This is a practical book giving complete and simple directions
for making all the most useful and ornamental knots in common
use, with chapters on Splicing, Pointing, Seizing, Serving, etc.
This book is fully illustrated with 154 original engravings,
which show how each knot, tie or splice is formed, and its
appearance when finished. The book will be found of the greatest
value to Campers, Yachtsmen, Travelers, Boy Scouts, in fact, to
anyone having occasion to use or handle rope or knots for any
purpose. The book is thoroughly reliable and practical, and is
not only a guide, but a teacher. It is the standard work on the
subject. Among the contents are: 1. Cordage, Kinds of Rope.
Construction of Rope, Parts of Rope Cable and Bolt Rope.
Strength of Rope, Weight of Rope. 2. Simple Knots and Bends.
Terms Used in Handling Rope. Seizing Rope. 3. Ties and Hitches.
4. Noose, Loops and Mooring Knots. 5. Shortenings, Grommets and
Salvages. 6. Lashings, Seizings and Splices. 7. Fancy Knots and
Rope Work. 128 pages, 150 original engravings. 2nd Revised
Edition. Price =75 cents=

~LATHE WORK~

=Lathe Design, Construction, and Operation, with Practical Examples of
Lathe Work.= By OSCAR E. PERRIGO.

A new, revised edition, and the only complete American work on
the subject, written by a man who knows not only how work ought
to be done, but who also knows how to do it, and how to convey
this knowledge to others. It is strictly up-to-date in its
descriptions and illustrations. Lathe history and the relations
of the lathe to manufacturing are given; also a description of
the various devices for feeds and thread-cutting mechanisms from
early efforts in this direction to the present time. Lathe
design is thoroughly discussed, including back gearing, driving
cones, thread-cutting gears, and all the essential elements of
the modern lathe. The classification of lathes is taken up,
giving the essential differences of the several types of lathes
including, as is usually understood, engine lathes, bench
lathes, speed lathes, forge lathes, gap lathes, pulley lathes,
forming lathes, multiple-spindle lathes, rapid-reduction lathes,
precision lathes, turret lathes, special lathes, electrically
driven lathes, etc. In addition to the complete exposition on
construction and design, much practical matter on lathe
installation, care and operation has been incorporated in the
enlarged new edition. All kinds of lathe attachments for
drilling, milling, etc., are described and complete instructions
are given to enable the novice machinist to grasp the art of
lathe operation as well as the principles involved in design. A
number of difficult machining operations are described at length
and illustrated. The new edition has nearly 500 pages and 350
illustrations. Price =$2.50=

WHAT IS SAID OF THIS BOOK:

"This is a lathe book from beginning to end, and is just the
kind of a book which one delights to consult--a masterly
treatment of the subject in hand."--_Engineering News._

"This work will be of exceptional interest to any one who is
interested in lathe practice, as one very seldom sees such a
complete treatise on a subject as this is on the
lathe."--_Canadian Machinery._

=Practical Metal Turning.= By JOSEPH G. HORNER.

A work of 404 pages, fully illustrated, covering in a
comprehensive manner the modern practice of machining metal
parts in the lathe, including the regular engine lathe, its
essential design, its uses, its tools, its attachments, and the
manner of holding the work and performing the operations. The
modernized engine lathe, its methods, tools and great range of
accurate work. The turret lathe, its tools, accessories and
methods of performing its functions. Chapters on special work,
grinding, tool holders, speeds, feeds, modern tool steels, etc.
Second edition =$3.50=

=Turning and Boring Tapers.= By FRED H. COLVIN.

There are two ways to turn tapers; the right way and one other.
This treatise has to do with the right way; it tells you how to
start the work properly, how to set the lathe, what tools to use
and how to use them, and forty and one other little things that
you should know. Fourth edition =25 cents=

~LIQUID AIR~

=Liquid Air and the Liquefaction of Gases.= By T. O'CONOR SLOANE.

This book gives the history of the theory, discovery and
manufacture of Liquid Air, and contains an illustrated
description of all the experiments that have excited the wonder
of audiences all over the country. It shows how liquid air, like
water, is carried hundreds of miles and is handled in open
buckets. It tells what may be expected from it in the near
future.

A book that renders simple one of the most perplexing chemical
problems of the century. Startling developments illustrated by
actual experiments.

It is not only a work of scientific interest and authority, but
is intended for the general reader, being written in a popular
style--easily understood by every one. Second edition. 365
pages. Price =$2.00=

~LOCOMOTIVE ENGINEERING~

=Air-Brake Catechism.= By ROBERT H. BLACKALL.

This book is a standard text-book. It covers the Westinghouse
Air-Brake Equipment, including the No. 5 and the No. 6 E.-T.
Locomotive Brake Equipment; the K (Quick Service) Triple Valve
for Freight Service; and the Cross-Compound Pump. The operation
of all parts of the apparatus is explained in detail, and a
practical way of finding their peculiarities and defects, with a
proper remedy, is given. It contains 2,000 questions with their
answers, which will enable any railroad man to pass any
examination on the subject of Air Brakes. Endorsed and used by
air-brake instructors and examiners on nearly every railroad in
the United States. Twenty-sixth edition. 411 pages, fully
illustrated with colored plates and diagrams. Price =$2.00=

=American Compound Locomotives.= By FRED H. COLVIN.

The only book on compounds for the engineman or shopman that
shows in a plain, practical way the various features of compound
locomotives in use. Shows how they are made, what to do when
they break down or balk. Contains sections as follows: A Bit of
History. Theory of Compounding Steam Cylinders. Baldwin
Two-Cylinder Compound. Pittsburg Two-Cylinder Compound. Rhode
Island Compound. Richmond Compound. Rogers Compound. Schenectady
Two-Cylinder Compound. Vauclain Compound. Tandem Compounds.
Baldwin Tandem. The Colvin-Wightman Tandem. Schenectady Tandem.
Balanced Locomotives. Baldwin Balanced Compound. Plans for
Balancing. Locating Blows. Breakdowns. Reducing Valves.
Drifting. Valve Motion. Disconnecting. Power of Compound
Locomotives. Practical Notes.

Fully illustrated and containing ten special "Duotone" inserts
on heavy Plate Paper, showing different types of Compounds. 142
pages. Price =$1.00=

=Application of Highly Superheated Steam to Locomotives.= By ROBERT
GARBE.

A practical book which cannot be recommended too highly to those
motive-power men who are anxious to maintain the highest
efficiency in their locomotives. Contains special chapters on
Generation of Highly Superheated Steam; Superheated Steam and
the Two-Cylinder Simple Engine; Compounding and Superheating;
Designs of Locomotive Superheaters; Constructive Details of
Locomotives Using Highly Superheated Steam. Experimental and
Working Results. Illustrated with folding plates and tables.
Cloth. Price =$2.50=

=Combustion of Coal and the Prevention of Smoke.= By WM. M. BARR.

This book has been prepared with special reference to the
generation of heat by the combustion of the common fuels found
in the United States and deals particularly with the conditions
necessary to the economic and smokeless combustion of bituminous
coal in Stationary and Locomotive Steam Boilers.

Presentation of this important subject is systematic and
progressive. The arrangement of the book is in a series of
practical questions to which are appended accurate answers,
which describe in language free from technicalities the several
processes involved in the furnace combustion of American fuels;
it clearly states the essential requisites for perfect
combustion, and points out the best methods of furnace
construction for obtaining the greatest quantity of heat from
any given quality of coal. Nearly 350 pages, fully illustrated.
Price =$1.00=

=Diary of a Round-House Foreman.= By T. S. REILLY.

This is the greatest book of railroad experiences ever
published. Containing a fund of information and suggestions
along the line of handling men, organizing, etc., that one
cannot afford to miss. 176 pages. Price =$1.00=

=Link Motions, Valves and Valve Setting.= By FRED H. COLVIN, Associate
Editor of "American Machinist."

A handy book for the engineer or machinist that clears up the
mysteries of valve setting. Shows the different valve gears in
use, how they work, and why. Piston and slide valves of
different types are illustrated and explained. A book that every
railroad man in the motive-power department ought to have.
Contains chapters on Locomotive Link Motion, Valve Movements,
Setting Slide Valves, Analysis by Diagrams, Modern Practice,
Slip of Block, Slice Valves, Piston Valves, Setting Piston
Valves, Joy-Allen Valve Gear, Walschaert Valve Gear, Gooch Valve
Gear, Alfree-Hubbell Valve Gear, etc., etc. Fully illustrated.
Price =50 cents=

=Locomotive Boiler Construction.= By FRANK A. KLEINHANS.

The construction of boilers in general is treated and, following
this, the locomotive boiler is taken up in the order in which
its various parts go through the shop. Shows all types of
boilers used; gives details of construction; practical facts,
such as life of riveting, punches and dies; work done per day,
allowance for bending and flanging sheets and other data.
Including the recent Locomotive Boiler Inspection Laws and
Examination Questions with their answers for Government
Inspectors. Contains chapters on Laying-Out Work; Flanging and
Forging; Punching; Shearing; Plate Planing; General Tables;
Finishing Parts; Bending; Machinery Parts; Riveting; Boiler
Details; Smoke-Box Details; Assembling and Calking; Boiler-Shop
Machinery, etc., etc.

There isn't a man who has anything to do with boiler work,
either new or repair work, who doesn't need this book. The
manufacturer, superintendent, foreman and boiler worker--all
need it. No matter what the type of boiler, you'll find a mint
of information that you wouldn't be without. Over 400 pages,
five large folding plates. Price =$3.00=

=Locomotive Breakdowns and their Remedies.= By GEO. L. FOWLER. Revised
by WM. W. WOOD, Air-Brake Instructor. Just issued. Revised pocket
edition.

It is out of the question to try and tell you about every
subject that is covered in this pocket edition of Locomotive
Breakdowns. Just imagine all the common troubles that an
engineer may expect to happen some time, and then add all of the
unexpected ones, troubles that could occur, but that you have
never thought about, and you will find that they are all treated
with the very best methods of repair. Walschaert Locomotive
Valve Gear Troubles, Electric Headlight Troubles, as well as
Questions and Answers on the Air Brake are all included. 312
pages. 8th Revised Edition. Fully illustrated. Price =$1.00=

=Locomotive Catechism.= By ROBERT GRIMSHAW.

The revised edition of "Locomotive Catechism," by Robert
Grimshaw, is a New Book from Cover to Cover. It contains twice
as many pages and double the number of illustrations of previous
editions. Includes the greatest amount of practical information
ever published on the construction and management of modern
locomotives. Specially Prepared Chapters on the Walschaert
Locomotive Valve Gear, the Air-Brake Equipment and the Electric
Headlight are given.

It commends itself at once to every Engineer and Fireman, and to
all who are going in for examination or promotion. In plain
language, with full, complete answers, not only all the
questions asked by the examining engineer are given, but those
which the young and less experienced would ask the veteran, and
which old hands ask as "stickers." It is a veritable
Encyclopedia of the Locomotive, is entirely free from
mathematics, easily understood and thoroughly up to date.
Contains over 4,000 Examination Questions with their Answers.
825 pages, 437 illustrations, and 3 folding plates. 28th Revised
Edition. Price =$2.50=

=Practical Instructor and Reference Book for Locomotive Firemen and
Engineers.= By CHAS. F. LOCKHART.

An entirely new book on the Locomotive. It appeals to every
railroad man, as it tells him how things are done and the right
way to do them. Written by a man who has had years of practical
experience in locomotive shops and on the road firing and
running. The information given in this book cannot be found in
any other similar treatise. Eight hundred and fifty-one
questions with their answers are included, which will prove
specially helpful to those preparing for examination. Practical
information on: The Construction and Operation of Locomotives,
Breakdowns and their Remedies, Air Brakes and Valve Gears. Rules
and Signals are handled in a thorough manner. As a book of
reference it cannot be excelled. The book is divided into six
parts, as follows: 1. The Fireman's Duties. 2. General
Description of the Locomotive. 3. Breakdowns and their Remedies.
4. Air Brakes. 5. Extracts from Standard Rules. 6. Questions for
Examination. The 851 questions have been carefully selected and
arranged. These cover the examinations required by the different
railroads. 368 pages, 88 illustrations. Price =$1.50=

=Prevention of Railroad Accidents, or Safety in Railroading.= By GEORGE
BRADSHAW.

This book is a heart-to-heart talk with Railroad Employees,
dealing with facts, not theories, and showing the men in the
ranks, from every-day experience, how accidents occur and how
they may be avoided. The book is illustrated with seventy
original photographs and drawings showing the safe and unsafe
methods of work. No visionary schemes, no ideal pictures. Just
Plain Facts and Practical Suggestions are given. Every railroad
employee who reads the book is a better and safer man to have in
railroad service. It gives just the information which will be
the means of preventing many injuries and deaths. All railroad
employees should procure a copy, read it, and do their part in
preventing accidents. 169 pages. Pocket size. Fully illustrated.
Price =50 cents=

=Train Rule Examinations Made Easy.= By G. E. COLLINGWOOD.

This is the only practical work on train rules in print. Every
detail is covered, and puzzling points are explained in simple,
comprehensive language, making it a practical treatise for the
Train Dispatcher, Engineman, Trainman, and all others who have
to do with the movements of trains. Contains complete and
reliable information of the Standard Code of Train Rules for
single track. Shows Signals in Colors, as used on the different
roads. Explains fully the practical application of train orders,
giving a clear and definite understanding of all orders which
may be used. The meaning and necessity for certain rules are
explained in such a manner that the student may know beyond a
doubt the rights conferred under any orders he may receive or
the action required by certain rules. As nearly all roads
require trainmen to pass regular examinations, a complete set of
examination questions, with their answers, are included. These
will enable the student to pass the required examinations with
credit to himself and the road for which he works. 2nd Edition,
Revised. 256 pages, fully illustrated, with Train Signals in
Colors. Price =$1.25=

=The Walschaert and Other Modern Radial Valve Gears for Locomotives.= By
WM. W. WOOD.

If you would thoroughly understand the Walschaert Valve Gear you
should possess a copy of this book, as the author takes the
plainest form of a steam engine--a stationary engine in the
rough, that will only turn its crank in one direction--and from
it builds up, with the reader's help, a modern locomotive
equipped with the Walschaert Valve Gear, complete. The points
discussed are clearly illustrated: Two large folding plates that
show the positions of the valves of both inside or outside
admission type, as well as the links and other parts of the gear
when the crank is at nine different points in its revolution,
are especially valuable in making the movement clear. These
employ sliding cardboard models which are contained in a pocket
in the cover.

The book is divided into five general divisions, as follows: 1.
Analysis of the gear. 2. Designing and erecting the gear. 3.
Advantages of the gear. 4. Questions and answers relating to the
Walschaert Valve Gear. 5. Setting valves with the Walschaert
Valve Gear; the three primary types of locomotive valve motion;
modern radial valve gears other than the Walschaert; the Hobart
All-free Valve and Valve Gear, with questions and answers on
breakdowns; the Baker-Pilliod Valve Gear; the Improved
Baker-Pilliod Valve Gear, with questions and answers on
breakdowns.

The questions with full answers given will be especially
valuable to firemen and engineers in preparing for an
examination for promotion. 245 pages. 3rd Revised Edition. Price
=$1.50=

=Westinghouse E-T Air-Brake Instruction Pocket Book.= By WM. W. WOOD,
Air-Brake Instructor.

Here is a book for the railroad man, and the man who aims to be
one. It is without doubt the only complete work published on the
Westinghouse E-T Locomotive Brake Equipment. Written by an
Air-Brake Instructor who knows just what is needed. It covers
the subject thoroughly. Everything about the New Westinghouse
Engine and Tender Brake Equipment, including the standard No. 5
and the Perfected No. 6 style of brake, is treated in detail.
Written in plain English and profusely illustrated with Colored
Plates, which enable one to trace the flow of pressures
throughout the entire equipment. The best book ever published on
the Air Brake. Equally good for the beginner and the advanced
engineer. Will pass any one through any examination. It informs
and enlightens you on every point. Indispensable to every
engineman and trainman.

Contains examination questions and answers on the E-T equipment.
Covering what the E-T Brake is. How it should be operated. What
to do when defective. Not a question can be asked of the
engineman up for promotion, on either the No. 5 or the No. 6 E-T
equipment, that is not asked and answered in the book. If you
want to thoroughly understand the E-T equipment get a copy of
this book. It covers every detail. Makes Air-Brake troubles and
examinations easy. Price =$1.50=

~MACHINE-SHOP PRACTICE~

=American Tool Making and Interchangeable Manufacturing.= By J. V.
WOODWORTH.

A "shoppy" book, containing no theorizing, no problematical or
experimental devices. There are no badly proportioned and
impossible diagrams, no catalogue cuts, but a valuable
collection of drawings and descriptions of devices, the rich
fruits of the author's own experience. In its 500-odd pages the
one subject only, Tool Making, and whatever relates thereto, is
dealt with. The work stands without a rival. It is a complete,
practical treatise, on the art of American Tool Making and
system of interchangeable manufacturing as carried on to-day in
the United States. In it are described and illustrated all of
the different types and classes of small tools, fixtures,
devices, and special appliances which are in general use in all
machine-manufacturing and metal-working establishments where
economy, capacity, and interchangeability in the production of
machined metal parts are imperative. The science of jig making
is exhaustively discussed, and particular attention is paid to
drill jigs, boring, profiling and milling fixtures and other
devices in which the parts to be machined are located and
fastened within the contrivances. All of the tools, fixtures,
and devices illustrated and described have been or are used for
the actual production of work, such as parts of drill presses,
lathes, patented machinery, typewriters, electrical apparatus,
mechanical appliances, brass goods, composition parts, mould
products, sheet-metal articles, drop-forgings, jewelry, watches,
medals, coins, etc. 531 pages. Price =$4.00=

=HENLEY'S ENCYCLOPEDIA OF PRACTICAL ENGINEERING AND ALLIED TRADES.=
EDITED by JOSEPH G. HORNER, A.M.I., M.E.

This set of five volumes contains about 2,500 pages with
thousands of illustrations, including diagrammatic and sectional
drawings with full explanatory details. This work covers the
entire practice of Civil and Mechanical Engineering. The best
known experts in all branches of engineering have contributed to
these volumes. The Cyclopedia is admirably well adapted to the
needs of the beginner and the self-taught practical man, as well
as the mechanical engineer, designer, draftsman, shop
superintendent, foreman, and machinist. The work will be found a
means of advancement to any progressive man. It is encyclopedic
in scope, thorough and practical in its treatment on technical
subjects, simple and clear in its descriptive matter, and
without unnecessary technicalities or formulæ. The articles are
as brief as may be and yet give a reasonably clear and explicit
statement of the subject, and are written by men who have had
ample practical experience in the matters of which they write.
It tells you all you want to know about engineering and tells it
so simply, so clearly, so concisely, that one cannot help but
understand. As a work of reference it is without a peer.
Complete set of five volumes, price =$25.00=

=The Modern Machinist.= By JOHN T. USHER.

This is a book, showing by plain description and by profuse
engravings made expressly for the work, all that is best, most
advanced, and of the highest efficiency in modern machine-shop
practice, tools and implements, showing the way by which and
through which, as Mr. Maxim says "American machinists have
become and are the finest mechanics in the world." Indicating as
it does, in every line, the familiarity of the author with every
detail of daily experience in the shop, it cannot fail to be of
service to any man practically connected with the shaping or
finishing of metals.

There is nothing experimental or visionary about the book, all
devices being in actual use and giving good results. It might be
called a compendium of shop methods, showing a variety of
special tools and appliances which will give new ideas to many
mechanics, from the superintendent down to the man at the bench.
It will be found a valuable addition to any machinist's library,
and should be consulted whenever a new or difficult job is to be
done, whether it is boring, milling, turning, or planing, as
they are all treated m a practical manner. Fifth edition. 320
pages. 250 illustrations. Price =$2.50=

=THE WHOLE FIELD OF MECHANICAL MOVEMENTS COVERED BY MR. HISCOX'S TWO
BOOKS=

_We publish two books by Gardner D. Hiscox that will keep you
from "inventing" things that have been done before, and suggest
ways of doing things that you have not thought of before. Many a
man spends time and money pondering over some mechanical
problem, only to learn, after he has solved the problem, that
the same thing has been accomplished and put in practice by
others long before. Time and money spent in an effort to
accomplish what has already been accomplished are time and money
LOST. The whole field of mechanics, every known mechanical
movement, and practically every device are covered by these two
books. If the thing you want has been invented, it is
illustrated in them. If it hasn't been invented, then you'll
find in them the nearest things to what you want, some movements
or devices that will apply in your case, perhaps; or which will
give you a key from which to work. No book or set of books ever
published is of more real value to the Inventor, Draftsman, or
practical Mechanic than the two volumes described below._

=Mechanical Movements, Powers, and Devices.= By GARDNER D. HISCOX.

This is a collection of 1,890 engravings of different mechanical
motions and appliances, accompanied by appropriate text, making
it a book of great value to the inventor, the draftsman, and to
all readers with mechanical tastes. The book is divided into
eighteen sections or chapters, in which the subject-matter is
classified under the following heads: Mechanical Powers;
Transmission of Power; Measurement of Power; Steam Power; Air
Power Appliances; Electric Power and Construction; Navigation
and Roads; Gearing; Motion and Devices; Controlling Motion;
Horological; Mining; Mill and Factory Appliances; Construction
and Devices; Drafting Devices; Miscellaneous Devices, etc. 15th
Edition. 400 octavo pages. Price =$3.00=

=Mechanical Appliances, Mechanical Movements and Novelties of
Construction.= By GARDNER D. HISCOX.

This is a supplementary volume to the one upon mechanical
movements. Unlike the first volume, which is more elementary in
character, this volume contains illustrations and descriptions
of many combinations of motions and of mechanical devices and
appliances found in different lines of machinery, each device
being shown by a line drawing with a description showing its
working parts and the method of operation. From the multitude of
devices described and illustrated might be mentioned, in
passing, such items as conveyors and elevators, Pony brakes,
thermometers, various types of boilers, solar engines, oil-fuel
burners, condensers, evaporators, Corliss and other valve gears,
governors, gas engines, water motors of various descriptions,
air ships, motors and dynamos, automobile and motor bicycles,
railway lock signals, car couplers, link and gear motions, ball
bearings, breech-block mechanism for heavy guns, and a large
accumulation of others of equal importance. One thousand
specially made engravings. 396 octavo pages. Fourth edition.
Price =$3.00=

=Machine-Shop Tools and Shop Practice.= By W. H. VANDERVOORT.

A work of 555 pages and 673 illustrations, describing in every
detail the construction, operation and manipulation of both hand
and machine tools. Includes chapters on filing, fitting and
scraping surfaces; on drills, reamers, taps and dies; the lathe
and its tools: planers, shapers, and their tools; milling
machines and cutters; gear cutters and gear cutting; drilling
machines and drill work; grinding machines and their work;
hardening and tempering; gearing, belting and transmission
machinery; useful data and tables. Sixth edition. Price =$3.00=

=Machine-Shop Arithmetic.= By COLVIN-CHENEY.

This is an arithmetic of the things you have to do with daily.
It tells you plainly about: how to find areas in figures; how to
find surface or volume of balls or spheres; handy ways for
calculating; about compound gearing; cutting screw threads on
any lathe; drilling for taps; speeds of drills; taps, emery
wheels, grindstones, milling cutters, etc.; all about the Metric
system with conversion tables; properties of metals; strength of
bolts and nuts; decimal equivalent of an inch. All sorts of
machine-shop figuring and 1,001 other things, any one of which
ought to be worth more than the price of this book to you, as it
saves you the trouble of bothering the boss. 6th Edition. 131
pages. Price =50 cents=

=Modern Machine-Shop Construction, Equipment and Management.= By OSCAR
E. PERRIGO.

The only work published that describes the Modern Shop or
Manufacturing Plant from the time the grass is growing on the
site intended for it until the finished product is shipped. Just
the book needed by those contemplating the erection of modern
shop buildings, the rebuilding and reorganization of old ones,
or the introduction of Modern Shop Methods, time and cost
systems. It is a book written and illustrated by a practical
shop man for practical shop men who are too busy to read
theories and want facts. It is the most complete all-round book
of its kind ever published. Second Edition, Revised. 384 large
quarto pages. 219 original and specially made illustrations. 2nd
Revised and Enlarged Edition. Price =$5.00=

=Modern Milling Machines: Their Design, Construction, and Operation.= By
JOSEPH G. HORNER.

This book describes and illustrates the Milling Machine and its
work in such a plain, clear and forceful manner, and illustrates
the subject so clearly and completely, that the up-to-date
machinist, student or mechanical engineer cannot afford to do
without the valuable information which it contains. It describes
not only the early machines of this class, but notes their
gradual development into the splendid machines of the present
day, giving the design and construction of the various types,
forms, and special features produced by prominent manufacturers,
American and foreign. 304 pages, 300 illustrations. Cloth. Price
=$4.00=

="Shop Kinks."= By ROBERT GRIMSHAW.

A book of 400 pages and 222 illustrations, being entirely
different from any other book on machine-shop practice.
Departing from conventional style, the author avoids universal
or common shop usage and limits his work to showing special ways
of doing things better, more cheaply and more rapidly than
usual. As a result the advanced methods of representative
establishments of the world are placed at the disposal of the
reader. This book shows the proprietor where large savings are
possible, and how products may be improved. To the employee it
holds out suggestions that, properly applied, will hasten his
advancement. No shop can afford to be without it. It bristles
with valuable wrinkles and helpful suggestions. It will benefit
all, from apprentice to proprietor. Every machinist, at any age,
should study its pages. Fifth edition. Price =$2.50=

=Threads and Thread Cutting.= By COLVIN and STABEL.

This clears up many of the mysteries of thread-cutting, such as
double and triple threads, internal threads, catching threads,
use of hobs, etc. Contains a lot of useful hints and several
tables. Third edition. Price =25 cents=

~MANUAL TRAINING~

=Economics of Manual Training.= By LOUIS ROUILLION.

The only book published that gives just the information needed
by all interested in Manual Training, regarding Buildings,
Equipment, and Supplies. Shows exactly what is needed for all
grades of the work from the Kindergarten to the High and Normal
School. Gives itemized lists of everything used in Manual
Training Work and tells just what it ought to cost. Also shows
where to buy supplies, etc. Contains 174 pages, and is fully
illustrated. Second edition. Price =$1.50=

~MARINE ENGINEERING~

=The Naval Architect's and Shipbuilder's Pocket Book of Formulæ, Rules,
and Tables and Marine Engineer's and Surveyor's Handy Book of
Reference.= By CLEMENT MACKROW and LLOYD WOOLLARD.

The eleventh Revised and Enlarged Edition of this most
comprehensive work has just been issued. It is absolutely
indispensable to all engaged in the Shipbuilding Industry, as it
condenses into a compact form all data and formulæ that are
ordinarily required. The book is completely up to date,
including among other subjects a section on Aeronautics. 750
pages, limp leather binding. Price =$5.00 net=

=Marine Engines and Boilers: Their Design and Construction.= By DR. G.
BAUER, LESLIE S. ROBERTSON and S. BRYAN DONKIN.

In the words of Dr. Bauer, the present work owes its origin to
an oft felt want of a condensed treatise embodying the
theoretical and practical rules used in designing marine engines
and boilers. The need of such a work has been felt by most
engineers engaged in the construction and working of marine
engines, not only by the younger men, but also by those of
greater experience. The fact that the original German work was
written by the chief engineer of the famous Vulcan Works,
Stettin, is in itself a guarantee that this book is in all
respects thoroughly up-to-date, and that it embodies all the
information which is necessary for the design and construction
of the highest types of marine engines and boilers. It may be
said that the motive power which Dr. Bauer has placed in the
fast German liners that have been turned out of late years from
the Stettin Works represent the very best practice in marine
engineering of the present day. The work is clearly written,
thoroughly systematic, theoretically sound; while the character
of the plans, drawings, tables, and statistics is without
reproach. The illustrations are careful reproductions from
actual working drawings, with some well-executed photographic
views of completed engines and boilers. 744 pages, 550
illustrations and numerous tables. Cloth. Price =$9.00 net=

~MINING~

=Ore Deposits, with a Chapter on Hints to Prospectors.= By J. P.
JOHNSON.

This book gives a condensed account of the ore deposits at
present known in South Africa. It is also intended as a guide to
the prospector. Only an elementary knowledge of geology and some
mining experience are necessary in order to understand this
work. With these qualifications, it will materially assist one
in his search for metalliferous mineral occurrences and, so far
as simple ores are concerned, should enable one to form some
idea of the possibilities of any he may find. Illustrated.
Cloth. Price =$2.00=

=Practical Coal Mining.= By T. H. COCKIN.

An important work, containing 428 pages and 213 illustrations,
complete with practical details, which will intuitively impart
to the reader not only a general knowledge of the principles of
coal mining, but also considerable insight into allied subjects.
The treatise is positively up-to-date in every instance, and
should be in the hands of every colliery engineer, geologist,
mine operator, superintendent, foreman, and all others who are
interested in or connected with the industry. 3d Edition. Cloth.
Price =$2.50=

=Physics and Chemistry of Mining.= By T. H. BYROM.

A practical work for the use of all preparing for examinations
in mining or qualifying for colliery managers' certificates. The
aim of the author in this excellent book is to place clearly
before the reader useful and authoritative data which will
render him valuable assistance in his studies. The only work of
its kind published. The information incorporated in it will
prove of the greatest practical utility to students, mining
engineers, colliery managers, and all others who are specially
interested in the present-day treatment of mining problems. 160
pages, illustrated. Price =$2.00=

~PATTERN MAKING~

=Practical Pattern Making.= By F. W. BARROWS.

This book, now in its second edition, is a comprehensive and
entirely practical treatise on the subject of pattern making,
illustrating pattern work in both wood and metal, and with
definite instructions on the use of plaster of paris in the
trade. It gives specific and detailed descriptions of the
materials used by pattern makers, and describes the tools, both
those for the bench and the more interesting machine tools,
having complete chapters on the Lathe, the Circular Saw, and the
Band Saw. It gives many examples of pattern work, each one fully
illustrated and explained with much detail. These examples, in
their great variety, offer much that will be found of interest
to all pattern makers, and especially to the younger ones, who
are seeking information on the more advanced branches of their
trade.

In this second edition of the work will be found much that is
new, even to those who have long practised this exacting trade.
In the description of patterns as adapted to the Moulding
Machine many difficulties which have long prevented the rapid
and economical production of castings are overcome; and this
great, new branch of the trade is given much space. Stripping
plate and stool plate work and the less expensive vibrator, or
rapping plate work, are all explained in detail.

Plain, every-day rules for lessening the cost of patterns, with
a complete system of cost keeping, a detailed method of marking,
applicable to all branches of the trade, with complete
information showing what the pattern is, its specific title, its
cost, date of production, material of which it is made, the
number of pieces and core-boxes, and its location in the pattern
safe, all condensed into a most complete card record, with cross
index. The book closes with an original and practical method for
the inventory and valuation of patterns. Containing nearly 350
pages and 170 illustrations. Price =$2.00=

~PERFUMERY~

=Perfumes and Cosmetics: Their Preparation and Manufacture.= By G. W.
ASKINSON, Perfumer.

A comprehensive treatise, in which there has been nothing
omitted that could be of value to the perfumer or manufacturer
of toilet preparations. Complete directions for making
handkerchief perfumes, smelling-salts, sachets, fumigating
pastilles; preparations for the care of the skin, the mouth, the
hair, cosmetics, hair dyes and other toilet articles are given,
also a detailed description of aromatic substances; their
nature, tests of purity, and wholesome manufacture, including a
chapter on synthetic products, with formulas for their use. A
book of general as well as professional interest, meeting the
wants not only of the druggist and perfume manufacturer, but
also of the general public. Among the contents are: 1. The
History of Perfumery. 2. About Aromatic Substances in General.
3. Odors from the Vegetable Kingdom. 4. The Aromatic Vegetable
Substances Employed in Perfumery. 5. The Animal Substances Used
in Perfumery. 6. The Chemical Products Used in Perfumery. 7. The
Extraction of Odors. 8. The Special Characteristics of Aromatic
Substances. 9 The Adulteration of Essential Oils and Their
Recognition. 10. Synthetic Products. 11. Table of Physical
Properties of Aromatic Chemicals. 12. The Essences or Extracts
Employed in Perfumery. 13. Directions for Making the Most
Important Essences and Extracts. 14. The Division of Perfumery.
15. The Manufacture of Handkerchief Perfumes. 16. Formulas for
Handkerchief Perfumes. 17. Ammoniacal and Acid Perfumes. 18. Dry
Perfumes. 19. Formulas for Dry Perfumes. 20. The Perfumes Used
for Fumigation. 21. Antiseptic and Therapeutic Value of
Perfumes. 22. Classification of Odors. 23. Some Special
Perfumery Products. 24. Hygiene and Cosmetic Perfumery. 25.
Preparations for the Care of the Skin. 26. Manufacture of
Casein. 27. Formulas for Emulsions. 28. Formulas for Cream. 29.
Formulas for Meals, Pastes and Vegetable Milk. 30. Preparations
Used for the Hair. 31. Formulas for Hair Tonics and Restorers.
32. Pomades and Hair Oils 33. Formulas for the Manufacture of
Pomades and Hair Oils. 34. Hair Dyes and Depilatories. 35. Wax
Pomades, Bandolines and Brilliantines. 36. Skin Cosmetics and
Face Lotions. 37. Preparations for the Nails. 38. Water
Softeners and Bath Salts. 39. Preparations for the Care of the
Mouth. 40. The Colors Used in Perfumery. 41. The Utensils Used
in the Toilet. Fourth edition, much enlarged and brought up to
date. Nearly 400 pages, illustrated. Price =$5.00=

WHAT IS SAID OF THIS BOOK:

"The most satisfactory work on the subject of Perfumery that we
have ever seen."

"We feel safe in saying that here is a book on Perfumery that
will not disappoint you, for it has practical and excellent
formulæ that are within your ability to prepare readily."

"We recommend the volume as worthy of confidence, and say that
no purchaser will be disappointed in securing from its pages
good value for its cost, and a large dividend on the same, even
if he should use but one per cent. of its working formulæ. There
is money in it for every user of its
information."--_Pharmaceutical Record._

~PLUMBING~

=Mechanical Drawing for Plumbers.= By R. M. STARBUCK.

A concise, comprehensive and practical treatise on the subject
of mechanical drawing in its various modern applications to the
work of all who are in any way connected with the plumbing
trade. Nothing will so help the plumber in estimating and in
explaining work to customers and workmen as a knowledge of
drawing, and to the workman it is of inestimable value if he is
to rise above his position to positions of greater
responsibility. Among the chapters contained are: 1. Value to
plumber of knowledge of drawing; tools required and their use;
common views needed in mechanical drawing. 2. Perspective versus
mechanical drawing in showing plumbing construction. 3. Correct
and incorrect methods in plumbing drawing; plan and elevation
explained. 4. Floor and cellar plans and elevation; scale
drawings; use of triangles. 5. Use of triangles; drawing of
fittings, traps, etc. 6. Drawing plumbing elevations and
fittings. 7. Instructions in drawing plumbing elevations. 8. The
drawing of plumbing fixtures; scale drawings. 9. Drawings of
fixtures and fittings. 10. Inking of drawings. 11. Shading of
drawings. 12. Shading of drawings. 13. Sectional drawings;
drawing of threads. 14. Plumbing elevations from architect's
plan. 15. Elevations of separate parts of the plumbing system.
16. Elevations from the architect's plans. 17. Drawings of
detail plumbing connections. 18. Architect's plans and plumbing
elevations of residence. 19. Plumbing elevations of residence
(_continued_); plumbing plans for cottage. 20. Plumbing
elevations; roof connections. 21. Plans and plumbing elevations
for six-flat building. 22. Drawing of various parts of the
plumbing system; use of scales. 23. Use of architect's scales.
24. Special features in the illustrations of country plumbing.
25. Drawing of wrought-iron piping, valves, radiators, coils,
etc. 26. Drawing of piping to illustrate heating systems. 150
illustrations. Price =$1.50=

=Modern Plumbing Illustrated.= By R. M. STARBUCK.

This book represents the highest standard of plumbing work. It
has been adopted and used as a reference book by the United
States Government in its sanitary work in Cuba, Porto Rico and
the Philippines, and by the principal Boards of Health of the
United States and Canada.

It gives connections, sizes and working data for all fixtures
and groups of fixtures. It is helpful to the master plumber in
demonstrating to his customers and in figuring work. It gives
the mechanic and student quick and easy access to the best
modern plumbing practice. Suggestions for estimating plumbing
construction are contained in its pages. This book represents,
in a word, the latest and best up-to-date practice and should be
in the hands of every architect, sanitary engineer and plumber
who wishes to keep himself up to the minute on this important
feature of construction. Contains following chapters, each
illustrated with a full-page plate: Kitchen sink, laundry tubs,
vegetable wash sink; lavatories, pantry sinks, contents of
marble slabs; bath tub, foot and sitz bath, shower bath; water
closets, venting of water closets; low-down water closets, water
closets operated by flush valves, water closet range; slop sink,
urinals, the bidet; hotel and restaurant sink, grease trap;
refrigerators, safe wastes, laundry waste, lines of
refrigerators, bar sinks, soda fountain sinks; horse stall,
frost-proof water closets; connections for S traps, venting;
connections for drum traps; soil-pipe connections; supporting of
soil pipe; main trap and fresh-air inlet: floor drains and
cellar drains, subsoil drainage; water closets and floor
connections; local venting; connections for bath rooms;
connections for bath rooms, _continued_; examples of poor
practice; roughing work ready for test; testing of plumbing
systems; method of continuous venting; continuous venting for
two-floor work; continuous venting for two lines of fixtures on
three or more floors; continuous venting of water closets;
plumbing for cottage house; construction for cellar piping;
plumbing for residence, use of special fittings; plumbing for
two-flat house: plumbing for apartment building, plumbing for
double apartment building; plumbing for office building;
plumbing for public toilet rooms; plumbing for public toilet
rooms, _continued_; plumbing for bath establishment; plumbing
for engine house, factory plumbing, automatic flushing for
schools, factories, etc.; use of flushing valves; urinals for
public toilet rooms; the Durham system, the destruction of pipes
by electrolysis; construction of work without use of lead;
automatic sewage lift; automatic sump tank; country plumbing;
construction of cesspools; septic tank and automatic sewage
siphon; water supply for country house; thawing of water mains
and service by electricity; double boilers; hot water supply of
large buildings; automatic control of hot-water tank;
suggestions for estimating plumbing construction. 407 octavo
pages, fully illustrated by 57 full-page engravings. Third,
revised and enlarged edition, just issued. Price =$4.00=

=Standard Practical Plumbing.= By R. M. STARBUCK.

A complete practical treatise of 450 pages, covering the subject
of Modern Plumbing in all its branches, a large amount of space
being devoted to a very complete and practical treatment of the
subject of Hot Water Supply and Circulation and Range Boiler
Work. Its thirty chapters include about every phase of the
subject one can think of, making it an indispensable work to the
master plumber, the journeyman plumber, and the apprentice
plumber, containing chapters on: the plumber's tools; wiping
solder; composition and use; joint wiping; lead work; traps;
siphonage of traps; venting; continuous venting; house sewer and
sewer connections; house drain; soil piping, roughing; main trap
and fresh air inlet; floor, yard, cellar drains, rain leaders,
etc.; fixture wastes; water closets; ventilation; improved
plumbing connections; residence plumbing; plumbing for hotels,
schools, factories, stables, etc.; modern country plumbing;
filtration of sewage and water supply; hot and cold supply;
range boilers; circulation; circulating pipes; range boiler
problems; hot water for large buildings; water lift and its use;
multiple connections for hot water boilers; heating of radiation
by supply system; theory for the plumber; drawing for the
plumber. Fully illustrated by 347 engravings. Price =$3.00=

~RECIPE BOOK~

=Henley's Twentieth Century Book of Recipes, Formulas and Processes.=
Edited by GARDNER D. HISCOX.

The most valuable Techno-chemical Formula Book published,
including over 10,000 selected scientific, chemical,
technological, and practical recipes and processes.

This is the most complete Book of Formulas ever published,
giving thousands of recipes for the manufacture of valuable
articles for everyday use. Hints, Helps, Practical Ideas, and
Secret Processes are revealed within its pages. It covers every
branch of the useful arts and tells thousands of ways of making
money, and is just the book everyone should have at his command.

Modern in its treatment of every subject that properly falls
within its scope, the book may truthfully be said to present the
very latest formulas to be found in the arts and industries, and
to retain those processes which long experience has proven
worthy of a permanent record. To present here even a limited
number of the subjects which find a place in this valuable work
would be difficult. Suffice to say that in its pages will be
found matter of intense interest and immeasurably practical
value to the scientific amateur and to him who wishes to obtain
a knowledge of the many processes used in the arts, trades and
manufacture, a knowledge which will render his pursuits more
instructive and remunerative. Serving as a reference book to the
small and large manufacturer and supplying intelligent seekers
with the information necessary to conduct a process, the work
will be found of inestimable worth to the Metallurgist, the
Photographer, the Perfumer, the Painter, the Manufacturer of
Glues, Pastes, Cements, and Mucilages, the Compounder of Alloys,
the Cook, the Physician, the Druggist, the Electrician, the
Brewer, the Engineer, the Foundryman, the Machinist, the Potter,
the Tanner, the Confectioner, the Chiropodist, the Manicurist,
the Manufacturer of Chemical Novelties and Toilet Preparations,
the Dyer, the Electroplater, the Enameler, the Hat Maker, the
Ink Manufacturer, the Optician, the Farmer, the Dairyman, the
Paper Maker, the Wood and Metal Worker, the Chandler and Soap
Maker, the Veterinary Surgeon, and the Technologist in general.

A mine of information, and up-to-date in every respect. A book
which will prove of value to EVERYONE, as it covers every branch
of the Useful Arts. Every home needs this book; every office,
every factory, every store, every public and private
enterprise--EVERYWHERE--should have a copy. 800 pages. Price
=$3.00=

WHAT IS SAID OF THIS BOOK:

"Your Twentieth Century Book of Recipes, Formulas, and Processes
duly received. I am glad to have a copy of it, and if I could
not replace it, money couldn't buy it. It is the best thing of
the sort I ever saw." (Signed) M. E. TRUX, Sparta, Wis.

"There are few persons who would not be able to find in the book
some single formula that would repay several times the cost of
the book."--_Merchants' Record and Show Window._

"I purchased your book, 'Henley's Twentieth Century Book of
Recipes, Formulas and Processes,' about a year ago and it is
worth its weight in _gold_."--WM. H. MURRAY, Bennington, Vt.

"ONE OF THE WORLD'S MOST USEFUL BOOKS"

"Some time ago I got one of your 'Twentieth Century Books of
Formulas,' and have made my living from it ever since. I am
alone since my husband's death with two small children to care
for and am trying so hard to support them. I have customers who
take from me Toilet Articles I put up, following directions
given in the book, and I have found everyone of them to be
fine."--MRS. J. H. MCMAKEN, West Toledo, Ohio.

~RUBBER~

=Rubber Hand Stamps and the Manipulation of India Rubber.= BY T. O'CONOR
SLOANE.

This book gives full details on all points, treating in a
concise and simple manner the elements of nearly everything it
is necessary to understand for a commencement in any branch of
the India Rubber Manufacture. The making of all kinds of Rubber
Hand Stamps, Small Articles of India Rubber, U. S. Government
Composition, Dating Hand Stamps, the Manipulation of Sheet
Rubber, Toy Balloons, India Rubber Solutions, Cements,
Blackings, Renovating, Varnish, and Treatment for India Rubber
Shoes, etc.; the Hektograph Stamp Inks, and Miscellaneous Notes,
with a Short Account of the Discovery, Collection and
Manufacture of India Rubber, are set forth in a manner designed
to be readily understood, the explanations being plain and
simple. Including a chapter on Rubber Tire Making and
Vulcanizing; also a chapter on the uses of rubber in Surgery and
Dentistry. 3rd Revised and Enlarged Edition. 175 pages.
Illustrated =$1.00=

~SAWS~

=Saw Filing and Management of Saws.= By ROBERT GRIMSHAW.

A practical hand-book on filing, gumming, swaging, hammering,
and the brazing of band saws, the speed, work, and power to run
circular saws, etc. A handy book for those who have charge of
saws, or for those mechanics who do their own filing, as it
deals with the proper shape and pitches of saw teeth of all
kinds and gives many useful hints and rules for gumming,
setting, and filing, and is a practical aid to those who use
saws for any purpose. Complete tables of proper shape, pitch,
and saw teeth as well as sizes and number of teeth of various
saws are included. 3rd Edition, Revised and Enlarged.
Illustrated. Price =$1.00=

~STEAM ENGINEERING~

=American Stationary Engineering.= By W. E. CRANE.

This book begins at the boiler room and takes in the whole power
plant. A plain talk on every-day work about engines, boilers,
and their accessories. It is not intended to be scientific or
mathematical. All formulas are in simple form so that any one
understanding plain arithmetic can readily understand any of
them. The author has made this the most practical book in print;
has given the results of his years of experience, and has
included about all that has to do with an engine room or a power
plant. You are not left to guess at a single point. You are
shown clearly what to expect under the various conditions; how
to secure the best results; ways of preventing "shut downs" and
repairs; in short, all that goes to make up the requirements of
a good engineer, capable of taking charge of a plant. It's plain
enough for practical men and yet of value to those high in the
profession.

A partial list of contents is: The boiler room, cleaning
boilers, firing, feeding; pumps, inspection and repair;
chimneys, sizes and cost; piping; mason work; foundations;
testing cement; pile driving; engines, slow and high speed;
valves; valve setting; Corliss engines, setting valves, single
and double eccentric; air pumps and condensers; different types
of condensers; water needed; lining up; pounds; pins not square
in crosshead or crank; engineers' tools; pistons and piston
rings; bearing metal; hardened copper; drip pipes from cylinder
jacket; belts, how made, care of; oils; greases; testing
lubricants; rules and tables, including steam tables; areas of
segments; squares and square roots; cubes and cube root; areas
and circumferences of circles. Notes on: Brick work; explosions;
pumps; pump valves; heaters, economizers; safety valves; lap,
lead, and clearance. Has a complete examination for a license,
etc., etc. 3rd Edition. 345 pages, illustrated. Price =$2.00=

=Engine Runner's Catechism.= By ROBERT GRIMSHAW.

A practical treatise for the stationary engineer, telling how to
erect, adjust, and run the principal steam engines in use in the
United States. Describing the principal features of various
special and well-known makes of engines: Temper Cut-off,
Shipping and Receiving Foundations, Erecting and Starting, Valve
Setting, Care and Use, Emergencies, Erecting and Adjusting
Special Engines.

The questions asked throughout the catechism are plain and to
the point, and the answers are given in such simple language as
to be readily understood by anyone. All the instructions given
are complete and up-to-date; and they are written in a popular
style, without any technicalities or mathematical formulæ. The
work is of a handy size for the pocket, clearly and well
printed, nicely bound, and profusely illustrated.

To young engineers this catechism will be of great value,
especially to those who may be preparing to go forward to be
examined for certificates of competency; and to engineers
generally it will be of no little service, as they will find in
this volume more really practical and useful information than is
to be found anywhere else within a like compass. 387 pages. 7th
Edition. Price =$2.00=

=Modern Steam Engineering in Theory and Practice.= By GARDNER D. HISCOX.

This is a complete and practical work issued for Stationary
Engineers and Firemen, dealing with the care and management of
boilers, engines, pumps, superheated steam, refrigerating
machinery, dynamos, motors, elevators, air compressors, and all
other branches with which the modern engineer must be familiar.
Nearly 200 questions with their answers on steam and electrical
engineering, likely to be asked by the Examining Board, are
included.

Among the chapters are: Historical: steam and its properties;
appliances for the generation of steam; types of boilers;
chimney and its work; heat economy of the feed water; steam
pumps and their work; incrustation and its work; steam above
atmospheric pressure; flow of steam from nozzles; superheated
steam and its work; adiabatic expansion of steam; indicator and
its work; steam engine proportions; slide valve engines and
valve motion; Corliss engine and its valve gear; compound engine
and its theory; triple and multiple expansion engine; steam
turbine; refrigeration; elevators and their management; cost of
power; steam engine troubles; electric power and electric
plants. 487 pages, 405 engravings. 3rd Edition. Price =$3.00=

=Steam Engine Catechism.= By ROBERT GRIMSHAW.

This unique volume of 413 pages is not only a catechism on the
question and answer principle but it contains formulas and
worked-out answers for all the Steam problems that appertain to
operation and management of the Steam Engine. Illustrations of
various valves and valve gear with their principles of operation
are given. Thirty-four Tables that are indispensable to every
engineer and fireman that wishes to be progressive and is
ambitious to become master of his calling are within its pages.
It is a most valuable instructor in the service of Steam
Engineering. Leading engineers have recommended it as a valuable
educator for the beginner as well as a reference book for the
engineer. It is thoroughly indexed for every detail. Every
essential question on the Steam Engine with its answer is
contained in this valuable work. 16th Edition. Price =$2.00=

=Steam Engineer's Arithmetic.= By COLVIN-CHENEY.

A practical pocket-book for the steam engineer. Shows how to
work the problems of the engine room and shows "why." Tells how
to figure horsepower of engines and boilers; area of boilers;
has tables of areas and circumferences; steam tables; has a
dictionary of engineering terms. Puts you on to all of the
little kinks in figuring whatever there is to figure around a
power plant. Tells you about the heat unit; absolute zero;
adiabatic expansion; duty of engines; factor of safety; and a
thousand and one other things; and everything is plain and
simple--not the hardest way to figure, but the easiest. 2nd
Edition. Price =50 Cents=

=Engine Tests and Boiler Efficiencies.= By J. BUCHETTI.

This work fully describes and illustrates the method of testing
the power of steam engines, turbines and explosive motors. The
properties of steam and the evaporative power of fuels.
Combustion of fuel and chimney draft; with formulas explained or
practically computed. 255 pages, 179 illustrations. Price
=$3.00=

=Horsepower Chart.=

Shows the horsepower of any stationary engine without
calculation. No matter what the cylinder diameter of stroke, the
steam pressure of cut-off, the revolutions, or whether
condensing or non-condensing, it's all there. Easy to use.
accurate, and saves time and calculations. Especially useful to
engineers and designers. Price =50 Cents=

~STEAM HEATING AND VENTILATION~

=Practical Steam, Hot-Water Heating and Ventilation.= By A. G. KING.

This book is the standard and latest work published on the
subject and has been prepared for the use of all engaged in the
business of steam, hot-water heating, and ventilation. It is an
original and exhaustive work. Tells how to get heating
contracts, how to install heating and ventilating apparatus, the
best business methods to be used, with "Tricks of the Trade" for
shop use. Rules and data for estimating radiation and cost and
such tables and information as make it an indispensable work for
everyone interested in steam, hot-water heating, and
ventilation. It describes all the principal systems of steam,
hot-water, vacuum, vapor, and vacuum-vapor heating, together
with the new accelerated systems of hot-water circulation,
including chapters on up-to-date methods of ventilation and the
fan or blower system of heating and ventilation. Containing
chapters on: I. Introduction. II. Heat. III. Evolution of
artificial heating apparatus. IV. Boiler surface and settings.
V. The chimney flue. VI. Pipe and fittings. VII. Valves, various
kinds. VIII. Forms of radiating surfaces. IX. Locating of
radiating surfaces. X. Estimating radiation. XI. Steam-heating
apparatus XII. Exhaust-steam heating. XIII. Hot-water heating.
XIV. Pressure systems of hot-water work. XV. Hot-water
appliances. XVI. Greenhouse heating. XVII. Vacuum vapor and
vacuum exhaust heating. XVIII. Miscellaneous heating. XIX.
Radiator and pipe connections. XX. Ventilation. XXI. Mechanical
ventilation and hot-blast heating. XXII. Steam appliances.
XXIII. District heating. XXIV. Pipe and boiler covering. XXV.
Temperature regulation and heat control. XXVI. Business methods.
XXVII. Miscellaneous. XXVIII. Rules, tables, and useful
information. 367 pages, 300 detailed engravings. 2nd
Edition--Revised. Price =$3.00=

=Five Hundred Plain Answers to Direct Questions on Steam, Hot-Water,
Vapor and Vacuum Heating Practice.= By ALFRED G. KING.

This work, just off the press, is arranged in question and
answer form; it is intended as a guide and text-book for the
younger, inexperienced fitter and as a reference book for all
fitters. This book tells "how" and also tells "why". No work of
its kind has ever been published. It answers all the questions
regarding each method or system that would be asked by the steam
fitter or heating contractor, and may be used as a text or
reference book, and for examination questions by Trade Schools
or Steam Fitters' Associations. Rules, data, tables and
descriptive methods are given, together with much other detailed
information of daily practical use to those engaged in or
interested in the various methods of heating. Valuable to those
preparing for examinations. Answers every question asked
relating to modern Steam, Hot-Water, Vapor and Vacuum Heating.
Among the contents are: The Theory and Laws of Heat. Methods of
Heating. Chimneys and Flues. Boilers for Heating. Boiler
Trimmings and Settings. Radiation. Steam Heating. Boiler,
Radiator and Pipe Connections for Steam Heating. Hot Water
Heating. The Two-Pipe Gravity System of Hot Water Heating. The
Circuit System of Hot Water Heating. The Overhead System of Hot
Water Heating. Boiler, Radiator and Pipe Connections for Gravity
Systems of Hot Water Heating. Accelerated Hot Water Heating.
Expansion Tank Connections. Domestic Hot Water Heating. Valves
and Air Valves. Vacuum Vapor and Vacuo-Vapor Heating. Mechanical
Systems of Vacuum Heating. Non-Mechanical Vacuum Systems. Vapor
Systems. Atmospheric and Modulating Systems. Heating
Greenhouses. Information, Rules and Tables. 200 pages, 127
illustrations. Octavo. Cloth. Price =$1.50=

~STEEL~

=Steel: Its Selection, Annealing, Hardening, and Tempering.= By E. R.
MARKHAM.

This work was formerly known as "The American Steel Worker," but
on the publication of the new, revised edition, the publishers
deemed it advisable to change its title to a more suitable one.
It is the standard work on Hardening, Tempering, and Annealing
Steel of all kinds. This book tells how to select, and how to
work, temper, harden, and anneal steel for everything on earth.
It doesn't tell how to temper one class of tools and then leave
the treatment of another kind of tool to your imagination and
judgment, but it gives careful instructions for every detail of
every tool, whether it be a tap, a reamer or just a
screw-driver. It tells about the tempering of small watch
springs, the hardening of cutlery, and the annealing of dies. In
fact, there isn't a thing that a steel worker would want to know
that isn't included. It is the standard book on selecting,
hardening and tempering all grades of steel. Among the chapter
headings might be mentioned the following subjects:
Introduction; the workman; steel; methods of heating; heating
tool steel; forging; annealing; hardening baths; baths for
hardening; hardening steel; drawing the temper after hardening;
examples of hardening; pack hardening; case hardening; spring
tempering; making tools of machine steel; special steels; steel
for various tools; causes of trouble; high-speed steels, etc.
400 pages. Very fully illustrated. Fourth edition. Price =$2.50=

=Hardening, Tempering, Annealing, and Forging of Steel.= By J. V.
WOODWORTH.

A new work treating in a clear, concise manner all modern
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288 pages. 201 illustrations. Price =$2.50=

~TRACTORS~

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~TURBINES~

=Marine Steam Turbines.= By DR. G. BAUER and O. LASCHE. Assisted by E.
LUDWIG and H. VOGEL.

Translated from the German and edited by M. G. S. Swallow. The
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~WATCH MAKING~

=Watchmaker's Handbook.= By CLAUDIUS SAUNIER.

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~WELDING~

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=The Norman W. Henley Publishing Co.,=

=2 West 45th Street, New York=

+-----------------------------------------------------------------+
| TRANSCRIBER'S NOTES |
| |
| General remarks: |
| There are some differences in wording between the Table of |
| Contents, the lists of sections per chapter, and the actual |
| section titles. Their meaning is clear, and they have been |
| left as they were in the original work. |
| Page 56, table: Fig. 8 in the first column does not refer to |
| Fig. 8 in this work. |
| The original work does not have a Figure 89. |
| Page 303, table: it is uncertain what "free with kerosene" |
| means, there may be a word omitted. |
| Page 544, entirely censored. It is not clear what this page |
| originally contained (possibly a table), since text and |
| numbering of illustrations are uninterrupted. The text |
| "CENSORED" has been moved to after the first paragraph of the |
| section on Mercedes Engines. |
| The List of Illustrations does not occur in the original work.|
| |
| Changes made: |
| The text of the original work (including inconsistencies in |
| accents, spelling, hyphenation and lay-out, and differences |
| between the main text, illustrations and advertisements) has |
| been followed, except when listed below. Only some minor |
| obvious typographical errors have been corrected silently. |
| Where the author used x for multiplication, this has been |
| replaced by × in the body of the text (not in the |
| advertisements or illustrations). |
| The illustrations have been moved so as not to disrupt the |
| flow of the text. |
| Engine and aircraft types are not always named consistently in|
| the original; Curtiss engine O X 2, OX-2 and 0X2 have all |
| been changed to OX-2, Curtiss aircraft JN4 and JN-4 to JN-4. |
| Multi-page tables: repeated headings have been removed, and |
| the tables treated as one consecutive table. |
| Page 22: "The product of" has been moved into the first |
| formula. |
| Page 25: "When B × r = M" changed to "When P × r = M". |
| Page 74: ".225 ÷ 775 = .2905" changed to ".225 ÷ .775 = |
| .2905". |
| Page 137 (caption): "Bavary" changed to "Baverey" as |
| elsewhere. |
| Page 172: "evidently" changed to "evident". |
| Page 214: "drop to O" changed to "drop to 0". |
| Page 248: "actual from a common" changed to "actuated from a |
| common". |
| Page 256: "values" changed to "valves". |
| Page 280: "Fig. 6" changed to "Fig. 112". |
| Page 306: "Fig. 127, B" changed to "Fig. 127, C" (2nd |
| reference). |
| Page 324: "Rhone" changed to "Le Rhone" as elsewhere. |
| Page 334: "Check values" changed to "Check valves". |
| Page 364: "LeRhone" changed to "Le Rhone" as elsewhere. |
| Page 390: "Fig. 62, D" changed to "Fig. 168, B". |
| Page 408: "Stilson" changed to "Stillson" as elsewhere. |
| Page 490: "both valves" changed to "both halves". |
| Page 514: "standard ratio is 5.3" changed to "standard ratio |
| is 5:3". |
| Page 529: "gallons per minute 1,400 R. P. M." changed to |
| "gallons per minute at 1,400 R. P. M." |
| Page 546: "Hispano Suiza" changed to "Hispano-Suiza" as |
| elsewhere. |
| Page 556: "Diameter of crank-shaft, 56 mm." changed to |
| "Diameter of crank-shaft, 55 mm." |
| Page 7 (advertisements): "Hazlehurst Field" changed to |
| "Hazelhurst Field". |
| Page 21 (advertisements): "Rhose Island Compound" changed to |
| "Rhode Island Compound". |
| Index: "Shebler" changed to "Schebler", "camshaft" to |
| "cam-shaft", "wristpin" to "wrist-pin", etc. (all as in text).|
+-----------------------------------------------------------------+

*** End of this LibraryBlog Digital Book "Aviation Engines - Design—Construction—Operation and Repair" ***

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