Practical Hand Book of Gas, Oil and Steam Engines - Stationary, Marine, Traction Gas Burners, Oil Burners, - Etc. Farm, Traction, Automobile, Locomotive A simple, - practical and comprehensive book on the construction, - operation and repair of all kinds of engines. Dealing with - the various parts in detail and the various types of engines - and also the use of different kinds of fuel.

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Title: Practical Hand Book of Gas, Oil and Steam Engines - Stationary, Marine, Traction Gas Burners, Oil Burners, - Etc. Farm, Traction, Automobile, Locomotive A simple, - practical and comprehensive book on the construction, - operation and repair of all kinds of engines. Dealing with - the various parts in detail and the various types of engines - and also the use of different kinds of fuel.
Author: Rathbun, John B.
Language: English
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*** Start of this LibraryBlog Digital Book "Practical Hand Book of Gas, Oil and Steam Engines - Stationary, Marine, Traction Gas Burners, Oil Burners, - Etc. Farm, Traction, Automobile, Locomotive A simple, - practical and comprehensive book on the construction, - operation and repair of all kinds of engines. Dealing with - the various parts in detail and the various types of engines - and also the use of different kinds of fuel." ***

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Internet Archive)

[Illustration:

Eight Cylinder “V” Type Curtiss Aero Motor Having Two Rows of Four
Cylinders Per Row. The Carburetor is Shown at the Left Hand Lower
Corner Below the Motor. For Front Elevation See Fig. F-3 on Page 23.
]

PRACTICAL HAND BOOK
_of_
GAS, OIL AND STEAM ENGINES
STATIONARY, MARINE, TRACTION

GAS BURNERS, OIL BURNERS, ETC.
FARM, TRACTION, AUTOMOBILE, LOCOMOTIVE

A simple, practical and comprehensive book on the
construction, operation and repair of all kinds of
engines. Dealing with the various parts in detail and
the various types of engines and also the use of
different kinds of fuel.

_By_

JOHN B. RATHBUN,

Consulting Gas Engineer, Editor “Ignition,” Instructor
Chicago Technical College, Author Gas Engine Troubles
and Installation.

Published by
CHARLES C. THOMPSON CO.
CHICAGO, U. S. A.

_Practical Hand Book Gas, Oil & Steam Engines_

------------------------------------------------------------------------

Table of Contents

CHAPTER I—HEAT AND POWER

Heat Energy—Mechanical Equivalent of Heat—Expansion Heat Units—Heat
Engines—Efficiency—External and Internal Combustion
Engines—Compression—Working Medium 5

CHAPTER II—FUELS

Calorific Values of Fuels—Solid, Liquid and Gaseous
Fuels—Kerosene—Gasoline—Crude Oil—Producer Gas—Illuminating
Gas—Coal—Benzol 27

CHAPTER III—WORKING CYCLES

Definitions of Cycle—Four Stroke Cycle—Two Stroke Cycle—Two Port,
Two Stroke—Three Port, Three Stroke—Reversing—Scavenging—Junker
Two Stroke Cycle 58

CHAPTER IV—INDICATOR DIAGRAMS

Practical Use of the Indicator—Pressure Measurement—Reading the
Card—Four Stroke Cycle Card—Defects in Practical Working—Two
Stroke Cycle Card—Diesel Card—Effects of Mixture—Effects of
Ignition 72

CHAPTER V—TYPICAL FOUR STROKE CYCLE ENGINES

Single Cylinder—Four Cylinder Automobile—Opposed Type—V
Type—Tandem—Twin Tandem—Rotary Cylinder—Radial
Diesel—Knight—Argyle—Rotary Valve 87

CHAPTER VI—TYPICAL TWO STROKE CYCLE ENGINES

Two Port—Three Port—Marine—Controlled
Port—Aeronautic—Oechehauser—Gnome Rotary Two Stroke, Koerting 144

CHAPTER VII—OIL ENGINES

Elyria—Marine Diesel—Installation—Aspiration Types—Fairbanks
Morse—Kerosene—Carburetion Diesel—Semi Diesel—Combustion of Heavy
Oils 160

CHAPTER VIII—IGNITION SYSTEMS

Hot Tube System—Low Tension System—High Tension System—Details of
Make and Break Batteries—Low Tension Magnetos—High Tension
Magnetos—Coils—Adjustment—Troubles 195

CHAPTER IX—CARBURETORS

Principles of Carburetion—Jet Carburetors—Water Jacketing—Fuel
Supply—Different Types of Auto Carburetors—Adjustment Carburetor
Troubles 271

CHAPTER X—LUBRICATION

Forced Feed—Splash System—Oil Pumps—Lubrication Troubles 285

CHAPTER XI—COOLING SYSTEMS

Evaporation Systems—Radiators—Air Cooling 299

CHAPTER XII—SPEED GOVERNORS

Automobiles—Stationary—Adjustment—Mixture—Control—Hit and
Miss—Mixed Systems 308

CHAPTER XIII—TRACTORS

Gasoline and Oil Tractors—Mechanism of Various Types 324

CHAPTER XIV

Steam Tractors 349

CHAPTER XV—OIL BURNERS

Combustion—High Pressure System—Low Pressure System—Mixed
System—Burners for Furnaces, Locomotives, etc. 363

Gas, Oil and Steam Engines

CHAPTER I
HEAT AND POWER

(1) The Heat Engine.

Heat engines, of which the steam engine and gas engine are the most
prominent examples, are devices by which heat energy is transformed into
mechanical power or motion. In all heat engines, this transformation of
energy is accomplished by that property of heat known as “expansion,” by
which an increase or decrease of temperature causes a corresponding
increase or decrease in volume of the material subjected to the varying
temperatures. The substance whose expansion and contraction actuates the
heat engine is known as the “working medium,” and may be either a solid,
liquid, or a gas. The extent to which the working medium is expanded
depends not only upon the change of temperature but also on its
composition.

In all practical heat engines, the heat energy is developed by the
process of combustion, which is a chemical combination of the oxygen of
the air with certain substances, such as coal or gasoline, known as
“fuels.” The heat producing elements of the fuels are generally
compounds of carbon and hydrogen, which when oxydized or burnt by the
oxygen form products that are unlike either of the original components.
It is due to this chemical change that heat energy is evolved, for the
heat represents the energy expended by the sun in building up the fuel
in its original form, and as energy can neither be created nor
destroyed, heat energy is liberated when the fuel is decomposed. The
heat energy thus liberated is applied to the expansion of the working
medium to obtain its equivalent in the form of mechanical power.

During the period of expansion, the heat obtained by the combustion is
absorbed by the working medium in proportion to its increase in volume,
and as this increase is proportional to the mechanical effort exerted by
the engine, it will be seen that the output of the engine in work is a
measure of the heat applied to the medium. The quantity of heat absorbed
by the medium represents the energy required to set the molecules of the
medium into their new positions in the greater volume, or to increase
their paths of travel. In the conversion of heat, each heat unit applied
to the medium results in the production of 778 foot pounds of energy,
providing that there are no heat or frictional losses.

In explanation of these terms or units, we wish to say, that the unit of
heat quantity, called the =BRITISH THERMAL UNIT= is the quantity of heat
required to raise one pound of water, one degree Fahrenheit, and the
=FOOT POUND= is the work required to raise one pound through the
vertical distance of one foot. As the British Thermal Unit = 778 foot
pounds it is equivalent to the work required to raise 778 pounds one
foot or one pound 778 feet, or any other product of feet and pounds
equal to the figure 778.

As liquids expand more than solids with a given temperature, and gases
more than either, the mechanical work returned for a given amount of
thermal energy (the =EFFICIENCY=) will be greater with an engine using
gas as a working medium than one using a solid or liquid working medium.
The steam engine and the gas engine are both examples of heat engines
using gaseous working mediums, the medium in the steam engine being
water vapor and in the gas engine, air and the gaseous products of
combustion. For this reason the working medium will be considered as a
gas in the succeeding chapters.

Practically the only way of obtaining mechanical effort from an
expanding gas is to enclose it in a cylinder (c) fitted with a freely
sliding plunger or piston (p) as shown in Fig. 1. Two positions of the
piston are shown, one at M indicated by the dotted lines, and one at N
indicated by the full lines. It will be assumed that the space between
the cylinder head P and the piston at M represents the volume of the gas
before it is heated and expanded, and that the volume between O and N
represents the volume after heating and expansion have occurred. The
vessel B represents a chamber containing air that is periodically heated
by the lamp L, and which is connected to the working cylinder C by the
pipe O.

[Illustration:

=Figs. 1–2–3.= Showing Expansion in an External Combustion Engine, the
Cycle of Operations in an Internal Combustion Engine, and the
Pressure Diagram of the Latter Engine Giving the Pressures at
Various Points in the Stroke.
]

With the piston at M, the lamp L is lighted and placed under the retort
B which results in the immediate expansion of the air in B. The expanded
air passes through O into the cylinder, and if sufficient heat is
supplied, exerts pressure against the piston since it occupies much more
than its original volume. Providing that the friction of the device and
the load on the shaft S are low enough the pressure on the piston will,
move it to the position N in the direction of the arrow, thus
accomplishing mechanical work. The motion of the piston revolves the
crank to which it is connected by the rod X from D to E. During the trip
from M to N the volume of gas has greatly increased being supplied
continuously with heat from the lamp. As a considerable amount of heat
has been radiated from the cylinder during the piston travel, and a
considerable portion of the mechanical work lost through the friction of
the piston on the cylinder walls, and by the crank, not all of the heat
units are represented at the crank as mechanical effort.

Because of the limiting length of the cylinder, and the temperature
limits of the lamp it is not possible to expand the working medium and
increase the temperature indefinitely, therefore there must be a point
where the application of heat must cease and the temperature be reduced
in order to bring the gas back to its original volume and the piston to
its original position so that the expansion may be repeated. This
condition results in a very considerable loss of heat and power in
addition to the losses previously mentioned, as the heat taken from the
medium to reduce it to its original volume is thrown away as far as the
production of power is concerned. To return the piston to its former
position without expending energy on the engine, the volume and pressure
may be reduced either by allowing the gas to escape to the atmosphere by
means of a valve, or by removing the lamp and cooling the air by the
application of water, but in any case the heat of the air is lost and
the efficiency of the engine reduced.

To increase the efficiency of the engine and reduce the loss just
mentioned, nearly all heat engines, either steam or gas, have the
working medium at the highest temperature for only a small portion of
the stroke, after which no heat is supplied to the cylinder. As the
pressure forces the piston forward the volume increases, and as no more
heat is supplied, both the pressure and the temperature continue to
decrease until the end of the stroke is reached, thus utilizing the
greater part of the heat in the expansion. Since the temperature at the
end of the stroke is comparatively low, very little heat is rejected
when the valve is opened for the return stroke. This loss would be the
least when the temperature of the gas at the end of the stroke was equal
to the temperature of the surrounding air. With both the internal and
external temperatures equal, there would be no difference between the
pressure of the gas in the cylinder and that of the surrounding air.

[Illustration:

=Fig. 1-a.= Fairbanks-Morse Two Cylinder, Type “R E” Stationary Engine
Direct Connected to a Dynamo.
]

It will be seen from the example just given that the heat engine
performs mechanical work by dropping the working medium from a high to a
low temperature, as it receives the medium at a high temperature from
the lamp and rejects it at atmospheric temperature after delivering a
small percentage of useful work. This may be compared to a water wheel
which receives the working medium (water) at a high pressure and rejects
it at a lower pressure. Carrying this comparison still further, it is
evident that an increase in the range of the working temperatures (high
and low) would increase the output of the heat engine in the same way
that an increase in the range of pressures would increase the output of
the water wheel. The temperature at which the engine receives the
working medium and the temperature at which it is rejected determines
the number of heat units that are available for conversion into
mechanical energy, and therefore, if the range be increased by either
raising the upper limit of temperature or by reducing the lower limit,
or by the combined increase and decrease of the limits, the available
heat will be increased.

Based on the temperature range, the maximum possible efficiency of the
heat engine may be expressed by the ratio—

=Reception Temperature—Rejection Temperature=
E = ———————————————————————————————————————————
=Reception Temperature=

This maximum defined by Carnot establishes a limit that can be exceeded
by no engine, whatever the construction or working medium.

According to the methods adopted in applying the heat of combustion to
the working medium, heat engines are divided into two general classes,
(1) External combustion engines, (2) Internal combustion engines. The
expressions “Internal” or “External” refer to the point at which
combustion takes place in regard to the working cylinder, thus an
internal combustion engine is one in which the combustion takes place in
the working cylinder, and an external combustion engine is one in which
the combustion takes place outside of the working cylinder. The steam
engine is an example of an external combustion engine, the fuel being
burned in the furnace of a boiler which is independent of the engine
cylinder proper. As the fuel is burned directly in the cylinder of a gas
engine it is commonly known as an internal combustion engine.

An external combustion engine, such as the steam engine is subject to
many serious heat losses because of the indirect method by which the
heat is supplied to the working cylinder, aside from the losses in the
cylinder. Much of the heat goes up the smoke stack and much is radiated
from the boiler settings and the steam pipes that lead to the engine.
The greatest loss however is due to the fact that the range of
temperatures in the working cylinder is very low compared to the
temperatures attained in the boiler furnace, for it is practically
impossible to have a greater range than 350°F to 100°F with a steam
engine, while the furnace temperatures may run up to 2500°F and even
beyond.

High temperatures with a steam engine result in the development of
enormous pressures, a temperature of 547°F corresponding to an absolute
pressure of 1000 pounds per square inch. This pressure would require an
extremely heavy and inefficient engine because of the terrific strains
set up in the moving parts. The pressures established by air as a
working medium are very much lower than those produced by air or any
permanent gas at the same temperature, and for this reason it is
possible to exceed a working temperature of over 3000°F in the cylinder
of a gas engine without meeting with excessive pressures. This high
working temperature is one of the reasons of the extremely high
efficiency of the gas engine.

In order to compete with the gas engine from the standpoint of
efficiency, the steam engine builders have resorted to super-heating the
steam after it has left the boiler in order to increase the temperature
range in the cylinder. By applying additional heat to the steam after it
has passed out of contact with the water it is possible to obtain up to
600°F without material increase in the pressure, but the practical gains
have not been great enough to approach the gas engine with its 3000°F.
After reaching his maximum temperature at this comparatively low
pressure, the steam engineer has still to eliminate a number of other
losses that do not obtain with the gas engine.

Since the radiation losses of a burning fuel are proportional to the
time required for burning, it is evident that the rate of combustion has
much to do with the efficient development of the heat contained in it,
and it is true that rapid combustion develops more useful heat from a
given fuel than slow. In the gas engine the combustion is practically
instantaneous with a low radiation loss, but in the steam engine the
rate is slow, and with the excess of air that must necessarily be
supplied, a great part of the value of the fuel is lost before reaching
the water in the boiler. The temperature of the medium determines the
efficiency of the engine and as rapid combustion increases the
temperature it is evident that the gas engine again has the best of the
problem.

In the case of the gas engine where the fuel (in gaseous form) is drawn
directly into the working cylinder in intimate contact with the working
medium (air) and in the correct proportions for complete combustion,
each particle of fuel, when ignited, applies its heat to the adjacent
particle of air instantly and increases its volume with a minimum loss
by radiation.

A gas engine is practically a steam engine with the furnace placed
directly in the working cylinder with all intervening working mediums
removed, the gases of combustion acting as the working medium. It
derives its power from the instantaneous combustion of a mixture of fuel
and air in the cylinder, the expansion of which causes pressure on the
piston. Under the influence of the pressure on the piston, the crank is
turned through the connecting rod and delivers power to the belt wheel
where it is available for driving machinery. Whether the fuel be of
solid, liquid, or gaseous origin it is always introduced into the
cylinder in the form of a gas.

[Illustration:

Fig. 1-b. The English Adams Automobile Motor (End View), Showing the
Magneto Driven by Spiral Gears at Right Angles to the Crank-Shaft.
]

(3) Combustion In the Cylinder.

As the working medium in an internal combustion engine is in direct
contact with the fuel it must not only be uninflammable but it must also
be capable of sustaining combustion and must have a great expansion for
a given temperature range. Since atmospheric air possesses all of these
qualifications in addition to being present in all places in unlimited
quantities it is natural that it should be used exclusively as the
working medium for gas engines. Unlike the vapor working medium in a
steam engine the medium in the gas engine not only acts in an expansive
capacity but also as an oxydizing agent for burning the fuel, and
therefore must bear a definite relation to the quantity of the fuel in
the cylinder to insure complete combustion.

In the gas engine the use of gaseous fuel is imperative since there must
be no solid residue existing in the cylinder after combustion and also
for the reason that the fuel must be in a very finely subdivided state
in order that the combustion shall proceed with the greatest possible
rapidity. In addition to the above requirements the introduction of a
solid fuel into the cylinder would involve almost unsurmountable
mechanical problems in regard to fuel measurement for the varying loads
on the engine. This limits the fuel to certain hydrocarbon or compounds
of hydrogen and carbon in gaseous form of which the following are the
most common examples:

(a) =CARBURETED AIR= consisting of a mixture of atmospheric air and the
vapor of some hydrocarbon (liquid) such as gasoline, kerosene or
alcohol.

(b) =OIL GAS= formed by the distillation of some heavy, nonvolatile oil,
or the distillation of tar or paraffine.

(d) =COAL GAS=, made artificially by the distillation of coal, commonly
called “illuminating” gas.

(e) =PRODUCER GAS=, some times known as “fuel gas,” produced by the
incomplete combustion of coal in a form of furnace called a “producer.”

(f) =BLAST FURNACE GAS=, the unconsumed gas from the furnaces used in
smelting iron, somewhat similar to producer gas but lower in heat value.

It should be noted that there is no essential difference between engines
using a permanent gas or an oil as in either case the fuel is sent into
the cylinder in the form of a vapor. In the case of oil fuel, the vapor
is formed by an appliance external to the engine proper. In this book,
the heat action of an engine using one form of fuel applies equally to
the engine using another. The selection of a particular fuel for use
with a gas engine depends not only upon its value in producing heat, but
also upon its cost, the ease with which it meets the peculiar conditions
under which the engine is to work, and its accessibility.

Neglecting for the moment, all of the items that do not affect the
operation of the engine from a power producing standpoint, the principal
requirement of a fuel is the production of a high temperature in the
cylinder since the output is directly proportional to the temperature
range. Since a very considerable mass of air is to be raised to this
high temperature, the heat value, or =CALORIFIC VALUE= of the fuel in
British Thermal units is of as much importance as the temperature
attained in the combustion. The calorific value of different fuels vary
widely when based either on the cubic foot or pound, and a considerable
variation exists even among fuels of the same class owing to the
different methods of production or to the natural conditions existing at
the mine or well from which they originated. The principal elements of
gas engine fuels, carbon and hydrogen, exist in many different
combinations and proportions, and require different quantities of air as
oxygen for their combustion because of this difference in chemical
structure.

Since complete combustion is never obtained under practical working
conditions, the actual evolution of heat and the actual temperatures are
always much lower than those indicated by the =CALORIMETER= or heat
measuring device. Besides the loss of heat due to imperfect combustion,
there are many other losses such as the loss by radiation, connection,
and slow burning, the latter being the principal cause of low combustion
temperatures. From the statements in the foregoing paragraphs it will be
seen that the theoretical or absolute calorific value of a fuel is not
always a true index to its efficiency in the engine.

Complete combustion results in the carbon of the fuel being reduced to
carbon dioxide (CO_{2}) and the hydrogen to water (H_{2}O), with the
liberation of atmospheric nitrogen that was previously combined with the
fuel, and some oxygen. The reduction of the fuel to carbon dioxide and
water produces every heat unit available since the latter compounds
represent the lowest state to which the fuel can be burned. Carbon
however may be burned to an intermediate state without the production of
its entire calorific contents when there is not sufficient oxygen
present to thoroughly consume the fuel. Incompletely consumed carbon
produces a gas, carbon monoxide, as a product of combustion, and a
quantity of solid carbon in a finely subdivided state known as “soot.”
Unlike the products of complete combustion, both the carbon monoxide and
soot may be burned to a lower state with a production of additional heat
when furnished with sufficient oxygen, both the soot and the monoxide
being reduced to carbon dioxide during the process.

[Illustration:

Fig. F-2. Sunbeam Engine with Six Cylinders Cast “En Bloc” (in one
piece). At the Right and Under the Exhaust Pipe is the Compressed
Air Starting Motor that Starts the Motor Through the Gear Teeth
Shown on Flywheel. _From “Internal Combustion.”_
]

As the soot and monoxide have a calorific value it is evident that much
of the heat of the fuel is wasted if they are exhausted from the
cylinder without further burning at the end of the stroke. To gain every
possible heat unit it is necessary to furnish sufficient oxygen or air
to reduce the fuel to its lowest state. As the free oxygen and nitrogen
contained in the fuel are without fuel value, their rejection from the
cylinder occasions no loss except for that heat which they take from the
cylinder by virtue of their high temperature.

With complete combustion the =TEMPERATURE= attained increases with the
rate of burning, while the number of heat units developed remain the
same with any rate of combustion. Because of the conditions under which
the fuel is burned in the gas engine the fuel is burned almost
instantaneously with the result that high temperatures are reached with
fuels of comparatively low calorific value. With a given gas the rate of
combustion is increased with an increase in the temperature of the gas
before ignition and remains constant for all mixtures of this gas in the
same proportion when the initial temperature is the same. The rate of
combustion also varies with the composition of the gas, hydrogen burning
more rapidly than methane. As a rule it might be stated that the rate of
burning decreases with the specific gravity of the gas, the light gases
such as hydrogen burn with almost explosive rapidity, while the heavier
gases such as carbon dioxide are incombustible or have a zero rate of
combustion. In practice an increased rate of burning is obtained by
heating the charge before ignition by a process that will be explained
later.

Another factor governing the output of an engine with a given size
cylinder is the amount of air required to burn the fuel. The quantity of
air necessary for the combustion of the fuel determines the amount of
fuel that can be drawn into a given cylinder volume, and as we are
dependent upon the fuel for the expansion it is evident that with two
fuels of the same calorific value, the one requiring the least air will
develop the most power. Since the air required to burn hydrogen gas is
only one fourth of that required to burn the same amount of methane it
is clear that more hydrogen can be burned in the cylinder than methane.
This great increase in output due to the hydrogen charge is however,
considerably offset by the greater calorific value of the methane.

Should the air be in excess of that required for complete combustion, or
should a great quantity of incombustible gas, such as nitrogen be
present in the mixture, the fuel will be completely burned, but the
speed of burning will be reduced owing to the dilution. As the air is
increased beyond the proper proportions the explosions become weaker and
weaker as the gas becomes leaner until the engine stops entirely.
Because of the fact that it is impossible in practice to so thoroughly
mix the gas and air that each particle of gas is in contact with a
particle of air, the volume of air used for the combustion is much
greater than that theoretically required. A =SLIGHT= excess of air,
making a lean mixture, increases the efficiency of combustion although
it reduces the temperature and pressure attained in the cylinder. This
is due to the fact that while the temperature of the mixture is lower
than with the theoretical mixture the temperature of the burning gas
itself is much higher. A mixture that is too lean to burn at ordinary
temperatures will respond readily to the ignition spark if the
temperature or pressure is raised.

(4) Compression.

In the practical gas engine the gas is not ignited at the beginning of
the suction stroke by which it is drawn into the cylinder, but is
compressed in the front end of the cylinder by the return stroke of the
piston, and then ignited. The process of compression adds greatly to the
power output of a given sized cylinder and increases the efficiency of
the fuel and expansion. In order to understand the relation that the
compression bears to the expansion let us refer to Fig. 2 in which C is
the working cylinder, P the piston and G the crank. While the piston is
moving towards the crank in the direction of the arrow A it draws the
mixture, indicated by the marks x x x x x, into the cylinder, the
quantity being proportional to the position of the piston. In this
particular case let us assume that the area of the piston is 50 square
inches and that the entire stroke (B) of the piston is 12 inches. To
prevent confusion due to considerations of heat loss we will further
assume that the cylinder is constructed of non-conducting material.

With the piston at the position H, midway between J and I, the volume D
is filled with the explosive mixture at atmospheric pressure and a
temperature of 500° absolute. Since D = 6 inches and the area of the
piston is 50 square inches, the volume D is equal to 6 × 50 = 300 cubic
inches, and the entire volume is 2 × 300 = 600 cubic inches. On igniting
this mixture (at atmospheric pressure) the temperature will rise
immediately, say to 1000°F with the piston at H. According to a law
governing the expansion of gases, known as Gay-Lussac’s Law, the
expansion (v × T)/t = V where v = the initial volume of the gas before
ignition = 300 cubic inches; t = the temperature before ignition 500°
absolute; V = the volume of the gas after expansion; and T = temperature
after ignition = 1000° absolute. Inserting the values in numerical form
we have as the final volume:—(300 × 1000)/500 = 600 cubic inches = the
volume after expansion, or twice the original volume of gas. This means
that the expansion is capable of driving the piston from H to I before
the pressure is reduced again to atmospheric pressure. As the volume is
expanded to twice that of the original volume at atmospheric pressure
(14.7 pounds per square inch), the pressure against the piston before it
starts moving will be 2 × 14.7 = 29.4 pounds per square inch.

Let us now consider the case in which the charge is compressed before
ignition occurs and compare the expansion and pressure established with
that produced by ignition at atmospheric pressure. To produce the
compression the piston will travel through the entire stroke to the
position I on the suction stroke filling the entire cylinder volumes of
600 cubic inches with the mixture. On the return stroke the piston stops
at H, reducing the original volume of 600 cubic inches to 300 cubic
inches, doubling the pressure of the gas. The initial and final
temperatures will be considered as being the same as those in the first
example, 500° and 1000°. From Gay-Lussac’s Law—(v × T)/t = V and
substituting the numerical values (600 × 1000)/500 = 1200 cubic inches,
or the expanded volume will be four times the compressed volume, or four
times the initial volume of the first case where the gas was ignited at
atmospheric pressure.

It should be noted however, that while the expansion has been greatly
increased by the compression, that this is not all gain, as equivalent
work has been expended in compressing the charge. With the exception of
doubling the fuel taken into the cylinder, and consequently doubling the
output for a certain cylinder capacity, there has been no increase in
fuel efficiency except that due to conditions other than the mere
reduction in volume. In the second case the volume was increased four
fold which resulted in a piston pressure of 4 × 14.7 = 58.8 pounds per
square inch before the piston increased the volume by moving from H to
I.

The work done by the engine on the charge in compressing is converted
into heat energy causing a rise in the temperature of the gas. This
would not be a loss as it would reappear as mechanical energy on the
return stroke of the piston through its expanding effect on the gas.
This heat would, in effect, be added to the temperature due to ignition,
and the sum would produce its equivalent expansion. The temperature due
to the combustion may be determined by reversing Gay-Lussac’s Law—

t I Pt
— = — or T = ——
p P p

Where t = initial temperature; T = temperature combustion; P = pressure
after combustion; p = pressure before combustion.

Because of the fact that the act of compressing the charge in the
cylinder before ignition increases the temperature of the working
medium, the compression will increase the speed of combustion and
efficiency of the fuel as the rate of combustion increases with the
initial temperature. This increased temperature due to initial
compression of course results in a greater temperature range and output
due to the increased rate of burning, and this rate of combustion may be
varied for different fuels by changing the compression pressure. In a
previous paragraph it was explained that the fuel efficiency was
increased by a slight dilution or excess of air, and that while the
temperature and pressure of the mixture were reduced by the dilution the
temperature of the fuel was increased, provided that the inflammability
was not decreased.

Compression affords a means of using dilute mixtures without loss of
inflammability, as the heat gained by the compression restores the
inflammability lost by the effects of dilution. Increased compression
pressures increases the possible range of dilution, so that extremely
lean gases and mixtures may be used with success with appropriately high
compression. As an example of this fact we can refer to the engine using
blast furnace gas, a fuel that is so lean that it cannot be ignited
under atmospheric pressure. By increasing the piston speed, the heat of
the compression can be made more effective as the gas lies in contact
with the cylinder walls for a shorter time which of course reduces the
heat to the jacket water.

(5) Efficiency and Heat Losses.

Up to the present time we have considered an engine in which there is no
heat loss or loss from friction, but in the actual engine such losses
are large and tend to materially reduce the values of heat and pressure
to be obtained from a fuel with a given calorific content. Applying the
rule for heat engines given in a previous section where the efficiency
is—

T – t
E = —————
T

We have the theoretical efficiency of a gas engine, neglecting friction,
loss to the cylinder walls, and loss through the rejection of heat with
the exhaust gas, equal to—

1960 – 520
E = —————————— = 73.5 percent.
1960

In substituting the numerical values in the above calculation it was
assumed that the temperature of the burning mixture would be 1500° F
above zero, and that the exhaust temperature would be as low as 60.
Since the calculation is made from absolute zero, which is 460° below
the zero marked on our thermometers, the temperature of the burning
charge, T = 1500 + 460° = 1960° above absolute zero. Similarly the
absolute temperature of the exhaust would be, t = 60 + 460 = 520°
absolute. The application of the absolute temperatures will be seen from
the calculation for efficiency. The value given, 73.5 per cent, it
should be understood is the theoretical efficiency and is at least 20
per cent above the best results obtained in practice. The best record
that we have had to date, is that established by a Diesel engine which
returned 48.2 per cent of the calorific value of the fuel in the form of
mechanical energy. In order that the reader may have some idea of the
losses that occur in the engine, and their extent we submit the
following table. These are the results of actual tests obtained from
different sources and represent engines built for different services and
of various capacities:

═════════════════════════╤══════════╤══════════╤═══════════╤═══════════
LOSSES—DATA │Automobile│Stationary│Stationary │
│ Motor │ Engine │ Engine │
─────────────────────────┼──────────┼──────────┼───────────┼───────────
Horse-power │ 30. │ 200 │ 1000 │
│ │ │ │Loss at per
Heat lost to jacket water│ 35.8% │ 31.0% │2970 B.T.U.│Horse-power
│ │ │ │in B.T.U.’s
Heat lost in exhaust │ 24.6% │ 30.0% │2835 B.T.U.│
Friction loss │ 8.6% │ 6.5% │810 B.T.U. │
Heat lost by radiation │ 15.4% │ 8.2 │540 B.T.U. │
Heat available as power │ │ │2700 B.T.U.│
Efficiency (per cent) │ 15.6% │ 24.3 │ │
Fuel │ Gasoline │ │ Producer │
│ │ │ Gas │
─────────────────────────┴──────────┴──────────┴───────────┴───────────

The remarkable efficiency of the Diesel engine is due principally to the
extremely high compression pressure, which was from 500 to 600 pounds
per square inch. When this is compared to the 60 to 70 pounds
compression pressure used with automobile engines it is easy to see
where the Diesel gains its efficiency. It is evident that as much
depends on the manner in which the fuel is used in the engine as on the
calorific value of the fuel.

(6) Expansion of the Charge.

When an explosive mixture is ignited in the cylinder with the piston
fixed in one position thus making the volume constant, the increase of
temperature is accompanied by an increase of pressure. If the piston is
now allowed to move forward increasing the volume, the increase of
volume decreases the pressure. Since in the operation of the gas engine
the piston continuously expands the volume on the working stroke it is
evident that there is no point in the stroke where the pressures are
equal, and that the pressure is the least at the end of the stroke, it
being understood of course that no additional heat is supplied to the
medium after the piston begins its stroke.

This distribution of pressure in the cylinder in relation to the piston
position is best represented graphically by means of a diagram as shown
by Fig. 3, in which K is the cylinder and P the piston. Above the
cylinder is shown the diagram HGDE the length of which (HE) is equal to
the stroke of the piston shown by (BC). Intersecting the line HI are
vertical lines, A, a, b, c, C, which represent certain positions of the
piston in its stroke. The height of the diagram H G represents to scale
the maximum explosion pressure in pounds per square inch, and the line
HG is drawn immediately above the piston position B which is at the
inner end of the stroke. To the left of the line HS is drawn a scale of
pressures ML divided in pounds per square inch so that the pressures may
be read off of the pressure curve GD. The line JI represents atmospheric
pressure, and the divisions on ML, of course, begin from this line and
increase as we go up the column. As an example in the use of the scale
we find that the point F is at 50 pounds pressure above the atmospheric
line JI.

We will consider that the clearance space AB is full of mixture at the
point B, and that it is moved toward the left to the point C filling the
space AC full of mixture at atmospheric pressure. The location of the
piston on the diagram is shown by D and E. The opening through which the
gas was supplied to the cylinder is now closed, and the piston starts on
its compression stroke, moving from C to A. As the volume is reduced
from AC to AB, there is an increase of pressure which is shown
graphically by the rising line EF. This line rises gradually from the
line JI in proportion to the reduction in volume until the piston
reaches the end of the compression stroke at B, at which point the
compression is at a maximum. The extent of this pressure is shown by the
length of HF which on referring to the scale of pressure at the left
will be found to be 50 pounds per square inch.

Ignition now occurs and the pressure increases instantly from the
compression pressure at F to the maximum pressure at G which on
referring to the scale will be found to equal 200 pounds. The actual
increase of pressure due to ignition above the compression pressure will
be shown by the length of the line FG which is equal to 150 pounds. As
the pressure is now established against the piston it will begin to move
forward with an increase of volume and a corresponding decrease in
pressure, until it reaches the point C. This point at the end of the
stroke is indicated on the diagram by D which by reference to the scale
will be found equal to 25 pounds above atmosphere. An exhaust valve is
now opened allowing the gas to escape to the atmosphere which reduces
the pressure instantly from D to E on the atmospheric line. Expansion
along the line GD is not complete as the pressure is not decreased to
atmospheric pressure in the cylinder which means that there is a
considerable loss of heat in the exhaust. In practice the expansion is
never complete, but ends considerably above atmospheric pressure as
shown.

[Illustration:

Fig. F-3. Front Elevation of Curtiss “V” Type Aeronautical Motor. This
is the Front View of the Motor Shown in the Frontispiece. See
Chapter V for Description of this Type of Motor.
]

Complete expansion is shown by the dotted line GE which terminates at E
on the atmospheric line. By following the vertical lines up from the
points a, b, c, and d, the pressures corresponding to these piston
positions can be found by measuring the distance of the curve from the
atmospheric line, on the given lines a, b, c or d. To find the pressure
at the position a, for instance, follow upwards along the line a to the
point c on the curve, the length of the line ef from the curve to the
atmospheric represents the pressure, which by reference to the scale ML
will be found equal to 125 pounds. The pressure at any other point can
be found in a like manner. Compression pressures may be found at any
point by measuring from the atmospheric line to the compression curve FE
along the given line. It will be noted that the combustion is so quick
that the pressure rises in a straight line along GH, indicating that
combustion was complete before the piston had time to start on the
outward stroke. The expansion curves GE and GD are similar to the
compression curve FE. With the actual engine the shape of the ideal card
as shown by Fig. 3 is sometimes considerably deformed owing to the
effects of defective valves, leaks, or improperly timed ignition.

Pressure curves of actual engines are of the greatest value as they show
the conditions within the cylinder at a glance and make it possible to
detect losses due to leaks, poor valve settings, etc. These curves are
traced by means of the =INDICATOR= which is an instrument consisting of
a small cylinder which is connected to the cylinder of the engine, and
an oscillating drum that is driven to and fro by the engine piston. The
piston in the indicator cylinder is provided with a spring that governs
its movements and communicates its motion to a recording pencil through
a system of levers. The spring is of such strength that a pressure of so
many pounds per square inch in the cylinder causes the pencil to draw a
line of a definite length, this line being equivalent to the pressure
line GH in Fig. 3. A piece of paper is wrapped about the indicator drum,
and the drum is attached to the piston in such a manner that it turns a
certain amount for every piston position, the complete stroke of the
piston turning the drum through about three-quarters of a revolution.
Rotation of the drum traces the horizontal lines of the diagram and the
movement of the piston draws the vertical lines, so the combined
movements of the drum and piston records the pressures and piston
positions as shown by Fig. 3.

Since the movement of the indicator piston represents the pressures in
the cylinder to scale it is possible to compute the power developed in
the cylinder as the output in mechanical units is equal to the product
of the average force acting on the piston multiplied by the speed of the
piston in feet per minute. This product of the force and velocity (known
as “foot pounds per minute”) divided by 33,000 (one horse-power = 33,000
foot pounds) gives the output of the engine, in horse-power.

As the pressure on the piston fluctuates throughout the stroke, it would
be wrong to consider the force, in the calculation for power as being
equal to the explosion pressure, and so the effective pressure is taken
as being the average of all the pressures from the point of explosion to
the exhaust. The average pressure or “mean effective pressure” as it is
called is computed from the indicator diagram by dividing it into a
number of equal parts along the horizontal line, adding the lengths of
the pressure lines such as CH, CF, etc., and dividing the total length
by the number of the lines. After the average height of the diagram is
thus determined, the average length is multiplied by the scale of the
indicator or the pressure that is shown by it per inch.

[Illustration:

Fairbanks-Morse Gasoline Pumping Engine. Pump is Gear Driven From the
Engine Crank-Shaft at Reduced Speed.
]

Knowing the mean effective pressure, the total pressure on the piston,
or the force is found by multiplying the area of the piston in square
inches by the average pressure per square inch. This product is
multiplied by the piston speed in feet per minute and is divided by the
product of the number of strokes to the explosion and the quantity
33,000. Should there be more than one cylinder the result is multiplied
by the number of cylinders, and this is multiplied by 2 in the case of a
double acting engine. Stated as a formula this rule becomes:

A × P × 2R × L × N × O
H.P. = ——————————————————————
33000 × C

When A = Area of piston in square inches.
P = Average or mean effective pressure per square inch. About 75
pounds for Gasoline Engines. See Table on Page 31.
R = Revolutions per minute.
L = Stroke of piston in feet.
N = Number of cylinders.
O = 2 when engine is double acting, that is when explosions occur
on both sides of the piston.
C = Number of strokes per explosion. C = 4 in a four cycle engine,
and 2 in a two cycle.

It should be specially noted that the area of the piston is given in
square inches and the stroke of the piston in feet. The number of
revolutions per minute, R, is multiplied by two in order to obtain the
number of strokes, as there are two strokes per revolution. When the
engine governs its speed by dropping explosions to meet varying loads,
the quantity C should be omitted and the explosions counted.

* * * * *

Due to the fact that the incoming charge of the mixture is expanded by
the heat of the passages, a full charge computed at atmospheric
temperature is never obtained in the cylinder and for this reason the
gas should be kept as cold as possible before entering the passages in
order to obtain the maximum output. Friction due to restricted passages
and valve openings also reduces the amount of mixture available. Small
exhaust valves and pipes prevent the gases from escaping freely to the
atmosphere and produces a back pressure on the piston which cuts down
the effective pressures. All of these items are recorded by the
indicator and makes it possible to make alterations that will increase
the output of the engine.

Because of the reduced atmospheric pressures at high altitudes the
output and compression are reduced for every foot of elevation above sea
level. As the weight of the atmosphere is reduced, less mixture is drawn
into the cylinder. Taking the output of the engine as 100 per cent at
sea level, it is reduced to less than 62 per cent at an elevation of
15,000 feet.

CHAPTER II
FUELS AND COMBUSTION

(7) Combustion.

The phenomenon called combustion by which we obtain the heat energy
necessary for the operation of the internal combustion engine is a
chemical combination of the air with the fuel. This process results in
heat and some light which is equal in quantity to the energy required to
separate the fuel compound into its elements or to build it up in its
present form from the original elements. If the process is comparatively
slow, the compound is called a fuel, if it is instantaneous it is called
an explosive. Some substances produce mechanical force through an
instant, without the evolution of much heat, due to the disintegration
of an unstable compound. The effect of the latter type of which dynamite
is an example is static, that is to say, it is not capable of producing
power, but only pressure. For this reason, compounds having an
instantaneous effect without the ability to produce the pressure through
a distance, or an expansion, are not considered as suitable fuels for a
heat engine.

A fuel is essentially a substance which is capable of generating heat,
which is a form of energy, and not static pressure. The heat engine is
an instrument which transforms this energy into power which is again
dissipated into heat through the friction of the engine itself and by
the load that it drives. This is an illustration of the physical law
that “energy can neither be created nor destroyed,” that is, the heat
energy developed by the fuel is converted into mechanical energy which
is again transformed into heat energy through friction.

It should be understood that fuel belongs to that class of substances
that will not burn nor evolve energy under any temperature, pressure, or
shock, without an outside supply of oxygen. This is the characteristic
property of all fuels used with the internal combustion engine. Each
element, such as carbon and hydrogen, in a compound fuel, develops a
certain definite amount of heat during their complete combustion, and at
the close of the process certain compounds are formed that represent the
lowest chemical form of the compound. To restore the products of
combustion to their original form as fuel would require an expenditure
of energy equal to that given out in the combustion.

While all substances that are capable of oxydization or combustion can
be made to liberate heat energy, it does not follow that all of them can
be successfully used as fuels. A fuel suitable for the production of
power must be cheap, accessible and of small bulk, and must burn
rapidly. Such fuels must also be products of nature that require no
expenditure of energy in their preparation or completion.

[Illustration:

Fig. F-4. Fairbanks-Morse Producer Plant and Engine, Connected for
Operation.
]

In practical work, the natural fuels are coal, mineral oils, natural
gas, and wood, which are compounds of the elements carbon and hydrogen.
When these fuels are burned to their lowest forms the products of
combustion consist of carbon dioxide and water, the first being the
result of the oxydization of carbon, and the latter a compound of oxygen
and hydrogen. In solid fuels, such as coal, a portion of the compound
consists of free carbon and the remainder of a compound of carbon and
hydrogen known as a =HYDROCARBON=. In liquid fuels there is little, if
any, free carbon, the greater proportion being in the form of a
hydrocarbon compound. Natural gas is a hydrocarbon compound.

It should be noted that a definite amount of oxygen is required for the
complete combustion of the fuel elements, and that a smaller amount of
oxygen than that called for by the fuel element results in incomplete
combustion, which produces a product of higher form than that produced
by the complete reduction. The product of incomplete combustion
represents a smaller evolution of heat than that of the complete
process, but if reburned in a fresh supply of oxygen the sum of the
second combustion together with that of the first will equal the heat of
the complete oxydization. When pure carbon is incompletely burned the
product is carbon monoxide (CO) instead of carbon dioxide (CO_{2}).

Carbon completely burned to carbon dioxide produces 14,500 British
thermal units per pound of carbon, while the incomplete combustion to
carbon monoxide evolves only 4,452 British thermal units, or less than
one-third of the heat produced by the complete combustion. Theoretically
one pound of carbon requires 2.66 pounds of oxygen to burn it to carbon
dioxide. On supplying additional oxygen, the carbon monoxide may be
burned to carbon dioxide and the remainder of the heat may be recovered,
or 10,048 British thermal units. When a hydrocarbon, either solid,
liquid or gaseous is burned with insufficient oxygen, solid carbon is
precipitated together with lower hydrocarbons, and tar. In an internal
combustion engine the precipitated solid carbon is evident in the form
of smoke.

Since the carbon and hydrogen elements of a fuel exist in many different
proportions and conditions in coal and oil, different amounts of oxygen
are required for the consumption of different fuels. It should also be
borne in mind that a greater quantity of air is required for the
combustion of a fuel than oxygen, as the air is greatly diluted by an
inert gas, nitrogen, which will not support combustion. Because of the
impossibility of obtaining perfectly homogenous mixtures of air and the
fuel, a greater quantity of air is used in practice than is
theoretically required.

In a steam engine the fuel can be used in any form, solid, liquid, or
gaseous, but in an internal combustion, it must be in the form of a gas
no matter what may have been the form of the primary fuel. Fortunately
there is no fuel which may not be transformed into a gas by some process
if not already in a gaseous state. The petroleum products are vaporized
by either the heat of the atmosphere or by spraying them on a hot
surface. Coal is converted into a gas by distilling it in a retort or by
incomplete combustion. The heat energy developed by a gas when burning
in the open air depends on its chemical combustion, but its mechanical
equivalent in power when burned in the cylinder of the engine depends
not only upon its composition but upon the conditions under which it is
burned as stated in the chapter devoted to the subject of heat engines.

(8) Gaseous Fuels.

While the calorific values of the different gases given in the
accompanying table are approximately correct for gases burning in the
open air at atmospheric pressure they develop widely different values in
the cylinder of an engine because of the effects of compression and
preheating. The table serves, however, as an index to the relative
values of the fuels under ordinary conditions without compression. While
natural gas has nearly eight times the calorific value of producer gas
in the open air, its actual heat value in the cylinder is only about 45
per cent greater. While acetylene has an exceedingly high calorific
value and explodes five times as fast as gasoline gas, it develops only
20 per cent more power in the same cylinder. Another item affecting the
value of a gas is the rate at which it burns, which is in part a
characteristic of the fuel and partly a factor of the conditions under
which it is burnt. This subject is treated of in the chapter devoted to
the heat engine.

The calorific value of a gas may either be computed from its chemical
composition or by burning it in an instrument known as a =calorimeter=.
A gas calorimeter consists of a small boiler or heating tank which is
carefully covered with some non-conducting material so as to prevent a
loss of heat to the atmosphere. The gas under test is burned in the
boiler whose extended surface catches as much of the heat as possible
and transfers it to the water in the boiler. The weight of the water
heated and its temperature are taken when a certain amount of the gas
has been burned (say 100 cubic feet), and from this data, the heat units
per cubic foot of gas are computed.

FUEL GASES.

══════════════╤══════╤═════════════════════════╤═══════════╤══════
GAS │B.T.U.│ Cubic Feet of Air │ Usual │Ratio
│ per │Required to Burn 1 Cubic │Compression│of Gas
│Cubic │ Foot of Gas │ Lbs. per │to Air
│ Foot │ │ Sq. Inch │
│ │ │ │
──────────────┼──────┼────────────┬────────────┼───────────┼──────
│ │ Actual │Theoretical │ │
──────────────┼──────┼────────────┼────────────┼───────────┼──────
Natural Gas │ 1000.│ 12.60│ 9 │ 130│1–12.6
Natural Gas │ 1000.│ │ │ 110│1–6
Coal Gas │ 650.│ 9.00│ 5.85 │ 80│1–9
Producer │ 140.│ 1.20│ 1.85 │ 160│1–1.2
Anthracite │ │ │ │ │
Producer │ 160.│ 3.20│ 2.20 │ │
Bituminous │ │ │ │ │
Water Gas │ 290.│ 3.60│ 2.20 │ │
(Uncarb.) │ │ │ │ │
Water Gas │ 500.│ 8.50│ 5.15 │ │1.8
(Carb.) │ │ │ │ │
Blast Furnace │ 94.│ 1.10│ 0.70 │ 170│
Gas │ │ │ │ │
Acetylene │ 1500.│ 20.00│ 12.60 │ │
Gasolene Vapor│ 520.│See Table of Liquid Fuels│ 70│1.12
Gasolene Vapor│ 520.│See Table of Liquid Fuels│ 70│1.8
Gasolene Vapor│ 520.│See Table of Liquid Fuels│ 70│1.6
Kerosene Vapor│ │See Table of Liquid Fuels│ 60│1.8
Coke Oven Gas │ 520.│ 7.│ 5.4 │ │
Alcohol │ │ │ │ 180│
──────────────┴──────┴────────────┴────────────┴───────────┴──────

══════════════╤═════════╤═══════════╤═══════════╤══════╤══════╤═════════
GAS │Explosion│Temperature│ Ignition │Weight│Candle│ Mean
│Pressure │ of │Temperature│ per │Power │Effective
│ in Lbs. │Combustion │ F° │Cubic │ │Pressure
│ per Sq. │ F° │ │Foot, │ │
│ In. │ │ │ Lbs. │ │
──────────────┼─────────┼───────────┼───────────┼──────┼──────┼─────────
│ │ │ │ │ │
──────────────┼─────────┼───────────┼───────────┼──────┼──────┼─────────
Natural Gas │ 375│ │ 1100│.0459 │ │ 94.00
Natural Gas │ 245│ │ 1000│ │ │ 72.00
Coal Gas │ 285│ │ 1200│.035 │ 18.00│ 85.00
Producer │ 360│ │ 1450│.065 │ │ 88.00
Anthracite │ │ │ │ │ │
Producer │ │ │ 1350│ │ │
Bituminous │ │ │ │ │ │
Water Gas │ │ │ │.044 │ │
(Uncarb.) │ │ │ │ │ │
Water Gas │ │ │ │ │ 22.00│
(Carb.) │ │ │ │ │ │
Blast Furnace │ │ │ 1560│.080 │ │ 77.5
Gas │ │ │ │ │ │
Acetylene │ │ │ │ │ │
Gasolene Vapor│ 245│ 1865│ 1550│ │ │ 79.00
Gasolene Vapor│ 360│ 2950│ 925│ │ │ 82.00
Gasolene Vapor│ 410│ 3160│ 910│ │ │ 84.50
Kerosene Vapor│ 285│ │ 945│ │ │ 85.00
Coke Oven Gas │ │ │ │.042 │ │
Alcohol │ 450│ │ │ │ │
──────────────┴─────────┴───────────┴───────────┴──────┴──────┴─────────

As a British thermal unit is the amount of heat required to raise the
temperature of one pound of water through one Fahrenheit degree (at
about 39.1° F.), the total heat per cubic foot of gas as observed by the
calorimeter is equal to the weight of the water multiplied by its rise
in temperature in degrees, divided by the number of cubic feet of gas
burned in the calorimeter. Since a British thermal unit is equal to 778
foot pounds in mechanical energy, its mechanical equivalent is equal to
the number of British thermal units multiplied by 778.

Another difference between the actual and theoretical results obtained
is that due the perfect combustion in the calorimeter and the imperfect
combustion in the engine. Since some gases require more air for their
combustion than others, less of the first gas will be taken into the
cylinder on a charge than the latter, which tends still further to
balance the heating effect of rich and lean gases in the cylinder.

(9) Gasifying Coal.

=Coal Gas= or =Illuminating Gas= is generated by baking the coal in a
closed retort or chamber out of contact with the air so that no
combustion takes place either complete or incomplete. The hydrocarbon
gases and tars are set free from the coal as permanent gases and are
then piped to a gas holder after going through various purifying
processes to remove the tars, oils, moisture and dust. The free or solid
part of the coal remains in the retort in the form of =coke=, which is
again burned for fuel.

Because of its high carbon content, coal gas burns with a
yellowish-white flame and is extensively used for lighting purposes,
hence the name =illuminating gas=. In many ways coal gas is an ideal
fuel for power purposes as it has a high calorific value (650–750 B.T.U.
per cubic ft.), is supplied by the illuminating company at practically a
constant pressure, and is uniform in quality. Its only drawback is its
comparatively high cost.

This gas is always obtained from the city service mains as its
preparation is too expensive and complicated for the gas engine owner.
Because of its cost, the use of coal gas is restricted to small engines.

(10) Water Gas.

Water gas is made by blowing air through a thick bed of some coal that
is low in hydrocarbons until the coal becomes incandescent, the gases
that are formed are allowed to escape to the atmosphere. At this point a
jet of steam is blown into the incandescent bed, which is broken up into
its elements, oxygen and hydrogen, by the heat of the fuel. As there is
no air present the oxygen combines with the carbon of the fuel to form
carbon monoxide while the hydrogen goes free. Both of these gases,
carbon monoxide and hydrogen, are collected and supplied to the engine.
The production of water gas is intermittent, as the steam blast cools
down the fuel bed, and requires further blowing before more steam can be
passed. While this gas has a lower heating value than coal gas, it is
much cheaper to make and all of the coal is consumed in the process.

Water gas is high in hydrogen and is too “snappy” for gas engines; the
hydrogen places a limit on the allowable compression.

For each thousand feet of =water gas= generated, approximately 24 pounds
of water are required.

By the introduction of hydrocarbons or vaporized oil, illuminating value
is given to water gas, this process is called =carburetion=. Carbureted
gas is not usually used for power, as it is expensive, and is not
proportionately high in heating value.

(11) Blast Furnace Gas.

Many steel companies are utilizing the unconsumed gas of the blast
furnaces for power.

Blast furnace gas is of very low calorific value, rarely if ever,
exceeding 85 B.T.U. per cubic foot. This allows of very high
compression, which greatly increases the actual power delivered by the
engine.

A smelter produces approximately 88,000 cubic feet of gas per ton of
iron smelted.

Blast furnace gas is so lean that it cannot be burned satisfactorily
under a boiler; the high compression of the gas engine makes its use
possible.

(12) Producer Gas.

Producer gas which is generated by the incomplete combustion of fuels in
a deep bed is the most commonly used gas for engines having a capacity
of 50 horsepower and over, because of the simplicity and economy of its
production. While producer gas has been obtained from practically every
solid fuel, of which coal, coke, wood, lignite, peat, and charcoal are
examples, the fuel most generally used is either coal or coke. While
producer gas is much lower in calorific value than either natural or
illuminating gas it gives admirable results in the gas engine and is a
much cheaper fuel than coal gas in units above 50 horse-power capacity.
The fuel is completely burned to ash in the producer without the
intermediate coke product that exists in the manufacture of coke.

A producer consists of three independent elements as shown by Fig. F-6;
the =PRODUCER= or generator (A), the steam boiler (B), and the
=SCRUBBER= or purifier (C). The incandescent fuel (F) in the form of a
cone lies on the grate bars (G) at the lower end of the producer. Above
the burning fuel is a deep bed of coal (D) which reaches to the top of
the producer at which point it is admitted to the bed through the
charging valve or gate (H). The gas resulting from the combustion in the
producer is drawn out of the tank through the gas outlet pipe (E) by the
suction of the engine. The air for the combustion is drawn up through an
opening in the ash pit (J) by the engine.

When the oxygen of the air strikes the incandescent fuel on the grate it
combines with a portion of it forming carbon dioxide (CO_{2}) which is
an incombustible gas, but on passing through the burning fuel above this
point, one atom of the oxygen in the CO_{2} recombines with the fuel
forming the combustible gas—carbon monoxide (CO). Because of the
distilling effect of the heat in the bed, the volatile hydrocarbons of
the coal are set free and mingle with the CO formed by the combustion.
The producer gas consists, therefore, principally of CO, with a certain
proportion of the volatile hydrocarbons of the coal such as marsh gas,
ethylene, and some oil vapor.

Since the hydrocarbons are easily condensed on coming into contact with
the coal walls of the piping, to form trouble making tars and oils, they
must either be washed out of the gas in the purifier or passed again
through the high temperature zone to convert them into permanent gases.
In the usual producer, the hydrocarbons are reheated, as they form a
considerable percentage of the heat of the gas. After the volatile
constituents are reheated, the gases pass through the boiler (B), which
absorbs the heat of the gas in generating steam, and from this point the
gases enter the scrubber where the dust and the residual tars are
removed. The scrubber, which is a sort of filter, is an important factor
in the generating plant, for if the dust and dirt were allowed to pass
into the cylinder of the engine it would only be a question of a short
time until the valves and cylinder would be ground to pieces.

When the steam from the boiler is allowed to flow into the ash pit of
the producer and up through the incandescent fuel, the heat separates
the water vapor into its two elements, oxygen and hydrogen. The oxygen
set free combines with the carbon in the coal forming more carbon
monoxide, while the hydrogen which is unaffected by the combustion adds
to the heat value of the gas. The last additions to the combustion due
to the disassociation of the steam are really what is known as “water
gas.” A limited amount of steam may be admitted continuously in this
manner without lowering the temperature of the fuel below the gasifying
point, and its presence is beneficial for it not only provides more CO
and hydrogen but produces it without introducing atmospheric nitrogen.
The steam is also a great aid in preventing the formation of clinkers on
the grate bars. Since the air used in burning the fuel in the first
reaction contains about 79 per cent of nitrogen, which is an inert gas,
the producer gas is greatly diluted by this unavoidable admixture, which
accounts for its low calorific value.

[Illustration:

Fig. F-6. Diagram of Suction Gas Producer Showing the Generator,
Boiler and Washer.
]

While the air required for the combustion of the fuel is drawn through
the producer by the suction of the engine in the example shown (=SUCTION
PRODUCER=), there is a type in common use called a =PRESSURE PRODUCER=
in which the air is supplied under pressure to the ash pit by a small
blower, which causes a continuous flow of gas above atmospheric
pressure.

Gas producers are divided into two classes: suction producers and
pressure producers. The suction producer presents the following
advantages:

1. The pipe line is always less than atmospheric pressure, hence no
leaks of gas to the air are possible.

2. The regulation of the gas supply is automatic.

3. No gas storage tank is required.

4. The production of gas begins and stops with the engine.

5. Uniform quality of gas.

The suction producer is limited to power application and cannot be used
where the gas is to be used for heating, as in furnaces, ovens, etc., or
where the engine is at a distance from the producer, unless pumped to
its destination.

The pressure producer does not yield a uniform quality of gas, hence
requires a storage tank where low quality gas will blend with gas of
higher calorific values and produce a gas of fairly uniform quality.

The pressure producer is adapted to the use of all grades of fuels, such
as bituminous coal and lignite.

Anthracite coal contains little volatile matter and is an ideal fuel for
the manufacture of producer gas, while bituminous coal with its high
percentage of volatile matter and tar, requires more efficient
scrubbing, as these substances must be removed from the gas.

On starting the producer shown by Fig. 6, the producer is filled with
the proper amount of kindling and coal, and a blast of air is sent into
the ash pit by a small blower, the products of combustion being sent
through the by-pass stack (K) until the escaping gas becomes of the
quality required for the operation of the engine. The by-pass valve is
now closed, and the gas is forced through the scrubber to the engine
until the entire system is filled with gas. When good gas appears at the
engine test cock the engine is started, and the blower stopped, the gas
now being circulated by the engine piston. The volume of gas generated
by the producer is always equal to that required by the engine so that
no gas receiver or reservoir is required. Because of the friction of the
gas in passing through the fuel, scrubber and piping, its pressure at
the engine is always considerably below that of the atmosphere, which of
course reduces the amount of charge taken into the cylinder. Because of
the weak gas and the low pressure in the piping, it is necessary to
carry a much higher compression with producer gas than with natural or
illuminating gas.

The efficiency of a producer is from 75 to 85 per cent, that is, the
producer will furnish gas that has a calorific value of an average of 80
per cent of the calorific value of the fuel from which it is made, the
remaining 15 to 20 per cent being consumed in performing the combustion.
This is far above the efficiency of the furnace in a steam boiler, as an
almost theoretically exact amount of air can be supplied in the producer
to effect the combustion, while in the boiler furnace about ten times
the theoretical amount is passed through the fuel bed to burn it.
Heating up this enormous volume of air to the temperature of the
products of combustion consumes a large amount of fuel and reduces the
efficiency of the furnace considerably. Because of the reduction in the
air supply, a gas fired furnace is always more efficient than one fired
with coal. Producer gas with 300,000 British thermal units per thousand
cubic feet, and oil having 130,000 British thermal units per gallon will
result in 1,000 cubic feet of gas being equal to about 2.30 gallons of
fuel oil.

If the gas is to be used for heating ovens or furnaces in connection
with the generation of power, the character of the fuel will be
determined to a great extent by the requirements of the ovens and by the
type of producer used, as each fuel will give the gas certain
properties. Thus gas used for firing crockery will not be suitable for
use in open hearth steel furnaces, as the impurities in the various
fuels may have an injurious effect on the manufactured product. The cost
of the fuel, cost of transportation, heat value, purity, and ease of
handling are all factors in the selection of a fuel.

The size and condition of a fuel is also of importance. Exceedingly
large lumps and fine dust are both objectionable.

Wet fuel reduces the efficiency of the producer, as the water must be
evaporated, this causing a serious heat loss.

With careful attention a producer gas engine will develop a horse-power
hour on from 1 to 1¼ pounds of anthracite pea coal, and in many
instances the consumption has been less than this figure. The efficiency
in dropping from full load to half load varies by little, one test
showing a consumption of 1.1 pounds of coal per horse-power hour at full
load and 1.6 pounds of coal at half load. Producer gas power is nearly
as cheap as water power, in fact the producer gas engine has displaced
at least two water plants to the writer’s knowledge. According to an
estimate made by a well known authority, Mr. Bingham, it is possible for
a producer gas engine to generate power for only .1 of one cent more per
K.W. hour than it is generated at Niagara Falls.

According to the United States Bureau of Mines,

“The tests in the gas producer have shown that many fuels of so low
grade as to be practically valueless for steaming purposes, such as
slack coal, bone coal and lignite, may be economically converted into
producer gas and may thus generate sufficient power to render them of
high commercial value.

“It is estimated that on an average each coal tested in the producer-gas
plant developed two and one-half times the power that it would develop
in the ordinary steam-boiler plant.

“It was found that the low-grade lignite of North Dakota developed as
much power when converted into producer gas as did the best West
Virginia bituminous coals burned under the steam boiler.

“Investigations into the waste of coal in mining have shown that it
probably aggregates 250,000,000 to 300,000,000 tons yearly, of which at
least one-half might be saved. It has been demonstrated that the
low-grade coals, high in sulphur and ash, now left underground, can be
used economically in the gas producer for the ultimate production of
power, heat and light, and should, therefore, be mined at the same time
as the high-grade coal.

“As a smoke preventer, the gas producer is one of the most efficient
devices on the market, and furthermore, it reduces the fuel consumption
not 10 to 15 per cent, as claimed for the ordinary smoke preventing
device offered for use in steam plants, but 50 to 60 per cent.”

(13) Producer Gas From Peat.

The production of gas from peat having a low water content (up to about
20 per cent) for use in suction gas engines has already met with
considerable success in Germany, but for a number of years efforts have
been made to utilize peat with a water content as high as 50 to 60 per
cent and thus eliminate the costly process of drying the raw material.

Difficulties have been encountered in preventing a loss of heat through
radiation and other causes, and in getting rid of the dust and tar
vapors carried over by the gases to the engine; but great strides have
been made recently in overcoming these obstacles. Peat with a water
content up to 60 per cent has been found to be a suitable fuel. Owing to
its great porosity and low specific gravity it presents a large
combustion surface in the generator, so that the oxygen in the air used
as a draft can easily unite with the carbon of the peat.

[Illustration:

Fig. F-7. German Producer for Generating Producer Gas from Peat.
]

One of the great difficulties is to eliminate the tar vapors that clog
up many of the working parts of the engine. The passing of the gas
through the wet coke washers and dry sawdust cleansers does not appear
to have thoroughly remedied the evil. Efforts were therefore made to
remove the tar-forming particles of the gas in the generator itself or
to render them harmless. That of the Aktien-Gesellschaft Gorlitzer
Maschinenbau Ansalt und Eissengiesserei of Gorlitz, was displayed at the
exposition at Posen in 1911. The gas from the generating plant was
employed in a gas suction engine of 300 horse-power used to drive a
dynamo for developing the electric energy for the exposition. The fuel
used was peat with a water content of about 40 per cent. The efficiency
and economy results obtained were very promising.

The advantages claimed for the Gorlitz engine are that the sulphurous
gases and those containing great quantities of tar products are drawn
down by the suction of the engine through burning masses of peat and
thus rid of their deleterious constituents. The air for the combustion
purposes is well heated before entering the combustion chamber, thereby
producing economical results. It is claimed also that the gas produced
by its system is so free from impurities that the cleaning and drying
apparatus may be of the simplest kind.

In _Stahl und Eisen_, an abstract is given of a paper by Carl Heinz
describing a peat gas producer, built by the Goerlitzer
Maschinenbauanstalt. We are indebted to _Metallurgical and Chemical
Engineering_ for the translation of this paper:

Air and fuel enter the producer at the top, and the gas exit is in the
center of the bottom so that the air is forced to pass through the
center of the producer, decomposing the volatile matter into gases of
calorific value. The moisture which is present in the peat fuel in
considerable quantities must be taken into consideration. For its
decomposition which passing through the hot-fire zone only a certain
amount of heat is available. It is, therefore, important that the heat
from the gasification be fully utilized.

There are two kinds of heat losses in a gas producer, due to radiation
and to the sensible heat of escaping gases. Both these amounts of heat,
however, are utilized according to the special design of this producer.
The air circulates first through the lower conduit and comes so in
contact with the warm scrubber water. A part of the air which has been
preheated is carried upwards through the pipe =A= in the center of the
producer where it is thoroughly preheated by the hot gases and enters
then the air superheater =B= in which the temperature rises to a still
higher degree.

The other part of the air passes through the feet of the producer into
an air jacket which envelops the whole shell of the producer and enters
finally the producer by the reversing valve =C= on top of the producer.
In this way the outer surface of the producer is maintained at a
temperature hardly higher than that of the surrounding air. The escaping
gases are cooled down so far that the gas outlet into the scrubber may
be touched by hand. All ordinary heat losses are thus made use of in the
gasification process.

If there is a large excess of moisture in peat, the process is somewhat
modified by regulating both air supplies in such a way that the
gasification in the upper part of the fuel-bed takes place in two
directions, one downwards and the other upwards.

It seems that a content of 80 per cent moisture and 20 per cent dry fuel
in the peat is about the limit permitting evaporation of the water, but
it is, of course, impossible to obtain in this case a gas of calorific
value.

The modification of the process for very wet fuel is as follows:

When the fire on top of the fuel bed appears to disappear, the heater
opens the stack and valve =D=. Valve =C= is then closed, to prevent air
from entering on top. The preheated air enters by =D= causing a down
draft combustion due to the suction of the gas engine and an upward
combustion due to the draft in the stack. The moisture is evaporated and
escapes through the stack. When the fire has burned through at the top,
the valve is switched over. The bad smelling gases rising from the
scrubber enter the producer together with air and are there consumed.

In commercial use at the exhibition in Posen the whole plant worked
continuously day and night and cleaning of the gas engines was necessary
only every three months. Slagging of ashes is done during the operation
of the producer, without any nuisance from dust.

The highest percentage of moisture in peat gasified was 50 per cent. The
fuel consumption per horse-power hour is 2.2 lb. (1 kg.) of peat.
Careful tests made by Prof. Baer, of Breslau, showed that with a cost of
peat of $1 per ton the kw-hour at the switchboard costs 0.15 cent.

(14) Crude Oil Producers.

The development of the crude oil gas producer, for which there is great
demand, in oil regions remote from the coal field, has been exceedingly
slow but it is believed that definite progress has recently been made
along this line. The most recent notes on this subject relate to the
Grine oil producer. In this type steam spray is used for atomizing the
oil which is introduced into the upper part of the generator where
partial combustion takes place. The downdraft principle is then applied
and the hydrocarbon broken up and the tar fixed by passing through a bed
of incandescent coke. Mr. Grine reports that a power plant using one of
these producers has been in operation a year in California. With crude
oil as a fuel costing 95 cents per barrel, or 2.3 cents per gallon, the
plant is reported to develop the same amount of power per gallon of
crude as is ordinarily developed by the standard internal combustion
engine operating on distillates at 7 cents per gallon. Including the
cost of fuel, labor, supplies, interest, depreciation and taxes, Mr.
Grine states the cost per b.h.p. hour to be 0.76 cents for a plant of
100 h.p. rating.

(15) Operation of Producers.

A good producer operator is simply a good fireman, he must know how to
keep a uniform bed of coal and how to draw the fire. While there are
many thousands of men running producer plants without previous
mechanical training, there are now but few steam engineers running steam
engines of the same capacity but what have had at least two years’
training and sufficient mechanical knowledge to pass an examination and
obtain a license. While a considerable amount of skill is necessary to
obtain the best efficiency from a producer, it is a knack that is easily
acquired in a short time by “sticking around” the plant. Skill in
operating a producer consists chiefly in keeping the right sort of a
fire without damage to the lining by poking down ashes and clinkers.
When a new plant is installed, the manufacturer generally sends an
instructor to operate the plant for a short time so that with a few days
running in his hands any man with ordinary intelligence can overcome the
difficulties which arise from time to time.

While there are many types of producers, the main difference will be
found in the character of the draft, that is whether it is up, down, or
crossways. Down draft producers are generally used with bituminous
coals, as the tars and oils that emanate from the coal are drawn through
the fire which converts them into a permanent gas, and avoids the
difficulty of removing great quantities of the tar from the producer. An
up draft producer will not do this as the gas is drawn directly into the
mains without coming into contact with the fire. This would result in
considerable expense due to the frequent cleaning. Anthracite coal which
does not contain much tar can be used successfully in an up draft
producer.

A compromise between the up draft and down draft producer is had in the
=DOUBLE ZONE= producer, which “burns the candle at both ends” as it
were, a fire being at both the top and bottom of the producer. Nearly
any class of fuel may be used with this type.

It should be remembered that a hot fire and fuel are required for the
manufacture of gas, and that the ash pit and grate must be kept clear of
the ashes and clinkers that not only reduce the temperature of the fire,
but also reduce the gas available at the cylinder by increasing the
friction. Shaking down and cleaning out will in nearly every instance
start a bucking producer into operation.

When operating under full load a much hotter fire is required than when
operating under a reduced load, or the producer will not furnish the
necessary gas. According to the size of the producer, the depth of the
incandescent fuel will run from 30 inches in the large sizes to 15
inches in the smaller. After being charged up, suction producers will
continue to give gas in sufficient quantities with the bed at half this
depth. This is only possible with a hot producer, and when no fuel is
being fed, as the feeding of a cold charge will reduce the output. A
steady depth of fire should be kept to maintain a uniform quality of
gas.

In suction producers careful watch should be kept for leaks, as the gas
being below atmospheric pressure gives no outward signs of dilution. If
water seals are used in the system they should be given careful
attention. When using coals that are rich in tar or hydrocarbons, or
with fuels that have much fine dust, considerable trouble is had with
some types of producers due to “caking” or to the adhesion of the coal
particles to the walls of the producers or to their adhesion to one
another. In the latter case the “stickiness” of the fuel prevent the
proper feed. This difficulty may often be overcome by a change in the
rate of feeding or by regulating the depth of the incandescent bed.

Porosity of the fuel, and the rate at which the air is supplied to the
producer determines the depth of the incandescent bed. Particular care
should be taken that the blast or draft occurs evenly over the fire
surface, and that no holes occur in the fire which will cause more rapid
combustion in one spot than in another. Neglect of this precaution not
only causes a waste of fuel but often results in the fuel “arching” and
preventing further feed. The producer should be so proportioned that at
full load, the rate of combustion does not exceed 24 pounds of fuel per
square foot of producer area per hour.

In his researches, Professor Bone (Iron and Steel Institute, May, 1907)
has shown that up to 0.32 lbs. of steam per lb. of coal can be
completely decomposed in a producer, but that, from 0.45 lbs. to 0.55
lbs. should be used, approximately 80% more.

Now, in considering the question of the proper proportion of steam for
the production of gas for power purposes we must bear in mind that as
much heat as possible should be utilized in the producer itself. Some
manufacturers of plant go so far as to state that as much as 1 lb. of
steam per lb. of coal should be used, but we are safe in saying that 0.5
lb. to 0.7 lb. should be the figure for a power plant. The common
practice is to use a blast saturation of 55% whenever the clinkering
character of the coal renders it possible. This figure corresponds to
about .57 of steam per lb. of coal gasified.

It is of the utmost importance that the proportion of steam and air
should be constant, and the best figure being determined, it should not
be varied to any degree. It is equally important that the fuel depth
should be left constant. By this I mean that not only should the coal in
the producer be kept at a specific level, but the position of the fire
on the ash bed should be kept as near as possible a fixed point. Ashes
should be drawn at regular intervals, or, if desired, continuously by
mechanical means.

Further, the supply of air and steam should be regularly distributed, so
that the velocity of the gases through the fuel shall be as nearly as
possible regular across its whole area.

In some cases the by-products of a producer, such as ammonia, tar, etc.,
have a commercial value, and if a large amount of gas is generated it
will sometimes pay to select a fuel that is rich in these particular
substances.

(16) Coal.

Coal which is the basis of producer gas, is composed generally speaking
of the combustible matter, moisture, ash and sulphur. The combustible
element may be subdivided into the =HYDROCARBONS, OR VOLATILES=, and the
solid fixed carbon. The exact composition of coal is generally given by
what is known as =PROXIMATE= analysis, which analysis divides the
constituents of the coal into five groups, viz.: =MOISTURE=,
=VOLATILES=, =FIXED CARBON=, =ASH=, and =SULPHUR=. Ultimate analysis
resolves the coal into its ultimate chemical elements, such as hydrogen,
carbon, nitrogen, sulphur, etc., and being a difficult and tedious
process it is not much used.

The proximate analysis gives all the necessary information and takes
less time to perform.

VALUES OF COAL

══════════════════╤══════════════════════════════════════════╤═════════
Location of Mine │ PROXIMATE ANALYSIS │Calorific
│ │Value in
│ │ B.T.U.
│ │ per Lb.
│ │ of Coal
──────────────────┼────────┬────────┬───────┬───────┬────────┼─────────
│Moisture│Volatile│ Fixed │ Ash │Sulphur │
│ │ Matter │Carbon │ │ │
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
=ANTHRACITE= │ │ │ │ │ │
Northern Pa. │ 3.39│ 4.41│ 83.30│ 8.17│ .73│ 13,200
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Eastern Pa. │ 3.70│ 3.07│ 86.42│ 6.18│ .63│ 13,440
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Western Pa. │ 3.12│ 3.76│ 81.60│ 10.61│ .53│ 12,875
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
=SEMI-ANTHRACITE= │ 1.25│ 8.15│ 83.30│ 6.27│ 1.63│ 13,900
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
=SEMI-BITUMINOUS= │ │ │ │ │ │
Pennsylvania │ .80│ 15.60│ 77.40│ 5.35│ .85│ 14,900
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Pennsylvania │ 1.55│ 16.45│ 71.50│ 8.63│ 1.87│ 14,200
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Pocahontas Va. │ 1.00│ 21.00│ 24.40│ 3.02│ .58│ 15,100
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
West Virginia │ .90│ 17.83│ 77.70│ 3.30│ .27│ 15,230
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
=BITUMINOUS= │ │ │ │ │ │
Youghiogheny Pa. │ 1.00│ 36.50│ 59.00│ 2.59│ .86│ 14,400
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Sample No. 2 │ 1.20│ 30.18│ 59.00│ 8.84│ .78│ 14,400
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Hocking Valley │ 6.5│ 35.06│ 48.80│ 8.05│ 1.59│ 12,100
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Kentucky │ 4.00│ 34.00│ 54.70│ 7.00│ .03│ 12,800
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Indiana │ 8.00│ 30.20│ 54.20│ 7.60│ │ 12,500
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Illinois │ 10.50│ 36.15│ 37.00│ 12.90│ 3.45│ 10,500
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
Colorado │ 6.00│ 38.01│ 47.90│ 8.09│ │ 12,200
──────────────────┼────────┼────────┼───────┼───────┼────────┼─────────
=LIGNITE= │ 9.00│ 42.26│ 44.30│ 3.27│ 1.18│ 11,000
──────────────────┴────────┴────────┴───────┴───────┴────────┴─────────

The =CALORIFIC VALUE= of a fuel may be calculated from its analysis, or
may be determined by means of the =CALORIMETER= from a sample of the
coal; the latter method is the most reliable. Table gives approximately
the calorific values, and the proximate analysis of several
representative coals from various sections of the country. The values
given in the table are not exact, as the coal from each locality varies
considerably in quality, but the figures will indicate what may be
expected from each type of coal.

Connellsville, Pa., Coke has a calorific value of approximately 13,000
B.T.U.’s per pound, contains no volatile matter, and has an approximate
content of 10% ash. Coke is a valuable fuel for the gas producer, but is
rather expensive. It is clean and the absence of volatile matter reduces
the “scrubbing” problem to a minimum.

Small coal such as buckwheat and pea contain a much higher percentage of
moisture than given in the table, running from 5% to 10% higher than the
given values.

Bituminous coal is high in hydrocarbons or volatiles which condense
easily and form tar. If the tar is not removed or converted into a
permanent gas, it will clog the passages of the producer and the engine
and cause trouble.

The removal of the tar and ash from a gas is called =SCRUBBING=, and is
performed by a device much resembling a filter. Anthracite coal and coke
are low in volatiles or hydrocarbons, and therefore do not cause trouble
with tar deposits.

A high percentage of volatile matter also causes trouble by the tar
cementing the particles of fuel together. This interferes with the
proper action of the producer.

Fuels having a high percentage of ash call for perfect filtering or
“scrubbing” as such fuels will fill the gas passages with dust. Dust
should be kept out of the engine at all costs, for the dust even in a
quantity will cause wear in the cylinder.

Depending on the quality of the fuel, bituminous coal will produce about
4½ pounds of ammonia and 12 gallons of tar with about 5% of sulphur.

Anthracite coal will produce approximately six pounds of tar, and two
pounds of ammonia with traces of sulphur.

Loose Anthracite coal requires approximately 40 cubic feet of storage
space per ton of 2240 pounds and weighs about 56 pounds per cubic foot
(market sizes).

Loose Bituminous coal requires approximately 45 cubic feet of storage
space per ton of 2240 pounds, and weighs about 52 pounds per cubic foot
in market sizes.

Dry coke requires approximately 85 cubic feet of storage space per ton
of 2240 pounds, and weighs about 26 pounds per cubic foot.

(17) Fuel Oils.

Crude oil, a natural product, is the base of the fuels most commonly
used in internal combustion engines, especially in the smaller sizes.
From this compound the following derivatives are obtained by the process
of distillation, a separation possible because of the different boiling
points of the various oils. As each derivative or =DISTILLATE= has a
different boiling point, the temperature of the crude oil is maintained
at the boiling point of that product that is desired, and the resulting
vapor is condensed. The following list is not anywhere near complete for
there are several hundred distinctly different distillates, but it
contains those that are of the most interest to the engine man.

1. Crude Oil.
2. Gasoline.
3. Naphtha.
4. Solar Oil.
5. Kerosene.

The specific gravity of the crude oil as obtained in the field will
range from 12° to 56° Beaumé scale. The crude from Pennsylvania will
average 40° Beaumé while that from Texas will average 20°. The
accompanying table will give the calorific values and general properties
of the principle liquid fuels. It should be noted that the weight or
density of the liquids is given in terms of specific gravity or Beaumé
scale, in which the =SPECIFIC GRAVITY= of the fuel is the ratio of its
weight per unit volume to the weight of an equivalent volume of water.
The specific gravity of a liquid is generally determined by an
instrument known as a =HYDROMETER= which consists of a glass tube sealed
at both ends carrying a graduated scale on the upper portion of the
stem, and a ballast weight of shot or mercury at the bottom.

The hydrometer is floated in the liquid to be tested, and the lower the
specific gravity, the lower the hydrometer sinks, and vice versa. The
specific gravity of the liquid is read directly from the graduation on
the stem that are on a level with the surface of the liquid under test.
As in the case of thermometers, hydrometers are all graduated in two
different scales, the specific gravity scale and the Beaumé scale. The
specific gravity scale reads at 1.00 when floated on distilled water,
and the Beaumé at 10.00 when floated on the same liquid.

A difference in temperature affects the density of a liquid, hence all
hydrometers are graduated for a standard temperature of 60°F unless
otherwise specified. For a difference of 10°F there is a variation of
one degree gravity in the Beaumé scale, and for a difference of 20°F in
temperature there is a change of one degree on the specific gravity
scale. If the temperature differs from 60°F, the corresponding
correction should be made in the reading.

To convert the Beaumé reading (B) to terms of the specific gravity scale
(S) use the following formula:

140
S = ——————— = specific gravity.
130 + B

140
B = ——— = Beaumé scale.
S

PROPERTIES OF OILS

Degrees Specific Weight B.T.U.’S B.T.U.’S
Beaumé Gravity per gal. per lb. per gal.
Gasoline 67.2 .7125 5.932 21120 125,284
Heavy naphtha 64.6 .7216 6.011 20527 123,388
Kerosene 48.8 .7848 6.538 20018 130,877
W. Virginia crude 40.0 .8251 6.874 19766 135,871
Penn. fuel oil 31.9 .8660 7.215 19656 141,818
Kansas crude 29.0 .8816 7.345 19435 142,750
Fuel oil 22.7 .9176 7.645 19103 146,042
California crude 22.5 .9248 7.710 18779 144,786
California crude 15.2 .9646 8.036 18589 149,381
Alcohol, 95% 41.9 .816 6.798 10500 71,380

It will be noted that the petroleum products contain an enormous amount
of heat energy, nearly 25% more than that of the same weight of pure
carbon. It will also be noted that the lighter products such as
gasoline, kerosene, etc., have more heat per pound but less per gallon
than the heavier oils. This is rather confusing at first, but as will be
seen after deliberation that the heavier fuel is the most economical
since the least is used per horse-power, and is bought by the gallon.
The calorific values given in the table are obtained by a calorimeter,
and are burnt in the open air, and consequently have a different heating
value when under compression in the cylinder of the engine.

In all cases the liquids are vaporized before being introduced in the
cylinder, the more volatile liquids such as gasoline being converted
into vapor at atmospheric temperature, and the heavier non-volatiles by
being sprayed into a heated vessel or preheated air. The percentage of
liquid fuel contained in a cubic foot of air vapor mixture depends on
the temperature, the boiling point of the liquid and upon the pressure
and humidity.

Gasoline consists principally of compounds of the methane series, the
one representative of gasoline being Hexane (C_{6}H_{14}). It requires
15.5 pounds of air for combustion theoretically and about 10 per cent.
more in practice. The formation of gasoline vapor produces a drop in
temperature of 50°F, and should be heated 100°F above the atmosphere for
the best results. The volume of air required for the combustion is about
192 cubic feet. With alcohol at 20 cents per gallon and gasoline at 12½
cents the number of B.T.U.’s for one cent in the case of alcohol is 3594
and 9265 in the case of gasoline. In the engine the difference is not so
great owing to the difference in compression pressures.

(18) Tar for Fuel.

Because of the increasing interest in the Diesel type engine and the low
grade fuels that it has made possible, we quote the specifications laid
down by Dr. Rudolph Diesel, the inventor, before the English Institution
of Engineers.

(1.) Tar-oils should not contain more than a trace of constituents
insoluble in xylol. The test on this is performed as follows:—25 grammes
(0.88 oz. av.) of oil are mixed with 25 cm.^3 (1.525 cub. in.) of xylol,
shaken and filtered. The filter-paper before being used is dried and
weighed, and after filtration has taken place it is thoroughly washed
with hot xylol. After re-drying the weight should not be increased by
more than 0.1 gr.

(2.) The water contents should not exceed 1 per cent. The testing of the
water contents is made by the well-known xylol method.

(3.) The residue of the coke should not exceed 3 per cent.

(4.) When performing the boiling analysis, at least 60 per cent. by
volume of the oil should be distilled on heating up to 300° C. The
boiling and analysis should be carried out according to the rules laid
down by the Trust. (German Tar Production Trust on Essen-Ruhr.)

(5.) The minimum calorific power must not be less than 8,800 cal. per
kg. For oils of less calorific power the purchaser has the right of
deducting 2 per cent of the net price of the delivered oil, for each 100
cal. below this minimum.

(6.) The flash-point, as determined in an open crucible by Von Holde’s
method for lubricating oils, must not be below 65° C.

(7.) The oil must be quite fluid at 15° C. The purchaser has not the
right to reject oils on the ground that emulsions appear after five
minutes’ stirring when the oil is cooled to 8°.

Purchasers should be urged to fit their oil-storing tanks and oil-pipes
with warming arrangements to redissolve emulsions by the temperature
falling below 15° C.

(8.) If emulsions have been caused by the cooling of the oils in the
tank during transport, the purchaser must redissolve them by means of
this apparatus.

Insoluble residues may be deducted from the weight of oil supplied.

Coal tar oil is the distillate of the tar obtained from gas works, from
which all valuable commercial materials such as aniline have been
removed. Coal oil tar is also known as creosote oil and anthracene oil,
the heat value of which is not quite 16,000 B.T.U. per pound.

(19) Residual Oils.

Residual oil is the residue left after the lighter oils have been
distilled from the petroleum, which before the advent of the Diesel
engine were useless. Residual oil which was hardly fluid at ordinary
temperatures has been successfully used in the Diesel and semi-Diesel
types of engines, by preheating it before admission to the inlet valves.
The enormously increased demand for gasoline has resulted in a great
increase of the formerly useless residual oil so that it is possible
that the demand for gasoline will make the production of the residual
great enough so that it can be seriously considered as a fuel.

(20) Gasoline.

Gasoline is by the far the most widely used fuel for internal combustion
engines because of its great volatility and the ease with which it forms
inflammable mixtures with the air at ordinary temperatures. Another
point in its favor is the fact that it burns with a minimum of sooty or
tarry deposits, without a disagreeable smell with moderate compression
pressures and without preheating through a wide range of air ratios.
Gasoline is a product of crude oil from which it is obtained by a
process of distillation, and as it forms but a small percentage of the
crude oil it is rapidly becoming more and more expensive as the demand
increases. Some Pennsylvania crude oils will yield as much as 20 per
cent of their weight in gasoline, while the low grade Texas and
California crudes very seldom contain more than 3 per cent.

When considered as a term applying to some specific product, the word
“Gasoline” is a very flexible expression as it covers a wide range of
specific gravities, boiling points, and compositions, the latter items
depending on the demand for the fuel and the taste of the manufacturer.
Since the specific gravity of gasoline is a factor that determines its
suitability for the engine, at least in regard to its evaporating power
or volatility, it is graded according to its density in Beaumé degrees
as determined by the hydrometer. According to this scale gasoline will
range from 85° to 60° Beaumé, and even lower, although 60° is supposed
to mark the lowest limit and to form the dividing line between gasoline
and naphtha.

The density of the gasoline in Beaumé degrees is an index to the
volatility, for the higher the degree as indicated on the hydrometer,
the higher is the volatility at a given temperature, consequently a high
degree gasoline will give a better mixture at a low temperature than one
of a low degree. In cold weather all gasoline should be tested with a
hydrometer when purchased to insure a grade that will be volatile enough
for easy starting when the engine is cold. In cold weather the gasoline
should not be lower than 68°, and for the best results should be above
72°, at least for starting the engine. Good gasoline should evaporate
rapidly and should produce quite a degree of cold when a small amount is
spread on the palm of the hand, and it should leave neither a greasy
feeling nor a disagreeable odor after its evaporation.

The high gravity gasoline is of course the most expensive, as there is
less of it in a gallon of the crude oil from which it is made; gasoline
of 76° Beaumé being approximately 15c. per gallon in carload lots, while
naphtha of 58° Beaumé brings 8½c. per gallon.

The calorific value of gasoline increases as the gravity Beaumé
decreases per gallon; 85° gasoline having approximately 113,000 B.T.U.
per gallon while 58° naphtha has an approximate value of 122,000 B.T.U.
per gallon. The calorific value remains nearly constant per pound for
all gravities.

It should be remembered that heat is absorbed in evaporating gasoline as
well as in evaporating water, and that effects of cold weather are
greatly increased by the amount of heat absorbed, (or cold produced) by
the vaporization of the fuel. While the heat absorbed by evaporating a
given quantity of gasoline is only .45 per cent of that absorbed by an
equal amount of water, it is a fact that this heat must be supplied from
some source to prevent a reduction in the vapor density. In starting the
engine, the heat of evaporation is supplied by the atmosphere, and
should the temperature of the air be below that required for a given
vapor density, the engine will refuse to start.

By the use of two tanks and a three way valve, it is possible to use two
grades of fuel: one tank containing high gravity gasoline, and the other
low gravity; the high gravity being used for starting the engine in cold
weather, and the cheaper, low gravity, being used for continuous running
after the engine is warmed up—the change of fuels being made by throwing
over the three way valve.

The =VAPOR DENSITY= of gasoline vapor is the ratio of the weight of the
vapor compared with the weight of an equal volume of dry air at the same
temperature. If the weight of a cubic foot of gasoline vapor is divided
by the weight of a cubic foot of air at the same temperature the result
will be the vapor density of the gasoline vapor. Compared to air, the
gasoline vapor is quite heavy so that if a small quantity of gasoline is
poured on the top of a table, the vapor will flow over the edge of the
table and drop to the floor where it will remain until it has united
with the air by the process of diffusion. Experiments have shown that
pure, dry gasoline vapor has a density of about 3.28, or in other words
weighs 3.28 times as much as an equal volume of dry air. This weight of
course is the weight of pure vapor which is considerably heavier than
the mixture of vapor and air that is used in the cylinder of the engine.

Dampness, or the presence of water vapor in the air reduces the quantity
of gasoline vapor taken up by the air, but only by a small amount, the
maximum difference being only about 2 per cent. Since it is very likely
that the water vapor is broken up into its original elements, oxygen and
hydrogen, by the heat of the combustion it is likely that there is no
heat loss due to the vapor passing out through the exhaust. The
principal trouble due to dampness is the mixture of water and liquid
gasoline caused by the condensation of the water vapor.

All gasolines and oils contain water to a more or less degree, hence
provision should be made for the draining of the water which collects in
the bottom of the tank. Water in liquid fuels is the cause of much
trouble.

Water in gasoline may be detected by dropping scrapings from an
indelible pencil into a sample of the suspected fluid. If water is
present in any quantity the gasoline will assume a violet color.

In filling a supply tank with gasoline, a chamois filter or chamois
lined funnel should always be used, as the chamois skin allows the
gasoline to pass but retains the water and impurities contained therein.
There are many funnels of this type now on the market.

The rate at which gasoline burns depends on the amount of surface
presented to the air by the fluid, for a given quantity of gasoline
burns faster in a wide shallow vessel than in a deep jar. Since a spray
of minute particles presents an enormously greater surface than the
liquid its burning speed is correspondingly greater, and as a true vapor
has an almost limitless area, its speed is much greater than that of the
spray, the combustion under the latter condition being almost
instantaneous. Besides the question of subdivision of the liquid, the
rate of combustion also depends on the intimacy of contact of the vapor
with the air and on the pressure applied to the vapor as previously
explained under the head of “=COMPRESSION=” in another chapter.

=CARBURETING AIR=, or producing an explosive mixture of gasoline vapor
and air is accomplished by two different methods, first by passing the
air over the surface of the liquid, or by passing it through the liquid
in bubbles; second by spraying the liquid into the air. The latter is
the method most generally in use at the present time, the spray being
formed by the suction of the intake air upon the open end of the spray
nozzle. The vapor density of the mixture thus formed depends on the
suction of the air and upon the nozzle opening, either of which may be
varied in the modern carburetor to vary the richness of the mixture.

As a suggestion to the users of gasoline we append the following
remarks.

Gasoline vapor will readily combine with air to form explosive mixtures,
at ordinary temperature. This property at once makes it the most
suitable fuel and the most dangerous to handle.

Never fill tanks or expose gasoline to the air in the presence of an
open flame, or do not attempt to determine the amount of gasoline in a
tank with the aid of a match. There are a number of people who have
successfully accomplished this feat, and a very great number who have
not.

Be very sparing in the use of matches around a gasoline engine; there
are such things as =leaks=.

Always carefully replace the stopper or filler cap in a gasoline tank
after filling. Never use the same funnel for water and gasoline, and
avoid any possibility of water finding its way into the tank.

If you do succeed in igniting a quantity of free gasoline, do not
attempt to extinguish the fire with water. Pouring water on burning
gasoline spreads the fire. Extinguish it with earth or sand, or by the
use of one of the dry powder extinguishers now on the market.

Water may be removed from gasoline by placing a few lumps of desiccated
calcium chloride in the tank, the amount depending on the quantity of
water.

Calcium chloride, has a great capacity for absorbing water, and in a
short space of time will absorb all of the moisture contained in the
tank.

The best way to introduce the chloride is to wrap the lumps in a sheet
of wire gauze and lower into tank with a wire, the wire allowing it to
be easily removed when saturated with water.

(21) Benzol.

Benzol has been used to some extent in Europe as a fuel, its use being
due to the rapidly increasing cost of gasoline.

Benzol is a distillate of coal tar, and is a by-product of the coke
industry. In England benzol brings approximately the same price as
gasoline (called petrol), but benzol proves economical for the reason
that it develops more power per gallon.

Benzol is not as volatile as gasoline, but is sufficiently volatile to
allow of easy motor starting.

Benzol is also used for denaturing alcohol.

(22) Alcohol.

Alcohol is of vegetable origin, being the result of the destructive
distillation of various kinds of starchy plants or vegetables. Starch is
the base of alcohol.

As a fuel, alcohol has much in its favor, as it causes no carbon
deposit, has smokeless and odorless exhaust, can stand high compression,
and requires less cooling water than gasoline, as the heat loss is less
through the cylinder walls, and for this reason it is more efficient
fuel than gasoline.

At the present time the price of alcohol prohibits its general use. In
order that alcohol equal gasoline in price per horse-power hour, it
should sell for 10c. per gallon, the price of gasoline being 15c. per
gallon.

Alcohol can be used in any ordinary gasoline engine with readjustment of
carburetor and the compression.

The nozzle in the carburetor has to be of larger bore for alcohol than
for gasoline, and the compression for alcohol in the neighborhood of 180
pounds per square inch.

The inlet air should be heated to about 280°F for alcohol fuel;
approximately 6% of the heat of the alcohol is required for its
vaporization. Alcohol is much safer to handle than gasoline owing to its
low volatility.

90% alcohol has a calorific value of 10,100 B.T.U. per pound, its
specific gravity being .815.

=WOOD=, or =METHYL= alcohol is made by distilling the starch contained
in the fibres of some species of wood (Poisonous).

=GRAIN=, or =ETHYL= alcohol is the result of the distillation of the
starch contained in grains, potatoes, molasses, etc. =ETHYL=, or =GRAIN=
alcohol rendered unfit for drinking by the addition of certain
substances, is called =DENATURED ALCOHOL=. The process of denaturing
does not affect the calorific value of alcohol to any extent.

(23) Kerosene Oil.

Kerosene is a fractional distillate of crude oil which has a
considerably higher vaporizing temperature than gasoline. It does not
form an inflammable mixture with the air at ordinary temperatures, but
is vaporized in practice by spraying it into a chamber heated to above
200°F. Kerosene forms a greater percentage of crude oil than gasoline
and as there has been less demand for it up to the present time it is
much cheaper. Pennsylvania crude oil produces only 20 per cent of
gasoline while the kerosene contents will average nearly 42 per cent
according to figures at hand.

Kerosene has a very high calorific value per gallon, 8.5 gallons of
kerosene having the same heating effect as 10 gallons of gasoline.
Because of its high calorific value and its low cost per gallon, many
types of engines have been developed for its use during the last few
years, several of which have been very successful. Before the advent of
the modern kerosene engine much difficulty was experienced with the fuel
because of its high vaporizing temperature and its tendency to carbonize
in the cylinder, but as the price of gasoline continued to rise, the
inventive genius of the gas engine builder overcame these troubles so
that the kerosene engine is now as reliable as any form of prime mover.

[Illustration:

Kerosene Vaporizer on Fairbanks-Morse Engine. The Engine is Started on
Gasoline and When Hot, the Kerosene Feed is Turned on.
]

Any gasoline engine will run on kerosene, after a manner, if the engine
is thoroughly heated to insure the vaporization of the kerosene, and if
the fuel is heated in the carburetor. Such an arrangement is make-shift,
however, and is not productive of good results in continuous service. If
kerosene is to be used as a regular fuel, a kerosene engine should be
used to avoid vaporizing and carbonizing difficulties as well as the
sooty, offensive exhaust, and the loss of fuel represented by the soot.

Many kerosene engines are arranged to start on gasoline, and, after
becoming heated, have the running feed of kerosene admitted through a
three way valve. The gasoline feed is then stopped.

The above arrangement admits of easy starting in all weathers and
temperatures.

In the Diesel engine there is no evaporating of fuel, and no deposits of
carbon because of the high temperature of the combustion chamber. With
engines that draw the mixture of vapor and air into the cylinder there
are several methods of applying heat to the liquid, and the combustion
of the vapor thus formed is perfected by the injection of water into the
combustion chamber. It has been found by experiment that a small amount
of water vapor introduced into the cylinder of a kerosene engine makes
the engine run more smoothly and prevents a smoky exhaust and carbon
deposits in the cylinder. The water is introduced into the cylinder
through an atomizer in the form of a mist or fog, the particles of water
being in a very finely subdivided state.

[Illustration:

Kerosene Vaporizer on Fairbanks-Morse Vertical Engine. Started on
Kerosene Directly by Heating Vaporizer with Torch.
]

The deposits of free carbon (soot) caused by the “cracking” or
decomposition of the kerosene vapor before ignition, due to the high
temperature of the cylinder, are burnt to carbon dioxide by the oxygen
of the water which is also set free by the heat of the cylinder. This
produces an odorless gas (CO_{2}) which indicates complete combustion.
Besides the increase of fuel efficiency due to the water vapor, the
cylinder is more thoroughly cooled and is more efficiently lubricated
because of the reduction in temperature.

CHAPTER III
WORKING CYCLES

(24) Requirements of the Engine.

In order that an internal combustion engine shall operate and develop
power continuously the following routine of events must occur in the
cylinder in the following order, no matter what the type of engine.

(1) The cylinder must be filled with a combustible mixture of air and
gaseous fuel at as nearly atmospheric pressure as possible.

(2) The mixture must be compressed in order to develop the value of the
fuel.

(3) Ignition must take place at the end of the compression stroke or at
the highest point of compression.

(4) Complete combustion of the fuel must follow the ignition of the
charge, with an increase of temperature and pressure which will act on
the piston to the end of the power stroke.

(5) After the piston has completed the working stroke the products of
combustion must be ejected from the cylinder completely to make way for
the admission of the new combustible mixture.

With the exception of the Diesel engine which (1) fills the cylinder
with pure air without the fuel, and (2) injects the fuel after
compression, all internal combustion engines not only perform each of
these operations but proceed with events in the order given as well. The
accomplishment of the five acts is called a “cycle of events,” or a
“=CYCLE=,” and the series is performed in different ways in different
types of engines. In the operation of the engine, the series of events
occur over and over again, always in the same order, 1–2–3–4–5,
1–2–3–4–5, 1–2–3–4–5, etc. The five events are generally given in terms
of the number of strokes of the piston taken to accomplish the complete
routine, thus a two stroke cycle engine performs the series in two
strokes, and a four stroke cycle engine in four strokes, and so on.

In order to obtain the benefits of high compression, perfect scavenging
of the products of combustion from the cylinder and perfect mixtures, a
great variety of engines have been developed in which the number of
strokes taken to accomplish the five events varies. In some engines the
cycle is accomplished in two strokes, in other engines it is
accomplished in six strokes, but in the great majority of cases the
cycle is performed in either two or four strokes, and as these are by
far the most common routines, we will confine our description to engines
of these types.

(25) Four Stroke Cycle Engine.

The four stroke cycle engine, some times improperly called the “four
cycle” engine is the most widely used type for all classes of service,
except possibly for marine work. Its extended use is due to its superior
scavenging, high efficiency and reliability, although it is somewhat
more complicated than the two stroke cycle type. Its ability to function
properly under a wide variation of speed has driven the two stroke cycle
type out of the automobile field, and its many admirable characteristics
have cut a wide swath in the marine field, the stronghold of the two
stroke cycle type.

A four stroke cycle engine performs the cycle of events in four strokes
or two revolutions, only one of the strokes being a power of working
stroke. In a single cylinder engine the explosion in the working strokes
supplies enough power to the fly-wheel to carry the engine and its load
through the remaining three strokes. Thus the energy stored in the fly
wheel is sufficient to carry not only the load during the idle strokes
but to “inhale” and compress the charge as well. Due to the long
interval that exists between explosions, they are corresponding heavy
and are productive of heavy strains in the engine and are the cause of
considerable vibration.

To reduce the ill effects of the heavy intermittent blows, the majority
of automobile and stationary engines are provided with two or more
cylinders, the power being equally divided among them. In a four
cylinder engine, there are four times as many impulses as in a single
cylinder engine and the blow dealt by the individual cylinder is only
one-quarter as great. While a single cylinder engine has an impulse only
once in every other revolution, the four cylinder has two impulses in
one revolution. Besides the advantages gained by increasing the
impulses, the mechanical balance of a multiple cylinder engine is always
better than that of a single and is also much lighter in weight since
less material is required to resist shocks of the explosions.

[Illustration:

Fig. 4. Diagrammatic View of Four Stroke Cycle Engine with the Piston
in Various Positions Corresponding with the Five Events. Diagram
A—Suction. Diagram B—Compression. Diagram C—Ignition. Diagram
D—Working Stroke. Diagram E—Release. Diagram F—Scavenging Stroke.
]

Engines with more than four cylinders have “overlapping” impulses, that
is some cylinder on the engine is always delivering power, for before
one cylinder reaches the end of the stroke, another has fired its charge
and has started to deliver power. Thus the impulses “overlap” one
another, and the result is an even and smooth application of power and a
minimum of strain is imposed on the engine.

Aeronautical and speed boat engine builders have carried the multiple
cylinder idea to an extreme because of the nature of their work. Eight
cylinder aeronautical engines are very common and there are several
built having sixteen cylinders. The latter type of engine gives eight
impulses per revolution. To avoid a great multiplicity of cylinders, and
to save on floor space, the great majority of heavy duty stationary
engines are built double acting, that is an explosion occurs alternately
in either end of the cylinder. In effect, a double acting cylinder is
the same thing as a two cylinder single acting engine, as it gives twice
the number of impulses obtained with a single acting cylinder.

The order in which the events occur in a four stroke cycle engine is as
follows:

=STROKE 1.= First outward stroke of the piston causes a partial vacuum
in the combustion chamber thus drawing a charge of combustible gas into
the cylinder through the open inlet valve. The exhaust valve is closed.
See diagram A in Fig. 4. (Suction Stroke.)

=STROKE 2.= Inlet valve closes at the end of the suction stroke and the
piston starts on the inward stroke compressing the charge in the
combustion chamber. See diagram B. (Compression Stroke.) At the end of
the compression stroke, or a little before, the spark “S” occurs causing
the ignition of the charge. See diagram C.

=STROKE 3.= Working Stroke. As the pressure is now established in the
cylinder, the piston moves down on the working stroke forcing the crank
around against the load and supplying sufficient energy to the fly wheel
to carry the engine through the three idle strokes. See diagram D. When
the piston reaches the end of the working stroke, or a little before,
the exhaust valve opens to reduce the pressure and to allow the greater
part of the burnt gas to escape. See diagram E.

=STROKE 4.= Scavenging Stroke. The exhaust valve remains open and the
inwardly moving piston expels the remainder of the burnt gas through the
exhaust valve, clearing the cylinder for the next fresh charge of
mixture. See diagram F. The next stroke is the suction stroke explained
under “Stroke 1.”

In all of the diagrams the crank is supposed to turn in a right handed
direction as indicated by the arrow, the piston moving in the direction
shown by the arrow under the piston head. The valves are operated by
cams on an intermediate shaft known as the “cam shaft.” As the valves go
through their series of movements in two revolutions of the crank shaft,
and as the cam shaft must perform all of these operations in one
revolution, it is evident that the cam shaft must run at exactly
one-half the crank-shaft speed. This change of speed is accomplished by
means of gearing between the cam shaft and crank-shaft from which the
cam shaft is driven.

In some engines, notably the Diesel engine, pure air is drawn into the
cylinder on stroke No. 1 instead of the entire mixture. Fuel is supplied
in this type immediately after the end of the compression stroke.

While an electric spark is shown as the igniting medium in the diagrams,
the ignition is sometimes performed by a hot tube, or simply by the heat
of the compression as in the Diesel engine.

In the sliding sleeve type of four stroke cycle motor, the poppet or
lifting type of valve as shown in Fig. 4, is replaced by a peculiar type
of slide valve similar in action to the slide valves used on steam
engines, except that it is cylindrical in form and entirely surrounds
the piston. While there is a change in the form of the valve, and in a
number of small details, the gases are drawn into the cylinder,
compressed, ignited, and released in exactly the same way and in the
same rotation, as in the poppet valve engine just described. A
description of the Knight engine which is the most prominent example of
the slide sleeve motor will be found in a succeeding chapter. Since the
success of the slide valve type has been acknowledged by many prominent
automobile manufacturers, there have been several similar types placed
on the market, some with two sleeves and some with one, but in all cases
the designers have had but two points in view, that is quiet running and
free passages.

(26) Two Stroke Cycle Engine.

Two stroke cycle engines perform the five events of aspiration
(suction), compression, ignition, expansion and release in two strokes
or one revolution. Providing that these events are performed as
efficiently as in the four stroke cycle engine, it is evident that with
equal cylinder capacity, the two stroke cycle engine would have twice
the output of a four stroke cycle since it gives twice the number of
impulses per revolution. Unfortunately it is impossible to attain twice
the output of the four stroke cycle type with the small two stroke
engines built at the present time because of their imperfect scavenging
and poor fuel economy. In the larger two stroke engines, the pumps and
blowers used for scavenging the cylinders consume a considerable
percentage of the output.

[Illustration:

Fig. 5. Diagram of Two Port—Two Stroke Cycle Engine, Showing the
Events in the Crank-Case and Cylinder.
]

A general classification of the two stroke cycle engine is not so simple
a matter as that of the four stroke because of the differences in
construction of large and small sizes. This difference between the large
stationary engine and the small type commonly used on boats is due to
the efforts of the builders of the large engine to obtain great fuel
economy, while the chief endeavors of the builders of small engines is
to build a simple and reliable engine for the use of inexperienced
persons. While the smaller type of two stroke engine (less than 25
horse-power) has not been used in stationary practice to any extent,
owing to the defects just named, or on automobiles, it has been widely
used on motor boats, a service for which it is peculiarly adapted. Its
extended use on boats is due to the fact that in such service it runs at
practically a constant speed and works against a steady load, the
conditions that are most favorable to the type. With automobiles where
the motor speed is constantly varying, as well as the load, this type of
motor is not flexible enough to meet the continually varying conditions.

The small two stroke motors are divided into two principal classes, the
two port and three port type, depending on the method by which the
charge is transferred to the cylinder. No valves are used in the
cylinders of either type for the admission or release of the gases. As
the two strokes of the cycle are the compression stroke and working
stroke, it is evident that the charge must be introduced into the
cylinder by means other than by the suction of the piston and at a time
when there is no pressure in the cylinder. This is accomplished by a
preliminary compression of the charge in the crank case which places the
mixture under sufficient pressure to force it into the cylinder at the
end of the working stroke and at the same time to displace the burnt
gases left from the previous explosion. It should be noted that the
incoming mixture is a substitute for both the suction and scavenging
strokes of the four stroke cycle engine.

A diagrammatic view of a two port, two stroke cycle engine is shown by
Fig. 5, in which P is the piston, C the crank case, I the transfer port,
V the inlet valve, E the exhaust, and S the spark plug for igniting the
charge. It should be noted that there are no valves in the cylinder and
only three moving parts. The cycle of events for the two port type is as
follows:

=STROKE 1.= We will consider the piston to be moving up on the
compression stroke as shown in view (A), compressing the mixture in the
combustion chamber D. While moving upwards in the direction of the
arrow, the piston creates a vacuum in the crank case C drawing fresh
mixture into the crank case. The piston at this time is covering the
opening of the transfer port I and the exhaust port E so that the
compressed mixture in the cylinder cannot escape. On reaching the end of
the compression stroke, a spark occurs at S which drives the piston down
and turns the crank towards the right as shown by the arrow.

=STROKE 2.= When the piston uncovers the exhaust port E on its downward
working stroke as shown by view B, the exhaust gases being under
pressure rush out into the atmosphere as shown by the arrows, and
relieve the pressure in the cylinder. Some of the burnt gas remains in
the cylinder at atmospheric pressure as there is no scavenging action up
to this point. While the piston has moved down on the working stroke it
has compressed the mixture in the crank case ready for admission to the
cylinder. The valve V prevents the escape of the gas during the
compression.

On reaching the end of the stroke the piston uncovers the transfer port
which allows the compressed mixture in the crank case to rush into the
cylinder through I, as shown by view C. Owing to the shape of the
deflector plate Z on the piston head, the stream of mixture issuing from
I is thrown up toward the top of the cylinder, as shown by the arrows,
and consequently sweeps the remainder of the burnt gas before it through
the exhaust port E. In this way the fresh mixture from the crank case
scavenges the cylinder and fills it in one operation. Being filled with
gas, the piston now moves up on the compression stroke for the next
explosion as shown by view A.

Unfortunately the scavenging action of the incoming gas is not complete
for the whirling motion of the charge causes it to mix with the residual
gas to a certain extent which, of course, reduces the heating effect of
the fuel and reduces the power output. Another factor that reduces the
output of this type of engine is the loss of explosive mixture through
the exhaust port at low engine speeds with an open throttle. In this
case, the piston speed being low, part of the mixture has time to pass
over the deflector plate and through the exhaust opening before the
piston closes the exhaust port. At very high speeds the charge is
diluted by a considerable quantity of burnt gas which has not had time
to escape through the port causing a further loss of power. With the
throttle nearly closed on a light load, the impact of the incoming
mixture is so slight that the percentage of exhaust gas left in the
cylinder is very high. This dilution is so great that with moderately
low speeds (easily within the capacity of the four stroke cycle engine)
it is either impossible to ignite the charge or it is impossible to
ignite two in succession.

In marine service where the loads are constant, and the speeds fairly
uniform, there is but little trouble from the last mentioned source, and
as the fuel is usually a smaller item than the repair bill, the
simplicity of the small two stroke engine with its freedom from
mechanical troubles usually gives satisfactory results in the hands of
the novice.

(27) Three Port—Two Stroke Cycle Engine.

The principal difference between the three port and two port types of
the two stroke cycle engine is in the manner in which the charge is
admitted to the crank case for the initial compression. In the two port
motor, as previously described, the check valve “V” opens to admit the
charge, and closes during its compression in order to prevent its escape
through the opening by which it was admitted to the cylinder. With the
three port type there is no check valve in the crank case, the admission
and the retention of the charge being controlled by the movement of the
piston in practically the same way that the piston controls the opening
and closing of the exhaust and transfer ports in the cylinder.

[Illustration:

Fig. 6.
]

[Illustration:

Fig. 7
]

Figs. 6–7. Diagram of Three Port—Two Stroke Cycle Engine in Two
Positions.

By the piston control of the gases in the crank case, the valve is
eliminated, which makes one less moving part to cause trouble and
expense, and permits the use of the same type of carburetor that is used
on the four stroke cycle engine. As the check valve opens and closes at
a high speed, (twice that of the valves on a four stroke cycle engine),
there is considerable wear on the valve seats due to the continuous
banging, which results finally in a loss of the initial compression.
When the initial compression is reduced in this way the engine loses
power because of the reduction of the charge in the cylinder.

While the three port type is free from valve leakage troubles, it has a
steady loss due to the high vacuum that exists in the crank chamber when
the piston is on its upward stroke. This vacuum drags against the piston
and absorbs a considerable amount of power until the piston reaches the
upper end of the stroke. At this point the inlet port is opened and the
vacuum is broken by the rush of the mixture through the inlet port.
Besides the power loss, the vacuum has a bad effect on the lubrication
of the main crank shaft bearing.

[Illustration:

Elevation of Fairbanks-Morse Three-Port Two Stroke Marine Motor
Showing Warming Device for Carburetor Air.
]

Described by strokes, the cycle of events in the three port, two stroke
cycle engine is as follows:

=STROKE 1.= In Fig. 6, the piston is shown at the end of the compression
stroke with ignition taking place in the combustion chamber C. The
pressure due to the expansion drives the piston down on the working
stroke at the same time causing the initial compression of the mixture
in the crank case as shown by Fig. 7. The gas in the crank case cannot
escape during compression as the inlet port A is covered by the piston.

(a) As the piston descends, its upper edge uncovers the exhaust port D,
allowing the greater portion of the exhaust gases to escape and reduces
the pressure in the cylinder to that of the atmosphere.

(b) Descending a little farther, the top of the piston uncovers the
opening of the transfer port B, allowing the compressed gases in the
crank case to enter the cylinder as shown by the arrows. These gases,
guided by the deflector plate on the top of the piston are thrown
upwardly, as shown by the arrows, and sweep the residual burnt gases
before them through the exhaust port. The cylinder is now filled with
the combustible mixture ready for compression.

=STROKE 2.= The piston now moves up on the compression stroke,
compressing the charge in the cylinder and at the same time creates a
vacuum in the crank-case. Just before the piston reaches the end of the
exhaust stroke, the lower edge of the piston uncovers the inlet port A
(See Fig. 7), which allows the mixture from the carburetor to flow into
the partial vacuum and fill the crank case ready for the next initial
compression. When the end of the stroke is reached, the charge in the
combustion chamber C is fired and the cycle is repeated. It should be
noted that the incoming gas and the initial compression are controlled
entirely by the action of the lower edge of the piston on the inlet port
A.

(28) Reversing Two Cycle Motors.

As the admission and exhaust in the two stroke cycle engine each occur
once per revolution, and are controlled directly by the piston position
at opposite ends of the stroke, it is evident that the direction of
rotation is not affected by gas control or valve timing, as in the case
of the four stroke cycle engine. The factor that does determine the
direction of rotation in the two stroke engine is the time at which
ignition occurs in regard to the angular position of the crank. By
changing the relation between the crank position at the end of the
compression stroke and the time at which the spark occurs, it is
possible to reverse the engine even when it is running.

Should the engine be standing still in the position shown by Fig. 6,
with the crank on the dead center, when ignition occurred, there would
be no more tendency to turn the crank to the right than to the left,
providing of course, that there was no effect from the momentum of a
revolving fly wheel. If ignition occurred with the crank inclined ever
so little toward the right, the pressure of the piston would force the
crank downwards in a right handed direction. If the crank were inclined
to the left, the tendency would be for left handed rotation.

If the ignition system were arranged so that the spark occurred when the
crank was inclined towards the right every time that the piston came up
on the compression stroke, we should have continuous rotation in a right
hand direction. By shifting the sequence of the spark so that it
occurred with the crank on the left we would cause the engine to stop
and reverse to left handed rotation. This is exactly the method used in
reversing two stroke motors in practice, the change in the ignition
being accomplished by advancing or retarding the mechanism that
dispatches the spark (“Timer” or “Commutator”).

[Illustration:

Fig. F-9. Cross Section of Fairbanks-Morse Three Port—Two Stroke Cycle
Engine, with Parts Named.
]

This is an advantage not possessed by the four stroke cycle engine of
the ordinary type, as the cams and valve mechanism require reversal as
well as a reversal of the ignition system. This relation between the
valve action and rotation in a four stroke cycle engine may be
illustrated by the following example. Consider the piston at the end of
the compression stroke in an engine designed for right hand rotation.
After ignition, under the proper conditions, the piston would descend
turning the crank to the right until it reached the bottom of the
stroke, at which point the exhaust valve would open and relieve the
pressure in the cylinder.

Let us now consider an attempt at reversing the engine by causing the
spark to occur before the piston reached the end of the compression
stroke with the crank still inclined toward the left. In this case the
piston would force the crank down in a left hand direction until it
reached the end of the stroke. The exhaust valve would not open to
relieve the pressure, as the exhaust cam would be moving away from the
valve rod instead of toward it. Should the crank swing a little past the
dead center, because of its momentum, the inlet valve would be opened
instead of the exhaust, and the contents of the cylinder would shoot
through the intake pipe and carburetor. This would bring matters to a
close as far as rotation was concerned.

The opening of the inlet valve on the reversed working stroke would
occur as the inlet valve closes one stroke, or one-half revolution,
before the end of the compression stroke. As the engine turned backward
one-half revolution, the inlet cam would again be brought into contact
with the inlet valve rod, opening the valve and allowing the burned
gases to pass through the carburetor. Should the pressure be
sufficiently reduced by inlet valve to allow the piston to reach the end
of the second stroke, it would start on the third stroke by inhaling a
“charge” of burnt gas through the exhaust valve which would now be open.

(29) Scavenging Engines.

As the piston does not sweep out all the cylinder volume because of the
space left at the end of the cylinder for compression, more or less
burned gas remains in the combustion chamber which dilutes the active
mixture taken in on the suction stroke. Not only are the residual gases
useless in generating heat but they also occupy a considerable space in
the cylinder that might otherwise be filled with a heat producing
mixture. Their diluting effect also prevents the complete combustion of
a certain percent of the fuel actually taken into the cylinder for which
the burnt gas is incapable of supporting combustion.

The amount of burnt gas remaining in the cylinder depends upon the cycle
of the engine and also upon the valve timing and size of the exhaust
piping. In the four stroke cycle engine the volume of residual gas is
equal to the volume of the combustion chamber, in the two stroke cycle
it varies from one-tenth to one-third of the entire cylinder volume,
depending on the load and speed. With correct design and free exhaust
passages, the gas held in the clearance space of a four stroke cycle
engine is at a pressure considerably below that of the atmosphere, and
consequently its actual volume is even less than the volume of the
combustion chamber.

Many systems have been devised for the purpose of clearing the cylinder
of burnt gas in order to minimize the loss of fuel in large engines, but
owing to their complication have never been successfully applied to
small engines of the automobile or marine types. In general, the
“scavenging” is accomplished by pumping out the clearance space at the
end of the scavenging stroke, while fresh air is admitted to the
cylinder through the inlet valves, or by blowing out the clearance space
by a blast of pure air furnished from an air pump attached to the
engine.

There have been several systems proposed by which the gas in the
cylinder is withdrawn by the inertia of the exhaust gas in specially
designed ejectors, and by the compression of fresh air in the crank case
of the engine. The former system known as “organ pipe ejection,” is by
far the simplest method of all as the ejector is simply a tube without
moving parts, and it also possesses the additional advantage of reducing
the back pressure on the piston. Unfortunately these advantages are
obtained only at certain loads, and with certain velocities of the
exhaust gases, which makes it impossible to obtain even approximately
correct scavenging at other loads and speeds.

When air pumps are used for scavenging, a great percentage of the
economy obtained is offset by the power required to operate the pumps.
In addition to the frictional losses of the pumps, are the increased
maintenance charges and repair bills.

CHAPTER IV
INDICATOR DIAGRAMS

(35) General Description.

A brief description of the indicator as a means of recording the
pressures in the cylinder of a simple heat engine in relation to the
piston position was given in paragraph (6), Chapter I, and as this
instrument is so peculiarly adapted to locating the events taking place
in the cylinder we will devote some space on its application to the
practical gas engine cycles described in the preceding chapter. Since
each event in the cycle is accompanied by a corresponding increase or
reduction in pressure, the beginning or end of an event will be
indicated on the diagram by a change in the vertical height of the curve
above the atmospheric line, at some particular piston position. The
piston position will be in the same relation to the total stroke as the
pencil position will be to the horizontal length of the card.

If the event, for example, as indicated by a drop in pressure, be at the
center of the card, it will show that the drop in pressure took place
when the piston was in the center of the cylinder or at mid-stroke.
Should the pressure change at a point one-quarter of the card length
from the starting point of the pencil, it shows that the event took
place in the cylinder when the piston had accomplished the first quarter
of its stroke, and so on. It should be noted that horizontal distances
on the indicator card denote piston positions, and the vertical
distances, pressures.

As explained in a former paragraph the length of the vertical lines
represents certain definite pressures, each inch of length representing
so many pounds as per square inch, the exact amount per inch depending
on the indicator spring strength or adjustment. To make this point
clear, all of the indicator diagrams shown in this chapter will be
provided with a scale of pressures at the left of the diagram by which
the pressure at any point may be accurately measured off for practice.
It should be noted that points on the curves which are above the
atmospheric line represent positive pressures above the atmosphere, and
that the points lying below the atmospheric line represent partial
vacuums which may be expressed as being so many pounds per square inch
below the atmosphere. The vacuum pressures indicate the extent of the
“suction” created by the piston when drawing in a charge of air and gas.

Straight vertical lines show that the increase of pressure along that
line has been practically instantaneous in regard to the piston
velocity, for if the pressure increased at a slow rate this line would
be inclined toward the direction in which the piston was moving, as the
piston would have moved a considerable distance horizontally while the
pencil was moving vertically. This inclination of the vertical line
gives an idea of the rate at which the pressure increases in relation to
the piston speed, the greater the inclination, the slower is the rate of
pressure increase. Straight horizontal lines that lie parallel to the
atmospheric line denote a constant pressure or vacuum.

The rate at which horizontal lines descend or incline to the atmospheric
line represents the rate at which the pressure increases or decreases,
in respect to the piston position (not piston velocity). A steep curve
represents a rapid expansion or compression from one piston position to
the next. A waving or rippling line indicates vibration due to valve
chattering or explosion vibrations. A straight inclined line shows that
the pressure is decreasing or increasing in direct proportion to the
piston position.

(36) Diagram of Four Stroke Cycle Engine.

By referring to paragraph 25, Chapter III, it will be seen that the five
events of suction, compression, ignition, expansion and exhaust are
accomplished in four strokes, in the following order:

Stroke 1. Suction—(Mixture drawn into cylinder).
Stroke 2. Compression—(Mixture compressed).
Stroke 3. { Ignition.
{ Expansion (working stroke).
Stroke 4. Exhaust—(Scavenging stroke).

These events with the pressures incident to each drawn to some relative
scale are shown graphically in Fig. 10 by four lines representing the
four strokes of the piston. In order to show the relation between the
diagram and the piston, a sketch of the cylinder with a stroke equal to
the length of the diagram is shown directly beneath the curve. The
vertical line IJ is the scale of pressures (somewhat exaggerated in
order that the small vacuum and scavenging pressures shall be clearly
shown). The line marked “atmosphere” represents atmospheric pressure and
it is from this line that all measurements of pressure are taken.

[Illustration:

Figs. 10–11–12. Showing Respectively a Typical Four Stroke Diagram,
Retarded Combustion and Retarded Spark.
]

Consider the piston starting on the suction stroke, the piston moving
from the position L to K, or from left to right. The movement creates a
partial vacuum in the combustion chamber N which is shown on the diagram
as the distance OA, equal to 2 pounds below atmosphere according to the
pressure scale. The suction line remains at this distance below the
atmospheric line until within a short distance of the end of the stroke
when it rises to meet the atmospheric line at B when the piston reaches
the end of the stroke at K. This rise at the end of the stroke is due to
the fact that the piston moves more slowly when approaching the end of
the stroke while the velocity of the incoming gases remains nearly
constant so that the piston exerts no pull nor suction. On the diagram
the entire suction stroke is represented by AB.

The piston now returns on the compression stroke from K to J compressing
the mixture in the combustion chamber N. On the diagram this stroke is
shown beginning at B, with the pressure slowly rising until the pressure
is a maximum at the point C at the end of the stroke. During the
compression, the pressure has risen from that of the atmosphere at B to
125 pounds pressure at C as shown by the scale. At a point slightly
before C is reached, ignition occurs, and the pressure rapidly rises
from C to D, due to the expansion of the heated gas. In this case the
combustion is practically instantaneous as shown by the straight,
vertical combustion line CD.

At D the piston starts on the working stroke from left to right
increasing the volume of the gas and at the same time diminishing the
pressure because of the expansion until the maximum pressure of 400
pounds per square inch at D is reduced to 30 pounds per square inch at
E, the line DE being called the expansion line. During this time the
heated gas has been performing work on the piston. At E the exhaust
valve opens and the pressure drops from E to T, a point still about 10
pounds above atmospheric pressure. Theoretically the pressure should
drop instantly from E to atmosphere, or from 30 pounds per square inch
to zero, but practically this is impossible because of the back pressure
due the slow escape of the exhaust gases through the comparatively small
valve openings and exhaust pipes. Since considerable pressure is exerted
by the piston on the return stroke in forcing the gases out of the
exhaust valve, the exhaust line TO on the diagram is nearly 10 pounds
above the atmospheric pressure from T to O. At a point near O, the
piston slows up on nearing the end of the stroke so the gases have more
time to escape through the valves, and the pressure drops to the
atmosphere, ready for the succeeding suction stroke.

It should be noted that the points A, B, E, and F represent periods of
valve action. At A the inlet valve opens; at B the inlet closes; at E
the exhaust opens; at F the exhaust closes, and at A the inlet again
opens at the beginning of the suction stroke AB. That this is true is
apparent from the fact the inlet must open at the beginning of the
suction stroke, and both valves must be closed from the point B to the
point E in order to prevent the escape of the compressed charge and
expanded gases from the cylinder. At the end of the working stroke the
exhaust valve must liberate the gases and remain open to the end of the
scavenging stroke to eliminate the residual gas while the closed inlet
valve prevents the burnt gases from being forced through the inlet pipe
and carburetor.

As shown on the diagram, the exhaust valve closes at the same time that
the inlet opens, as F, and O both occur on the same vertical line DL.
This is true theoretically, but owing to the different conditions met in
practice, the actual setting of the valves may vary slightly from that
shown on the diagram. Some makers of high speed engines open the inlet
slightly before the exhaust closes as it is claimed that the inertia of
the exhaust gas passing through the exhaust pipe creates a slight vacuum
that is an aid in filling the cylinder with a fresh charge. It should be
borne in mind that this condition only exists when the piston has come
to rest and exerts no pressure on the exhaust gas. The vacuum is due to
the velocity inertia of the gas after it has been reduced to atmospheric
pressure. Other makers close the exhaust valve a very little before the
inlet opens, but no matter what the setting, the difference in the time
of opening and closing is very small, and the results obtained probably
differ by an almost negligible amount.

During the suction and scavenging strokes, the fly wheel of the engine
is expending energy on the gas since it is moving a considerable volume
at a fairly high pressure. In the case of the scavenging stroke, the
piston is working against 10 pounds back pressure, which on a 10 inch
piston would amount to a force of 785 pounds. With the 2 pound vacuum
the drag on the piston would amount to 157 pounds, no small item when
the velocity of the piston is considered. Of course the pressure of 10
pounds per square inch is rather high, but it is often attained with
long and dirty exhaust pipes. It is items of this nature that cut into
the efficiency of the engine, and increase the fuel bills, and it is
only by the indicator that we can determine the extent of such “leaks”
and remedy them.

Since the area of the indicator card represents the power of the engine,
it is evident that we lose the power represented by the area included in
the rectangle FEBO on the scavenging stroke plus the area BOA on the
suction stroke. The area included in BCO represents the work taken from
the engine in compressing the charge, but this is returned to us during
the next stroke plus the benefits gained by compressing the mixture. The
arrows show the direction in which the piston is moving during that
event.

An actual engine does not follow the form of the diagram shown by Fig.
10 exactly because of certain conditions met with in practice such as
imperfect mixtures, faulty valve and ignition timing, small valve areas
or leakage. The combustion in the real engine is neither instantaneous
nor complete but it approximates the “=IDEAL=” cycle just described more
or less closely with a high compression and a fairly well proportioned
mixture.

(37) Detecting Faults With the Indicator.

For the best results the gas must be completely ignited at the point of
maximum compression, and the pressure must be established on the dead
center, so that the indicator card will show a straight and vertical
combustion line. As all gases require a certain length of time in which
to burn, the ignition should have =LEAD=, that is, should be started
before the end of the stroke so that combustion will be complete at dead
center. The amount of ignition lead required depends on the fuel and the
compression. In Fig. 10 the point of ignition (I) is shown as occurring
before the end of the compression at (C), which insures a straight
combustion line CD.

With a lean or slow burning gas, that is, a gas slower than used on the
diagram, combustion would not be complete at the end of the stroke if
the same point of ignition were used. This effect is shown by Fig. (11),
in which the full line diagram BCDE represents the ideal diagram (Y),
and BCFG represents the slow burning mixture with the same point of
ignition (X). The compression curves of both diagrams are coincident as
far as C, the ideal diagram shooting straight up at this point and the
weak mixture diagram staying at the same level. When under the influence
of the mixture (X) the piston starts from left to right and reaches the
point F before the slow burning gas reaches its maximum pressure. During
this part of the stroke there has been very little pressure on the
piston and it will be noticed that the maximum pressure is far below
that of the ideal diagram. This low maximum is due principally to the
reduced compression under which the gas has been burning, from C to F.

[Illustration:

Figs. 13–14. The First Diagram (13) Shows a Two Port Two Stroke
Diagram, the Second Shows a Typical Diesel Card.
]

As the gas has but a small part of the stroke left in which to expand,
the pressure at the point of release is much higher than the release
pressure of the ideal diagram, which means that a considerable amount of
heat and pressure have been wasted through the exhaust pipe. Besides the
heat loss, the high temperature of the escaping gas has a bad effect on
the exhaust valve and passage. The great volume of gas passing through
the exhaust valve also increases the back pressure on the scavenging
stroke.

Delayed or retarded ignition will cause a low combustion pressure and
slow combustion with any type of fuel or compression pressure as will be
seen from Fig. 12. In this case the compression pressures of the ideal
diagram Y and the diagram X showing the retarded spark are of course the
same, the compression line extending from B to C in the direction of the
arrows. At C the ignition occurs for curve Y, and the pressure
immediately rises to D. In the case of curve X, ignition does not occur
until the point I is reached, the compression falling on the line CI
with the forward movement of the piston as far as the point I. At this
point the compression pressure is very low which results in the slow
combustion indicated by the slant of the combustion line IF. The point
of maximum pressure F is much below D of the ideal curve, and as there
is no opportunity for complete expansion during the rest of the stroke,
the release pressure is high causing a great heat loss. If running on a
=LATE= or =RETARDED= spark is continued for any length of time the
excessive heat that passes out of the exhaust will destroy the valves.

It is apparent that for the best results, the spark should occur
slightly before ignition in order to gain the effects of the
compression, and a high working pressure on the piston. It is also
evident that the point of ignition should be varied for different
mixtures that have different rates of burning. With engines that govern
their speeds by throttling or by changing the quality of the mixture it
is necessary for the best results, to vary the point of ignition with
each quality of fuel that is admitted by the governor. The retard and
advance of the ignition is very necessary on an automobile engine
because of the throttling control and constant variation of the load and
speed. All automobilists know of the heating troubles caused by running
on a retarded spark.

(38) Two Stroke Cycle Diagram.

In the two stroke cycle diagram, the lines showing the suction and
scavenging strokes are missing if the indicator is applied only to the
working cylinder.

Starting at the beginning of the working stroke as at A in Fig. 13, the
gas expands during the working stroke until the piston uncovers the
exhaust port at B where the pressure drops to C. A slight travel
uncovers the inlet port with the pressure still above atmosphere due to
the pressure in the crank case filling the cylinder. The crank case
pressure continues from C to D or to the end of the stroke, the pressure
dropping slightly at the latter point.

The compression stroke now takes place with the piston moving from right
to left, the compression pressure reaching a maximum at F. Ignition
occurs slightly before the point of greatest compression, at I, and the
expanded gas increases in pressure until the point A is reached. From
this point the same cycle of events is repeated. Because of the dilution
of the charge by the burnt gases of the preceding combustion, the
mixture burns slowly as will be seen from the inclined combustion line
FA. Due to this delayed combustion, the piston travels the distance S on
the working stroke before the pressure reaches a maximum. This diagram
is typical of the small marine type of two stroke cycle engine which has
no further scavenging than that performed by the rush of the entering
mixture. The diagram of the pressures and vacuums in the crank case are
similar to those of suction and compression in the four stroke cycle
type.

(39) Diagram of Diesel Engine.

A diagram of the Diesel engine is different in many particulars from
that of an ordinary gas engine, as will be seen from the diagram in Fig.
14. The pressures rise in an even, gradual line from the end of the
compression curve, and instead of having a sharp peak at the end of the
combustion, as in a gas engine, the top of the curve is broad and
greatly resembles the indicator diagram of a steam engine. The
compression curve constitutes a greater proportion of the pressure line
than that of a steam engine, the rise of pressure due to the ignition
being very slight in comparison to the height of the compression curve.
There is no explosion in the usual sense of the word, only a slight
increase in pressure as distinguished from the rapid combustion in the
gas engine.

Starting at the beginning of the compression stroke at H, the pressure
of the pure air charge increases to about 500 pounds to the square inch
at I, the point at which the fuel is injected. From I to C is the
increase of pressure due to the combustion. The pressure stays at a
constant height from C to D as the fuel supply is continued between
these points, and is cut off when the piston reaches the position D. It
will be seen that the admission of the fuel through the distance A
covers a considerable proportion of the working stroke, and that the
points of fuel injection and ignition are coincident.

From the point of fuel cut-off at D expansion begins and is continued in
the usual manner to F, the point of release.

When the load is increased, the period of oil injection is also
increased, the other events remaining constant. Should the light load
require an oil injection period as shown by A, the greater load would
require injection for the period B. In the latter case, the expansion
line would be EG, which would produce a diagram having a greater area
than the line DF, and there would be a great increase in the release
pressure GH as well.

It will be seen from the diagram that the quantity of air taken into the
cylinder and the compression pressure remain constant with any load, and
that for this reason it is possible to have a constant point of
ignition, or rather point of fuel injection. As there is no mixture
compressed, there are no difficulties encountered at light loads due to
attenuated mixtures. An excess of air over that required to burn the
fuel is also present at every load within the range of the engine. For
the sake of simplicity, the suction and scavenging lines on the Diesel
engine have been omitted, but they are the same in all respects as the
corresponding lines shown in the diagram, Fig. 14.

(40) Gas Turbine Development.

In the attempt to gain mechanical simplicity, small weight, and
diminutive size of the steam turbine, many able experimenters have
endeavored to obtain an internal combustion motor in which the energy of
the expanding gas is converted into mechanical power by its reaction on
a bladed wheel, but so far the problem is far from being solved. In 1906
two experimental turbines were built by René Armengand and M. Lemale, of
the constant pressure type, one of which developed 30 Brake horse-power
and the other 300 horse-power.

A 25 horse-power De Laval steam turbine was altered by Armengand says
Dugald Clerk so that it operated with compressed air instead of steam.
The compressed air was passed into a combustion chamber together with
measured quantities of gasoline vapor, and the mixture was ignited by an
incandescent platinum wire as it entered the chamber, thus maintaining a
constant pressure with continuous combustion. Around the carborundum
lined combustion chamber was imbedded a coil in which steam was
generated by the heat of the burning gas, the steam being used to reduce
the temperature of the gas from 1800°C to about 400° as it issued from
the orifice and came into contact with the running wheel. The working
medium was therefore composed of two elements, the products of
combustion and the steam at the comparatively low temperature of 400°C.

The constant pressure maintained in the combustion chamber was about 10
atmospheres, and the hot gases were allowed to expand through a conical
Lava jet in which the expansion produced a high velocity, and reduced
the temperature of the fluid. At this reduced temperature and high
velocity the gases impinged upon the Laval wheel, and rotated the wheel
in the same way as steam would have done. The experiments showed that
under these conditions the total power obtained from the turbine
separate from the compressor was double that necessary to drive the
compressor.

In the large 300 H. P. turbine the first part of the combustion chamber
was lined with carborundum, backed by sand, but the second part was
surrounded by a coil through which water was circulated. The water kept
the temperature of the combustion chamber within safe limits, and after
absorbing heat, it passed also around the jet nozzle, and was discharged
into the passage leading to the jet, and there converted into steam by
the hot gases. A mixture of products of combustion and steam thus
impinged upon the turbine wheel. The expanding jet was arranged to
convert the whole of the energy into motion before the fluid struck the
wheel; the temperature was thus reduced to a minimum before the gases
touched the blades. Notwithstanding this, the wheel itself had passages
through which cooling water flowed, and each blade was supplied with a
hollow into which water found its way. In the large turbine the
compressor was mounted on the turbine spindle; it was of the Rateau
type, and consisted of an inverted turbine of four stages, which
delivered the compressed air finally to the combustion chamber at a
pressure of 112 lb. per sq. in. absolute. The efficiency of this turbine
compressor was found to be about 65 per cent. The total efficiency of
the combined turbine and compressor was low, as the fuel consumption
amounted to nearly 3.9 lb. of gasoline per B. H. P. hour. An ordinary
gasoline engine with a moderate compression can readily give its power
at the rate of 0.5 lb. of gasoline per B. H. P. hour. The combined
turbine and compressor was stated to have run at 4,000 R. P. M. and to
have developed 300 H. P. over and above the negative work absorbed by
the compressor.

A gas turbine in which there was no compression was built in the
following year by M. Karovodine which gave 1.6 horsepower at a speed of
about 10,000 revolutions per minute.

It contained four explosion chambers having four jets actuating a single
turbine wheel, which wheel was of the Laval type, about 6 inches
diameter, having a speed of 10,000 R. P. M. The explosion chambers were
vertical, and had a water jacket surrounding the lower end. The upper
portion contained the igniting plug on one side, and the discharge pipe
connecting with the expanding jet on the other. In the lower
water-jacketed part there was provided a circular cover, held in place
by a screwed cap. This circular plate was perforated with many holes,
and it carried a light steel plate valve of the flap or hinging type,
which pulled down by a spring contained within the admission passage.
This spring could be adjusted, and the lift of the valve was regulated
by means of a set screw passing diagonally through the water jacket. Air
was admitted at one side by a pipe leading into the valve inlet chamber
and a corresponding passage or pipe admitted gasoline and air or gas to
mix with the air before reaching the thin plate valve. Adjusting
contrivances were supplied in both air and fuel ducts. To start the
apparatus, an air blast was forced through the valve, carrying with it
sufficient gasoline vapor to make the mixture explosive. The electrical
igniter was started, and the spark kept passing continuously. Whenever
the inflammable mixture reached the upper part of the combustion chamber
ignition took place, and the pressure rose in the ordinary way, due to
gaseous explosion. The gases were then discharged through the pipe and
nozzle on the Laval wheel. The cooling of the flame after explosion and
the momentum of the moving gas column reduced the pressure within the
explosion chamber to about 2 lb. per sq. in. below atmosphere. Air and
gasoline vapor then flowed in to fill up the chamber, and as soon as the
mixture reached the igniter, explosion again occurred. In this way a
series of explosions was automatically obtained, and a series of gaseous
discharges was made upon the turbine wheel. Diagrams taken from the
explosion chamber showed a fall in pressure during suction of 2 lb. per
sq. in.; ignition occurred while the pressure was low, and the pressure
rapidly rose to about 1 1–3 atmospheres absolute. The pressure
propelling the gas column and jet was thus only 5 lb. per sq. in. above
atmosphere. The pressure rapidly fell, and the whole process was
repeated again. According to the diagrams taken, a complete oscillation
required about 0.026 second, so that about 40 explosions per second were
obtained.

[Illustration:

Fig. 15. Cross-Section of the Combustion Chamber of the Holzwarth Gas
Turbine. From the Scientific American.
]

The most promising type of turbine that has been built to date is that
designed by Hans Holzwarth, an engineer of some prominence in the steam
turbine field. A 1000 horse-power machine has been built at this writing
and as experimental machines go has made most remarkable performance.

The turbine in general arrangement outwardly resembles the Curtis steam
turbine, in that the turbine wheel rotates in a horizontal plane, the
spindle or shaft is vertical and a dynamo is mounted on this spindle
above the turbine. In the Holzwarth turbine ten combustion chambers are
provided, each of a pear or bag shape. They are arranged in a circle
around the wheel, and are cast so as to form the base of the machine.
The wheel is of the Curtis type, with two rows of moving and one row of
stationary blades.

In this turbine the energy of the fuel is liberated intermittently by
successive explosions, instead of by continuous combustion, and in much
the same way that the explosions occur in a reciprocating engine. Tests
made on the new machine have shown that it is in no way inferior in
efficiency to the ordinary type of motor, and that at full load, the
weight per horse-power is only about one-quarter of that of the
reciprocating engine. The weight factor, as is well known, is of the
utmost importance in marine service and should prove of value to the
marine engineer, if this alone were its only characteristic.

Any of the ordinary power gases may be used with success, as well as
vaporized liquid fuels, and the lower grade oils such as crude and
kerosene have given much better results in the turbine, than in
reciprocating engines, even at this early stage of its development. As
the heat losses are much smaller than met with in ordinary practice, the
temperature is higher, which, of course, greatly facilitates the
vaporization of the lower grade liquids.

Mr. Holzwarth does not give the dimensions of his turbine wheel, but
from the drawings and some of the velocities given by him it appears to
be about 1 m. in external diameter. The lower part of each combustion
chamber carries gas and air inlet valves, and the upper part carries a
nozzle arranged to cause the gases to impinge upon the first row of
moving blades. This nozzle is connected to and disconnected from the
combustion chamber by means of an ingeniously operated valve. The
explosion chambers are charged with a mixture of gas and air, which
appears to attain a pressure of about two atmospheres within the chamber
before explosion. The air and gas are supplied under sufficient pressure
from turbine compressors, actuated by steam raised from the waste heat
of the explosion and the gases of combustion, so that whatever work is
done in compression is obtained by this regenerative action, and does
not put any negative work upon the turbine itself. The combustion
chambers are fired in series, by means of high-tension jump spark
ignition.

Referring to the cut, the explosion chamber A is filled intermittently
with the explosive mixture at a low pressure (about 8 to 12 pounds per
square inch). When ignition has occurred, the pressure of explosion
opens the nozzle valve F, allowing the compressed gases to flow through
the nozzle G to the bladed turbine H, on which the energy is to be
expended. The expansion of the heated gases in the nozzle reduces the
pressure to that of the exhaust, with the resulting increase in the
velocity of the gas. By means of fresh air, the nozzle valve F is kept
open throughout the expansion and scavenging periods.

After the expansion has been completed, the air that is forced through
the valve D, at a low pressure, thoroughly scavenges or removes the
residual burned gases left in the combustion chamber and nozzle, forcing
it into the exhaust. When the scavenging has been completed, the nozzle
valve and the air valve D are closed. The combustion chamber A is now
filled with pure cold air, which not only enables a fresh charge of gas
to be introduced into the chamber but which also aids in keeping the
chamber cool.

Pure fuel gas, or atomized oil, is now injected through the fuel valve
E, forming an explosive mixture ready for the ensuing cycle of events. A
number of these chambers are arranged around the turbine wheel in order
to have a uniform application of power, by having the several chambers
working intermittently. This is in effect, the same proposition as
increasing the number of cylinders on a reciprocating engine.

CHAPTER V
TYPICAL FOUR STROKE CYCLE ENGINES

(41) Essential Parts of the Gas Engine.

On all gas engines of accepted type are found certain devices necessary
for the performance of the events or cycles outlined in the preceding
section.

For the sake of simplicity these devices are treated as a part complete
in itself. The details of construction, and the refinements found
necessary in the actual construction will be described in the succeeding
chapters.

The names and purpose of these essential components, and their relation
to the operation of the engine as a whole, will be found in the
following outline:

1. The =CARBURETOR= is a device whose purpose is to vaporize the liquid
fuel, and mix the vapor thoroughly and in correct proportions with the
air required for the combustion, in the engine cylinder.

The combustible mixture thus formed is drawn into the cylinder of the
four stroke cycle engine or into the crank chamber of the two stroke
cycle engine.

=GENERATOR VALVES= or =MIXING VALVES= are similar to the carburetor in
principle but are slightly different in detail.

2. The =CYLINDER= is the containing vessel in which the combustion and
expansion of the gas takes place.

The cylinder as its name would suggest has a circular opening or bore
extending from end to end, the bore being smoothly finished to receive
the reciprocating piston.

3. The =PISTON= is a plunger or movable plug fitting the bore closely
enough to prevent the escape of gas, but at the same time is capable of
sliding freely to and fro.

When pressure is established in the cylinder from the combustion,
pressure is also exerted on the end of the piston tending to force it
out of the cylinder. The extent of this force is governed by the area of
the end of the piston and also by the pressure of the gas.

Thus the purpose of the piston is to convert the pressure of the
expanding gas into direct mechanical force, and also to transform the
increasing volume of gas into motion. Another, and no less important
function of the piston is to compress the combustible gas in the upper
end of the cylinder for ignition.

[Illustration:

Piston and Connecting Rod of the Sturtevant Aero Motor, Showing Three
Piston Rings.
]

4. The =CONNECTING ROD= (Sometimes called the Pitman) transmits the
pressure on the piston to the crank, the connecting rod being the means
through which the to and fro motion of the piston is transmitted into
the rotary motion of the crank; its action being similar to that of the
human arm turning the crank of a pump or windlass.

5. The =CRANK= receives the pressure and motion of the piston from the
connecting rod, changing the reciprocating motion of the piston into the
rotary motion required by the machinery which the engine drives.

In the majority of cases the crank revolves, while the cylinder stands
still, but in some of the recently developed aeronautic motors this is
reversed, the cylinders revolving with the crank stationary. The
relative motion, however, is the same in both cases.

(6.) The =CRANK SHAFT=, of which the crank is an integral part,
transmits the rotary motion of the crank to the driving pulley.

(7.) The admission and release of the gases to and from the cylinder are
controlled by the =INLET VALVE= and =EXHAUST VALVE=, respectively, in a
four stroke cycle engine.

The valves are merely gates, allowing the gas to flow, or stopping it,
at the proper intervals, depending on the event taking place at that
time in the cylinder.

In the two stroke cycle engine there are no valves, the admission and
release of the gas being controlled by the position of the piston, and
the openings cut in the cylinder walls.

6. =IGNITION= or the firing of the combustible charge is accomplished by
the =IGNITION SYSTEM=. In most modern engines the mixture is ignited
when it is under the greatest pressure or at the end of the stroke.

For maximum efficiency the mixture should be ignited when it is under
the greatest pressure or compression. The time at which ignition occurs
is also controlled by the ignition system.

7. The =GOVERNOR= regulates the speed of the engine; either by changing
the richness of the mixture, by changing the number of working strokes
in a given time or by altering the quantity of gas admitted to the
cylinder, or sometimes by a combination of these methods.

8. The =BELT WHEELS= or =PULLEYS= are the means of transmitting the
power of the engine to the work to be performed. The engine is generally
connected to the driven machinery by a belt connecting the engine pulley
with the pulley of the driven machine.

9. The =FLY WHEELS= by reason of their mass and their momentum, store up
a portion of the energy expended during the working stroke, and return
it to the engine in order to carry it through the idle strokes of
compression, admission and expulsion. In some engines the fly wheels
serve in double the capacity as pulleys.

10. The =BASE= or =FRAME= of the engine acts as a foundation for the
various working parts, holding them in their proper positions.

(42) Application of the Four Stroke Principle.

While the five events of every commercial four stroke cycle engine are
accomplished in exactly the same order, or routine as explained in
paragraph (8), Chapter 3, the actual design and method of applying the
cycle varies greatly in different makes of engines. This great
difference in the details of construction often makes it difficult for
the novice to identify the cycle of operations in that particular
engine. The different forms of valve gears that are used to perform the
same functions in the cycle are good examples of the variation in
design, some makers using the poppet or disc type, some the sliding
sleeve, and others the rotary type.

[Illustration:

Fig. 16. Ball Bearing Crank Shaft, Pistons and Connecting Rods of the
“Maximotor,” in Their Relative Positions.
]

Multiple cylinder engines vary in the cylinder grouping or arrangement,
the arrangement and number of cylinders depending on the service for
which the engine is intended, the amount of vibration permissible, or
the weight. The question of speed also introduces modifications in the
design, but no matter what valve arrangement is adopted or what grouping
of cylinders is used, a four stroke cycle engine performs the five
events of suction, compression, ignition, expansion and exhaust in four
strokes, in each and every cylinder. With the exception of fuel
injection (which in reality corresponds to the ignition event) in the
four stroke Diesel engine, the indicator cards of all four stroke cycle
engines passes the same characteristics as the diagram shown in Fig. 10.

In this chapter, the engine will be described without regard to the fuel
used, or to the means adopted in vaporizing it, for the vaporizing
appliances are considered as being external to the engine proper, except
in some of the heavy oil engines, and as the fuel is gasified before
entering the cylinder the question of fuel does not affect the general
construction of the engine. The majority of engines are readily
converted from gasoline to gars, or in some cases kerosene, by changes
in the vaporizing device, and with the exception of changing the
compression pressure, little further alteration is needed. Since the
vaporization and admission of the heavier oils, such as crude oil and
kerosene has a more intimate relation to the engine than the use of
gasoline or gas, the heavy oil engines will be described in a separate
chapter in order that the process of oil burning may be more fully
explained. It should not be understood that the cycle, or principle of
the oil engine differs from that of any other engine, but that the
vaporizer forms such a close connection with the engine proper that they
must be described as one unit.

(43) Horizontal Single Cylinder Engine.

An example of a modern single cylinder engine operating on the four
stroke cycle principle is the “Muenzel” engine shown in Section by Fig.
17. It is of the single acting type, that is, the pressure of the gases
acts only on the left end of the piston which reciprocates in a
horizontal direction. Surrounding the cylinder in which the piston
slides, is the water jacket (shown by the short horizontal dashes) which
keeps the cylinder walls from becoming overheated by the successive
explosions of the mixture. The cooling water is pumped into the jacket
through the pipe shown over the cylinder, and flows out of the jacket
through an outlet near the bottom of the cylinder.

[Illustration:

Fig. 17. Longitudinal Section Through the Muenzel Horizontal Engine.
]

Both the inlet and exhaust valves are situated in an extended portion of
the combustion chamber to the left of the piston, the upper valve being
the inlet and the lower valve, the exhaust. The valves are held on their
seats by means of coil springs that act on the upper ends of the valve
springs. Admission of the explosive mixture is controlled by the upper
valve, and the release of the burnt gases by the lower. Pipes at the
bottom of the cylinder marked “Gas Supply” and “Exhaust” convey the
gases to and from the inlet and exhaust valves respectively.

[Illustration:

Fig. 18. Elevation of Muenzel Engine Showing Lay Shaft and Valve
Connections.
]

The inlet valve, and the inlet valve spring are held in one unit by a
removable metal housing known as a “Valve Cage”, which is arranged so
that the cage, valve, and spring may be removed as one piece from the
cylinder casting when the valves need attention by removing a few bolts.
As the cage is directly over the exhaust valve, and is considerably
larger in diameter, it is possible to remove the exhaust valve through
the opening left by the removal of the inlet valve cage. Both valves are
surrounded by a water jacket, as are the passages that lead to them.

Both the inlet and exhaust valves are opened and closed at the proper
moments in the stroke by means of cams mounted on the horizontal cam
shaft shown by Fig. 18 through a system of levers. The cam shaft is the
shaft running parallel to the engine bed from the crank-shaft to the end
of the cylinder and turns at one-half the speed of the crank-shaft. At a
point directly below the inlet valve in Fig. 18, will be seen an
enlargement on the shaft on which rests the rod running from the inlet
valve to the cam shaft. This is the cam.

A cylindrical casing shown above the cylinder contains the governor
which maintains a constant speed at all loads by operating a valve in
the intake pipe which varies the quantity of mixture entering the
cylinder in proportion to the load. The governor is driven from the
cam-shaft by spiral gears. The igniter which furnishes the spark for
igniting the gas is located between the two valves at the extreme left
of the combustion chamber (Fig. 17).

It should be noted that the cylinder head which closes the left end of
the cylinder, and which carries the valves is separate from the main
body of the Cylinder. By unscrewing the bolts that hold it to the
cylinder, the head may be removed when it becomes necessary to remove
dirt and carbonized oil from the combustion chamber, or when it becomes
necessary to remove the piston. The cylinder barrel in which the piston
works may also be removed through the opening left by the piston head
when it becomes worn, and another barrel or liner may be substituted,
thus practically renewing the engine at a small fraction of the cost of
a new cylinder. The liner is fastened firmly to the outer cylinder
casting at the left but is free to slide back and forth in the casting
at the right hand end, this end being provided with a packed joint. This
play given to the liner allows it to expand and contract freely with the
different changes of temperature without causing strains either in the
cylinder or in the liner.

(44) Multiple Cylinder Engines.

Since the power exerted by a single cylinder four stroke cycle engine is
intermittent, the explosive force exerted on each power stroke is much
heavier than would be the case if the power application were continuous,
as the explosions must be heavier to compensate for the idle periods. To
reduce the strain on the engine and the vibration as well and to obtain
an even turning moment it has been customary to provide more than one
cylinder on engine of over 10 horse-power capacity. In this way the
total power is divided among a number of cylinders, and as no two
cylinders are under ignition at any one time the turning moment is more
even, the vibration is less, and the strain on the engine is
considerably reduced.

Dividing the power in this way makes it possible to reduce the weight of
the engine as less material is required to resist the strains and a
small fly-wheel may be used because of the even engine torque. In order
to gain the full benefit of this reduction in weight, the builders of
aeronautic motors have carried the multiplication of cylinders to an
extreme, the Antoinette for example having sixteen cylinders. Engines
having more than six cylinders exert a continuous pull as the impulses
“overlap,” that is, ignition occurs in one cylinder before another
cylinder in the series ends its working stroke. The greater the number
of cylinders, the more continuous will be the torque or turning moment.
The multiple cylinder engine may be considered as a group of single
cylinder engines connected together, and receiving their fuel from a
common source, the only difference between the single and multiple being
in the inlet and exhaust piping and the ignition system.

[Illustration:

Fig. F-12. Six Cylinder Maximotor.
]

[Illustration:

Fig. F-13. Four Cylinder Buffalo Motor for Marine Service.
]

As a single cylinder four stroke cycle engine has one working impulse in
every two revolutions, a two cylinder engine will have an impulse for
every revolution as there are twice as many impulses in the same time.
It should be remembered that the number of impulses given per revolution
by a four stroke cycle engine is equal to the number of cylinders
divided by two. Thus, a six cylinder engine has 6 ÷ 2 = 3 impulses per
revolution, and an eight cylinder, 8 ÷ 2 = 4 impulses, providing of
course, that the engine is single acting.

Arrangement of the cylinders varies with the service for which the
engine is intended and the perfection of balance that is required, the
principal arrangements being the “V,” the “upright,” the opposed, the
“radial,” “tandem,” and “twin.” The upright engine has the cylinders all
on one side of the crank-shaft in a straight line, as in the four
cylinder automobile engine. In this form, each cylinder has an
individual crank throw the number of throws being equal to the number of
cylinders. This engine is fairly well balanced in the four, six and
eight cylinder types, as one-half of the connecting rods and throws are
up, while the other half are down, but as the connecting rods do not all
make equal angles with the center line of the cylinder at the same time
there is a slight unbalance in the four and six cylinder types. Because
of the ignition sequence, two cylinder vertical motors are in no better
balance than the single cylinder type since both crank throws and
connecting rods are on the same side of the shaft at the same time. For
this reason the two cylinder engine is most commonly built in the
opposed type which gives perfect balance.

In “V” type arrangement, one-half of the cylinders are set at an angle
of about 90° with the rest of the cylinders, or in the two cylinder “V”
the cylinders are set in the same plane, perpendicular to the shaft, at
angle varying from 57½° to 90°. The “V” type arrangement is adopted
where light weight and compactness are the principal requirements, as
the weight and length are both reduced by putting the cylinders opposite
to one another by pairs, the “V” being practically one-half the length
of an upright having the same number of cylinders. This arrangement
permits the use of one-half the number of crank throws used in the
vertical type as each crank throw acts for two cylinders. For the reason
that both the cylinders of a two cylinder “V” act on a common crank
throw, the two cylinder “V” is in no better balance than a single
cylinder engine.

[Illustration:

Fig. 18-a. G. H. H. Double Acting Tandem Cylinder Engine (German). It
will be Noted that an Inlet and Exhaust Valve Are Placed at Both
Ends of Each Cylinder. The Exhaust Valves Are Below and the Inlets
Above the Cylinders. As this Engine is of the Four Stroke Cycle
Type, Each Cylinder Gives One Impulse per Revolution, or Two
Impulses per Revolution for Both Cylinders. The Piston and Piston
Rod Are Both Cooled by Water, and Are Supported by the Cross Heads
so that Their Weight is Taken Off the Cylinder Bore.
]

An “opposed” type engine is in the most perfect mechanical balance of
any engine as the crank shafts and connecting rods are not only on
opposite sides of the crank-shaft, but make equal angles with the center
line of the cylinders as well, at all points in the revolution. The
explosive impulses occur at equal angles in the revolution as in the
four and six cylinder vertical type. An opposed engine may be considered
as a “V” having a cylinder angle of 180°. In the opposed type, one crank
throw is provided for each cylinder, the pistons of the opposite
cylinders traveling in opposite directions at the same time.

A “radial” or “Fan” type motor, as the name would suggest has the
cylinders arranged in one or two rows around the crank case, each
cylinder being on a radial line passing through the center of the
cylinder with one crank throw for each row. The Gnome engine illustrated
elsewhere in the book is an example of this type, the seven equally
spaced cylinders acting on a common crank throw. When more than seven
cylinders are used on this engine, as in the fourteen cylinder engine,
two cranks are provided, each crank serving seven cylinders. This
arrangement cuts down the weight of a motor enormously because of the
short crank shaft and case. With the ignition properly timed and the
cylinders correctly spaced the firing impulses occur at equal angles.

“Tandem” cylinders are employed only on stationary engines, the
cylinders being placed on the same center line, one in front of the
other, and when this arrangement is adopted it is the usual practice to
make the cylinders double acting. The two pistons are connected by a rod
known as the “piston rod” which extends from the rear end of one
cylinder into the front of the following cylinder. Tandem cylinders
require too much room for use on automobiles or motor boats, and for
this reason are seldom seen in this service.

The “twin” engine is a modification of the vertical cylinder
arrangement, both cylinders being on the same side of the shaft and in
line with one another. It is the type most generally used on very large
stationary engines that have more than one cylinder, and instead of
being vertical as in their prototype are generally laid horizontally.
Since the twin engine is generally double acting, the crank throws are
placed on opposite sides of the shaft.

(45) Four Cylinder Vertical Auto Motor.

A common type of four cylinder vertical motor is shown by Fig. 19, which
is of the type commonly used on automobiles. In order to show the
general construction of the cylinder, each cylinder is cut through at a
different point. The cylinder at the extreme left is shown in elevation,
or as we would see it from the outside. In the second cylinder from the
left, the section is taken through the valve chamber, which projects
from the side of the cylinder. A section through the center of the
cylinder is shown on the third cylinder, and the fourth cylinder is in
elevation.

On cylinder No. 1, (left) is seen the exhaust pipe (32) and the inlet
pipe (31) entering to valve chamber and connected to the exhaust valve
and inlet valve respectively. The pipes are held in place by the clamp
or “crab” (33). The exhaust pipe connects with the exhaust valve of each
cylinder, and terminates at the fourth cylinder as shown by (32).
Screwed into the top of the valve chamber on cylinder No. 1 are the two
spark plugs (34) and the relief cock (35).

Referring to cylinder No. 2, the inlet valve (42) is shown at the left
of the chamber and the exhaust valve also shown by (42) is shown at the
right. Above the valves are the spark plugs (34) which project into the
space above the valves. Pressing against the lower ends of the valve
stems and holding the valves tight on their seats are the springs (44)
which fit into the washers (45) fastened to the stems. The valve stems
terminate in a nut at (48). The valve stem guides (43) form a support
for the valves and at the same time form an air tight connection for the
stems to slide in.

Immediately beneath the stems are the push rods (46) which are provided
with an adjustment (48) at the upper end, and a roller (49) at the lower
end. The rollers (49) rest directly on the cams mounted on the cam shaft
(27), and as the irregular cams revolve, the push rods are moved up and
down which in turn act on the valve stems and raise the valves at the
proper moment. The cams raise the valves and the springs close them. The
two cams (exhaust and inlet) appear as two rectangular enlargements on
the shaft (27). The bearings (53), support the cam shaft, one being
supplied for each cylinder.

At the extreme left of the crank shaft is shown the half time gear (20)
which meshes with the gear on the crank-shaft and drives the cams. Next
to this gear is the large cam shaft bearing 26. It should be noted that
the section through the valve chamber taken on cylinder No. 2 is at a
point considerably back from the center line of the cylinders and not in
the same plane as the section shown on cylinder No. 3, which is taken
through the center line of the cylinders.

[Illustration:

Fig. 19. Cross-Section Through Typical Four Cylinder Automobile
Engine. Courtesy of the Chicago Technical College.
]

In the section of cylinder No. 3, we see the water space surrounding the
upper portion of the cylinder with the opening (37) connected to the
water manifold (36), through which the water leaves the cylinder and
passes to the radiator. At the lower end of the stroke is the piston,
one-half of which is shown in section and one-half in elevation so that
internal and external appearance may be readily seen. The piston pin
(60) is located approximately in the center of the piston to which it is
secured by means of the set-screw (61).

By means of the connecting rod (56), the motion of the piston is
transmitted to the crank-shaft throw (54), both ends of which are
provided with bronze bushings (59) and (58), fitting on the piston pin
and crank-pin respectively. Between each crank throw are the main crank
shaft bearings (55) which are provided with the bronze bushings (54).
Below the connecting rod ends is the small drip trough containing oil
into which the pipes on the rod ends dip when passing around the lower
end of the stroke. When the pipes enter the oil puddle a small amount of
lubricating oil is driven into the crank-pin bearing because of the
force of impact, this force also causing oil to splash about in the
crank case for the lubrication of the main crank shaft bearings and cam
shaft. In order to maintain a constant level of oil in the puddle so
that the bearings shall receive a constant supply of oil, a small
overflow opening is placed in the center of the puddle which allows an
excess of oil to overflow into the return oil sump below.

This excess of oil drains by gravity back to the oil circulating pump
(73), at the right which again forces the oil to the various bearings.
In this way, the same oil is used over and over again until it becomes
unfit for lubricating purposes because of dirt or decomposition. The oil
pump is driven from the cam-shaft through the level gears (66) and the
vertical shaft (72). To the right of the oil pump is the fly-wheel (75)
which furnishes the power for the idle strokes of the engine.

At the upper end of the vertical shaft that drives the oil pump is an
extension (68) which passes through the bearing (70) and drives the
ignition timer shown at the top of the housing (69). The timer controls
the period of ignition in the cylinders in regard to the piston position
so that the spark occurs at the end of the compression stroke. At the
extreme left of the engine is the radiator fan (1) which is driven from
the crank-shaft pulley (16), the belt (10), and the fan pulley (1122).
This fan increases the amount of cold air that is drawn through the
radiator, (mounted to the left of the engine) and increases its capacity
for cooling the jacket water of the engine. The water circulating pump
is located on the opposite side of the motor.

[Illustration:

Fig. 19-a. Buda Four Cylinder Automobile Motor. Carburetor Side.
]

[Illustration:

Fig. 19-b. Buda Motor, Pump Side, Cylinders “En Bloc.”
]

In this motor both the inlet and exhaust valves are located on the same
side of the cylinder which arrangement classifies the engine as an “L”
type, the extended valve pockets forming an “L” with the center line of
the cylinder. In the motor shown by Figs. F-14-F-15, the inlet and
exhaust valves are on opposite sides of the cylinder as shown in the
cross-section, which classifies the motor as a “T” type, as the valve
chambers together with the cylinder forms a “T.” The latter type of
motor has several advantages over the “L” type, but as it requires two
cam shafts, one for the inlet and one for the exhaust valves, it is not
adopted by the builders of the cheaper grades of automobiles. Since the
exhaust valves are on the opposite side of the cylinder, in the “T”
type, the inlet air is not expanded nor the output diminished by the
heat of the exhaust passages. The piping is less complicated which
permits of a more effective arrangement of the carburetor and magneto.
Since the piping in the latter type can be arranged to better advantage,
less back pressure is the result.

[Illustration:

Fig. F-14. Cross-Section Through Wisconsin Truck Motor. “T” Type.
]

[Illustration:

Fig. F-15. Longitudinal Through Wisconsin Truck Motor.
]

As in the previous case, the valves are acted on directly by the cams
and push rods, one cam shaft being provided on each side of the
cylinders. In order to reduce the noise made by the push rods and
springs, all of the springs are enclosed by sheet metal housings or
tubes. The circulating pump is shown at the left nearly on a line with
the left hand cam shaft, the pump outlet being inclined toward the
cylinder so that it enters the water jacket under the exhaust valves.
Water leaves the jacket by the pipe shown on the cylinder tops.

From the longitudinal section it will be seen that the cylinders are
cast in pairs, two cylinders to the pair, instead of singly as in the
previous case. The large pipe crossing at about the center of the
cylinders is the exhaust pipe (shown in front of the left pair), and the
pipe shown under the exhaust is the water inlet pipe from the
circulating pump. It will be seen from the longitudinal section that the
main crank-shaft bearings are fastened to the upper half of the crank
case, and are entirely independent of the lower half which acts simply
as an oil shield. This construction allows the oil shield (lower half)
to be removed without disturbing the adjustment of the bearings, when it
becomes necessary to inspect the internal mechanism.

[Illustration:

Six Cylinder Rutenber Automobile Motor, with Cylinders Cast in Pairs.
]

Large removable plates cover the top of the water jackets so that it is
a simple matter to clean out the water space in case that it becomes
coated with deposits from the water. This is an important feature as a
great many of the heating troubles may be overcome by having access to
the interior of the water jacket. The water outlet pipes connect with
the jacket covers. Both cam shafts are driven by the gears at the right
which connect with the crank shaft pinion. Fan is belt driven from an
extension to the cam shaft.

All bearings are supplied with oil by a high pressure force feed pump,
the crank pins receiving their supply through channels drilled in the
crank shaft and pin, which in turn are connected to the oil supply of
the main bearings, no dependence being placed on a splash system. After
leaving the bearings, the oil drops into the crank case and drains into
the sump shown at the left of the longitudinal section. From the sump,
the oil returns to the oil pump from which point it is returned to the
circulating system under high pressure.

(46) Stationary Four Cylinder Engine.

An English stationary engine, the Browett-Lindly, similar in many
respects to the automobile engines just described, is shown in
longitudinal and cross-section by Figs. 20 and 21. This is of the “L”
type of valve arrangement, but instead of having the valves side by side
as in the preceding case, the inlet valve is placed over the exhaust as
will be seen from the cross-section view.

[Illustration:

Fig. 21. Cross-Section Through Browett-Lindly Engine.
]

The exhaust valve is operated directly from the cam shaft by the push
rod as in the auto engines, but the inlet valve receives its motion
through a long vertical rod and horizontal lever, the latter being
located on the cylinder head as shown by the longitudinal section. A
supplementary valve is mounted loosely on the stem of the inlet valve,
and this valve is held against the seat of the gas inlet port by a short
spring.

[Illustration:

Fig. 20. Section Through Browett-Lindly Four Cylinder Stationary
Engine.
]

A collar on the main valve spindle opens this gas valve, and, by
adjusting the position, a certain amount of lag can be given, so that
air first enters the cylinder and then, by further travel of the main
valve, the gas valve opens and the combined charge is taken in. This
prevents any “back fires” as the gas and air are entirely separated
until they enter the cylinder.

Starting is effected by means of compressed air, and is entirely
automatic. No compression release is provided, as this is unnecessary
under the system adopted. By opening the main compressed air valve
compressed air is admitted to two valve boxes placed underneath the cam
shaft, and the pressure of air raises the valves against their levers
and cams. Should the swell on the cam be opposite a lever as it will be
in the correct starting position, the valve cannot close, and the
compressed air then passes to the cylinder through a check valve on the
face of the cylinder, and the engine starts. The automatic check allows
the cylinders to take in a charge of mixture on the second stroke and
firing takes place immediately. When the explosion pressure is greater
than the air pressure the check remains closed and no more starting air
enters the cylinder.

[Illustration:

Fig. 21-a. Section Through Cylinder of Fairbanks-Morse Type “R E”
Engine, with Valves in the Head.
]

Governing is effected by varying both the quantity and quality of the
mixture.

The main valve, plunger, and rod springs, and all springs on the valves
and valve motion, are arranged to be in compression. The exhaust valves
are of cast-iron, and are fitted with renewable seats in the cylinders.
The admission valves are of nickel steel, and are arranged in boxes,
which, when removed from the cylinders, provide the ports which give
access to and space for the removal of the exhaust valves which are
withdrawn vertically.

Forced lubrication is fitted throughout all bearings, valves, plunger
guides, governor, cam shaft, etc., the oil under pressure being supplied
by two valveless pumps, either of which is sufficient to maintain the
working pressure of oil.

The normal output of the engine is 400 brake horse-power, with an
allowable overload of 40 horse-power for ½ hour. The exhaust pipe is
water jacketed, each section being supplied from the small pump shown at
the end of the cross section.

Double ignition is provided for an emergency, by two high tension
magnetos, each of which is connected to a separate set of plugs. When
starting the engine, an ordinary spark coil and storage battery are used
until the engine gets up to speed, when the coil is cut out and the
magneto is thrown in.

(47) The “V” Type Motor.

An example of the “V” type motor is shown by Fig. 22, which is a front
elevation of the Frontier aeronautic motor, a type that occupies a
minimum of space with a minimum of weight.

[Illustration:

Fig. 22. End Elevation of Frontier 8 Cylinder “V” Type Motor.
]

The cylinders are cast separately and are furnished either with iron or
copper water jackets, the copper jackets being deposited over the
cylinder barrels by an electrolytic process in much the same way as that
of the celebrated French Antoinette. Bolts passing through flanges on
the bottom of the cylinder fasten them to the base. A special aluminum
alloy is used for the base which is cast in a single piece with webs to
receive the bearings. A unit crank-case insures perfect alignment,
prevents a greater part of the oil leakage, and forms a much stronger
construction than the usual split pattern. A chamber is provided for the
cam shaft at the apex of the case through which issue the push-rods.
Shafts and piston pins are hollow. All push rods are adjustable for wear
and have steel balls running on the cams which eliminate the possibility
of mis-timing through wear.

Lubrication is by a bronze pump geared from the crank-shaft and is
connected to an oil tank located in the base from which the oil is
forced through the crank-shaft up through the hollow connecting rods to
the piston pins, thence to the cylinder walls, the surplus returning to
the tank in which the strainer is located.

The circulating pump is driven from the cam shaft as shown in the cut
and supplies the cylinders and radiator with water through the copper
water manifolds which are designed to give an equal supply to each
cylinder. Exhaust manifolds are of seamless steel tubing.

The cylinders are 4⅛ bore × 4⅜ stroke, and develop 60 to 70 horse-power
at 1,100 revolutions per minute, which speed has been attained with an
8-foot 6-inch propeller having a pitch of 5 feet. Without radiator or
propeller, the iron jacketed motor weighs 312 pounds, and copper
jacketed weighs 290 pounds, the latter making a difference of 22 pounds
in the weight.

A high tension Bosch magneto is used which is mounted on a pad cast on
the top of the crank-case and is driven from a gear meshing with the cam
shaft gear. Connection is made from the magneto to plugs placed over the
inlet valves in the valve caps.

A 100 horse-power aero engine of the “V” type is shown by Figs.
23–24–25, which is built by the All British Engine Company for the
aeronautical branch of the English War Department. It has eight
cylinders of 5 inch bore, by 4¼ inch stroke, and develops its rated
horse-power at 1,200 revolutions per minute. _Data from “Aero,” London._

[Illustration:

Fig. 23. Longitudinal Section Through A. B. C. 100 Horse-Power “V”
Motor.
]

The crankshaft, which is of three per cent nickel chrome steel, having
an ultimate tensile strength of 157,000 lbs. per sq. in., is of
distinctly large diameter, and is carried in plain bearings lined with
white metal. It is provided with four throws, each crank pin being
arranged to take the big end bearings of two connecting rods from
cylinders on opposite sides of the crank case. There is a bearing
between each throw, and in order to reduce the overall length of the
engine the cylinders are staggered on the crank case. The H section
connecting rods are stamped out of steel having a tensile strength of
90,000 lbs. per sq. in., and for the purpose of lubrication a hole is
drilled from end to end down the center of the web. As mentioned before,
the cylinders are staggered, and there is no overhanging of the big end
bearings at the point of attachment to the connecting rod. The bearings
themselves are lined with white metal. The small end bearings are
provided with phosphor bronze bushes, and the piston pin is of steel
bored out hollow and hardened.

[Illustration:

Fig. 24. Valves and Valve Motion of A. B. C. Motor. (“_Aero_,”
London.)
]

A very interesting detail of the engine is the combination of the water
outlet pipe from the top of the cylinder with the bearings for the
rocking arms (which are steel stampings) actuating the valves. This is
shown in Fig. 25. A hollow steel column is bolted to the top of the
cylinder and protrudes from the water jacket, which is fastened to it
with the usual shrunk ring. To this column is attached a hollow T shaped
pipe of phosphor bronze, the column of the T piece forming the outlet
for the water. On one arm of the T piece the exhaust rocker takes its
bearing and on the other the inlet rocker. Each T piece arm is connected
to its fellow on the next cylinder by means of rubber pip.

[Illustration:

Fig. 25. End Elevation of A. B. C. Motor.
]

A small bracket projecting from the T piece forms a saddle on which the
valve spring rests. This is a plain semi-elliptical leaf spring which
works both valves. It is slotted at each end and slightly turned up so
as to engage with a cotter pin passed through a slot in the end of the
valve stem.

The crank case is of rather unusual design, being absolutely circular in
section and machined all over. It is practically a tube with flanged
portions bolted on to form the ends. Having no horizontal joints, it is
strong and easily kept oil tight. Three radial arms, with slight webs
and reinforced with steel columns down the center, support each bearing.
The crank case is carried by four feet, which are arranged to
accommodate three different widths of engine bearer. To the fore end of
the crank case is bolted a long conical aluminum nose carrying at its
extremity a compound push and pull ball bearing 6 in. in diameter, which
supports an extension shaft bolted to the crankshaft by means of a
flanged coupling.

[Illustration:

Fig. 24-a. “Sixteen” Cylinder Favata Radial Type Aero Motor,
Consisting of Four Groups of Two Cylinders Per Group. Cylinders are
of the Double Acting Type and are Stationary.
]

At the outer end of this extension is a flange to which the propeller is
bolted, but the arrangement is specially devised to make quick
detachment possible. The boss of the propeller has a hollow hub and is
plate bolted permanently to it by twelve bolts.

The direct nose is interchangeable with a speed reduction gear so that
the propeller can be driven at a lower speed than the engine. Fitting
this gear nose raises the center line of the propeller-shaft some 5¼ in.
The gears are carried on substantial ball bearings, plain bearings being
used also in such a way that they take up the load if the ball bearings
through any cause should fail. The reduction is by means of silent
chains. The arrangement of the gear wheels is plain from the drawing,
and it will be noticed that there is no intermediate wheel between the
crankshaft pinion and the camshaft wheel, which are of steel and
phosphor bronze respectively. A separate gear wheel is provided on the
camshaft for driving the magneto. The water and oil pumps are carried
low down outside the crank case, and are driven by intermediate wheels
at double the engine speed. The shafts are joined together through
Oldham couplings, so that it is possible to remove the pumps separately.
Both these pumps are of the gear type.

The camshaft is made in one piece with the cams, and is hardened, being
drilled out for lightness. It is enclosed in a casing of steel tube,
which is practically separate from the crank case, being attached
thereto at one end by the timing gear case and at the other by a saddle.
The camshaft is carried in six bearings. An interesting point is the
fact that the gear wheels are bolted to flanges on the shafts instead of
being attached by keys. Carried in the tube directly above the camshaft
is a second shaft forming the fulcrum of the rocking arms for the cam
rollers. A very interesting point is the provision of an arrangement for
lifting the exhaust valves. The little rocking arms carrying the rollers
which bear upon the cams are provided with webs, parallel with the
camshaft and between it and the shaft carrying the rockers is a third
shaft, the sides of which normally just clear the webs of the rocking
arms on either side. This shaft is provided with wedge shape pieces
along it, so that by sliding it along the wedges lift the rocking arms
clear of the cams, and thus, through the tappet rods and rockers, the
valves themselves are opened.

[Illustration:

Fig. 26. Mesta Engines on Test Floor.
]

Not the least interesting particular of this engine is the thorough way
in which the lubrication is carried out. Four of the bolts which attach
the caps of the main bearings are prolonged through the bottom of the
crank case, and serve to carry a detachable oil sump which holds
sufficient oil for a run of six hours. As already mentioned, the oil
pump is driven at twice the engine speed, and maintains a pressure of
something like 110 pounds per square inch. It delivers directly into a
straight steel tube placed along the bottom of the crank case, and from
this tube a vertical tubular connection is taken to each of the caps of
the main bearings. The crankshaft and crank pins are hollow, and, as in
the previous engine, in the hollow portions tubes of a slightly smaller
diameter are placed, the tubes being expanded over at the ends, so that
closed annular spaces are formed which are used as lubrication leads.
The lubricating oil passes through the main bearings into these annular
spaces in the shafts, from them to the annular spaces in the crank pins,
and so to the big-end bearings. From the big-end bearings it travels up
the connecting rods to the gudgeon pins. It is interesting to note at
this point that the connecting rods work in slots in the crank case
which just allow sufficient clearance for their travel, in order to
prevent the flooding of oil into the cylinders. A steel-lined oil lead
is taken up to the saddle which supports the tubular camshaft casing at
the propeller end of the crank case. The bearings carrying the camshaft
are cut away at their lower edges clear of the tube so that the oil can
flow along the full length of the casing, the level being sufficient to
allow the cams to dip. Precautions are taken to keep oil from flowing
out of the bearings, and the casing over the gears is specially arranged
to prevent the oil from flooding below.

(48) Mesta Gas Engines.

The Mesta four stroke cycle, double acting gas engine, built by the
Mesta Machine Co., Pittsburgh, is an excellent example of American big
engine practice. Mesta engines are built in sizes from 400 horse-power
up to the largest used, and is built either in tandem or twin tandem
units. While the engine does not differ widely in either principle or
construction from engines of the same size it has several features
worthy of note that are not found on other engines.

Up to the medium sizes, the cylinders are cast in one piece, the largest
cylinders being made in two parts of cast steel with air furnace iron
bushings. The central part of the cylinder is open as will be seen from
the cuts, and is covered with a cast iron split band bolted at the
center line. The valve chambers are located directly opposite one
another on a vertical center line, the inlet valve being at the top and
the exhaust valve at the bottom. This arrangement gives a better
distribution of the mixture, increases the output with given size of
cylinder and equalizes the stresses occasioned by the explosions. As the
engine is double acting in all cases there is one inlet and one exhaust
at each end of the cylinder.

Both the inlet valve and the corresponding exhaust valve on each end of
the cylinder are operated by a single eccentric on the horizontal
lay-shaft shown running below and parallel to the cylinders. The
regulating valves which are controlled by the action of the governor are
perfectly balanced against the pressure in the cylinder which results in
a very small resistance to the governor action, therefore no oil relay
nor similar complications are required. Any of these valves are easily
removed for clearing, a point of great importance when running on a gas
that is laden with tar or other impurities.

[Illustration:

Fig. 27. End View of Mesta Engine.
]

The chrome-vanadium piston rod carries the pistons floating free from
the cylinder walls reducing the wear on the bore, while the piston rings
maintain a gas tight contact with the cylinder walls. Each piston rod is
made in two halves, the joint between the sections being made between
the cylinders at which point the rods are supported by an intermediate
cross-head and guide. Both parts of the rod are interchangeable. The
pistons are made in one casting. As will be seen from the accompanying
cuts the front end of the piston rod is carried by a cross-head which
relieves the pressure on the piston and packing glands.

Speed regulation is performed by the governor by controlling both the
quantity and the quality of the mixture. Independent valves in the gas
and air passages are actuated by the governor according to changes in
the load. This method of control combines all of the good features of
quantity and quality regulation.

Make and break ignition is used, with the igniter trip gear so designed
as to allow all of the igniters to be timed from one lever, or adjusted
independently as the case may require. Each combustion chamber is
supplied with two igniters, one at the top and one at the bottom, which
insures regular and rapid combustion and therefore gives a maximum of
efficiency and reliability.

Compressed air is introduced into the cylinders for starting at a period
corresponding to the power stroke in normal operation. This is
accomplished by cam operated poppet valves located in the air main and
check valves in the cylinders. By this system the engine can be started
and put on full load in less than one minute.

(49) Knight Sliding Sleeve Motor.

The Knight motor was the first four stroke cycle automobile motor to
employ an annular slide valve in place of the usual poppet valve. Its
success has led to the development of several other motors of a similar
type which follow the construction of the original engine more or less
closely. Being free from the slap bang of eight to twelve cam actuated
poppet valves which hammer on their seats at the rate of a thousand
blows per minute, the Knight motor is free from noise and vibration.
Instead of the jumping of a number of small parts, there is only the
slow sliding of the sleeves over well lubricated surfaces. They make no
noise because they strike nothing and can cause no vibration because
they are a perfect sliding fit in their respective cylinders.

Besides insuring noiseless operation, the valves increase the output,
efficiency and flexibility of the motor for they are positively driven
and are not affected in timing by fluctuations in the speed. The wear of
the reciprocating increases the efficiency of the sleeve instead of
destroying it. With poppet valves at high speeds, the valves do not seat
properly in relation to the crank position owing to the inertia of the
valves and to the gradual weakening of the valve springs which delays
the closing of the valves. Carbon also gets on the seats of the poppet
valves and prevents proper closure. These faults cannot exist with
sliding sleeves when they are once set right as they are positively
driven through a crank and connecting rod.

[Illustration:

Fig. 28. Section Through Knight Motor Showing the Sleeves, Eccentrics,
and Automatic Adjustment for Lubrication. Inlet is at the Right,
Exhaust at the Left.
]

At high engine speeds the velocity of the exhaust and inlet gases is
very high in the poppet valve type due to the many restrictions and
turns in the passages which causes back pressure and a considerable loss
of power. With the sliding sleeve type an ideal form of combustion
chamber is possible and the passages to and from the chamber are short
and direct. Very large port areas with a low gas velocity are also
possible. The sleeves are more effectively cooled than the poppet type,
being in direct contact with the water cooled walls for their entire
length. Because of the large port areas, the cylinders receive a full
charge of mixture, and as a result the engine accelerates and gets under
way with remarkable ease.

[Illustration:

Figs. 28–29–30. Showing Sleeve Positions on the Inlet Stroke. (Knight
Motor.)
]

The arrangement of the slide valves, or sleeves, is shown by Fig. 28,
which also gives an idea of the cylinder form, and the location of the
piston. Fitting the engine cylinder closely, one within the other, are
the two sliding valve sleeves, and within the inner sleeve slides the
power piston.

[Illustration:

Figs. 31–32–33. Showing Sleeve Positions on the Exhaust Stroke.
]

Each sleeve has two slots cut in it, one on each side, which form an
outlet and inlet for the exhaust and inlet gases respectively. When the
slots on the intake side of both the outer and the inner sleeves
register, or come opposite to one another, and also opposite to the
intake pipe, a charge of gas is drawn into the cylinder. After the
explosion has taken place, the sliding motion of the sleeves brings the
other two openings, on the exhaust side, opposite to one another, and
opposite the exhaust pipe, which allows the burnt gas to escape to the
atmosphere through the exhaust manifold.

The sleeves are driven from cranks on the half-time shaft shown at the
side of each cut, through the small connecting rods, which gives them a
reciprocating motion. Like the cam shaft on a poppet valve motor, the
lay shaft runs at half the crank shaft speed, since the engine is of the
four-stroke cycle type. The lower ends of the sleeves, to which the
connecting rods are fastened, are made thicker than the portion within
the cylinder, and are heavily ribbed for strength in the overhang.

The sleeves are of the same composition of cast iron as the cylinder and
are provided with oil grooves cut in their outer surfaces for gas
packing, and the distribution of oil. Leakage between the inner sleeve,
and the cylinder head is prevented by a packing ring, or “junk” ring
that is fastened to the bottom of the inwardly projecting cylinder head.
The junk ring not only prevents the leakage of gas during the explosion,
but it also serves another purpose.

The exhaust ports or slots in the inner sleeve are above the junk ring
during the explosion, in which position they are protected from contact
with the burning gas. The life of valves is greatly increased by this
protection. It will be noted that the entire surface of the sleeves is
in contact with water jacketed surfaces, making perfect lubrication and
smooth working possible. The two spark plugs for the dual ignition
system are shown in the depressed cylinder head.

Complete water jacketing encircles the cylinders, cylinder heads, the
circulation area enclosing the plugs and the gas passages so that a
uniform heat is maintained the entire length of the piston travel.

The half-time shaft, the magneto, and the water pump are driven by a
silent chain from the crank case; this drive being found superior to the
gears commonly used for this class of work. The cranks on the half-time
shaft are made in one integral piece with the shaft.

Although the piston on the Stoddard-Dayton Knight motor has a stroke of
5½ inches, it is scarcely as much as this considered as friction
producing travel, because the inner sleeve in which it rests moves down
in the same direction 1⅛ inches.

This distribution of the working stroke to two surfaces reduces the wear
on the side of the sleeve caused by the angularity or thrust of the main
connecting rod. On the compression stroke, both outer and inner sleeves
go up in the same direction as the piston, the inner sleeve moving the
faster. On the exhaust stroke and suction stroke the sleeves move in a
direction opposite to the direction of the piston, but on these strokes
there is very little work performed by the piston and consequently
little thrust is produced on the sleeves and walls of the cylinder.

It is a valuable feature to have the sleeves descend with the piston on
the working stroke because this is the stroke in which the piston has
the greatest amount of side thrust.

The up and down movement of the sleeves is very little compared with
that of the piston. A stroke of 5½ inches gives a piston speed of 916
feet per minute at a speed of 1,000 revolutions per minute. The stroke
of the sleeves is 1⅛ inches and its speed is but 93.7 feet per minute,
or a little more than one-tenth that of the piston. This fact makes the
problem of lubrication a feasible one, the slow-movement of the sleeves
distributing the oil thoroughly between them as well as between the
outer sleeves and the cylinder walls.

The action of the valves, and their position at different points in the
cycle, is shown in diagrammatic form by Figs. 28–29–30–31–32–33, the
particular event to which each diagram refers being marked at the foot
of the cuts. The direction of the sleeve movement is indicated by the
arrows at the bottom of the sleeves. Particular attention should be paid
to the position of the slots in the sleeves.

The first three diagrams show the position of the inlet slots that
govern the admission of the combustible gas from the carburetor. Fig. 28
shows the slots coming together to form an opening in the inlet port as
the lower edge of the outer sleeve separates from the upper edge of the
inner sleeve. The outer sleeve is now moving rapidly downward while the
inner sleeve is slowly rising, and as their motion is opposite the
opening is quickly formed. Fig. 29 shows the full opening with the slots
in register.

When closing (Fig. 30) the outer sleeve is nearly stationary while the
inner sleeve is rising rapidly. When the inner sleeve port is covered by
the lower edge of the junk ring, the valve opening is closed, the slot
in the outer sleeve remaining opposite the inlet opening.

The exhaust port opens (Fig. 31) when the lower edge of the slot in the
inner sleeve leaves the junk ring in the cylinder head, the sleeve
moving rapidly downward at the moment of opening. To obtain a rapid
opening of the exhaust, the ports are arranged so that the inner sleeve
is just about to reach its maximum speed at the time of opening.

The outer sleeve closes the port (Fig. 33), closure starting when the
upper edge of the outer sleeve coincides with the lower edge of the
cylinder wall port. At this time the outer sleeve is traveling downward
at maximum speed, so that the closing of the exhaust is as rapid as the
opening.

The lubrication of the Knight motor is accomplished by what is known as
the movable dam system, which overcomes the tendency of the motor to
over-lubricate. A movable trough is placed under each connecting rod, in
the crank case, that is connected to the carburetor throttle lever in
such a way that the opening and closing of the throttle raises and
lowers the troughs.

When the throttle is opened, raising the troughs, the points on the ends
of the connecting rods dip deeper into the oil which creates a splashing
of oil on the lower ends of the sliding sleeves. In this way the oil is
fed to the engine in direct proportion to the load and the heat produced
in the cylinder. When the motor is throttled down, the points barely dip
into the oil.

An excess of oil is fed to the troughs by an oil pump, which keeps them
constantly overflowing. The overflow is caught in the pumps located in
the crank case, and returned to the circulation so that it is used over
and over again.

Claims of great efficiency are made for this system, there having been
many tests made showing 750 miles per gallon of oil, while even as high
as 1,200 miles per gallon has been made under favorable conditions.

The oil pump is contained in the crank case, and is of the gear type,
insuring positive action. The pump also acts as a distributer, a slot
being cut in one of the gears which register successively with each of
the six oil leads. In this way it is possible to obtain the full pump
pressure in each lead should they become obstructed in any way.

In the upper half of the crank case are cored passageways through which
the air passes before reaching the carburetor. These passages not only
eliminate the rushing sound of the intake air, but also form an
efficient method of warming the air supplied to the carburetor and
cooling the crank-case. It is possible to furnish warm air after the
engine has been idle for several hours, as the oil in the crank case
remains warm longer than any other part of the engine.

(50) Reeves Slide Sleeve Valve.

A simple and compact form of slide sleeve valve gear has been developed
in England that is of more than passing interest. It permits of a
maximum area for both the inlet and exhaust gases which of course keeps
the velocity and back pressure at a minimum for a given valve lift. The
small lift also insures noiseless operation and a small amount of wear.
The sleeve is balanced at the end of the working stroke. The combustion
chamber is nearly hemispherical in shape which reduces the heat loss to
the walls.

[Illustration:

Fig. 34. Reeves Slide Valve Gear.
]

Referring to the section of the end of cylinder given in the diagram,
(34) A is an open-ended water-jacketed cylinder in which the piston B
works. At the upper end of the cylinder is attached a ring C forming an
extension of the stationary cylindrical head D carrying the sparking
plug. At the lower end of the head D is provided a seating E for the
sliding cylindrical inlet valve F, which takes its bearing around the
circular head. This inlet valve is provided with expanding rings G to
keep it gas-tight. Surrounding the inlet valve F is a second cylindrical
exhaust valve H, which is provided with an angular seating at J. The
outer circumference of the cylindrical exhaust valve H bears against the
walls of the cylinder.

Cast in the cylinder is an annular space K communicating with a passage
L for the admission of the inlet gases. These pass through suitable
ports cut in the sides of the exhaust valve H and the inlet valve F, so
that they are free to pass through the space made when the inlet valve F
is lowered from its seat. A similar type of annular space M is cast in
the cylinder in connection with an opening O for the passage of the
exhaust gas when the cylindrical valve H is raised from its seating at
J.

The cylinder head is not water jacketed as the builder states that the
continual passage of the intake gases keeps it reasonably cool. The
exhaust passages are thoroughly water cooled.

(51) Argyll Single Sleeve Motor.

The Argyll sliding sleeve automobile motor is unique in the fact that
only one sleeve is used to control both the inlet and exhaust gases
instead of the two sleeves commonly used on the Knight motor. This
sleeve, instead of having either a purely vertical or horizontal motion,
has a peculiar combination of the two, that is to say, it moves a
certain amount in rotation within the cylinder, and an equal amount
vertically, the combined motion constituting an ellipse. The external
appearance of the engine is shown by Fig. 35, which will give an idea of
the general arrangement of the cylinders, ports and piping.

In Fig. 36, is shown the successive movements and events determined by
the sleeve, and the method of opening and closing the inlet and exhaust
ports by the elliptical movement of the sleeve. The shaded ports are one
of the inlet and one of the outlet ports, respectively, which are cast
in the cylinder wall, and are afterwards machined true. The dotted port,
which changes its position in each diagram, is one of the ports in the
moving sleeve, its position in each of the figures is marked by the
event that is occurring in the cylinder at that time.

In diagram 1, the shaded port to the right is the exhaust port, and the
shaded port to the left, the inlet, this relative arrangement being
true, of course, in each of the succeeding diagrams. It will be noted,
that in the position shown, in the exhaust stroke (beginning of stroke),
the sleeve port has just started on its downward stroke, moving also a
trifle to the right as it progresses. Its progress to the right may be
more clearly seen by consulting diagram 2, for the movement.

By consulting the other five figures it will be seen that the dotted
port, in its relation to the shaded ports, first moves out to the right,
and then reverses, moving to the left, and this combined with the up and
down movement constitutes an elliptical path. In diagram 6 the exhaust
is closed, and the inlet port has just begun to open, the dotted port
now starting to move out to the left, and to rise.

[Illustration:

Fig. 35. Elevation of Argyll Single Sleeve Motor from The Motor,
London.
]

In diagram 10, the inlet is nearly closed, the sleeve port passing away
from the cylinder ports to the water jacketed portion of the cylinder
above.

[Illustration:

Fig. 36. Valve Motion Diagram of Argyll Motor Showing the Valve
Positions at Different Parts of the Working Stroke.
]

This series of diagrams shows the operation of the duplicated port of
the sleeve (which port is the one shown dotted) in relation with one of
the inlet ports and one of the exhaust ports in the cylinder wall, the
latter ports being marked respectively I and E. The elliptical movement
referred to in the text can be traced by following the different
positions of the dotted port in the sleeve. In the top row of diagrams
it is seen to come downwards and also to move over to the left, whilst
in the lower set it rises—bearing still to the left—until, after Fig.
10, it goes higher up for the compression and explosion strokes, during
which it bears over to the right and comes down again ready to commence
once more the cycle, as in Fig. 1. The other ports in the cylinder wall
are the same as those shown, and the other ports in the sleeve are akin
in shape to half of the dotted port, but they are without the little
tongue cut in the base of this double purpose port. This little tongue
in the duplicated port is designed to give as much lead to the exhaust
opening as possible, without interfering with the correct timing of the
inlet port. The way in which it just misses interfering with the closing
of the inlet port is seen in Fig. 10. We are indebted to “The Motor” for
these cuts.

(53) Sturtevant Aeronautical Motor.

The cylinders of the Sturtevant aeronautical motor are of the “L” type
and are cast separately with the cylinder barrel and water jacket in one
integral casting. A special iron is used for these castings that has an
ultimate tensile strength of 40,000 pounds per square inch. The valves
which are easily accessible through valve covers, are operated directly
from the cam shaft without valve rockers. A hollow cam shaft is used
with integral cams to insure a maximum of strength with a minimum of
weight, and bearings are placed between each set of cams. A bronze gear
fitted on the cam shaft meshes with a gear on the crank shaft without
intermediate idlers.

[Illustration:

Fig. 41. Six Cylinder Sturtevant Aero Motor.
]

Like the cam shaft, the crank is bored out from end to end with a
propeller flange applied on a taper at one end of the shaft. A bearing
is provided between each throw with an additional thrust bearing at the
forward end of the shaft which may be arranged to take either the thrust
or the pull of the propeller. Lubricating oil is applied to all the
bearings under a pressure of twenty pounds per square inch, this
pressure being maintained by a gear pump attached directly to the end of
the cam shaft. The oil is transferred from the pump to the bearings
through passages cast in the base, no piping being used. Oil enters the
hollow crank shaft at the main bearings and is conducted through the
arms to the connecting rod bearings. The oil flying from the crank shaft
falls into the oil sump at the bottom of the case where it is cooled
before being used again. A second gear pump in tandem with the first
takes the oil from the sump and forces it through a filter into the
tank.

[Illustration:

Fig. 43. Crank Shaft of Sturtevant Motor.
]

[Illustration:

Fig. 42. Crank Case of Sturtevant Motor.
]

This system enables the use of a more efficient filter than with the
suction type and eliminates any danger of its becoming clogged and
stopping the oil supply, since, in the event of such an occurrence the
pump would furnish sufficient pressure to burst the filter. However, the
filter is particularly accessible and may be instantly removed for
cleaning without disturbing the oil. The tank regularly fitted to the
motor holds sufficient oil for three hours’ use. If the engine is
required to operate for a longer time without opportunity for
replenishing the oil supply, a larger tank can be used. As no oil is
allowed to accumulate in the base with this system of lubrication, the
motor can be operated continuously at an angle.

Water circulation is maintained by a centrifugal pump of large capacity,
the impeller of which is mounted directly on an extension of the crank
shaft, eliminating the usual bearings and its grease cup.

The ignition is provided by a high-tension Mea magneto, its special
construction permitting the motor to be started under a retarded spark
avoiding the danger of back kick from the propeller.

The cylinder and all exposed parts are rendered absolutely weather-proof
by means of a heavy coat of nickel plating.

(54) The Rotating Cylinder Motor.

While it is the common belief that the rotary cylinder gasoline motor is
of French origin it may safely be said that this type of motor was in
actual use in America for several years before it even reached the
experimental stage in Europe. The Adams-Farwell Company of Dubuque,
Iowa, were driving automobiles successfully with a rotary cylinder motor
before Orville Wright flew at Fort Meyer, Va. Although the original
Farwell motor more than proved its right to existence by faithful
service under the most exacting conditions, the motor never received the
consideration that it deserved, probably because of its great divergence
from what is known as “accepted practice.”

In Europe no such prejudice existed, and consequently the type made
rapid strides, although, to the writer’s belief, the European model is
inferior in many ways to the original American type. The fact that this
type of motor holds practically all of the world’s aviation records
speaks for its practicability in spite of its unusual construction.

With the rotary motor, the cylinders and crank case revolve about a
stationary crank shaft, the latter part not only serving as a point of
reaction of the cylinders but as a support and intake pipe as well.
Since the crank throw remains stationary, the cylinders and pistons
revolve about two different centers, the cylinders revolving about the
crank case and the pistons and connecting rods about the crank pin.
Since the pistons, cylinders, and connecting rods must necessarily
revolve together, as one unit, there is absolutely no reciprocating
motion in regard to the crank shaft except for a very slight movement
due to the difference in angularity of the connecting rods. The motion
of all the parts is strictly rotary in every sense, except for the
relation of the pistons to the cylinders, and the motion is as
continuous as in a turbine. This insures freedom from vibration. As the
cylinders and crank case have considerable inertia there is no need of
the added weight of a fly-wheel. The movement of the piston in the
cylinder bore is brought about by the difference in the centers about
which these parts revolve. This gives cylinder displacement without the
reversal of stresses or shock or jar.

Because of the revolving cylinders, the mixture is supplied to the crank
case through a hollow shaft, the gas being drawn into the cylinder on
the suction stroke through an inlet valve placed in the head of the
piston. As a rule, the exhaust is direct to the air through the exhaust
valves and without manifolds or mufflers. The motion of the cylinders
through the air multiplies the efficiency of the radiating Fins.

(55) The Gyro Rotary Motor.

In the Gyro motor, made by the Gyro Motor Company of Washington, D. C.,
are embodied all of the principles of the typical revolving motor, but
with extensive improvements in the design and in the details. It weighs
3¼ pounds per horse-power, complete. This light weight is due to the
design of the motor and to the use of alloy steels, and is attained
without sacrificing strength or durability.

Each cylinder is machined out of a heavy 3½ per cent tubular nickle
steel forging that weighs nearly 40 pounds. After the metal is removed
and the cylinder worked down to size, the shell weighs but 6½ pounds.
The radiating ribs on the outside of the cylinder are machined out of
the solid bar, and are arranged in helicoid or screw-like formation
around the cylinder barrel. This adds to the strength of the cylinder
and also aids in the circulation of the air. The comparative thickness
of the cylinder wall may be seen from Fig. 44. The stiffening effect of
the radiating ribs will also be noted. The crank case to which the
cylinders are fastened is of vanadium steel, and is divided into two
parts. In addition to supporting the cylinders, the crank case also
serves as a mixing chamber for the gasoline and air. By removing the
bolts seen between each cylinder, the entire working mechanism can be
laid bare for inspection. The exterior of the case carries the exhaust
valve mechanism and the ignition distributer. The crank shaft is a
nickel steel forging with an elastic limit of 110,000 pounds. It is
bored hollow throughout its length and serves as an intake manifold by
conveying the mixture from the carbureter, attached to its outer end, to
the crank case.

[Illustration:

Fig. 45. Section Through Rotary Gyro Motor.
]

The intake valves in the heads of the piston are mechanically operated
by a specially patented movement which consists of two parts, a
counter-balancing member, and an operating member. The counter balance
balances the valve against the disturbing influence of the centrifugal
force, while the operating member, which is fastened to the connecting
rod, controls the opening or closing of the valve by the angular
position of the connecting rod. This valve action insures a full opening
of the valve and a full charge during practically all of the suction
stroke.

There are two separate paths provided for the exhaust gases, one being
through the auxiliary exhaust ports at the end of the stroke, and the
other path through the exhaust valve located in the cylinder head. The
auxiliary ports may be seen in the cross-section directly below the
piston head in cylinders 4 and 5. The auxiliary ports are uncovered by
the piston at the inner end of the working stroke, and it is at this
point that the greater percentage of the exhaust leaves the cylinder.
These ports or holes are formed on a projecting annular ring in which
enough material is provided to make up for the strength lost by boring
the ports. As these ports are, in the majority of cases, bored at an
acute angle with the center line of the cylinder, it is impossible for
the cylinder oil to escape.

All exhaust valves are operated by levers and push rods connected to a
cam mechanism on the outside of the crank case. A single cam ring
operates all of the valves except where a step-by-step compression is
desired. The exhaust mechanism is provided with a simple device by which
the closing of the exhaust valve may be delayed through any portion of
the exhaust stroke, thus reducing the compression and adding to the
facility of cranking. The motor is started with the compression entirely
released in which condition it can be spun about its shaft with ease.

After giving the motor its initial spin, the compression and spark are
thrown in and the engine begins its normal operation. The compression
release lever may be used for starting or slow running and in cutting
off the power regardless of the ignition advance or retard.

One connecting rod, called the “master” rod, is an integral part of the
spider that contains the ball bearings of the crank pin, thus
controlling the angular relation between the connecting rods and
cylinders. The remaining six rods are, of course, articulated on the
spider by pins so that the rods may move in regard to the spider when in
different parts of the stroke. The shell of the pistons is of a fine
grade of iron, very thin and elastic, so that it may conform readily to
the outline of the cylinder bore. The head of the piston consists
principally of the intake valve cage, the cage carrying the piston pin
as well as the valve.

Oil is supplied by a positive pump that measures the lubricant in exact
proportion to the load on the engine. Both the oil and the gasoline
mixture enter the crank case through the hollow crank shaft and mingle
in the form of a vapor. This oil mist reaches every moving part and
results in perfect lubrication. The pistons are provided with oil
shields which carry the oil directly to the cylinder walls and prevent
the loss of oil through the exhaust valve.

Ignition is performed by a high tension magneto through a distributer
which directs the current to the proper cylinder. As in all rotary
engines, the Gyro has an uneven number of cylinders (3, 5, and 7) in
order that the cylinders receive firing impulses through equal angles of
rotation. An even distribution of firing is impossible with an even
number of cylinders, as two adjacent cylinders out of six alternately
fire together and then 180° apart. This produces a very jerky turning
movement, and is productive of much vibration. In the seven cylinder
motor the magneto is driven by gears having a ratio of 4 to 7, and the
high tension current is distributed to the cylinders by 7 brushes, the
leads from the brushes being taken direct to the spark plugs.

(56) Gnome Rotary Motor.

The Gnome was the first rotary aviation motor built in Europe and is
still one of the most capable flight motors abroad as its many victories
and records prove. It is built in four sizes, 50, 70, 100, and 140
horse-power, the 50 and 70 horse-power motors having 7 cylinders, and
the 100 and 140 horsepower, having 14 cylinders, which consist of two
rows of 7 cylinders per row. The cylinders of all sizes rotate about a
stationary crank shaft while the pistons rotate in a circle, the center
of which is the crank pin. Vibration is practically eliminated at high
speed as the pistons do not reciprocate in the ordinary sense of the
word, but simply revolve in a circle, the reciprocating relation between
the cylinders and pistons being obtained by the difference in the
centers of the two revolving systems. The cooling effect of the
radiating ribs is greatly increased by the air circulation set up by the
rotation of the cylinders. This method of cooling introduces a great
loss of power due to the blower action of the cooling ribs, this loss
often amounting to 15 per cent of the output of the engine.

[Illustration:

Fig. 50. Cross-Section Through the Seven Cylinder Rotary Gnome Motor,
Showing the Crank Shaft Arrangement and Valves.
]

The crank shaft is stationary and acts as a support for the engine, one
end being fastened into a supporting spider which forms a part of the
aeroplane frame. The crank shaft is hollow and also serves to conduct
the mixture from the carburetor fastened at its outer end to the
crank-case of the motor. Only one crank throw is provided on the seven
cylinder engine as the cylinders are all arranged in one plane which
passes through the center of the crank throw. In the fourteen cylinder
engine where the cylinders are in two rows, there are two crank throws,
one for each row of cylinders.

The seven cylinders are arranged radially, as will be seen in Fig. 50,
each being spaced at an equal distance from the crank shaft and at equal
angles with one another, the arrangement in general being similar to
that of the “Gyro” motor shown in the preceding section. All cylinders
are turned out of solid forged steel bars, the cylinder walls being only
1.2 millimeters thick after the machining operation. This results in the
strongest and lightest cylinder possible to build, as all superfluous
material is removed and the chances of defects in the material are
reduced to a minimum as the character of the metal is revealed by the
extended machining operations.

[Illustration:

Fig. 51. Firing Diagram of Seven Cylinder Rotary Motor. On Starting at
Cylinder No. 1, and Following the Zig-Zag Line in the Direction of
the Arrows, it Will be Seen that Ignition Occurs at Every other
Cylinder at even Intervals Through Two Revolutions, Ending at
Cylinder No. 1.
]

As the motor operates on the four stroke cycle system, an odd number of
cylinders is chosen in order that the firing may be carried out through
equal angles in the revolution to obtain a uniform turning movement.
Since a four stroke motor must complete two revolutions before all of
the cylinders have fired, or completed their routine of events, it is
evident that the number of cylinders must be odd in order to bring the
last cylinder into firing position in the last revolution. When seven
cylinders are used, the cylinder are fired alternately as they pass a
given fixed point, that is, one cylinder is fired, the next skipped, the
third fired, and the fourth skipped, and so on around the circle, so
that the firing order in terms of the cylinder numbers is 1, 3, 5, 7, 2,
4, 6. The cylinders fired in the first revolution in order are 1, 3, 5,
7, and in the second revolution, 7, 2, 4, 6, the cylinder 7 being common
to both revolutions. The cylinders are numbered according to their
position on the engine, and =NOT= according to the firing sequence. See
Fig. 51.

[Illustration:

Fig. 52. Firing Diagram of Six Cylinder Rotary Motor. On Following the
Zig-Zag Line it Will be Seen that All of the Cylinders Are Not Fired
at Equal Intervals. In Some Cases Two Adjacent Cylinders Fire in
Sequence, and in Others Two or Three Spaces are Jumped.
]

With a six cylinder engine it is possible to fire the cylinders in two
ways, the first being in direct rotation; 1, 2, 3, 4, 5, 6 thus
obtaining, six impulses in the first revolution, and none in the second.
The second method is to fire them alternately, 1, 3, 5, 2, 4, 6, in
which case the engine will have turned through equal angles between
impulses 1 and 3, and 3 and 5, but through a greater angle between 5 and
2, and even again between 2 and 4, and 4 and 6. See Fig. 52.

Mixture is drawn into the cylinder by the suction of the piston through
an inlet valve in the piston head, in practically the same way as in the
“Gyro” motor, but unlike the latter motor, the valve is lifted by the
suction (automatic valve) and not by the mechanical actuation of the
connecting rod. The inlet valve is balanced against the effects of
centrifugal force by a small counter-weight in the piston head, and the
valve is held normally on its seat by a flat spring acting on the valve
stem. The gases are brought into the crank case from the carburetor
through the hollow crank-shaft as described elsewhere. See Fig. 53.

[Illustration:

Fig. 53. Longitudinal Section Through Gnome Rotary Motor.
]

All exhaust valves are located in the cylinder head and are actuated by
long push rods that are moved by individual cams in an extension of the
crank case. The exhaust valves are counter-balanced against centrifugal
force and are retained on their seats by a flat spring. The counter
weights do not entirely overcome the effects of the centrifugal force
but allow a slight excess to exist which will permit the engine to run
with a broken spring. All of the exhaust gases escape directly to the
atmosphere without piping or mufflers.

Owing to the fact that the advancing or leading face of the cylinder is
cooler than the trailing face, the cylinder bore is thrown out of line
by the difference in expansion between the two sides. Because of this
distortion of the bore, a special form of piston ring is used, which, by
its flexibility, adapts itself to variations in the bore. These rings
are of brass and are shaped like the pump leathers of a water pump so
that the pressure of the explosion acting on the inside of the ring
tends to force the thin shell against the cylinder. In spite of this
precaution, the compression pressure is very low at the best, in the
most of cases not over 45 pounds per square inch. The exhaust valve
screws into the end of the cylinder and may be removed, complete with
its seat, for the frequent regrinding necessary to efficient operation.
After the cylinders are ground with the greatest care and accuracy, the
finishing is carried still further by wearing-in the cylinder with an
actual piston carrying an “obturateur” or piston ring.

[Illustration:

Fig. 54. Gnome Motor on Testing Stand. From Scientific American.
]

The bushing into which the spark plug screws is not integral with the
cylinder as in a cast construction, but is welded into the side of the
cylinder head by means of the autogenous process. It is also evident
that this construction enables the inlet valves to be easily removed,
since these screw into the piston head. Both inlet and exhaust valves in
the Gnome engine are removed with the greatest ease, special socket
wrenches being supplied for the purpose. The castor oil, which is used
as a lubricant, and the gasoline, are fed by a positive acting piston
pump to the hollow crank shaft. The lubricant and fuel then pass through
the automatic inlet valve in the head of the cylinder.

[Illustration:

Fig. 55. Gnome Motor Running On Test Stand. From Scientific American.
]

The spark produced by the high tension magneto is led to the proper
cylinder through a brush that presses on a revolving ring of insulating
material in which is imbedded 7 metallic segments, one of the segments
being connected to a corresponding cylinder. As the distributor ring
revolves the segments come into contact with the brush in the proper
order. The magneto is stationary and is supported by a bracket in an
inverted position. A pinion on the magneto shaft meshes with a large
gear mounted on the revolving crank case so that the armature of the
magneto always bears a positive relation to the piston position. As the
engine requires seven sparks for every two revolutions, or 3½ sparks per
revolution it is evident that the magneto must turn 1.75 times as fast
as the engine, if the magneto is of the ordinary type that generates two
sparks per revolution. In other words the magneto speed is to the engine
speed as 7 is to 4.

[Illustration:

The “Indian” Rotary Aero Motor.
]

The arrangement of connecting rods is interesting, the big end of one
rod being formed into a cage for the reception of the crank-pin ball
race. The outer circumference of the cage carries the pins to which the
other six connecting rods are fastened. It is necessary that one rod be
integral with the cage to prevent its rotation in regard to the
cylinders. Annular ball bearings are used on both the main bearings, for
the thrust bearing to take the thrust of the propeller, and on the large
end of the master connecting rod. The large ends of the auxiliary
connecting rods and the small ends of all the rods have plain bearings.

CHAPTER VI
TWO STROKE CYCLE ENGINES

(30) The Junker Two Stroke Cycle Engine.

The Junker two stroke cycle engine stands unique among the large
stationary units not only in the principle of its working cycle but in
its construction as well, and while it may be considered freakish when
compared to standard practice it has proved its value in many European
installations. The combustion occurs in the center of an open ended
cylinder between two pistons that are forced in opposite directions by
the expansion of the gas, and as there is a single acting piston in each
end of the cylinder at the end of the stroke, there is no need of
stuffing boxes, cylinder heads or valves.

It is apparent that by moving the pistons in opposite directions, the
effective piston velocity is twice that of the actual velocity of either
of the pistons, and that it is therefore possible to gain a high heat
efficiency at high piston velocities with a low rate of rotation. The
double pistons increase the scavenging effects, reduce the losses to the
cooling water and increase the efficiency at light loads. A marked
reduction in weight over the four stroke cycle engine is made possible
because of the absence of valves and valve gear.

This engine is of the injected fuel type that is the fuel is sprayed
into the combustion chamber after the completion of the compression
stroke in a manner similar to the Diesel engine. By prolonging the
injection of fuel after the piston has started on the outward working
stroke it is possible to maintain the maximum pressure due to the
combustion for a considerable period. This gives an indicator card that
is very similar to that of a steam engine as the flat top of the
Junker’s card due to the continued combustion and pressure corresponds
to the admission line of the steam engine. As ignition is caused by the
high temperature of the compression, almost any low grade oil may be
used even down asphaltum oils and coal tar.

[Illustration:

Fig. 8. The Junker Two Stroke Cycle Engine.
]

In Fig. 8 five piston positions corresponding to five events are shown
by the diagrams a, b, c, d, e. From the diagrams one may also get an
idea of the arrangement of the principal parts of the engine and their
relation to one another. P and P2 are the two pistons, C the open ended
cylinder, G the connecting rod of the inner piston P, H-H the two
connecting rods of the piston P2, I-I the side rods of the piston P2,
and V is the three throw crank shaft which is acted on by the three
connecting rods H-H-G. The piston P2 is connected to the side rods
through the yoke Y. It will be noted that the crank throws controlling
the piston P2 are 180° from the crank connected to piston P, which
causes the pistons to move in opposite directions.

With the pistons together at the inner dead center, the space between
them is filled with highly compressed air from the previous combustion
stroke. At this point the fuel is injected into the highly heated air,
and the expansion of the charge begins, the combustion proceeding under
constant pressure during the first part of the stroke, or during that
part of the stroke in which the fuel is admitted to the cylinder. When
the supply of fuel is cut off the working stroke continues by the
increase of volume, or expansion of the gas, the gases being reduced to
nearly atmospheric pressure at the end of the stroke with the pistons at
the position shown by diagram (b). At this point the piston P is just
opening the edge of the exhaust port M, allowing the products of
combustion to escape to the atmosphere through the annular exhaust
passage that surrounds the port M.

As the pistons continue to move outwards the gases continue to issue
from the exhaust port at practically atmospheric pressure until the
position shown by diagram (c) is reached by piston P2. At this point P2
is just opening the inlet port N allowing fresh air to enter the
cylinder for the purpose of scavenging the engine. The passage of the
air through the intake port N and out through the exhaust port M
continues until the pistons pass the outer dead center, shown by diagram
(d), and begin to come back on the return stroke. In diagram (e) the
pistons have traveled far enough to close both ports, and as the space
between them is filled with pure air from that furnished by the port N,
the pistons will continue to move toward one another on the compression
stroke. When they have reached the end of their travel as shown by
diagram A, the fuel is injected into the cylinder and combustion occurs
due to the temperature of the high compression temperature.

This is the complete cycle of events made in two strokes, and it will be
noted that the cycle has been accomplished without the use of valves.
The compressed air for scavenging the cylinder is provided by air pumps
that are driven from the connecting rods by a link motion. One low
pressure pump for the scavenging and one high pressure pump for spraying
the fuel into the cylinder against compression are provided. As the
inside of the piston is always exposed to the atmosphere through the
open ends of the cylinder and is never exposed to the heat of
combustion, perfect cooling is secured, and as a matter of course,
perfect lubrication.

In the two cylinder engine in which four pistons are used, the cylinders
are arranged in tandem with the two adjacent pistons, and the two outer
pistons connected respectively. In fact the second cylinder pistons are
duplicates of those just shown and are connected to the linkage in such
a manner as to have the corresponding pistons in one cylinder act with
the corresponding pistons in the second.

(34) Koerting Two Stroke Cycle Engine.

One of the most prominent of the two stroke cycle scavenging engines
built for heavy stationary service is the Koerting engine. Because of
its peculiar scavenging arrangement, and as it is of the double acting
type, it will serve to illustrate the cycle of that class of engine
equipped with independent air pumps. Several of these engines are in use
in Europe that have an output of over 4,000 horse-power, the general
arrangement of which is the same as shown in the accompanying diagram
Fig. F-11.

[Illustration:

Fig. F-11. Koerting Two Stroke Cycle Engine with Scavenging and
Charging Cylinders.
]

Since the engine is double acting, two similar combustion chambers are
provided at each end of the piston as shown by C and C_{1}, and as each
of the chambers gives one impulse per revolution because of the two
stroke cycle, the single cylinder shown in the figure delivers two
impulses per revolution to the crank-shaft. In order to have one exhaust
port serve for both combustion chambers, the annular port E is placed in
the center of the cylinder so that it is alternately opened to C and
then C_{1} as the piston travels to and fro, the port being covered by
the piston at intermediate points in its travel. As the piston must
cover the port for a considerable portion of the stroke, it is made very
long, nearly as long as the stroke. The piston rod R that connects the
piston with the crank passes through the cylinder head of chamber C_{1},
surrounded by a gas tight packing that prevents the leakage of the
charge from C_{1}.

Unlike the ordinary type of two stroke cycle engine, the two combustion
chambers are provided with mechanically operated inlet valves,
V-V_{1}-V_{2}-V_{3} that are opened at definite points in the stroke by
the lay shaft X which is driven from the crank shaft. As the exhaust
port E serves all of the functions of an exhaust valve, there are no
valves provided at this point. Exhaust pipes connected to E carry the
burnt gases to the atmosphere.

Two auxiliary air pumps of the double acting type are provided, shown at
A and A_{2}, one pumping gas and the other air. They are driven from the
crank-shaft through the connecting rod Y, and are proportioned so that
together they force a mixture of the correct proportion for complete
combustion into the working cylinder at a pressure of about ten pounds
per square inch. Air and gas are compressed on one side of each pump
piston in the spaces B and B_{2}, and the air and gas are drawn in on
the other side as at H and H_{2}. The connections from the compressor
cylinders to the working cylinder are arranged so that the two crank
ends of the compressor cylinders discharge into the crank end of the
working cylinder, and the front ends of the compressors discharge into
the front end of the working cylinder, the exact moment of discharge
being controlled by the inlet valves V-V_{1}-V_{2}-V_{3}. The pumps are
arranged so that only pure air is admitted at first in order to force
the products of combustion through the exhaust port so that they will
not contaminate the following mixture of air and gas. The inlet valve
opens immediately after the piston of the working cylinder uncovers the
port E and reduces the pressure of the burnt gases to that of the
atmosphere.

By the action of the admission control, the scavenging air first
admitted, is prevented from mixing with the residual gas from the
previous explosion, and in the same way the device prevents the loss of
fuel through the exhaust ports, thus overcoming the principal objections
of the simple two stroke types described earlier in this chapter. The
compressor cylinders provide only enough air and mixture for one stroke
and no reservoir is provided for a surplus of air or mixture.

As the piston moves forward, on the compression stroke and covers the
exhaust port, the inlet valves also close, and the compressor pistons
arrive at the end of their stroke so that no more air or mixture is
delivered to the inlet valves. At the end of the compression stroke
ignition occurs and the expansion or working stroke begins. The piston
again moves to the right on the working stroke until the front edge
uncovers the port E where the exhaust gases escape to the atmosphere.

The valve gear on the gas compressing cylinder is arranged so that no
gas is delivered to the inlet valves of the working cylinder until the
air cylinder has provided sufficient air to insure perfect scavenging of
the products of combustion, this preventing the fuel from becoming
contaminated with the burnt gas. Speed regulation for varying loads is
effected by shifting the valve gear of the gas pump so that the gas is
delivered at an earlier or later period in the stroke of the working
piston, thus causing a variation in the quantity of gas delivered to the
working cylinder. This is controlled by the governor directly on the
valve gear of the pump or upon a by-pass in the pump cylinder or both.
The by-pass, when open returns all of the gas in the passage leading to
the inlet valve, that is beyond a certain pressure to the cylinder, so
that the gas is delivered to the cylinder at a constant pressure, and
therefore in proportion to the load and point of cut off.

This method of governing produces a mixture that varies in richness with
the different loads that are carried by the engine, but as the air
enters the cylinder first and is prevented from mixing to any extent
with the gas by the shape of the cylinder heads, the igniting value of
the mixture is not disturbed particularly as the rich gas remains in the
cylinder heads and in contact with the igniters.

Like all large engines, the Koerting is started by compressed air taken
from a reservoir. A special starting valve is provided for each end of
the cylinder which is operated from the cam shaft by means of an
eccentric. The air valves may be thrown in or out of gear by a clutch.

(57) Two Stroke Cycle Rail Motor Cars.

A unique application of the two stroke cycle motor will be seen in Fig.
56 which shows a Fairbanks-Morse two stroke cycle motor direct connected
to the driving wheel of a railway motor car. The three cylinders are
mounted between the driving wheel with the ends of the axle terminating
in the crank cases of the motors. Access to the bearings is had through
a cover on the crank-case. The simplicity of this motor and its freedom
from valves, cams, springs, gears, and other trouble causing parts makes
it particularly adapted for the service that it performs in the hands of
unskilled track laborers. As there is no water to freeze or leak, and as
the lubricant is mixed with gasoline, the car needs very little more
attention than the old type hand car.

The car is started by opening the gasoline supply cock, closing the
ignition switch, and pushing the car along the track until the first
explosion occurs. The speed is controlled in the usual manner by means
of the spark advance and throttle. As the motor is of the two stroke
cycle type, it may be reversed by simply changing the position of the
timer without the use of the gears. The speed is the same in either
direction. By the use of three cylinders, three impulses are obtained
per revolution which gives a distribution of power equal to that of the
ordinary six cylinder, four stroke cycle automobile motor.

[Illustration:

Fig. 56. Two Stroke Cycle Fairbanks Motor for Driving Railway Section
Cars.
]

For larger cars built for carrying large gangs of men, a three cylinder
motor is used which drives through a clutch and gears, similar to that
used on automobiles. It is located near the center of the axle and is
supported on a frame that is independent of the car proper. This motor
unit is easily removed from the car for inspection with all of the parts
intact. A universal coupling is provided on the motor shaft to prevent
strains due to changes in the alignment from being thrown into the
motor. The motor of this car is started with a crank, and may be left
standing with the motor running. As with the two cylinder car, the
engine is reversible, and is lubricated by mixing the lubricating oil
with the gasoline.

(58) Rotating Cylinder Two Stroke Cycle Motor.

An unusual type of two stroke cycle engine is that designed by M. Farcot
for aeronautic work. It is of the rotating cylinder type in which the
cylinders rotate about a stationary crankshaft, and unlike all previous
two stroke motors, whether of the revolving or stationary cylinder type,
no initial compression is performed either in the crank-case or
otherwise.

[Illustration:

Fig. 63. Farcot Rotary Two Stroke Motor.
]

Undoubtedly the two-cycle rotating multi-cylinder engine has a future
when some of the particularly difficult designing problems involved in
its production have been successfully tackled. Crank case compression
has had its devotees, but so far it has entailed the use of a low
compression, owing largely to the difficulties involved in lubricating
the bearings and maintaining gas-tight joints, besides other defects.
Some of these barriers appear to have been surmounted in this design.

Fig. 63 of the accompanying drawings is a sectional side elevation of
the engine, which, it will be seen, is similar in general disposition to
the usual arrangement of the rotating cylinder type. In this particular
case, however, the short end A of the stationary crankshaft is reduced
in diameter at B, and on this part are mounted ball bearings C carrying
the circular casing of a rotating centrifugal blower D. To the inner end
of the hub of this blower is attached a gear wheel E, the teeth of which
mesh with small intermediate pinions carried on a spider F attached to
the crankshaft. These pinions are in turn driven by an internally
toothed ring G attached to the hub of the crank case H. Thus the blower
D is driven in the opposite direction to the crank-case and at a higher
speed. In the interior of the blower casing radial blades K are
provided.

[Illustration:

Fig. 64. Farcot Fan Plates.
]

A hollow annular casing L is bolted to the cylinders, and communicates
with their interiors by means of inlet ports M covered and uncovered by
the pistons.

The blower casing D has on either side circumferentially flanged rings
N, which are a running fit in circular register slots provided in the
annular casing L and its cover plate P, in order to provide a gas-tight
joint between the opposite revolving casings D and L. Fan blades Q are
also provided in the casing L to accelerate still further the incoming
gas. The arrangement of the two sets of blades is made clear in the
sectional sketch (Fig. 64). It will be realized that by means of this
compound blower device a considerable pressure can be attained.

The crankshaft is drilled to provide a feed for the gasoline, which is
atomized by a device R in the large central opening of the blower casing
D by means of pressure fed from the annular casing L through suitable
leads S.

As each piston nears the bottom of its stroke, exhaust ports T, provided
with expansion cones for the purpose of increasing the velocity of the
exhaust gases, are opened. The inlet port M is then uncovered, and the
compressed charge rushes into the combustion chamber.

The general design of the engine is made plain by Fig. 63, but there is
one other point to which reference should be made, and that is the
provision of rings V, one on either side of the cylinders, to enhance
the strength of the construction.

Although the difficulty of compression appears to have been cleverly
tackled in this invention, the possibility of the compressed mixture in
the inlet casing and blower becoming ignited at the moment of admission
by a residue of exhaust gas in the combustion chamber still exists.
However, the effect of such a backfire should not prove quite so serious
as in some designs. Apart from other considerations, owing to the large
area of the blower intake, such an occurrence should merely have a more
or less elastic braking effect.

(60) Gnome Radial Two Stroke Motor.

The builders of the famous Gnome four stroke cycle rotary motor, Sequin
Frères, have recently developed a radial two stroke cycle motor that
bids fair to supplant their original type. Referring to the diagrammatic
cross-sections which show only a single cylinder unit, a very long
tubular piston will be seen that is divided into two independent
chambers, A and B. Both chambers are placed in communication with the
outside space, C and D.

The upper end of the piston is continued above the top division head of
the chamber A, and the extension is provided with the slot F. Near the
center of the piston, the walls of the piston are run out into a flat
circular plate or trunk piston E, which is the actual piston head that
receives the force of the explosion. The piston E reciprocates in the
large cylinder H, which is reduced at its upper end to the diameter of
the main piston barrel, for which it affords a sliding support, or
guide, and also serves to aid the exhaust port closure. The lower end of
the cylinder H is enlarged in diameter as shown by K so that a clear
annular space is left between the cylinder walls and the piston head E,
when the latter is at the bottom of the stroke. The cylinder diameter is
then reduced to the diameter of the main piston barrel.

The motor operates as follows:

Suppose the piston to be ascending (Fig. 1), compressing the mixture
above the piston head in the cylinder E, and at the same time the volume
of the space M, below E, is being increased until the piston reaches the
position shown in Fig. 2.

[Illustration:

Fig. 65. Gnome Rotary Two Stroke Motor Diagram. Diagrams 1 and 2.
]

Referring to Fig. 1; the interior chamber A of the piston is in direct
communication through the holes C with the space M, consequently as the
piston goes up, a partial vacuum will be formed in these two chambers.
When the piston reaches the top of its stroke as shown in Fig. 2, the
holes D in the lower end B of the piston are uncovered as they rise into
the increased diameter of the cylinder, and therefore the mixture is
sucked in from the crank case until the chambers A and M are filled to
atmospheric pressure.

The spark now occurs at the plug S, and the explosion takes place,
driving the piston downwards as shown by Fig. 3, just before the exhaust
takes place. The volume of the chamber M has now been decreased with the
result that the mixture will have been compressed into the chamber A.

In Fig. 4, the piston has now reached the bottom of the stroke, and the
ports F have opened as the slots carry below the upper end of the
cylinder where the bore is increased. At the same time, as the piston
plate E passes the bottom of the cylinder H into the enlarged diameter
K, the compressed mixture in A and M rushes through the annular space
opened around E into the combustion chamber and drives out the residual
burned gases which still remain after the explosion. On starting the
second revolution the piston rises and the cycle repeats as shown by
Fig. 1.

[Illustration:

Gnome Rotary, Diagrams 3 and 4.
]

This engine may be built with any number of the cylinder units
described, preferably with an uneven number, as in the case of the Gnome
radial four stroke cycle, and with twice the number of impulses of the
four stroke type a very uniform turning movement should be had.

[Illustration:

Fig. 64-b. Roberts Two Stroke Aero Motor Using a Rotating Tubular
Valve that Controls the Mixture from the Carburetor so that it
Enters Only One Crank Case at a Time. This Gives Each Cylinder an
Equal Charge of Gas.
]

[Illustration:

Fig. 64-c. Roberts Distributor Valve. The Ports Are Cut in the Valve
so that Only One Crank Case is in Communication with the Carburetor
at Any One Time. The Central Hole Connects with the Carburetor.
]

Since the valves are the parts that give the most trouble in the
four-stroke cycle Gnome, this motor should be better adapted for
aviation than the original type of Gnome.

(62) Variable Speed Two Stroke Motor.

A variable speed two stroke cycle motor is described by C. Francis
Jenkins in the _Scientific American_ that seems to solve many of the
problems encountered in designing a two stroke cycle motor for
automobile purposes. As is well known, the present design of the
crank-case compression type is wasteful of fuel, and ignites irregularly
at low speeds and light running, and as nearly all automobiles are well
throttled for a greater portion of the time it means that this type of
motor is working under the greatest disadvantage.

[Illustration:

Fig. 66. Jenkins Two Stroke Cycle Motor.
]

Since the greater part of the trouble is due to the dilution of charge
by the residual gases, and as the spark plug of the motor is situated in
the most diluted portion of the gas, it would seem that a change of
spark plug location, or a change in the circulation of the fresh mixture
in the cylinder would be a great aid in remedying the difficulty. With
the spark continually in contact with fresh undiluted mixture it would
be possible to run it as low speeds as with the four stroke motor, with
a corresponding increase in the efficiency, and opportunity to run with
a constant advance of the point of ignition. This is accomplished by any
or all of the following conditions:

(1.) By keeping good gas separate from bad.

(2.) By placing the spark near the intake port.

(3.) By leaving the plug in its present position and deflecting the
fresh gas to meet it.

(4.) By changing the location of the inlet port.

[Illustration:

Fig. 58-a. Two Cylinder Marine Engine, of the Two Stroke Type. Built
by Fairbanks-Morse and Company.
]

In the motor invented and described by Mr. Jenkins, the method given by
(4) is adopted as shown by Fig. 66, in which the spark plug is placed at
the point of admission of the gas and in a confined passage. The
operation of the motor is as follows:

Carbureted gas is drawn into crank-case from the carburetor (not shown)
in the usual manner, i. e., by the upward movement of the piston; and by
its downward movement is forced through the rectangular port in the wall
of the piston into the combustion passage within the water-jacket when
the port in the piston wall registers with the lower end of this
combustion passage, and drives ahead of it the bad gas remaining after
the previous explosion. If the throttle is wide open the combustion
space above the piston will be completely filled, and on the ignition of
the charge the maximum pressure will be exerted on the piston. If,
however, the throttle is but slightly open, the combustion passage only
may be filled and none overflow into the combustion space above the
piston. This small charge will be just as efficient in proportion to its
volume as was the large charge, for it was compressed to practically the
same extent and none was mixed with the bad gas of the previous
explosion. It will, therefore, be obvious that the spark-plug is always
swept by the fresh charge, be it large or small, and the ignition will
be just as certain in one case as in the other, although the charge and
consequent impulse may be only just sufficient to keep the engine
turning over, and without missing a single explosion.

[Illustration:

Fig. 64-d. Roberts Cylinder Showing Cellular Screen in the Intake
Port. This Screen Prevents Crank Case Fires by Chilling the Cylinder
Flame Before it Enters the Crank Case.
]

In the motor built to test and demonstrate this design, provision was
made for a second spark-plug to be located in the top of the cylinder
for speed work, if this was found necessary. No opportunity has yet been
had for making track tests, though without regret, as this two-cycle
motor will run idle without missing or “stuttering,” which was the thing
heretofore impossible.

CHAPTER VII
OIL ENGINES

(31) Diesel Oil Engine.

The Diesel engine marks the greatest progress in the internal combustion
field made in the last few years. It marks a distinct advance in both
thermal efficiency, and in the character of the fuel that it has made a
commercial possibility. By the use of cheap fuel heretofore unavailable
for any type of prime mover, such as the asphaltum residual oils, coal
tar, etc., it has lowered the cost of power production to a point where
it is unapproached by any type of heat engine. Besides its thermal
efficiency, the engine is free from the annoyances due to delicacy of
the auxiliary appliances such as the carburetor, and ignition system
which are indispensable with the ordinary type of gasoline engine.

This engine belongs to that type of engine in which combustion takes
place at constant pressure (Brayton Cycle), that is the combustion
pressure is maintained at a constant value for a considerable distance
on the working stroke of the piston. This method differs from the Otto
cycle in which the combustion proceeds at a constant volume, or the type
in which combustion is completed before the piston moves forward on the
working stroke.

In the Diesel cycle the first stroke of the piston draws pure air into
the cylinder; the piston then moves forward on the compression stroke,
compressing the air to 500 or 600 pounds per square inch and raising the
temperature of the air to about 1,000 degrees C, the exact temperature
and pressure depending on the character of the fuel used in the engine.
The high pressure is obtained by using a small clearance space in the
end of the cylinder. At the end of the compression stroke a spray of oil
is injected into the cylinder which is instantly ignited by the high
temperature of the compressed air.

The oil continues to burn as long as it is sprayed into the cylinder,
this period being from one-quarter to one-third of the working stroke.
After the oil is cut off, the hot gas is expanded to the end of the
stroke at which point the pressure is very considerably reduced due to
the mechanical work performed. It should be noted that the type of
engine just described performs the complete cycle in four strokes, the
fourth stroke being the scavenging stroke as in the ordinary four stroke
cycle engine. While the four stroke cycle type of Diesel engine is by
far the most common type, it is also built as a two stroke cycle that is
similar to the two stroke cycle gas engine previously described except
that pure air is received and compressed in the air compressor in place
of the combustible mixture.

[Illustration:

Fig. 9. Cross Section of Four Stroke Cycle Diesel Engine. The Center
Valve is the Fuel Admission Valve.
]

It will be noted, that as there is no fuel in the cylinder during the
compression stroke that there is no danger from preignition from an over
heated charge, nor is there trouble from decomposed fuels due to a
gradually increasing temperature so often met with in oil engines that
compress the entire mixture. As the clearance space is exceptionally
small there is a minimum of residual gas held in the cylinder after the
explosion with the result that the fuel is completely consumed, and that
a full charge is taken into the cylinder.

The speed and output are regulated by controlling the point in the
working stroke at which the oil spray is cut off, and as this has no
effect on the maximum pressure developed in the cylinder, as in the case
of the ordinary gas engine control, the pressure charge under varying
loads is not so severe. Because of the high compression, and the
continued combustion, there is a very gradual increase of pressure.
Since the amount of pure air admitted to the cylinder is the same at no
load as at full load there is always sufficient air for the complete
combustion of the fuel, and as there is a constant compression pressure
there is a constant ignition temperature and constant quantity of the
working medium. Because of the high compression obtained by the Diesel
type, it has an efficiency that is far beyond that of any other form of
internal combustion motor.

[Illustration:

Fuel Nozzle of the Koerting Diesel Engine Showing Operating Cam and
Lever, and Compressed Air Connection.
]

Since the fuel is introduced gradually into the combustion chamber the
combustion pressure rises very slowly so that it is not an explosive
engine in any sense of the word, the combustion pressure rising steadily
from the compression pressure to the maximum in proportion to the supply
of fuel. In the ordinary type of gas engine with a compression pressure
of from 60 to 70 pounds per square inch the pressure rises abruptly to
about three and one-half times the compression pressure, with a
correspondingly rapid drop in the pressure on the expansion stroke. In
the Diesel engine the drop of pressure in expansion is much more
gradual, the indicator diagram expansion curve being nearly horizontal.
The uniform pressures thus obtained result in smooth action and even
driving power, obtained with no other type of engine.

[Illustration:

Fuel Pump of Koerting Diesel Engine with Operating Cam.
]

As the fuels used vary from the lightest hydrocarbons to the heaviest
crude oils, there are many types of oil injection valves in use, the
valves being in general divided into two classes, those in which the oil
is vaporized mechanically by the pressure of a force pump, and those in
which the fuel is vaporized by the atomizing effect of compressed air.
Atomization by compressed air is however, the most common method since
less trouble is experienced with the air pumps than with the liquid
force pumps. The compressed air is supplied by pumps that are either
operated by the main engine or by an independent compressor engine.

The fuel valve is a plug screwed into the cylinder containing an
inwardly opening check valve in the inward end. The hole in the center
of the plug receives the oil charge under a few pounds pressure from the
tanks, during the compression stroke of the engine, and at the end of
the compression stroke, a blast of air at a pressure of about 250 pounds
above the compression pressure blows it into the cylinder in the form of
a fine spray. Injection valves of the forced feed type consist of a plug
with a small passage and a needle valve for regulating the spray. Fuel
is pumped into the valve at about 250 pounds above the compression
pressure of the engine by a small single acting pump which is built so
that the length of the stroke may be adjusted to meet the load. In
practice the length of stroke is regulated by the governor, so that the
full contents of the pump are delivered at full load, and a reduced
amount with a short stroke at small loads. On issuing from the fuel
nozzle, the liquid strikes a gauze screen by which it is broken up into
very fine spray.

Fluidity is practically the only factor that governs the quality of fuel
that may be used with the engine, since exceptionally heavy oils and
tars cannot be successfully sprayed. In Fig. 9 is shown a cross-section
of a Diesel engine cylinder in which the center valve in the cylinder
head is the fuel valve, and the valves to the right and left are the air
inlet and exhaust valves respectively. The two latter valves correspond
to the inlet and exhaust valves of the Otto cycle engine.

Compressed air is used in starting the engine, which is admitted to the
cylinder through an auxiliary valve which is operated by a starting cam
on the cam shaft. By this mechanism, high pressure air is furnished to
the cylinder during a portion of the working stroke, turning it over on
the first few revolutions as a common air engine. As soon as the engine
picks up speed, the starting valves are thrown out of operation, and the
engine proceeds on its regular working cycle with the oil fuel.

When used for marine purposes in sizes over 100 horse-power, where it is
not possible to use reverse gears, the Diesel engine whether of the two
stroke cycle or four stroke cycle type must be made reversible. This may
be accomplished by either of two methods, first, by changing the angular
position of the cams in regard to the piston position, and second by
using two sets of cams, one being for right hand rotation and the other
for left hand. When a single cam is used, the relation of the cam shaft
on which the oil pump cams and oil valve cams are located, is advanced
or retarded in respect to the crank shaft by means of sliding the two
spiral gears that drive the cam shaft, over one another, in a direction
parallel to their axes. The spiral gears are moved back and forth by a
hand controlled reverse lever. This type is used principally on the two
stroke cycle type of engine as there are not so many factors to contend
with as on the four stroke cycle.

With double cams, the system almost invariably used with the four stroke
cycle engine, the cams may be mounted either on one shaft, or the ahead
cams on one cam shaft and the reverse cams on another. When two shafts
are used they are arranged so that either set of cams may be swung under
the valve lifters by swinging the shafts in a radial direction by
brackets. The single type of cam shaft is usually moved back and forth
in a direction parallel to its axis, the ahead cams coming under the
valve lifts at one position, and the reverse cams at the other. In the
four stroke cycle Diesel it is evident that not only the relations of
the oil pump and oil valves must be changed in respect to the piston
position but the relations of the air inlet and exhaust valves must be
changed as well. This necessitates double cams for the inlet and exhaust
valves in order to reverse rotation.

Compressed air for starting and injection is generally supplied by a
three stage air compressor or a compressor in which the pressure is
built up in three different steps, the second cylinder taking the air
from the discharge of the first, and the third cylinder taking the air
from the second, and compressing it to about 250 pounds above the
compression pressure of the engine. Perfect scavenging is possible with
this engine because of the large excess of air supplied during the
suction stroke and the period of injection. On the marine type the air
pumps and water circulating pumps occupy about the same amount of space
as the condenser and circulating pumps of a steam engine having the same
outputs. In a recent test made with an Atlas-Diesel engine it was found
that 11 per cent of the output was lost in driving the air pumps or more
than 50 per cent of the total loss by friction and impact.

[Illustration:

Fig. 67. Cross-Section Through the Working Cylinders of the M. S.
Monte Penado Two Stroke Cycle Diesel Engine. From the _Motor Ship_,
London.
]

Unlike the ordinary gasoline engine in which an increase of speed
increases the output in an almost direct proportion, the output of the
Diesel engine decreases when the speed rises beyond a certain limit due
to imperfect combustion at speeds much over 350 revolutions per minute.
Because of this fact it has been practically impossible to apply the
type to automobile service which ordinarily requires a speed of from 400
to 800 revolutions per minute under ordinary conditions. In addition to
the speed limitations, the Diesel engine weighs approximately 70 pounds
per horse-power against an average weight of 17 pounds per horse-power
with the ordinary type of gasoline automobile motor. Of course these
objections may be overcome in time, as the engine is only in its
infancy, and the two stroke cycle Diesel has not yet been fully
developed, but at the present time it does not seem probable that this
engine will ever be an active competitor of the gasoline automobile
motor, at least from the standpoint of flexibility.

As the Diesel engine depends entirely upon compression for its
operation, it is necessary that all of the parts such as the pistons,
valves, etc., shall be perfectly fitted and air tight under extremely
high pressures. The careful workmanship required for such fitting and
the adjustments make the Diesel much more expensive to build than the
ordinary type of gas engine, and for this reason the first cost and
overhead charges cut into the fuel item to a considerable extent. A
description of the Diesel engines will be found in the chapter devoted
to oil engines.

(63) Diesel Engine (Marine Type).

As a practical example of a Diesel engine, which was described in
Chapter III, we will give a brief description of the two 850 horse-power
Diesel engines installed in the cargo vessel “M. S. Monte Penedo,” which
were built by Sulzer Brothers of Winterthur, Switzerland. We are
indebted to the _Motor Ship_, London, for the details.

The engines are of the two stroke cycle, single acting type, with four
working cylinders, a double acting scavenging pump cylinder, and a three
stage ignition compressor cylinder. The bore of the working cylinders is
18.8 inches, and the stroke 27 inches. While the crank case is of the
enclosed type, there are two sets of covers which can be easily removed
for inspection while the engine is running, for as the scavenging pump
performs the work of the crank case of the ordinary two stroke cycle
engine there is no need of a tight case to retain the compression.

[Illustration:

Fig. 68. Cross-Section Through the Air Cylinders of the Two Stroke
Diesel Motors on the M. S. Monte Penado.
]

The scavenging pump is mounted on one end of the engine and is driven
from the crank-shaft, the cross-head of the pump forming one piece with
the piston of the low pressure cylinder of the injection air cylinder.
All of the compressor stages are water cooled and fitted with automatic
valves. The double acting scavenging pump has a piston valve driven by a
link motion for reversing it when the engine is reversed. The air enters
the pump through the top valve chamber from a pipe leading into the
engine room. The air discharges a pressure of about 3 pounds per square
inch in a header that passes in front of all four working cylinders. By
means of a valve the air entering the low pressure stage of the
compressor can be taken either from the atmosphere or from the discharge
of the scavenging pump; taking the air from the latter allows of a
greater weight of air taken by the compressor and consequently a higher
compression for use in emergencies.

As in the ordinary type of two stroke cycle engine, two independent sets
of exhaust ports are used, one set being for the scavenging air and the
other for the exhaust gases, both sets being at the end of the stroke as
usual. The air inlet ports are divided into two groups, however, one
group being controlled by the piston of the working cylinder, and the
other group by an independent piston valve driven from the cam-shaft.
Both sets of ports connect with the main scavenging air header. By means
of the valve controlled ports it is possible to admit scavenging air
even after the other ports are closed by the piston, which greatly
increases the scavenging effect. With the air at 3 pounds pressure the
air from the valve controlled ports throw the scavenging air to the top
of the cylinder even after the exhaust ports are closed. This valve is
provided with a reverse mechanism. A single cam is used for operating
the fuel inlet valve and the air starting valve, and the reversal of the
engine is obtained by turning the cam shaft through a small angle
relative to the crank-shaft, which of course also reverses the lead of
the fuel valve. Starting is accomplished by compressed air, with the air
valve lever on the cam, and the fuel valve lever off. After turning
through a few revolutions, the air valve levers are raised, and the fuel
levers dropped back on the cams which results in the engine taking up
its regular cycle.

By moving the tappet rod of the fuel valve out of or into a vertical
position, the time of the fuel valve opening is regulated and the amount
of air is controlled. This movement is normally performed by a
compressed air motor, but in an emergency hand wheels may be used.

One of these serves to rotate the camshaft through the required angle in
order to set the cams in the positions for astern or ahead running and
also reverses the link motion of the scavenging pump valve by the
rotation of shaft, as mentioned above. The other auxiliary motor
operates the fuel and starting air valves by moving the small spindle
longitudinally to bring the tappet lever of the air valve about the
required cam for ahead or reverse and also lifts this or the fuel valve
tappet rod off its cam, according as it is desired to run on fuel or
air.

The spindle on which the valve levers are pivoted is in two parts,
divided at the center. This is to allow two of the cylinders to run on
air whilst the other two are running on fuel, and, as can be seen from
the dial where the pointer indicates the position, in starting up,
whether astern or ahead, first two cylinders are put on air, then four
on air, next two on air and two on fuel, and finally all four on fuel.
This allows very rapid attainment of full speed.

The amount of fuel entering each cylinder can be regulated separately by
small hand wheels.

Below the fuel pumps are arranged three auxiliary pumps, two of these
being oil pumps for the oil circulation, whilst the other is of the
piston cooling water. On the left of the engine and driven in a similar
manner from the cross-head by links are three other pumps, one for the
circulating water and the other for the general water supply of the
ship.

Lubrication for the cylinders is furnished by 8 small pumps, just above
the water pumps, two oil pumps being provided for each cylinder. As the
supply pipe is divided into two parts, the oil reaches the cylinder at
four points in its circumference. Four oil pumps are provided for the
air compressor.

Four steel columns are provided for the support of each cylinder in
addition to the cast iron frame of the base, and by this means the
explosion stresses are transmitted directly to the bed plate. The cast
iron columns provide guide surfaces for the cross-head shoes. The guides
are all water cooled.

(64) The M.A.N. Diesel Engine.

The Maschinenfabrik Augsburg-Nürnberg, A. G., a German firm have built
some remarkably large Diesel engines both of the vertical and horizontal
types. The peculiar merits of the horizontal type of Diesel engine of
which the M.A.N. company are pioneers are still open to discussion at
present, but there is no doubt but what this type will be the ultimate
form of very large engines when certain alterations are made in the
design.

[Illustration:

Fig. 69. Horizontal M. A. N. Diesel Engine at the Halle Municipal
Plant.
]

[Illustration:

Fig. 70. High Speed Mirlees-Diesel Engine.
]

In Fig. 69 is shown a 2,000 brake-horse-power horizontal M.A.N. Diesel
engine of the four stroke cycle type which is installed at the Halle
Municipal Electricity Works, Halle, Germany. It is of the double acting
type with twin-tandem cylinders giving four working impulses per
revolution. This engine was installed in addition to the six producer
gas engines already in place to take the peak load of the station at
different times during the day, the gas engines meeting the normal
steady demand.

This firm has built many thousands of the vertical type of Diesel engine
of all sizes, and has recently installed 13 engines of 4,500 brake
horse-power for operating the Kreff tramways. The company is now
building cylinders giving outputs of from 1,200 to 1,500 brake
horse-power per cylinder, giving outputs of from 5,000 to 6,000
horse-power in tandem twin type engines. As will be seen from the cut,
the horizontal Diesel engine is remarkably free from complicated valve
gear.

(65) Mirlees-Diesel Engines.

The Mirlees-Diesel engine is built by the English firm, Mirlees,
Bickerton and Day both for stationary and marine service. A generating
plant consisting of two, 200 horse-power Mirlees engines direct
connected to Siemens generators has been installed in the municipal
plant at Dundalk as shown by Fig. 71. On test these units consumed 0.647
pounds of oil per horse-power at full load and 0.704 pounds per
horse-power at half load with a regulation of 3.24 per cent from full
load to no load. All of the engines built by this firm are of the four
stroke cycle type.

[Illustration:

Fig. 71. Mirlees-Diesels at Dundalk.
]

(66) Willans-Diesel Engines.

The Willans-Diesel engines built by the Willans and Robinson Company of
Rugby, England, are in sizes up to 400 brake horsepower, and run at
speeds up to 250 revolutions per minute. They are all of the four stroke
cycle type and are applied principally to the driving of electric
generators. The cut shows one of the four, 280 horse-power units
supplied to the Alranza Company and the Rosario Nitrate Works in South
America.

[Illustration:

Fig. 72. Willans Vertical Diesel Engine.
]

Unlike the Mirlees engine, the Willans has an individual frame for each
cylinder as in steam engine practice. Like the steam engine frame, the
bottom is left open for the inspection of the connecting rod ends and
the main bearings which is a most desirable feature. The air compressor
and pumps are arranged in a most compact form at the left end of the
crank-shaft from which the pipes may be seen issuing to the four
cylinders. The valves and over head gear are of the conventional type,
which, with the exception of a few minor details are the same as those
on the recently developed Sulzer-Diesel. The individual grouping of the
cylinder units has many desirable features and should, we believe, be
more extensively copied.

(67) Installation and Consumption of Diesel Plant.

An English gas-electric station was completed at Egham, England, that is
a good example of the changes that have been made recently in the
electricity supply abroad, with Diesel power.

The generating plant comprises two 94 K. W. Diesel engines built by
Mirrlees, Bickerton and Day, direct connected to single phase
alternators generating at 2,000 volts. The exciters are direct connected
to the main shaft, and the plant is capable of generating an overload of
10 per cent for two hours. Space has been left for the installation of
two more units of a larger size.

The following fuel consumption was guaranteed for a load of unity power
factor, and the official tests show slightly better figures than the
guarantee.

Full load 0.68 lb. oil per K. W. H.
Three-quarter load 0.72 lb. oil per K. W. H.
Half load 0.79 lb. oil per K. W. H.
Quarter load 1.15 lb. oil per K. W. H.

[Illustration:

Cross-Section Through Egham, England Municipal Plant.
]

Particular attention has been given to the water supply for the jackets
of the engines; the circulation being by two electrically driven, direct
connected centrifugal pumps, one of which is a spare. A Little Company’s
cooler has been installed, which consists of a horizontal cylindrical
chamber, the lower part of which contains water. In the tank are
arranged a number of concentric metal cylinders spaced about ¼-inch
apart, and in several sections, that are carried on a slowly revolving
shaft, driven from the fan shaft. The cylinders are all of the same
length, and are open at both ends.

The lower half of the cylinders dips into the water in the casing, and
as they revolve, a thin film of water on each side of the plate is
carried into the upper portion of the casing where it meets a blast of
cold air from the fan. The fan is driven from the circulating pumps, and
passes the air through the chamber in a direction opposite to that of
the water, baffles being placed so that correct circulation is
maintained.

The small loss is made up by connecting the ball cock in the tanks with
another tank charged from the works well by means of a self-starting
rotary pump, electrically driven. Very little power is required for the
pumps and cooler. Fuel oil is stored in a tank outside the building, the
oil being supplied to the tanks from an oil wagon by means of a small
hand pump.

Oil is taken from the tanks and forced into the engine room by a rotary
pump, from which it enters two graduated tanks located in the roof of
the station. The graduations on the tanks allow the consumption of oil
to be carefully recorded by alternately filling and emptying the two
auxiliary fuel tanks.

The entire building is electrically heated, and the kitchen of the flat
above the station is equipped with an electric cooking-stove for the use
of one of the engineers who make it his residence.

DIESEL HORSE-POWER FORMULA

P. A. Holliday, in the _Engineer_, derives a new formula for computing
the horse-power of the four stroke cycle, single-acting engine. For each
horse-power developed by these engines about 21,000 cubic inches of
displacement is necessary, per minute.

D = Cylinder bore in inches.
S = Stroke in inches.
M.P.S. = Mean piston speed in feet per minute.
R = Ratio of stroke to bore.
N = Revolutions per minute, then
√(B.H.P. × 2220)
D = ————————————————
M.P.S.

6 M.P.S.
Knowing the value of D, N = ————————
S

For high speed, low ratio (R), four stroke cycle engines, approximately
22,000 cubic inches displacement per minute is required.

√(2,330 B.H.P.)
D = ———————————————
M.P.S.

In both formulae, the air compressor for fuel injection is included.

(32) Semi-Diesel Type Engine.

In the “Semi-Diesel” Type Engine the oil is injected into the cylinder
at the point of greatest compression in the same manner as in the Diesel
engine, and like the Diesel it compresses only pure air. In regard to
the compression pressure, however, it stands midway between the pressure
of the Diesel engine and that of the ordinary “aspirating” type oil
engine, as the compression averages about 150 pounds per square inch.
While this is a much higher pressure than that carried by the ordinary
kerosene engine which compresses a mixture of kerosene vapor and air, it
is not sufficiently high to ignite the oil spray by the increase in
temperature due to the compression, but ignites the charge by means of a
red hot bulb or plate placed in the combustion chamber.

This type of engine is built both in the two stroke and four stroke
cycle types, the events occurring in the same order as in the two stroke
and four stroke Diesel types, that is, pure air is drawn into the
cylinder on the suction stroke (four stroke cycle) or is forced in at
the beginning of the compression stroke (two stroke cycle), and is
compressed in the combustion chamber. At the end of the compression
stroke, the fuel is injected against the red hot bulb or plate by which
the charge is ignited. Expansion follows on the working stroke after the
fuel is cut off, and release occurs at the end of the stroke.

Fuel oil is supplied to the spray nozzles by a governor controlled pump
having a variable stroke or by compressed air as in the Diesel engine,
making the supply of fire proportional to the load. A separate pump is
generally supplied for each cylinder, which is capable of developing a
pressure of about 400 pounds per square inch. Several of the Semi-Diesel
type engines have water sprayed into the cylinder for the purpose of
cooling the cylinder and piston, and as an aid in the combustion. This
water spray increases the output of a given size cylinder by the amount
of the steam formed by the heat of the cylinder and piston walls, and by
the increased rate of combustion. The amount of water supplied to the
cylinder is equal, approximately to the amount of fuel oil. The water
connection is made in the air intake pipe so that the water spray and
the intake air are drawn into the cylinder at the same time.

There is very little difference in the efficiency of the Diesel and
Semi-Diesel in favor of the true Diesel type for both have accomplished
records of a brake horse-power hour on .45 pound of crude oil in units
of the same capacity. Neglecting the question of efficiency the
Semi-Diesel has many advantages which are due principally to the
differences in compression pressures. Valve and piston perfection in
regard to leakage is not as essential with the semi-type as with the
Diesel, as the former is not dependent on compression for its ignition.
This means that the Semi-Diesel has a lower first cost and a lower
maintenance expense. Its low compression pressure makes starting
possible without the use of compressed air with engines of a
considerable horse-power. As the explosion pressure is much lower than
with the Diesel type there is less strain on the working parts and
lubrication is much more easily performed.

Compared with the ordinary type of kerosene engine the Semi-Diesel is
much more positive in its action as the oil is sure to ignite when
sprayed on the hot surface of the bulb or plate when under the
comparatively high compression. In the engine where the air is mixed
with the vaporized fuel before it is drawn into the cylinder, it is
difficult to obtain perfect combustion because of the uncertain mixtures
obtained on varying loads by the throttling method of governing. At
light loads the only difficulty encountered with the Semi-Diesel type is
that of keeping the igniting surface hot enough to fire all of the
charges.

In the majority of cases the two stroke cycle type of Semi-Diesel
engines compress the scavenging air in the crank chamber in the same way
that a two stroke cycle gasoline motor performs the initial compression,
although there are several makes that compress the air in an enlarged
portion of the cylinder bore by what is known as a “trunk” piston. This
initial compression determines the speed of the engine, the pressure
limiting the time in which the air traverses the cylinder bore and
sweeps out the burnt gases of the previous explosion.

(68) De La Vergne Oil Engines.

Two types of four stroke cycle oil engines are built by the De La Vergne
Machine Company, which differ principally in the method and period of
injecting the fuel into the cylinder. While both types compress only
pure air in the working cylinder, the oil is injected in a heated
vaporizer during the suction stroke in the smaller engine (type HA), and
is injected directly into the combustion chamber of the larger engine
(type FH) at the point of greatest compression. This fuel timing
classifies the type FH as a semi-Diesel, while type HA comes under the
head of that class of engines known as aspirators.

[Illustration:

76-a. Elevation of De La Vergne Oil Engine, Semi-Diesel Type. Class F
H.
]

Semi-Diesel (Type FH)

During the suction stroke, air is drawn into the cylinder through the
inlet valve located on the top of the cylinder head, and on the return,
or compression stroke, the air is compressed to about 300 pounds per
square inch in the combustion chamber. The compression heats the air to
a high temperature which is still further increased by contact with the
hot walls of a cast iron vaporizer D, shown by Fig. 76-b. At the
completion of the compression, the fuel is injected in a highly atomized
state by compressed air through the spray nozzle F, the spray being
thrown into the vaporizer.

[Illustration:

76-b. Cross-Section of Type F H, De La Vergne Oil Engine.
]

The vapor formed by the contact of the spray with the walls of the
vaporizer mixes with the compressed air in the combustion chamber and is
ignited at the instant of fuel admission by the combined temperatures of
the vaporizer and compression pressure.

As the fuel is not injected until the proper instant for ignition, it is
possible to obtain a relatively high compression without danger of the
charge preigniting. The oil is supplied to the nozzle by a fuel pump
under pressure. The atomizing air takes the oil at pump pressure and
performs the actual injection. Details of the spray valve are shown by
Fig. 76, in which the oil and air are entered at a pressure of about 600
pounds per square inch.

[Illustration:

Fig. 76. De La Vergne Spray Nozzle.
]

The air and oil enter the nozzle at opposite sides of the cylinder B
which fits snugly into the valve body A. As the air and oil proceed side
by side along the outside of B, they are forced to pass through a series
of chambers connected by a system of fine diagonal channels on the
surface of B which results in a very fine subdivision and intimate
mixture. The charge is admitted to the cylinder by a sort of needle
valve about one-half inch in diameter which is provided with a spring
that holds it closed on its seat as shown by C, in Fig. 76. The needle
is so constructed that it may be readily removed at any time for
inspection. The spray valve is located on the right hand side of the
valve chamber directly opposite the vaporizer and is operated by an
independent cam on the camshaft.

[Illustration:

Fig. 76-c. De La Vergne Governor and Fuel Pump.
]

The vaporizer consists of an iron thimble having ribs on the inside to
increase the radiating surface. In starting, the vaporizer is heated for
a few moments until it reaches the temperature necessary for vaporizing
the fuel, but after the engine is running, the blast lamp is removed and
the temperature is maintained by the heat generated by the combustion of
the successive charges. Since the fuel is ignited at the instant that it
makes contact with the vaporizer, it is possible to accurately adjust
the point of ignition by adjusting the position of the fuel cam on the
camshaft.

Air for spraying the fuel is supplied by a two stage air compressor that
is driven from the crankshaft by an eccentric. The air compressed by the
first stage is stored in tanks at about 150 pounds pressure for starting
the engine. The second stage compresses the air to about 600 pounds
pressure, but is correspondingly small in volumetric capacity since it
handles only enough air to spray the oil which amounts to about 2 per
cent of the cylinder volume. A governor controlled butterfly valve in
the air intake pipe regulates the amount of air taken in on the second
stage to suit the varying charges of oil injected at each load.

In starting by compressed air, a quick opening lever operated valve on
the cylinder head is used to admit air from the tanks to turn the engine
over until the first explosion takes place. If the vaporizer is
sufficiently heated by the torch, the explosion occurs during the first
revolution of the crank shaft. At a point about 85 per cent of the
expansion stroke, the exhaust valve is opened, and the products of
combustion are expelled into the atmosphere. When starting, the
compression may be relieved by shifting the starting lever from the
exhaust cam to the auxiliary starting cam provided for that purpose.

Speed regulation is affected by a Hartung governor, driven from the
camshaft, which actuates the oil supply pump through levers by shifting
the point of contact between the pump levers and its actuating cam. This
lengthens or shortens the stroke of the pump in accordance with the
requirements of the load. The type FH engines are built in both single
and twin cylinders ranging from 90 to 180 horse-power in the single
cylinder type to 360 horse-power in the twin.

Since the fuel injection of the smaller engine type HA differs from that
just described, it will be described separately in the following
section.

The De La Vergne Oil Engine (Type HA)

In the small four stroke cycle De La Vergne Oil Engine, the fuel is
injected into a heated vaporizer during the suction stroke in such a way
that the vapor and intake air do not form a mixture in the cylinder
proper. On the return stroke of the piston, the compression of the pure
air takes place which forces the air into the vaporizer and into
intimate contact with the oil vapor. This forms an explosive mixture
which ignites and forces the piston outwardly on the working stroke. The
release and scavenging are performed in a similar manner to that of a
four stroke cycle gas engine. Both the inlet and exhaust valves are of
the mechanically operated poppet type, and as both the inlet and exhaust
gases pass through the same passage, the entering air is heated to a
comparatively high temperature.

The injection pump receives the fuel from a constant level stand pipe or
tank, located near the engine and injects the fuel into the vaporizer
through a spray nozzle. The vaporizer is a bulb shaped vessel that is
connected with the cylinder through a short post and really forms a part
of the combustion chamber. Since no water jacket surrounds the
vaporizer, it remains at a high temperature and vaporizes the oil at the
instant of its injection. Because of the residual gases remaining in the
chamber, ignition does not occur until air is forced through the passage
by the compression. The air inlet valve and the fuel injection valve are
opened at the same instant by a cam lever that also operates the pump.

On the compression stroke, the air which is at a pressure of
approximately 75 pounds per square inch enters the vaporizer, and
ignition occurs, partly because of the increased heat due to the
compression and partly because of the supply of additional oxygen.
Internal ribs provided in the vaporizer greatly increase the heat
radiating surface and add to the thoroughness with which the atomized
oil is vaporized. Since no mixture of air and fuel takes place in the
cylinder proper, sudden changes in the load do not affect the ignition
of the charge as the heated surfaces are surrounded with comparatively
rich gas under all conditions.

Before the engine is started, the vaporizing chamber is heated to a dull
red heat by means of a blast torch in order to vaporize the oil for the
first stroke. As soon as the engine is running, the lamp is cut out and
the temperature is maintained by the heat of the successive explosions.
The combustion attained by this method is very complete even with the
heaviest fuels, and whatever carbon deposit is formed occurs in the
vaporizer from which it is easily removed. The contracted opening of the
vaporizer passage effectually prevents the solid matter from working in
the bore or valves.

A Porter-type fly ball governor maintains a constant speed at varying
loads by regulating the quantity of fuel supply to the vaporizer, the
air intake remaining constant. A by-pass valve, controlled by the
governor divides the oil supplied by the pump, into two branches, one of
which leads to the spray nozzle and the other to the supply tank. In the
case where all of the oil is not supplied to the vaporizer because of a
light load, the by-pass valve will return the surplus to the tank, thus
maintaining a constant pressure at the spray nozzle.

When operating under ordinary loads, the governor opens only the small
inside valve which regulates the amount of oil injected into the
vaporizer. But should the engine speed up, due to a sudden change in the
load, the governor will not only open the small valve but also the large
concentric valve, in which case all of the oil will return to the tank.
The makers guarantee the following speed variation limits under the
different loads.

Ordinary Variation 2½ per cent.
Full load to one-quarter load 4 per cent.
Full load to no load 5 per cent.

(69) Operating Costs of the Semi-Diesel Type.

As the semi-Diesel type engine will operate successfully on the lowest
grades of crude oils, with an efficiency that compares favorably with
the true Diesel type, the operating expenses are very much lower than
with the gas or gasoline engine. With the same fuels, the semi-Diesel
will show greater net saving than the Diesel with a low load factor, as
the fuel saving is not eaten up by the high first cost, and overhead
charges of the true Diesel. Western crude oils with a specific gravity
of .960 (16° Beaumé) are being used daily with this type of engine while
nearly every builder of the semi-Diesel type will guarantee results with
oils up to 18° Beaumé (.948 Specific Gravity). Fuel of this grade will
cost anywhere from 1½ cents to 3½ cents per gallon in tank car lots,
depending on the distance of the engine from the wells or refinery.

With fuel oil weighing 7½ pounds per gallon, an engine consuming .65
pounds per horse-power hour (a usual guarantee) at full load, the cost
of a horse-power hour delivered at the shaft will be .26 cent with fuel
at 3 cents per gallon. This the lowest fuel expense of any prime mover
even with steam or gas units of great power. In a twenty-four hour test
of a De La Vergne oil engine running on 19° Beaumé oil, the consumption
was considerably below the figure assumed above, being .508 pounds per
horse-power hour. Even the engine was exceeded in a test made on a 175
horse-power engine by Dr. Waldo, which gave a consumption of .347 pounds
of oil per horse-power hour with oil of .86 Specific Gravity.

The following is a tabulation of reports received by the De La Vergne
Machine Company from the Snead Iron Works, giving the cost of power at
their plant under actual working conditions extending over a period of
twenty-four months. The plant consisted of a 17 × 27½ inch De La Vergne
semi-Diesel type engine of 180 horse-power rated capacity, the load
factor being 54.2 per cent. The total power produced during the record
was 552,217 horse-power hours, with a working period of 588 days. Fuel =
28.8° Beaumé = 7.35 pounds per gallon.

TABULATION

Items Total Cost Cost per Cost per
K.W. Hour H.P. Hour
Fuel Oil, 38,211 gallons $859.75 $.00232 $.00155
Lubricating Oil 228.72 .00061 .00041
Miscellaneous Stores and Repairs 123.20 .00032 .00022
Labor and Attendance 1361.42 .00368 .00246
——————— ——————— ———————
Total $.00693 $.00464

Fuel oil used = .761 pounds per K. W. hour = .508 pounds per horse-power
hour. Computing from the load factor of 54.2 per cent, the cost of power
produced under the above conditions would be $9.30 per horse-power year,
or $13.98 per kilowatt year. This result is obtained by assuming that
the horse-power hours would be increased from 552,217 to 1,077,354, or
in proportion to the actual load factor, the period, of course being the
same in both cases.

(70) Elyria Semi-Diesel Type.

A type of semi-Diesel type oil engine has been recently developed by the
Elyria Gas Power Co., Elyria, O., that presents many features of
interest. It operates on the two stroke cycle principle, and with the
exception of the spray nozzle has no valves in the working cylinder. The
principle of the semi-Diesel type cycle as distinguished from the true
Diesel engine, was described in Chapter III, as having the following
characteristics. (1) Fuel injection. (2) Medium compression pressure.
(3) Hot plate ignition. (4) An efficiency approximating that of the true
Diesel type.

[Illustration:

Fig. 77. Working Cylinder of Elyria Oil Engine.
]

It is claimed that the change from the ordinary four stroke cycle Diesel
cycle has been accomplished with practically no loss of thermal
efficiency, and that the elimination of the many moving parts of that
type has done away with many of the operating difficulties. By the
introduction of a false piston end and an unjacketed cylinder head, the
loss of efficiency due to the lower compression is compensated by the
reduction of heat loss to the jacket water. Because of the high
temperature it is possible to burn the heaviest fuels with a maximum
pressure not exceeding 400 pounds per square inch, and without trouble
due to missed ignition at light loads. With a given cylinder capacity
this heating effect has increased the output about 75 per cent. The loss
due to the friction of the scavenging apparatus causes a fuel
consumption of approximately 10 percent more than a standard four stroke
Diesel.

Unlike the Diesel, this engine automatically controls the quantity of
injection air admitted to the cylinder at different loads, the air
corresponding with the amount of fuel injected. This is in marked
contrast with the Diesel engine which admits a constant volume of air at
all loads. In place of the usual crank-case compression of the
scavenging air met with in the ordinary two stroke cycle engine, the
initial compression in the Elyria engine is performed by a “differential
piston” which acts in an enlarged portion of the cylinder bore. This
construction increases the volumetric efficiency from 70 percent, in the
case of the marine type, to well over 90 percent, and it also does away
with the bad effect of the compression on the lubrication of the main
crank shaft bearings.

[Illustration:

Fig. 78. Compressor Cylinder of Elyria Oil Engine.
]

The working piston and differential piston as shown by Fig. 77 is
separate castings fastened together by four studs, and the piston pin is
carried by the differential piston which acts as a cross-head, taking
all of the side thrust from the main piston. The working piston is
easily taken from the cylinder by removing the cylinder head and the
four nuts that fasten it to the differential piston casting. The
displacement of the differential piston is approximately 1.9 times the
displacement of the working piston which is more than enough for
thoroughly scavenging the cylinder and supplying air for combustion. The
air suction is controlled by a piston valve which eliminates much of the
loss encountered in the marine type of two stroke cycle.

In the figure may be seen the separate or auxiliary piston head which is
bolted to the piston proper, a construction that greatly increases the
working temperature, and allows a symmetrical form of piston. By
removing the cap over the inlet port, it is possible to inspect the
condition of the six piston rings with removing the piston from the
cylinder. Because of the clean burning of the fuel lubrication is easily
effected by the force pump which supplies oil at three points around the
cylinder wall.

Three stages of compression are employed for providing the air for fuel
injection, the first stage being accomplished by the differential
piston, and the remaining two stages by a separate air pump driven by an
eccentric from the crankshaft. This cylinder also supplies the air for
starting the engine, the air being taken from the second stage and piped
to the storage tank. The suction of the second stage pump which receives
its air from the differential pump (first stage) is controlled
automatically so that it is possible to keep the supply tank at any
desired pressure regardless of the pressure or amount of air used for
the fuel injection. Air from the tank (at approximately 200 pounds
pressure) is piped to the suction side of the third stage air pump. In
this suction line is a valve, controlled by the governor, which
regulates the amount of air admitted to the injection nozzle, and also
the amount. This pressure at the nozzle will vary from 500 pounds per
square inch to 1000 pounds depending on the load and the nature of the
fuel. The high pressure air travels directly from the pump to the fuel
valve casing, and is equipped with a safety valve and pressure gauge.

The fuel pump is driven by a Rites Inertia Governor located in the
fly-wheel which varies the stroke of the pump plunger and gives a
correct proportion of fuel to the load. This type of governor has been
extensively used on high speed engines and is exceeding accurate. The
fuel pump may be disconnected from the governor drive, and operated by
hand when it is necessary to provide fuel for starting. The spray or
injection valve is operated by a cam, which lifts the valve at the
proper moment in a very simple manner. The valve proper is made of a
single piece of steel with openings of ample size, so that there is no
danger of clogging with the heaviest fuels. As the valve only lifts 1/16
of an inch, the amount of work required to operate the valve is very
small.

Starting is accomplished by spraying cold gasoline into the cylinder
through the fuel valve in the same manner that the heavier oil is fed
during operation, and the ignition is performed by a high tension coil
and batteries. No spark time device is used, so that a continuous shower
of sparks is thrown into the mixture during the starting period. Within
a minute after the engine is started, the ignition switch may be opened,
the gasoline cut off, and the heavy oil turned on for continuous running
on full load. Starting by an electric spark avoids the inconvenience and
danger of torch starting with a retort.

Cooling water is admitted around the compressor cylinder from which
point it goes to the working cylinder, and is there discharged. Less
water is required for this type of engine than for the ordinary gasoline
engine, for with the water entering at 60°F, only 3 gallons per
horse-power hour is used. With fuel oil weighing 7.33 pounds per gallon
the makers claim a fuel consumption of .65 pounds per horse-power at the
rated load. The amount of cylinder oil used does not exceed 1 pint per
100 horse-power hours, while the loss of the bearing oil is extremely
small because of the return system.

(71) Remington Oil Engine.

The Remington Oil Engine is a vertical oil engine operating on the three
port, two stroke cycle, and is an oil engine in the strict meaning of
the word, the oil consumed being introduced into the combustion chamber
as a liquid and gasified within this chamber.

The method of gasifying and igniting the charge of oil in the Remington
Oil Engine is unique. Only clean air unmixed with any charge, is taken
into the crankcase. This air is afterwards passed up into the cylinder
and compressed until its temperature has raised to a point high enough
to vaporize the oil which is injected into it. The charge of oil is then
atomized into this hot compressed air and turns immediately into a
vapor, which finds itself well mixed with the charge of air, comes in
contact with a firing pin recessed in the head, ignite and burns. This
method of having the oil well gasified and mixed with air before
ignition begins, prevents the formation of carbon which is formed when
oil not well gasified and mixed with air comes suddenly in contact with
very hot surfaces.

This perfect system of gasifying the oil has the effect not only of
preventing the formation of carbon in the cylinder, but also of
increasing the mean effective pressure and therefore decreasing the
amount of fuel necessary for doing a certain amount of work. The engine
passes through its cycle of operations smoothly, and does not have to be
constructed with excessive weight.

[Illustration:

Fig. 79. Cross-Section of Remington Oil Engine.
]

The Remington Engine is of the valveless type, delivering a power
impulse in each cylinder for each revolution of flywheel. The gases are
moved in and out of the cylinder through ports uncovered by the movement
of the piston, which itself performs also the function of a pump.

On the up stroke of the piston a partial vacuum is created in the
enclosed crankcase, causing air to rush in when the bottom of the piston
uncovers the inlet port seen directly under the exhaust port (23), Fig.
79. On the next down stroke this air is compressed in the crankcase to
about four or five pounds pressure per square inch. Meanwhile the
mixture of oil vapor and air already in the cylinder is burning and
expanding. When the piston approaches the end of its down stroke, it
uncovers the exhaust port (23), permitting the burnt charge to escape,
until its pressure reaches that of the atmosphere. Directly afterward
the transfer port on the opposite side of the cylinder is uncovered by
the piston, thereby allowing a portion of the air compressed in the
crankcase to rush into the cylinder, where it is deflected upwards by
the shape of the top of the piston and caused to fill the cylinder,
thereby expelling the remainder of the burnt charge. The piston now
starts upward, compressing the fresh charge of air into the hot cylinder
head. Near the end of the stroke, a small oil pump, mounted on the
crankcase and controlled by the governor, injects the proper amount of
oil through the nozzle (13), into the compressed and heated air.

[Illustration:

Fig. 80. Remington Spray Nozzle.
]

This oil is atomized in a vertical direction through a hole near the end
of the nozzle. It is therefore vaporized and gasified before there is a
possibility of its reaching the cylinder walls.

The spray of oil is ignited by the nickel steel plug (12), which is kept
red hot by the explosions because the iron walls surrounding it are
protected from radiation by the hood (11). By the burning of the oil
spray in the air the pressure is gradually increased and the piston
forced downward, this being the power or impulse stroke. Near the end of
the down stroke, the exhaust port is again uncovered and the burnt gases
discharged.

[Illustration:

Fig. 81. Fuel Pump and Mechanism of Remington Oil Engine.
]

The operations above described take place in the cylinder and crankcase
with every revolution. Each upstroke of the piston draws fresh air into
the crankcase and compresses the air transferred to the cylinder. Each
down stroke is a power stroke, and at the same time compresses the air
in the crankcase preparatory to transferring it to the cylinder by its
own pressure at the end of the stroke.

The same volume of air enters the cylinder under all conditions, and the
power is regulated by modifying the stroke of the oil pump, which may be
done by hand or automatically by the governor in the flywheel. A
separate fuel pump is provided for each cylinder when multiple cylinders
are used, making it absolutely certain that each cylinder shall receive
the same amount of fuel for a position of the control lever.

When starting the engine, the hollow cast iron prong rising from the
cylinder head is heated by a kerosene torch, and when hot, a single
charge of oil is admitted to the cylinder by working the hand pump. The
flywheel is now turned backward, thereby compressing the charge which
ignites the fuel before the piston reaches the highest position. After
being started the engine, the torch may be extinguished.

[Illustration:

Fig. 82. Two Cylinder Remington Oil Engine Direct Connected to Dynamo.
]

The governor is of the centrifugal type. It has an L-shaped weight,
pivoted to the piece attached to the flywheel. As the engine speed
increases, the weight tends to swing outward toward the flywheel rim,
and thereby moves the arm attached to it so as to shift the cam along
the crankshaft toward the left.

This cam turns with the shaft, and operates the kerosene oil pump.
According to the position of the cam on the shaft, it will impart to the
pump plunger a long or a short stroke, thereby injecting more or less
oil into the cylinder. The lever pivoted on the bracket moves with the
cam and is used for controlling the engine’s speed by hand. To stop the
engine the handle of the lever is pulled towards the flywheel, thereby
interrupting the pump action altogether.

The handle of the control lever can be fitted with an adjustable speed
regulator when required. This device is for use on marine engines to
enable the operator to slow down the engine. The speed regulator does
not interfere with the action of the governor but acts in conjunction
with it. Whatever the speed of the engine may be, it is under the
control of the governor. The engine can be controlled from the pilot
house if such an arrangement is desirable.

The fuel pump is made of bronze. The valves are made of bronze and are
designed with very large areas. The plunger is made of tool steel. A
bronze cup strainer is attached to the lower end of the pump to prevent
sediment or foreign matter from reaching the pump valves. As a result of
the care used in its construction, the fuel pump is not only very
sensitive in measuring the oil required by the governor, but is also
very strong and durable.

The nozzle through which the fuel is atomized into the cylinder is
thoroughly water jacketed to prevent the formation of carbon within the
nozzle. It is so constructed that the water jacket spaces and fuel
spaces can be opened for inspection.

Lubrication of all the important bearing joints is effected by a
mechanical force feed oiler, pressure feed oiler or by gravity sight
feed oilers, depending upon the service for which the engine is
designed. Oil is fed in this manner to the piston, the main bearings and
the crankpin bearings. The oil for the crankpin is dropped from a tube
into an internally flanged ring attached to the crank by which it is
carried by centrifugal force to a hole drilled diagonally through the
crank and crankpin to the centre of the bearing. This insures that all
the oil intended for the crankpin shall reach it. This feature, as well
as the use of the sight feed oiler itself, is in line with the best
modern high speed engine practice, and is an important factor in the
reliability of the engine.

CHAPTER VIII
IGNITION SYSTEMS

(73) Principles of Ignition.

It is the purpose of the ignition system to raise a small portion of the
mixture to the combustion temperature, or the temperature at which the
air and fuel will start to enter into chemical combination. When
combustion is once started in a compressed combustible gas it will
spread throughout the mass no matter how small the original portion
inflamed. The rate at which the flame spreads through the combustion
chamber depends upon the compression pressure, the richness of the
mixture, the nature of the fuel and upon the number of points at which
it is ignited.

In practice perfect ignition is seldom realized. This is due not only to
the ignition system itself but to poor mixture proportions, imperfect
vaporizing of the fuel, and low compression; all of which tend to a slow
burning mixture with the attendant losses.

The best ignition system will be that which will cause the ignition to
occur invariably at the point of highest compression and which will
supply ample heat to start the process of combustion with a cold
cylinder, imperfect mixtures, and low compressions. An efficient and
reliable ignition system is without a doubt the most important unit in
the construction of a gas engine. As ignition systems have improved and
become more reliable, so has the gas engine become more widely used and
appreciated, and in almost a direct proportion to these improvements.

Many ingenious ignition systems have been proposed, but only two of
these have met with any degree of success in practice; i. e., electrical
ignition and ignition by means of the hot tube.

Sponge platinum has the peculiar property of igniting jets of hydrogen
gas, or hydrocarbons, without the aid of heat; this is due to the
condensing effect of the platinum on these gases.

It was proposed to ignite the gaseous charge of the gas engine by means
of the platinum sponge (catalytic ignition) but the system proved a
failure because of the clogging of the pores in the sponge by fine
particles of soot.

Dr. Otto employed an open flame which was introduced into the mixture by
means of a slide valve. This met with only a fair measure of success.

Cerium, Lanthum and several other rare metals cause a considerable spark
when brought into contact with iron or steel. The objection to this
method was the expense of the Cerium plugs which required frequent
renewal.

The writer remembers a quaint attempt at firing the charge by means of a
piece of flint and steel; the failure of this is obvious.

The Diesel Engine, a great success from a thermodynamic standpoint, is
fired by means of the heat produced by the compression of air, the fuel
being sprayed into air which is compressed to several hundred pounds
pressure.

Mr. Victor Lougheed proposes ignition by means of a platinum wire
rendered incandescent by a current of electricity. The plan sounds
feasible, but we are still waiting to be shown.

Electric ignition is applicable to all classes of engines; in fact this
system made the variable speed engine as used on automobiles, etc., a
possibility, as accurate timing with the electric spark covers the range
from the lowest possible speed to speeds of 4,500 revolutions per minute
and over.

(74) Advance and Retard.

While the combustion of the mixture is extremely rapid under favorable
conditions, there is, nevertheless, a perceptible lapse between the
instant of ignition and the final pressure established by the heat of
the combustion. For this reason it is necessary that ignition should be
started a certain length of time before the pressure is required if we
are to expect a maximum pressure at a definite point in the stroke of
the piston. The amount by which the time of ignition precedes that of
combustion is called the =ADVANCE=, and is usually given in terms of
angular degrees made by the crank in traveling from the time of ignition
to time of maximum pressure. Since the pressure is always required at
the extreme end of the compression stroke, the degree of advance is
given as the angle made by the center line of the cylinder with the
center line of the crank at the instant of ignition. Should the advance
be given as 10°, for example, it is meant that the crank is still 10°
from completing the compression when ignition occurs.

Owing to variations in the richness of the mixture, and changes in the
compression pressure, due to throttling the incoming charge, the rate of
inflammation varies from time to time under varying loads. To keep the
maximum pressure at a given point under these conditions it is necessary
to vary the point of ignition to correspond with the increase or
decrease of inflammation. This variation of advance to meet varying
loads is approximated by the governor in some engines, and manually in
others. The advance of an automobile is an example of manual ignition
control. Should the point of ignition vary from the theoretical point it
will result in a loss of fuel and power, and for this reason the
ignition should be under at least an approximate control. A wide
variation in engine speed has a very considerable effect on the ignition
point as there is less time in which to burn the mixture at high piston
speeds, and consequently the ignition must be further advanced to insure
complete combustion at the end of the stroke. This fact is evident to
those who have driven automobiles.

Should the ignition occur too early, so that combustion is complete
before the piston reaches the end of the stroke, there will be a loss of
power due to the tendency of the pressure to reverse the rotation of the
engine. When starting an engine, over-advanced ignition will throw the
crank over in the reverse direction from which it is intended to go, and
will not only prevent the engine from coming up to speed but will prove
dangerous to the operator.

Due to the effects of inertia and self induction in several types of
ignition apparatus, a greater advance will be required than that
demanded by the combustion rate of the mixture. This sluggishness of the
apparatus in responding to the piston position is called ignition =LAG=.
The total advance required to have the combustion complete at the end of
the stroke is equal to the advance required by the burning speed plus
the ignition lag. Since lag is principally due to inertia effects, it is
much greater at high speeds than at low, and it therefore causes an
additional advance at high speeds. Causing the ignition to occur before
the crank reaches the upper dead center is called =ADVANCED IGNITION=,
causing it to occur after the piston has reached the upper dead center,
or when on the outward stroke, is called =RETARDED IGNITION=.

Ignition is retarded when starting an engine to prevent it from taking
its initial turn in the wrong direction. As the combustion takes place
after the compression, with the piston moving on the working stroke, in
retard, it is impossible for the pressure to force the piston in any
direction but the right one. Excessively retarded ignition will cause a
power loss and will also cause overheating of the cylinder and valves as
the combustion is slower.

(75) Preignition.

Preignition which is in effect the same as over-advanced ignition as due
to causes within the cylinder such as incandescent carbon deposits or
thin sharp edges in the cylinder that have become incandescent through
the heat of the successive explosions. Preignition is very objectionable
since it causes heavy strains on the engine parts and causes a loss of
power in the same way as over-advanced ignition. Any condition that
causes the preigniting of the charge should be removed immediately.

(76) Misfiring.

The failure of the ignition apparatus to ignite every charge is called
=MISFIRING=. This missing not only causes a waste of fuel and a loss of
power but it also causes an increased strain on the engine parts because
of the violence of the explosion following the missed stroke. The heavy
explosion is due to the fact that the stroke following the “miss” is
more thoroughly scavenged by the two admissions of the mixture than the
ordinary working stroke, and consequently contains a more active charge.

(77) Hot Tube Ignition.

A combustible gas may be ignited by bringing it into contact with
surface heated to, or above the ignition temperature. It is upon this
principle that hot tube ignition is based.

In practice this surface is provided by the bore of a tube which is in
communication with the charge in the cylinder, the outer end of the tube
being closed or stopped up. Around this tube is an asbestos-lined
chimney which causes the flame from the Bunsen burner to come into
contact with the tube and also prevents draughts of air from chilling
it.

A Bunsen burner is located near the base of the tube and maintains it at
bright red heat. The gas for the burner is supplied from a source
external to the engine. When the fuel used is gasoline, a gasoline
burner is used, which is fed from a small supply tank located five or
six feet above the burner.

During the admission stroke, the hot tube is filled with the
non-combustible gases remaining from the previous explosion, therefore,
the fresh entering gases cannot come into contact with the hot walls of
the tube and cause a premature explosion, before the charge is
compressed.

As the compression of the new charge proceeds, the fresh gas is forced
farther and farther into the tube and at the highest point of
compression it has penetrated far enough to come into contact with the
hot portion. At this point the explosion occurs.

The tube being of small bore, does not allow of the burnt gases mingling
with the fresh within the tube; the waste gases in the tube acting as a
regulating cushion. The distance of travel of the new mixture is
proportional to the compression, hence the explosion does not occur
until a certain degree of compression is attained.

The length of the tube required for a given engine is a matter of
experiment, as is also the location of the heated portion. High
compression naturally forces the mixture farther into the tube than low,
therefore the flame should come into contact with the tube at a point
nearer the outer end with high compression than with a low compression.

Shortening the tube causes advanced ignition, as the mixture reaches the
heated portion sooner, or earlier in the stroke, because of the
decreased cushioning effect of the residue gases in the tube.

The length of tube and location of maximum heat zone should be so
proportioned that combustion will take place at the highest compression.
Moving flame to outer end of the tube retards ignition. Moving the flame
toward the cylinder advances it.

While the hot tube is the acme of simplicity in construction, it is not
the easiest thing to properly adjust, as the adjustment depends on
compression, temperature of the tube, and the quality of the mixture.
Any of these variables may cause improper firing.

The hot tube is rather an expensive type of ignition with high priced
fuel, as the burner consumes a considerable amount of gas, and is
burning continuously during the idle strokes as well as during the time
of firing.

It is practically impossible to obtain satisfactory results from a hot
tube on an engine that regulates its speed by varying the mixture or
compression, as engines running on a light load will not have sufficient
compression to cause the mixture to come into contact with the hot
surface, the engine misfiring on light loads.

The tubes are made of porcelain, nickel steel alloy, or common gas pipe,
and are of various diameters and lengths.

All of these materials have their faults. Porcelain being very brittle,
is liable to breakage. Gas pipe burns out and corrodes rapidly. Nickel
alloy is not liable to breakage, is not so susceptible to corrosion as
iron, but is far from being a permanent fixture.

Timing valves are a feature of some systems of hot tube ignition, which
correct to a certain extent the irregularity of firing of the plain type
of tube.

The timing valve is introduced in the passage connecting the cylinder
and tube, and prevents the gas in the cylinder from coming into contact
with the heated surface until ignition is desired.

The valve is operated by means of mechanism connecting it with the crank
shaft. It is evident that with sufficient compression in the cylinder,
the time of ignition can be obtained with certainty.

This mechanism is rather complicated, and subject to wear, and the
advantage gained by the fixed point of ignition is offset by mechanical
complication and consequent trouble.

The action of hot tube igniters is erratic and their use is not
advisable unless under unusual conditions. The open flame used in
heating the tube is a constant menace, as it is surrounded by
inflammable vapors. This feature alone condemns it in the eyes of the
insurance underwriters; in many places the use of the hot tube is
prohibited both by the underwriters and city ordinances.

The above inherent defects of hot tubes are supplemented by breakage,
“blowing,” and clogging of the tube or passage with soot and products of
corrosion, each factor of which will cause misfiring.

In case of misfiring, after determining that the tube is not broken or
clogged with soot or dirt, see that the engine is being supplied with
the proper mixture; that you are obtaining the proper compression; and
that the Bunsen burner is delivering a bright blue flame on the tube at
the proper point. Never allow the burner to develop a yellow sooty
flame. A yellow flame indicates that insufficient air is being admitted
to the burner. Remember that an overheated tube is quickly destroyed,
and will cause misfiring as surely as an underheated tube. Regulate the
gas supply to the burner.

A small leak near the outer end of the tube will destroy the cushioning
effect of the burnt gas, and hence will cause premature firing of the
charge. Procure a new tube.

Many engines are provided with a sliding burner and chimney which allows
of some adjustment of the flame on the tube. In cases of persistent
misfiring, move the chimney one way or the other. It may improve the
ignition.

(78) Electrical Ignition.

Ignition by means of an electric spark is by far the most satisfactory
method as it makes accurate timing and prompt starting possible. It is
the most reliable of all systems and is easily inspected and adjusted by
anyone having even a rudimentary idea of electricity or the gas engine.
For this reason electric ignition is used on practically all modern
engines (with the exception of the Diesel types). The spark is caused by
the current jumping an opening or gap in the conducting path of the
current, and the ignition of the charge is obtained by placing this cap
in the midst of the combustible mixture to which the spark communicates
its heat.

The method of producing the spark gap, and the method by which the
current is forced to jump the gap, divides the electrical ignition
system into two principal classes:

(1) The =MAKE AND BREAK=, or =LOW TENSION= system.
(2) The =JUMP SPARK= or =HIGH TENSION= system.

In either system the spark is produced by the electrical friction of the
current passing through the high resistance of the gas in the spark gap.
The incandescent vapor in the gap formed by this increase of
temperatures causes the flash that is known as the spark. The
temperature of the gap depends principally upon the current flowing
through it, the amount of heat developed being proportional to the
square of the current.

There is of course a practical limit to the amount of current used in
the ignition apparatus to produce spark heat. The limit is generally set
by considerations of the life of the battery furnishing the current,
expense of generating the current, and the life of the contact points
between which the spark occurs.

The heat developed by an electric current is proportional to the amount
of resistance offered to its flow and the strength of the current
employed. The greater the resistance, the more heat developed.

The resistance of copper wire (the usual conducting path), being very
low causes little rise in temperature, but the air in the opening or
break has a resistance of many thousands of times the resistance of the
copper; hence the current passing across the opening spark or gap raises
the air to an exceedingly high temperature.

With a comparatively heavy current flowing across the break, the
temperature developed is high enough to boil or vaporize any metal in
contact with the spark or flame, rendering the metallic vapors
incandescent. With sufficient current, the ends of the wires which
constitute the break may be melted away.

For the successful and continuous operation of the engine it is
imperative that ends of the conducting path or terminals be made of a
metal of a high fusing point in order to withstand the heat of the spark
and also that the current be kept to as low a value as possible.

In actual construction the spark gap terminals are generally made of
platinum or platino-iridium, or an alloy of high fusing point. Iron is
sometimes used, but deteriorates rapidly. Nickel steel lasts longer than
common iron or steel but is not as durable as platinum or its alloys.

As the temperature of the electric spark or arc is approximately 7,500°
F., and the ignition temperature of an ordinary rich gas at 70 lbs.
compression is 1,100° F., it is evident that the quantity of current for
ignition may be kept to an exceedingly low value. High compression
increases the resistance of the spark gap, and requires higher
electrical pressure to force a given current across a gap of given
length.

(79) Sources of Current.

The electric current that causes the ignition spark is usually generated
or supplied by one of the three following methods:—

1. By the primary battery which converts the chemical energy of metal,
and some corroding fluid, into electrical energy, by chemical means.

2. By the magneto or dynamo that converts mechanical work or energy into
electrical energy through the method of magnetic induction.

3. By the storage or secondary battery which acts as a reservoir or
storage tank for current that has been generated by either of the two
above methods. A storage battery simply returns electrical energy that
has been expended on it by an external generator. A storage battery does
not really generate electricity but as it is often used as a source of
current for an ignition system, we will consider it as a generator.

Current producers that convert chemical or mechanical energy into
electrical energy are called primary generators, and are represented by
the primary battery and dynamo. The above methods are used for
generating current for either the high or low tension systems.

Electricity may also be produced by friction, but as such current is
without heat value it is not used for ignition purposes. Electricity
produced by friction is called static electricity.

Primary and storage batteries always deliver a direct or continuous
current of electricity, that is a current which flows continually in one
direction. Dynamos are usually made to furnish a direct current, but can
be built to deliver either direct or alternating.

Alternating current, unlike the continuous current, changes the
direction of its flow periodically; flowing first in one direction and
then in the other, the flow alternating in equal periods of time.

Magnetos being a special form of dynamo can furnish either class of
current, but with few exceptions are built for generating alternating
current.

Either current may be used for ignition purposes for either high or low
tension systems.

Alternating current has several advantages not possessed by the
continuous current, when used for ignition purposes. The principal
advantages are:

1. Alternating current does not transfer the electrode metal of contact
points, and consequently causes less trouble with vibrators and “make”
and “break” ignitors.

2. Magnetos generating alternating current are less complicated, have
fewer parts to get out of order, and are cheaper to keep in repair.

3. Alternating current is not liable to burn out spark coils or overheat
with an excessive voltage.

4. Alternating current generators can be used at any speed without the
use of governors.

[Illustration:

43-a. The Esselbé Rotary Aero Motor. Four Pistons are Contained in the
Ring Shaped Cylinder at the Left Which are so Connected with Cranks
and Gears in the Gear Box that the Pistons and the Cylinder Rotate
in Opposite Directions. As the Pistons Rotate they also Oscillate
Back and Forth in Regard to One Another, so that the Working and
Compression Strokes are Performed. From Aero London.
]

When installing an ignition system give due consideration to the
reliability of the source of current. The gas engine is no more reliable
than its source of current. Failure of the current means the failure of
the engine.

(80) Primary Batteries.

Current is produced in a primary battery by the chemical action of a
fluid known as an =ELECTROLYTE= upon two dissimilar metals or solids
known as the electrodes. One of the electrodes, the negative, is usually
made of zinc which is more readily attacked by the electrolyte than the
positive electrode. As the metal of the negative electrode is dissolved
and passes into the solution during the process of current generation,
the electrolyte is also exhausted. The production of current is
accompanied by the liberation of hydrogen gas from the electrolyte from
which it is displaced by the zinc taken into solution.

When the electrodes are immersed in the electrolyte, and the outer ends
of the electrodes are connected with a wire, a current will flow from
the positive electrode to the negative through the wire, and from the
negative to the positive electrode through the fluid. It will be seen
that to complete the circuit between the electrodes it is necessary that
the current flows through the electrolyte.

Electrical energy is actually generated in the primary battery by the
chemical combustion of the negative electrode in the same way that heat
energy is developed by the burning of a fuel.

By connecting the binding posts of the electrodes to the two wires of
the external circuit, a current will flow through the circuit as long as
the electrodes remain undissolved, or until the positive electrode is
covered with hydrogen gas bubbles.

The bubbles of gas tend to insulate the positive electrode from the
electrolyte or fluid, thus breaking the circuit through the fluid, and
stopping the flow of current. This action is known as polarization.

When a battery is polarized, the only remedy is to disconnect it from
the circuit and allow it to rest or recuperate. The greater the current
drawn from a battery, the more rapid the polarization, and it is evident
that if the battery is to be used for long periods, polarization must be
eliminated, or the current must be considerably reduced in volume. A
battery that delivers a small current has a much greater capacity in
ampere hours than a battery that has a higher rate of discharge. The
greater the discharge rate the longer must be the rest periods.

A battery that is designed for continuous service, or for delivering
heavy currents of long duration, is called a closed-circuit battery.
Polarization is eliminated in closed circuit batteries by various
methods, the usual methods being to place some substance in the
electrolyte that will destroy the hydrogen film; or by packing some
solid oxidizing material around the positive electrode that will absorb
the hydrogen; or by making the positive electrode of some material that
will destroy the hydrogen as soon as it is developed.

Batteries that are capable of being operated only for short periods, on
account of polarization, are called open circuit batteries. Open circuit
batteries are cheaper and more simple than closed circuit batteries. For
ignition purposes, a battery is made that is a compromise between the
closed and open circuit cells, this being a battery in which the
polarization is only partially suppressed. As the demand for current on
an ignition battery is small with comparatively long rests between
contacts, the compromise battery answers the purpose and is fairly
cheap.

All primary batteries are in reality wet batteries, for the reason that
it would be impossible to cause a chemical reaction and a current with a
dry electrolyte. The action of dry and wet batteries is identical.

There are many types of wet battery in use for various purposes, but few
of them are adapted for gas engine ignition because of a tendency to
polarize or because of the cost of maintenance.

All wet batteries are not suitable for portable or automobile engines
because of the slopping of the liquid electrolyte and the danger of
breaking the containing jars. Their weight and bulk is also a drawback.

If the electrolyte or the electrodes be made of impure material local
currents will be generated. These currents decrease the life of the cell
without producing any useful current in the ignition circuit. Due to the
deteriorating effects of the local currents, batteries standing idle for
several months will often be found to be completely discharged and
worthless without having done any useful work. In the better grade of
cells this loss is reduced to a minimum.

A type of wet battery using a solution of caustic soda for an
electrolyte, and having zinc and copper oxide electrodes, is extensively
used for stationary ignition purposes, and is the most satisfactory type
of wet cell for continuous work with this class of engine. The caustic
soda battery is of the =CLOSED= circuit type, and is capable of
furnishing a strong uniform current without danger of polarization.

The hydrogen bubbles which cause polarization are oxidized or eliminated
by the copper oxide electrode as soon as they are formed. The hydrogen
combines with the oxygen of the copper oxide forming water.

The copper oxide is gradually reduced to metallic copper by the reaction
with the hydrogen, and in the course of time requires renewal. The
copper oxide element is rather expensive and cannot be obtained as
readily as the electrodes used in other cells.

It will be noted that both electrodes are consumed in the caustic
battery, the consumption of the zinc furnishing the current, and the
reducing of the oxide furnishing the chemical energy for depolarizing
the cell.

(81) Dry Batteries.

Dry batteries are by far, the most convenient and economical form of
primary battery to use, for there is no fluid to slop and leak, the
first cost is low, the output is large for the weight, and last but not
least, the cell can be thrown away when exhausted without great monetary
loss. This does away with the expense and annoyance of changing wet
cells, a factor that will be appreciated by those that are far from a
source of chemical supplies. Since the advent of the automobile the use
of dry cells has extended so that they may be obtained in almost any
country town or village.

While the cell is not dry, strictly speaking, the solution is held in
such a way that it cannot slop around in the cell nor leak out of the
seal. The only fault of a dry cell is its tendency to deteriorate with
age because of the constant contact of the electrolyte with the
electrodes.

The negative electrode of the dry cell (zinc) is in the form of a cup
which serves as a containing vessel for the electrolyte and the
depolarizer.

The electrolyte is usually composed of a solution of ammonium chloride,
with a small percentage of zinc sulphate, this fluid being held by some
absorbent material such as blotting paper, or paper pulp.

The electrolyte is applied to the electrodes by means of the saturated
blotting paper, which is also used to line the zinc container, thus
providing insulation between the electrodes.

A rod of solid carbon which forms the positive electrode is placed in
the center of the container, and the space between the rod and the zinc
is packed solidly with granulated carbon, the blotting paper lining
preventing contact of the zinc with the carbon.

Pulverized manganese dioxide is mixed with the granulated carbon for a
depolarizer.

[Illustration:

Brookes Four Cylinder Gasoline Engine Direct Connected to Dynamo.
]

After the zinc container is filled with the electrolyte and pulverized
carbon, the top of the container is closed hermetically by means of
sealing wax. Granulated carbon is used for it presents a large surface
to the electrolyte, reduces the internal resistance of the cell, and
therefore increases the current output of the battery.

As soon as the battery starts generating current, polarization begins,
with the liberation of hydrogen gas. If the cell is discharged at a high
rate, the manganese dioxide will be unable to absorb all of the gas, and
consequently pressure will be erected within the cell. The greater the
rate of discharge, the greater will be the amount of hydrogen set free,
and the higher the pressure.

If a short circuit exists for any length of time, the pressure of the
excess hydrogen will speedily ruin it, as the cell will puff up, or even
burst under the pressure. If the rate of discharge be kept so low that
all of the gas will be absorbed by the manganese, as soon as generated,
the cell will furnish a steady current until the elements of the cell or
the electrolyte are exhausted.

The steady current limit, or non-polarizing limit is about one-half
ampere and if long life of the cell is expected, the current drain
should be less than this amount. A good spark coil will develop a
satisfactory spark on a quarter to one-half ampere, so that the demand
of a good coil is well within the safe limits of battery capacity. The
voltage of the average dry cell when in good condition is 1.5 volts on
open circuit. When the cell is old or exhausted, the voltage falls
rapidly when any demand for current is made on the cell, and the voltage
also varies with the rate of current flow, the voltage decreasing with
an increase of current.

As there is not much difference in voltage between a new and old cell
when on open circuit, it will be seen that the ammeter giving the
current output will give a more accurate determination of the condition
of the battery. The voltage is independent of the size of cell.

The battery showing the greatest amperage is not necessarily the best
for general use, as cells having an unusually high current capacity are
generally short lived. The strong electrolyte used in high ampere
batteries causes them to burn out or deteriorate rapidly when not in
use.

Under ordinary conditions, a correctly proportioned No. 6 ignition cell
should show a current of from fifteen to twenty amperes on short circuit
when the cell is new, although higher results may be obtained safely
with some makes of cells.

While the voltage is the same for all sizes of batteries, and depends on
the material used in the construction, the amperes increase with the
size of the cell, and the area of the electrodes.

If a cell does not show more than ten amperes on short circuit, it
should be thrown out and another substituted for it, as the cell is
liable to go out of commission at any minute when reaching this point of
exhaustion.

A small battery testing voltmeter or ammeter should be in the kit of
every gas engine operator using a battery for ignition, as the exact
condition of a vital part of the power plant can be determined quickly
and with accuracy. For dry batteries an ammeter is preferable; for
storage batteries a voltmeter must be used.

When buying dry batteries insist on having new, fresh cells, as any
battery depreciates in value with age. Never take a cell without testing
it, as it is the practice of dealers to work off their old stock on
unsuspecting customers. Examine the battery closely for the makers’
dates, and if the battery is several months old, it is probable that the
electrolyte is dried up or that the electrodes are wasted through long
continued local action. As heat stimulates chemical action in the cell,
they should be stored in a cool place to retard the wasting action as
much as possible. Under all conditions, the cell should be kept dry,
since the moisture that is deposited on the cell forms a closed circuit
for the current which soon exhausts the battery. Cold retards chemical
action in the cell and consequently reduces the output in zero weather
to such an extent that starting is frequently impossible.

Multiple cylinder engines exhaust a battery quicker than those with a
single cylinder, as there are more current impulses in a given time and
consequently more current is used. A battery may be compared with a
bottle that holds a certain quantity of fluid. If the water is allowed
to drip out slowly it will last for a long time, but if allowed to flow
in a continuous stream will soon be exhausted.

With badly designed or poorly adjusted spark coil, the demand on the
batteries is greater than with one that is in proper condition. An
engine that runs continuously exhausts a battery faster than one that is
run at long intervals. Always open the battery switch when the engine is
to be idle for any length of time, as the engine may have stopped with
the igniter in contact, allowing the battery to expend its energy
uselessly.

Test batteries immediately after a run, as the batteries will recover
after standing a while, and will show a fictitious value.

A weak, partially exhausted battery will cause a poor spark that will
result in misfiring or a loss of power. It is poor economy to attempt
running an engine on a weak battery. An engine may run on a weak battery
for a short time, and then gradually decrease in speed until it comes to
a full stop. Misfiring is generally in evidence as the engine dies down.
In case of an emergency, weak batteries may be made to run an engine of
an automobile or boat to its destination, by stopping the engine
frequently and allowing the batteries to recuperate during the idle
periods. A battery that is temporarily weakened by hard service or by a
temporary short circuit will usually revive or partially recover its
strength if allowed to “rest” for a short time until the hydrogen is
absorbed by the depolarizing material. The life of a dry cell can be
extended for a few hours by punching a hole in the sealing wax on the
top of the battery, and pouring water, or a solution of water and
sal-ammoniac into the cell. This will reduce the internal resistance and
increase the current. The batteries will run under these conditions for
a short time only, and new cells should be procured at the earliest
possible moment. No old cell can be made as good as new by any method.
Never drop the cells on the floor nor subject them to hard usage
mechanically, for if the active material is loosened, the current output
will be reduced. A short circuit through a closed switch with the engine
stopped or a loose dangling wire will put the cells beyond repair.

If the binding screw on the carbon electrode does not make good contact
with the carbon, tighten it to decrease the resistance. Fasten the
connecting wires firmly under the binding screws and keep the
connections clean.

In the absence of an ammeter, a rough estimate of the condition of the
cell may be made by fastening a short wire tightly in the zinc binding
post, and touching the carbon surface lightly and intermittently with
the free end of the wire. When contact is made with the free end of the
wire, a small puff of smoke will arise and a red spark will be seen if
the cell is in good condition.

Sometimes the contact made on the carbon will produce only a small black
ring on the surface of the electrode. This indicates a battery that is
nearly exhausted, and one which is good for only a few more hours of
service.

When a number of cells are connected together in such a way that they
collectively form a single source of current, the group is called a
battery, and the resulting voltage and amperes of the group depends on
the way in which the cells are interconnected.

It is possible to connect the cells of a battery in such a way that
total voltage of the group or battery is equal to the sum of the
voltages of the individual cells. A battery connected in this manner is
said to be connected in series. While the voltage of a battery is
increased, by series connection, the number of amperes is the same as
that given by a single cell, the same current flowing through the set.

(82) Series and Multiple Connections.

Fig. 86 shows the cells connected in series, the carbon terminal of one
cell being connected to the zinc terminal of the second. The carbon of
the second cell is connected to the zinc of the third, and so on
throughout the series, the two remaining terminals of the battery being
connected with the ignition circuit. The number of watts or power
developed by the group is equal to the sum of the outputs of the
separate cells. If the voltage of each cell shown in diagram is 1.5
volts, the total voltage of the group of five cells will be 1.5 × 5 =
7.5 volts, and if the current of a single cell is 15 amperes, the
current output of the group will be 15 amperes, or the same as that of a
single cell. Almost all ignition apparatus now on the market requires
six volts for its operation, so with cells having a voltage of 1.5 volts
such apparatus would call for four cells in series, as 6 ÷ 1.5 = 4.

[Illustration:

Fig. 86. Five Cells in Series.
]

Owing to the increase of internal resistance caused by series
connections it is usual to add one more cell than is theoretically
required, making a group of five cells to supply the six volts required.
A large number of cells will give a hotter spark than a smaller, but the
excessive current causes the contact points of the igniter or vibrator
to burn off rapidly and also hastens the destruction of the cells
themselves.

Batteries connected in such a way that the total amperes of the group is
increased without increased voltage are said to be connected in multiple
or parallel. When batteries are connected in multiple, the total current
in amperes is equal to the sum of the amperes delivered by the separate
cells; and, while the current in amperes is increased by multiple
connection, the voltage of the group remains equal to that of a single
cell.

If each cell connected in multiple has an electromotive force of 1.5
volts, and can deliver 15 amperes, the total current delivered by this
system of connection will be 15 × 5 = 75 amperes with five cells, and
the electromotive force will be 1.5 volts as in the case of the single
cell. By connecting batteries in multiple, the resistance is reduced,
allowing a maximum flow of current. The demand on the individual cells
is reduced by multiple connection, as each cell only furnishes a small
part of the total current. The greater the number of cells, the less
will be the current required per cell, with a given total current. As
the life of a battery depends entirely upon the rate at which it is
discharged, it is necessary, for economical reasons, to keep the current
per cell as small as possible, therefore the multiple system would prove
of value as it reduces the load to the smallest possible limit. Enough
cells should be placed in multiple to reduce the current to less than a
quarter of an ampere per cell. The cells shown will not have sufficient
voltage to operate ordinary ignition apparatus requiring a potential of
six volts, hence the multiple system must be modified in order to have
an increased voltage, and at the same time secure the advantages of
multiple connections.

(83) Multiple-Series Connections.

A compromise is affected by the multiple series system of connections in
which are combined the advantages of both the series and multiple
systems of connection.

This arrangement allows sufficient voltage to operate 6 volt apparatus
and at the same time reduces the rate of discharge on the individual
cells. The series-multiple battery shown in the diagram 88 consists of
four groups of batteries connected in multiple, each group of which
consists of five cells that are connected in series. The current and
voltage in the various branches is shown in the diagram. The
series-multiple system is adapted for use with multiple cylinder
engines, as engines with more than one cylinder cause a severe drain on
the ignition system. Arranging the series groups in parallel increases
the life and efficiency of the cells. If an efficient coil is used, the
drain of a single cylinder is not too great to be met with a single set
of series cells. If possible the set should be provided with a
duplicate, so that the load could be transferred from one set to the
other at proper intervals by means of a double throw switch.

With a single set of batteries in series the working life of the cells
will be approximately twenty hours under ordinary conditions. With four
groups of four cells in series, the life of the cell will be
approximately 160 hours, or eight times the life of the single set under
similar conditions.

While the cost of the cells will be only four times that of the single
set, it will be seen that the cost of battery upkeep is halved by
reducing the demand on the cells.

Sometimes duplicate sets of series multiple connected batteries are used
for heavy duty engines, the engine running on one set for a while and
then on the other, allowing the first set to thoroughly recuperate
before it is again thrown in service, by means of the double throw
switch.

When batteries are multiple or series-multiple connected they should be
of the same size and make and of the same voltage. If the cells are of
different voltages useless local currents will circulate among the
cross-connections, shortening the life of the battery and reducing the
output.

[Illustration:

Fig. 88. Cells in Multiple Series.
]

In connecting a dry cell use a good grade of rubber insulated wire,
preferably wire with a stranded conductor, as it is less liable to break
or loosen at the binding screw of the battery. Carefully remove the
insulation from the end of the wire that is to be fastened under the
binding screw of the battery. Scrape it until it is bright and perfectly
free from dirt before fastening it in the battery terminal. Never allow
a dirty or corroded connection or a loose wire to exist. An open battery
circuit or loose connection will stop engine suddenly, or will prevent
starting.

The battery connections should be screwed down tight with the pliers,
care being taken that the screws are not broken by the tightening
process. See that frayed ends of the wire do not project beyond the
binding screw to which they are connected and make contact with other
cells or metal objects. Be sure that no insulation gets between the
contact braces of the binding screw.

(84) Operation of Dry Cells.

The following hints should be observed to obtain the best results with
dry cells.

(1) Never remove the paper jackets from the cells.

(2) Never lay tools or other metallic objects on top of the cells for
this will cause a “short” that will quickly exhaust them.

(3) Do not connect old and new cells together, especially with the
multiple-series system of connections, for the old cells will limit the
output of the new, or else will cause cross-currents that will exhaust
all of them.

(4) When trouble develops in the battery, test each cell separately and
remove the faulty cells. Do not reject all of the battery because of one
or two dead cells.

(5) Place the cells in a wooden box that will protect them from dirt or
moisture, and if possible divide the box off into pigeon holes with a
cell in each hole. For the best protection against moisture, the box
should be boiled in paraffine.

(6) Provide a battery switch on the box that will cut both leads from
the cells completely out of circuit when the engine is stopped.

(7) Never place a dry cell in a box that has contained storage cells
unless the box has been thoroughly washed out, for the residual acid of
the battery will destroy the zinc elements.

(8) Make all connections firmly with well insulated wire and take care
that the wire does not make contact with any part of the battery except
that to which it is connected.

(9) Keep the battery dry.

(85) Storage Batteries.

The purpose of the storage battery is to store or accumulate the current
generated by a dynamo until so that the current will be available when
the dynamo is not running. A storage cell does not “store” current in
the same way that water is held in a tank, but returns the energy
expended on it through the chemical changes caused in the cell by the
current.

When the charging current passes through the storage battery chemical
changes are produced in the electrodes and electrolyte, and the energy
expended on the cell is in the form of latent chemical energy, in which
state it remains until the electrodes are connected with one another by
a wire or some other conducting medium. When the electrodes are
connected through an external circuit, the electrolyte acts on the
electrodes causing them to assume their original composition. As they
pass into their previous chemical condition the latent chemical energy
is converted into electrical energy. The current thus produced may be
used in the same way as in a primary cell.

When discharging, the action of a storage battery is similar to that of
a primary battery, the current being produced by the action of a fluid
on two dissimilar electrodes. Instead of supplying new elements when the
battery is discharged, as in the case of the primary cell, the elements
are brought back to their original state by passing a current through
the cell in the opposite direction to that of the discharge.

There are several combinations of materials which may be used in the
making of storage battery electrodes and electrolytes, but with the
exception of the lead sulphuric battery and the new Edison battery none
have proven a commercial success.

The most common type of storage or secondary cell is the lead-sulphuric
type in which the electrolyte is dilute sulphuric acid and the
electrodes are lead plates, covered with a chemical composition known as
the active material. These plates usually consist of a lead grid, or
lattice frame in the pockets of which is pasted the active material. The
pockets or lattice bars of the plates are for the purpose of supporting
the active material which is of a weak and spongy nature. The active
material on the positive plate is usually litharge, while that on the
negative plate is red lead.

After charging, the active material on the positive plate is changed to
lead peroxide by the action of the current, and the active material on
the negative plate is changed into spongy metallic peroxide. The
composition of the active material on the plates determines the
direction of flow of the discharge, or secondary current. The current
flows from the positive plate to the negative through the external
circuit.

When fully charged, and in good condition, the positive and negative
plates may be readily distinguished by their colors, the positive plate
being a dark brown or chocolate color, and the negative a slate or grey
color.

The positive active material is hard, while the negative may be easily
cut into by the finger nail. The density of the material changes
slightly with the charge, as the material expands during the discharge.

The problem of holding the active material securely to the plates during
expansion and contraction has been a hard one to solve, each
manufacturer having some favorite form of grid or material plug to which
he pins his faith. While great improvements have been made in this
direction, it is certain that we have not yet reached perfection. Loose
active material will cause short circuits and will reduce the output of
the cell; loose active material frequently ruins a cell.

The current capacity of a storage battery depends on the area of the
plates or electrodes, and in order to increase the capacity of a
battery, and consequently the area, it is usual to use a number of
plates connected in parallel. A number of small plates of a given area
are to be preferred to two large plates of the same area, as the battery
will be of a more convenient size.

Customarily there is one more negative plate than positive, so that the
extreme end plates in a cell are negative, as the positive and negative
plates alternate with each other when assembled.

An ignition battery usually consists of two negative plates and one
positive. Cells used for power purposes have as high as sixty plates.

A single cell of storage battery should show about two volts when fairly
well charged. If more than two volts are desired more cells should be
connected in series. The total voltage will be equal to the number of
cells, in series, multiplied by the voltage per cell. The voltage per
cell should never be allowed to drop below 1.7 volts, as the cell is
likely to be destroyed when operated with a low voltage. Recharge as
soon as the voltage drops to 1.8 volts.

The ordinary six volt ignition battery consists of three separate cells
connected in series, which are encased in one protecting box.

The plates are prevented from touching each other within the cell by
means of a perforated sheet of hard rubber that is inserted in the space
between the plates. The perforations allow the liquid to circulate
between the plates.

The storage battery is furnished as standard equipment with several well
known gas engine builders, and its use is advocated by nearly all. When
used in connection with a low tension direct current magneto two
independent sources of current are at hand, either of which will ignite
the engine in an emergency.

With the magneto-storage battery combination, it is possible to obtain a
few small lights at any time, whether the engine is running or not, and
the engine is always ready to start on the first “over” with the storage
battery and a good mixture.

If a magneto is not used, difficulty is sometimes experienced in
obtaining a suitable source of charging current, as many localities do
not possess direct current plants. Batteries may be charged from the
direct current exciter in an alternating current station, or may be
charged by an alternating current rectifier such as is used by
automobile garages.

The principal objections to the storage cell are: inconvenience of
charging; sulphating of cell when standing without a charge; ease with
which the cell is ruined by short circuits; the damage caused by the
spilling of the electrolyte; and the fact that the cell gives no warning
of failing or discharged condition.

Since the composition of the plates depends on the direction in which
the current flows through the cell, it is obvious, that an alternating
current which periodically changes its direction of flow will first
charge the plates and then discharge them alternately. The result of an
attempt at charging with alternating current would be that the plates
would be in the same or a worse condition in a short space of time than
they were at the beginning. In charging a storage cell care should be
taken to determine the character of the current, especially when the
cell is to be charged from a magneto. When under charge, the cell is
connected to the charging circuit in such a way that the current flows
backwards through the cell or in a direction opposite to that when the
cell is discharging.

(86) Care of the Storage Cell.

The storage battery should never be left in an uncharged condition with
the acid electrolyte in the cell, for the solution will quickly attack
the uncharged plates and combine with them to form lead sulphate. As
lead sulphate has a high electrical resistance and is insoluble in the
electrolyte the sulphate coating will reduce the output or if present in
excess, ruin the cell. The sulphate appears as a white coating on the
surface of the plates. The only remedy for this condition at the hands
of the average engine operator is a prolonged charge, or over charge, at
a slow rate. There are several chemical processes but they are too
complicated for the average man.

As sediment collects on the bottom of the battery jars, and is liable to
cause a short circuit, the plates should be held about half an inch from
the bottom of the jar. Care should be taken that the cells of the
stationary type of battery are kept dry and clean. Do not allow dirt to
drop into the solution as it is liable to destroy the cell.

A volt meter should be used to determine the condition of the battery,
and should be used frequently. An ammeter should never be used on a
storage battery, as it is of very low resistance, and would probably
cause a rush of current that would destroy both the battery and the
instrument.

Never short circuit a storage battery, even for an instant, as excessive
current will cause the plates to buckle, or will loosen the active
material on the plates.

The plates are immersed in the electrolyte, which should cover the
entire plate or active surface. If the solution does not cover the
plate, the capacity of the cell will be reduced. Plates that are
partially covered with solution deteriorate rapidly from “sulphating.”
This is caused by the air and acid acting on the damp inactive portion
of the plate.

Usually the electrolyte consists of a dilute solution of sulphuric acid
and water, but in some ignition cells the solution is “solidified” by
some substance to about the consistency of table jelly. The object of
this thickened solution is to prevent the solution from slopping and
leaking when the battery is being transported.

The solution used in a storage battery is exceedingly corrosive in its
action, and if spilled on metal or wood will destroy it immediately.
Care should be taken in handling the electrolyte.

A cell should never be discharged below 1.7 volts for below this point,
the plates are likely sulphate. When the solution is replaced by fresh,
or water is added for the purpose of restoring the electrolyte to its
original level, use only distilled water, free from metallic salts and
suspended matter.

Many people “test” their cells by snapping a wire across the terminals
to “see if there is a good spark.” Nothing could be more injurious to
the battery, and as this test indicates nothing, the practice should be
discontinued. Make all your tests either with a hydrometer or a
voltmeter, the latter is preferable in the average case.

The electrolyte is a solution containing approximately 10% of chemically
pure sulphuric acid and 90% of distilled water. The specific gravity of
the fluid should be from 1,210 to 1,212 in all cases. A standard battery
hydrometer should be used by all storage battery users to ascertain the
exact density of the solution as the specific gravity is a direct index
to the condition of the cell. A gasoline hydrometer is useless for a
storage battery.

When mixing the electrolyte it should be placed in a glass or porcelain
jar, and the process should never be performed in the battery jar in the
presence of the plates. The solution is very active chemically and
should not be brought into contact with metallic or organic substances
because of the danger of contaminating the fluid. The acid should always
be poured into the water in a thin stream while the mixture is being
stirred with a glass or porcelain rod. Pouring the water into the acid
is likely to produce an explosion and should therefore be carefully
avoided.

As the acid heats the water during the mixing the hydrometer reading
should not be taken until the heat caused by the first addition of acid
has been reduced to that of the room. Taking a reading with a hot
solution will give inaccurate results, unless, of course, the reading is
reduced to normal by the method described in a previous chapter. When
the reading has been taken and found to be correct and the solution has
been reduced to the temperature of the room, the electrolyte may be
poured into the cell through the filler openings in the top of the cell.
Pour into each cell sufficient fluid to cover the plates but avoid
filling the cell to the top, or flooding it.

At the end of the charging time given by the maker, withdraw a sample of
the electrolyte by means of a syringe and test the specific gravity.
This should not be over 1,290 for a fully charged cell, and if the
solution exceeds this amount, pure water should be added until the
proper point is reached. Always correct the specific gravity in this way
every time the battery is charged as evaporation and internal chemical
changes cause the density to change from time to time. The voltage of a
good storage battery will be about 2.1 volts when fully charged.
Overcharging is wasteful and finally destroys the cell, the effects
being similar to those caused by excessive discharges, that is, buckled
plates and loosened active material. Overcharging a sulphated battery
may cure the trouble, a little overcharging at intervals being better
than a long continued overcharge.

An increase in the specific gravity of the electrolyte of from 30 to 50
degrees, with a corresponding rise of voltage, shows that the cell is
fully charged.

After the charging is completed remove all of the solution spilled on
the battery, preferably by washing, and wipe bone dry. If the solution
is higher in the air, remove the excess with the syringe.

(87) Make and Break System (Low Tension).

When a circuit carrying a current is opened or broken at any place in
its length, an electric spark will occur at the point at which the wires
or contacts are separated. This is due to what might be termed the
“momentum” of the current which causes it to persist in its course even
to the extent of jumping over a short distance of the highly resistant
air in the gap. The size and heat of the spark may be increased by
placing a coil of copper wire in series with the circuit that has an
iron core in the center of the turns. This coil increases the tendency
of the current to jump the gap, or in other words increases the momentum
of the circuit.

Each separation of the terminals of the circuit causes but a single
spark, so that in order to obtain another the terminals must be again
brought into contact and the current reestablished in the circuit before
the circuit is again opened. Thus the function of the make and break
igniter is to alternately make and break the circuit in the presence of
the combustible mixture. To obtain the greatest spark and most certain
ignition, the contact points should be opened with the greatest possible
speed, an action that is accomplished in the actual engine by springs
and triggers.

A typical cylindrical make and break coil consisting of an iron wire
core surrounded by a coarse copper wire core is shown by Fig. 91. At one
end of the coil will be seen the two terminal screws by which it is
connected with the circuit. Another make and break coil is shown by Fig.
92, which has the same type of winding, but differs in having the core
wire coil extended beyond the winding and heads. By closely examining
the cut, the iron wires will be seen in the projecting core tube at the
left end of the coil. A flat base is also provided for fastening it to a
stationary foundation.

A typical make and break igniter is shown by Fig. 93, together with the
usual circuit consisting of a primary coil and battery. In this figure,
A and C are the two electrodes provided with platinum contact points N
and O respectively. The electrode A is stationary and is insulated from
the iron casing K by the insulating washer H, and the insulating bushing
or tube I. The electrode C is oscillated intermittently by the engine
through its shaft E, and the trigger G, the springs S serving to snap
the platinum contact O away from N at the proper moment. This electrode
(C) is in electrical connection with the shell K, and the engine frame
at all times, and is provided with a brass bushing F for a bearing
surface. The outer containing casing K is bolted to the combustion
chamber of the engine by the bolts LL, so that the electrodes A and C
project into the combustion chamber.

[Illustration:

Fig. 91. Kingston Cylindrical Make and Break Coil.
]

[Illustration:

Fig. 92. Kingston Make and Break Coil. Short Type.
]

Current from the battery R passes through the coil winding P to the coil
terminal U from which it passes from V to the igniter binding post J.
From J it flows along the rod D to the stationary electrode A. Since the
rod D is surrounded by the insulating washers and tube H, T and I, the
current cannot escape directly to the casing K. With the two platinum
points N and O in contact, the current flows through C to the shell K
from which point it flows back to the battery R through the conducting
path V, completing the circuit. The greater portion of the path V
consists of the engine frame. When the electrode is moved in the
direction of arrow B, the current is opened and a spark occurs at the
point of separation M, in contact with the gas in the combustion
chamber. The electrode C being connected with the engine frame is said
to be “grounded.” If the stationary electrode A were not insulated from
the casting K, the current would pass directly from the terminal J back
to the battery R without passing through the contact points at all, and
consequently no spark would be produced on the separation of the points.

[Illustration:

Fig. 93. Diagram of Igniter and Connections.
]

A push rod which is actuated by a cam on the engine, engages with the
trigger G, and causes the spark to occur when the piston is on the end
of the compression stroke. In nearly all engines, the relation between
the time of the spark and the piston position can be regulated to suit
the requirements for advance and retard. This adjustment is necessary in
order that the spark may be varied to meet the difference between the
starting and running requirements.

While the ignition should be considerably advanced while running, it is
necessary to retard it when starting, as the engine is liable to “kick
back” with an advanced spark.

This advance and retard device should be accessible while the engine is
running, and the operator should be able to control the point of
ignition at all times. Many men have been seriously injured by the lack
of this device or by neglecting to use it.

The contact points make contact only for a short time before the spark
is required in order to reduce the amount of current to the minimum, and
therefore increase the life of the batteries.

The duration of the “make” or contact should be as short as possible.
Prolonged contact weakens the batteries and causes them to run down
rapidly. For the same reason the electrodes should remain separated
until the make is actually required.

A certain period of contact is necessary, however, to allow the spark
coil to “build up,” but with a properly designed coil the time required
is very short.

Some engines provide a device that cuts out the ignition current
altogether during the idle strokes. This adds materially to the life of
the batteries.

The igniter should be located near the inlet valve, as the cold incoming
gases tend to keep it cool and clean, besides insuring the presence of
combustible gas around the igniter electrodes. Improper placing of the
igniter will greatly reduce the efficiency of the engine. Avoid placing
the igniter in a pocket, or in the path of the exhaust gases.

The make and break ignition system has many good features, but cannot
successfully be applied to engines running over 500 revolutions per
minute, nor can it be applied to engines of less than 3 H. P. as the
parts would be too small and delicate to be durable.

The make and break igniter produces the largest and “hottest” spark of
any type of ignition, and is especially desirable for large or slow
running engines. Being operated at a low voltage, it is not as easily
affected by moisture, poor insulation, or dirt as the high tension or
jump spark system, nor is it liable to give the operator such a violent
“shock.”

Engines governing by the “hit and miss” system have a device that cuts
out the current during the “missed” power strokes. This effects a
considerable saving in battery current, especially on light loads when
the engine misses a great number of strokes.

While possessing many points of merit, the make and break system is open
to several serious objections:

1. Due to the high combustion temperature there is excessive wear of the
working parts in the cylinder, this wear causes a change in the ignition
timing.

2. The low voltage used in the make and break system calls for perfect
contact of the electrodes in the cylinder. This contact is often
interfered with or entirely prevented by the accumulation of carbonized
oil and soot deposited on the surfaces.

3. The wear of the operating spindle or shaft, which passes through the
cylinder wall causes leakage, which in turn causes a loss of compression
in the cylinder.

4. The wear of the external operating mechanism produces a change in the
timing. The edge of the fingers, wiper blades, etc., tend to cause an
advance in the ignition as a general rule, with the attendant danger of
broken crank shafts.

5. The system is mechanically complicated, correct operation calling for
constant care as to adjustment.

All ignition apparatus wears in the course of time and changes the
timing of the engine. The electrodes and push-rods wear and require
readjustment. Generally the tendency of worn parts is to advance the
ignition. This change in timing occurs so gradually that the operator
does not notice it until the engine begins to pound, or until the
efficiency has been considerably reduced.

When the engine is new it is well to mark the ignition mechanism in such
a way that the relative positions of the crank and igniter will be shown
at the time when the igniter trips. It will then be possible for the
operator to refer to the marks at any time to tell whether his ignition
is occurring at the proper time. Always mark the half-time gears when
taking the engine apart for the difference of one tooth when
reassembling will be sufficient to throw the engine out of time.

The usual method of marking the gears, is to center punch, or scratch
one tooth on the small gear, and then mark the two teeth of the large
gear that lie on either side of it. With these marks it is possible to
replace the gears in their original and proper positions.

The igniter should trip, causing the electrodes to separate just before
the end of the compression stroke is reached, or just before the crank
reaches the inner dead center. The distance lacking the exact dead
center represents the instant of time between the time of ignition and
the actual pressure established by the combustion.

As most engines have the ignition considerably retarded when starting,
the igniter will trip later with the lever in the “start” position than
when in the “running” position. Never fail to retard spark when starting
nor forget to advance it when engine is up to speed.

The actual advance given to an engine depends on the character of the
fuel and on the speed.

An engine is said to have an advance of 10°, if the crank lacks 10° of
having made the inner dead center at the time of ignition.

The most economical point of ignition is easily determined when the
engine is running on a steady load, by varying the point of ignition and
noting the position assumed by the governor.

(88) Operation of the Make and Break Igniter.

To keep the igniter in order, and to obtain the best results with the
least trouble, the following hints should be observed:

(1) Clean the igniter frequently, and remove all deposits of oil and
carbon. For cleaning, the igniter must be removed from the cylinder,
care being taken to avoid injury to the packing or gasket. Graphite
dusted on the gasket will prevent it from sticking to either the igniter
or cylinder.

(2) If the contact points are rough, pitted, or covered with a carbon
deposit, the scale should be removed, and the points smoothed down with
a fine file, taking care that the two faces are filed parallel with one
another.

(3) Insulating washers and tubes should be removed and washed in
gasoline. The hole through which the igniter rod passes should be
scraped free from any deposit for much trouble can be caused by a tight
working shaft.

(4) Examine the hole or bushing through which operating spindle passes,
for wear. A worn spindle or bushing may cause a serious loss of
compression; replace worn bushing at once.

See that the insulation of the stationary electrode is not broken. If it
is injured in the slightest degree, replace it with new.

(5) Often the sparking points may be cleaned temporarily without
removing the igniter from the cylinder by pulling upon the outside
finger or trigger until the points come together, and then pushing in
towards the cylinder several times on the movable electrode, which
slides them one on the other, scraping off the deposit. This method is
only a make shift.

(6) After removing igniter, replace all wires, screwing them firmly into
place. The ends of wires and connecting screws should be perfectly clean
when the connection is made; to insure perfect contact, the surfaces
should be scraped or sand-papered until bright and shining. See that no
foreign matter of any kind gets between the wires and the metal of the
binding screws. Wherever possible connections should be soldered.

(7) A small coil of the wire should be made at the point of connection;
i. e., the wire should be a trifle longer than necessary to reach the
binding screw, the excess wire being coiled up on a pencil. This coil
allows of removing igniter, allows for broken wire ends and reduces the
tendency to loosen the connection.

(8) Ground wires, or wires connected with the frame of the engine should
receive careful attention. They are generally fastened under some screw
or bolt on the engine which may become loose or fail to make contact,
thus opening the entire circuit and causing the engine to stop. The
ground wires are generally connected in inaccessible places, and require
all the more attention for this reason.

(9) For the primary of low tension wiring, use only the best grade of
stranded rubber covered wire. A special wire for ignition purposes is on
the market. It is rather expensive but is just the thing for the
service.

Never use cotton covered or waxed wire. This covering affords absolutely
no protection against moisture or abrasion.

(10) As the voltage of a primary circuit, or circuit for make and break
is very low, and the current comparatively high, it is well to have the
copper as large as possible. It should never be less than number 14
gauge. Don’t use solid wire if you can obtain stranded conductor.
(Stranded wire is made up of a number of fine wires which are twisted
into a cable or rope of the desired size.)

(11) Oil destroys rubber insulation and should be kept off the wiring.
Try to locate the conductors so that they will be out of range of oil
thrown by the moving parts.

(89) Jump Spark System (High Tension System).

Due to its simplicity and the light weight of its moving parts, the high
tension ignition system is applied to practically all small, high speed
engines running 500 R.P.M. or over. The high tension system is also
desirable from the fact that it has no moving parts in the cylinder of
the engine.

The principal objection to the high tension system is the ease with
which the high voltage current leaks or short circuits, moisture being
fatal to the operation of a jump spark engine.

Instead of producing the spark by breaking the circuit of a low tension
current, the spark is produced by increasing the voltage to such a point
that the current will jump directly across a fixed gap. To cause the
current to jump through the air requires an extremely high voltage, and
as the battery current is very low it is necessary to introduce a device
known as a “transformer” to stop the current up to the required tension.
In addition to the voltage required at atmospheric pressure (about
50,000 volt per inch of spark) we must also furnish sufficient pressure
to overcome the increased resistance due to the compression in the
cylinder.

Unlike the spark coil used on the low tension make and break system, the
induction coil or transformer coil has two separate and distinct coils,
that are thoroughly insulated from each other. One coil has a few turns
of heavy copper wire which is called the primary. The other consists of
many thousands of turns of very fine copper wire, and is called the
secondary. Both coils are wound around a bundle of soft iron wire called
the core, from which they are carefully insulated. When a battery or
magneto current flows through the primary coil, the core is magnetized,
and throws its magnetic influence through the turns of the secondary
coil.

In Fig. 94 the primary coil and the low tension battery and magneto
circuit are represented by heavy lines. The secondary coil, and high
tension circuit are represented by light lines.

In order to obtain a continuous discharge of sparks it is necessary to
make and break the current in the primary coil very rapidly. This is
done by means of the interrupter or vibrator, which is indicated in the
diagram by V. The interrupter consists ordinarily of a spring A on which
is fastened a soft iron disc D and a platinum contact point B. When the
core is magnetized it attracts the iron disc D which is pulled toward
the core, bending the spring A and breaking the contact between the
platinum point B and C. When the contact points are separated, and the
current broken, the core loses its magnetism, and the spring assumes its
normal position, which brings the platinum points B and C into contact
once more, and reestablishes the current through the primary. The core
is again magnetized and the primary current is again broken, and so on.
This make and break of the current is thus accomplished automatically,
the current being broken many thousands of times per minute, the
vibrator moving so fast as to cause a continuous hum.

As soon as the current starts flowing, the magnetic force spreads out
through the secondary coil and threads through the turns of which it is
composed. The instant that the current ceases, the magnetic force
decreases and the turns are again threaded by the magnetic field on its
return to the core.

Thus two magnetic waves are sent through the secondary coil, one when
the circuit is “made,” and one when the circuit is “broken.”

[Illustration:

Fig. 94. Diagram of High Tension Coil.
]

When a magnetic wave threads or spreads through the turns of a coil of
wire, a current of electricity is generated in the coil, the quantity
and pressure or voltage of which is proportional to the intensity of the
magnetism, and to the number of turns of wire in the secondary coil.

Thus it will be seen that at every make and break of the low tension
current in the primary coil, a current is generated in the secondary. As
the voltage generated in the secondary is roughly proportional to the
number of turns in the secondary, and as there are many thousands of
turns, it is evident that the voltage in the secondary will be very
high. Thus by the use of the induction coil, the low tension battery
current is transformed into a high tension current of sufficient voltage
to break down the high resistance of the spark gap.

The condenser is shown at L which has one wire leading to the vibrator
spring A, and one wire to the contact screw M. The function of the
condenser is to absorb the spark produced at the vibrator points so that
the break is made quickly, producing a maximum spark. The intensity of
the spark depends upon the quickness with which the primary current is
broken, and if it were not for the condenser the length and intensity of
the spark would be greatly reduced. This device consists of alternate
layers of paper and tin foil, every other leaf of foil being alternately
connected to the vibrator spring and to the contact screw.

A method of using two independent sets of battery is shown in the
diagram, so that either set may be thrown into circuit by means of the
double throw switch O. When handle J is in contact with E, the current
of battery set H flows through the coil as shown by the arrows. When J
is in contact with F, the battery C is thrown into circuit. The spark
gap is shown by X, which represents the spark plug in the cylinder.

In practice, the portion of the circuit shown by I-U is generally formed
by the frame of the engine, or is grounded. The terminal P of the high
tension circuit is always grounded through the threaded shell of the
spark plug, the grounded circuit being shown by the dotted lines.
Grounding saves wire and many connections, for with P and U connected to
ground it follows that one binding post will serve the place of one high
tension and one primary post, making three coil connections instead of
four.

In order that the spark will occur in the cylinder of the engine at the
proper time, a switch must be placed in the primary circuit of the coil,
that will open and close the circuit at proper intervals. Such a switch
is called a timer, and is always driven by the engine. The timer is
connected to the engine shaft in such a way that contact is made at, or
slightly before, the time at which the explosion is required, and as
soon as possible after spark occurs the current is cut off.

For multiple cylinder engines it is usual to provide one coil for each
cylinder, the primaries of which are controlled by a single timer and
battery. A high tension wire from each coil runs to the corresponding
cylinder. Instead of having a number of coils with a battery system,
there are two or three makes that operate with one coil in combination
with a special device known as a distributor which controls the high
tension current. The high tension distributor directs the current to the
proper cylinder that is in the order of firing, the timing being
performed by a timer similar to that used with multiple coils except
that a single contact sequent is supplied.

(90) Vibrator Construction.

Since the efficiency of the high tension coil depends largely on the
construction and efficiency of the vibrator, the different coil makers
have developed various types of vibrators that differ greatly from the
simple device shown in the coil diagram in details.

[Illustration:

Fig. 95. Kingston Vibrator.
]

The main objects in view in the construction of a successful vibrator
are:

1. To reduce the weight of the moving part as much as possible in order
to increase the speed of vibration, and to make the trembler instantly
responsive to the timer.

2. To cause the contact points to separate as rapidly as possible in
order to cause the maximum spark.

3. To have the contacts as hard and infusible as possible to resist wear
and the action of the spark between the contacts.

4. To make any adjustments that may be required, due to wear, as simple
and accessible as possible.

The types of vibrators are legion, and we have not the space to go into
the details of all the prominent makes, but will illustrate and describe
two well known types.

The Kingston vibrator made by the Kokomo Electric Company, is a good
example of a modern vibrator and is shown in detail by Fig. 95. All
adjustments between the contact points are made by means of the contact
screw A which carries a platinum point at its inner end. The retaining
spring D keeps the contact screw from being jarred out of place by the
engine vibration, without the use of lock nuts. Turning A against the
vibrator, the tension of the spring B is increased, raising the screw
decreases the tension. Increasing the tension screw increases the length
and heat of the spark, and also increases the current consumption. At N
is a separate thin iron plate which is acted on by the magnetized core,
a rivet fastening the plate to the main vibrator spring is shown at the
end of the spring. The current enters through the lug C, and from this
point the circuit is the same as shown in the coil diagram.

(91) Operation of the Jump Spark Coil.

The spark produced by a coil in good condition should be blue-white with
a small pinkish flame surrounding it, when the gap is ¼ of an inch or
less. The sparks should pass in a continuous stream with this length of
gap without irregular stopping and starting of the vibrator. Coils
giving a sputtering, weak discharge that causes sparks to fly in all
directions are broken down and should be remedied.

The secondary windings of coils are often punctured or broken down by
operating the coil with the high tension circuit open, or by trying to
cause long sparks by increasing the spark gap over ⅜ of an inch in the
open air. Coils are also broken down by allowing excessive currents to
flow in the primary coil. Never cause a spark to jump over ⅜ of an inch.

High compression in the cylinder shortens the jumping distance of a high
tension spark. Coils that will cause a stream of sparks to flow across a
gap of ½ an inch in the open air are often unable to cause a single
spark to jump a gap of 1/32 of an inch under a compression of 80 pounds
per square inch in the cylinder.

Remember that a hot spark causes rapid combustion, and will fire a
greater range of mixtures and “leaner” charges, than a straggling, thin,
weak spark. Spark coils that give poor results with a long spark gap
under high compression are often benefited by the shortening of the
spark gap. Shortening the gap will increase the heat of the spark, and
will insure the passing of a spark each time that the timer makes
contact. A good coil should have no difficulty in igniting a piece of
paper inserted between the wires forming the spark gap in the open air.

[Illustration:

Fig. 96. Kingston Dash Coil.
]

The adjusting screw affords a means of increasing or decreasing the
tension of the vibrator spring, and the amount of battery or magneto
current flowing through the primary coil. Increasing the tension of the
spring requires stronger magnetization of the core to break the circuit
of the contact points. This in turn calls for more current from the
battery; hence in order to lessen the demand for current on the battery,
the tension should be as little as possible to obtain the necessary
spark. An increased tension produces more spark as the magnetization of
the core is increased, but for the sake of your batteries decrease the
tension as much as possible with a satisfactory spark.

Almost all operators have a tendency to run with too stiff a vibrator,
and hence use too much current. An efficient coil should develop a
satisfactory spark with ¼ to ½ of an ampere of current in the primary
coil. I have often found coils that would work well with ½ ampere, that
were screwed up so tight that the coils were consuming 4 to 5 amperes or
8 to 10 times as much as they should.

A battery ammeter used for testing the current consumed by coil will
save its cost many times over in batteries and burnt points if used at
frequent intervals in the primary circuit.

An automobile or marine engine should be tested for vibrator adjustment
in the following way:

Adjust vibrator so that spring is rather stiff. Start engine and get it
thoroughly warmed up and running at full speed, then slowly and
gradually decrease the tension of the spring until misfiring starts in;
then slowly increase tension until misfiring stops. Increase the tension
no farther; this is the correct adjustment.

Poor vibrator adjustment is the cause of much trouble and expense as it
uses up the batteries and wastes fuel. The principles of correct
adjustment are simple, the adjustment easily made, and there is no
possible excuse for the high current consumption and rapid battery
deterioration met in every day practice. The usual practice of the
average operator is to tighten the vibrator until the spark (observed in
the open air) is at its maximum. This is commonly known as “adjusting
the coil;” shortly after you hear of him throwing out his batteries as
no good. After once getting the vibrator in proper trim the ear will
give much information as to the adjustment.

A vibrator adjusted too lightly will cause “skipping” or misfiring with
the consequent loss of power.

Never attempt to operate a coil that is damp; the coil will be ruined
beyond repair. Above all, do not place the coil in a hot oven to dry, as
the box is filled with wax, and if this is melted it will run out and
reduce the insulation of the coil. Dry coil gradually.

If the batteries are new or too strong the vibrator may be held against
the core of the coil so that the vibrator will not buzz. If this is the
case loosen the screw until it works at the proper speed. If the
batteries are weak, the coil may not be magnetized sufficiently to draw
the vibrator and break the circuit. If this is the case tighten the
screw. If the vibrator refuses to work with the battery and wiring in
good condition, and if you are sure that the current reaches the coil,
look for dirty or pitted contacts on the vibrator.

Should the contact points be dirty, clean them thoroughly by scraping
with a knife or sandpaper. Water on the points will stop the vibrator,
as will oil or grease.

If contact points are of a uniform gray color on their contact surfaces,
and are smooth and flat without holes, pits or raised points, they are
in good condition. If pits, discolorations or projections are noted, the
contact surfaces should be brought to a square, even bearing by means of
a small, fine file. The point should not come into contact on an edge,
but should bear on each other over their entire surface. Do not use sand
paper to remove pitting, as it is almost impossible to secure an even,
flat surface by this means.

It is best to remove the contact screw and vibrator blade for
examination and cleaning, as it is much easier to file the points square
and straight when removed from the coil.

Be careful not to bend the vibrator spring when cleaning, as the
adjustment will be impaired. When replacing contact screw and vibrator
blade in coil, be careful that they are in exactly the same relative
position as they were before removing. Also be sure that the contacts
meet and bear uniformly on their surfaces.

(92) Primary Timer.

The duty of the primary timer is to close the primary circuit of the
spark coil at, or a little before the time at which the explosive of the
charge is required. The exact time at which the timer closes the circuit
depends on the load, the speed, and the nature of the fuel. The lapse of
time between the instant that the timer closes the circuit and the
instant at which the piston reaches the end of the compression stroke is
called the “advance” of the timer. When the timer closes the circuit
after the piston reaches the end of the stroke, the timer is said to be
“retarded.” The timer is constructed so that the time of ignition or the
advance and retard can be varied between wide limits. Advancing the
spark too far will cause hammering and power loss as the piston will
work against the pressure of the explosion.

Retarding the spark will cause a loss of power, as the compression will
be less when the piston starts on the outward stroke; and also for the
reason that more of the heat will be given up to the cylinder walls as
the combustion will be slower. The pressure in the cylinder is less with
retarded ignition. Greatly retarded ignition often causes overheating of
the cylinder walls, especially with air cooled engines, and also
overheats and destroys the seat and valve stem of the exhaust valve. Do
not expect the engine to develop its rated horse-power or run
efficiently with a late, or retarded spark.

When the engine is installed, and before the timer wears or has a chance
to get out of adjustment, look it over carefully and see whether the
maker has left any marks relating to the timing of the spark. If there
are no marks, it is well to determine the relation between the position
of the piston and the timer, as the efficiency of the engine depends to
a great degree upon the firing point.

Timers are advanced and retarded by partially rotating the housing
either in one direction or the other. When the timer is mounted directly
on the cam shaft with the cam shaft traveling in a direction opposite to
that of the crank shaft, the timer will be retarded by moving it in the
same direction as the cam shaft travels, moving it against cam shaft
rotation advances the spark.

Timers for two stroke cycle engines rotate at crank shaft speed, and the
direction of advance and retard varies with the methods adopted for
driving the timer.

(93) Timer Construction.

Fig. 97 shows a typical timer and circuit arranged for a four cylinder
engine. The device can be arranged for any number of cylinders, however,
by changing the number of sectors, the sectors being equal to the number
of cylinders. There are timers on the market that differ from the one
shown in the diagram but the principle of operation is the same with
all. The shaft E is usually connected to the cam shaft and is
electrically grounded to the engine frame at L by means of the bearing
in which the shaft rotates.

The lever F mounted on the shaft E carries the pivoted arm H which is
free to move on the pivot to a limited extent to allow for wear on the
walls W-W-W-W. At one extremity of H is the roller I which rotates on
the pin J, as the roller runs around W-W-W-W. At the other extremity of
H is fastened the spring S, which forces I into contact with the walls.
A-B-C-D are metallic contact sectors whose connections lead to the four
spark coils.

When the metal roller I comes into contact with one of the sectors as at
B, the sector is grounded to the engine frame by the roller, the current
traveling through the roller and its pin, through lever H and its pin,
through the lever F and shaft E to ground at L, the course of the
current being indicated by the arrows.

[Illustration:

Fig. 97. Timer Diagram.
]

As the shaft E rotates and carries with it roller I, the roller makes
contact with the sectors in order B-C-D-A, if rotated in the direction
shown by arrow, which rotation grounds the primary coils of the spark
coils R^3-R^4-R^1-R^2 in succession; the connection from the timer to
the primary being to the primary binding posts P^3-P^4-P^1-P^2. A high
tension spark occurs at each contact of the roller with the sectors, as
the contact allows current to flow through the primary of the coils. The
high tension binding posts S^1-S^2-S^3-S^4 are connected with the spark
plugs or spark gaps U^1-U^2-U^3-U^4 by means of high tension cables. As
soon as the timer grounds a coil, the coil produces a high tension spark
in its corresponding spark plug.

It is evident from the foregoing that the timer not only determines the
time at which a spark will take place, but it also determines the
cylinder in which the spark will be produced, providing of course that a
spark coil is provided for each cylinder.

The contact sectors A-B-C-D are insulated from each other by the
insulating walls W-W-W-W, the inner surface of which provides a path on
which the contact roller I revolves.

The contact sectors and insulating walls are encased by the protective
housing Z, to which they are rigidly fastened.

The housing Z can be moved back and forth on the shaft E for advance and
retard, by means of the lever K.

The current flows from the battery terminal V (with the roller in the
position shown) through the switch M, through coil R^3, post P^3 to
sector B, from which it passes through the roller I, levers H and F to
ground. From the ground on the engine frame the current flows back to
its source, the battery O, thus completing the circuit. When the roller
makes contact with sector C, the coil R^4 is energized, contact with D
energizes R^1, and so on. No two coils can be thrown on simultaneously
as only one coil is grounded at a time. The high tension current flows
from each coil to its plug as soon as the current passes through the
primary of that coil.

In some timers, the current is taken from the revolving arm through a
separate connection to ground instead of grounding the shaft through the
bearings. With these timers, the connection is not affected by worn
bearings or an oil film that tends to insulate the shaft from the
bearings.

(94) Operation of Timers.

Timers frequently cause misfiring which is generally due to dirt or oil
getting between the contacts, or to the wear of the insulating walls
W-W-W-W, or to the wear of the moving parts.

Dirt or gummy oil will prevent the contact coming together and
completing the circuit, or will clog up the rollers or levers so that
they cannot perform their functions properly. This will of course
interfere with production of the spark.

The contacts and moving parts of the timer should be kept as clean as
possible, all dirt and heavy oil being removed by means of gasoline at
regular periods. Make a practice of cleaning out the timer at intervals
not greater than one month; oftener if possible.

Parts subject to wear, such as the roller pin J and the bearings should
be well lubricated, none but the lightest oil being employed for this
purpose. Heavy grease will gum the contacts and cause trouble. There
should be no rough places or shoulders on the contact sectors or on the
walls W-W-W-W as roughness will cause the roller to jump over the high
places which in turn result in misfiring. The remedy is to machine the
surfaces of the sectors and walls by grinding or turning in the lathe.
Care should be taken in this operation to have the interior perfectly
smooth and the sectors perfectly flush with the walls. Repair black or
burnt sectors immediately by grinding or sand paper.

Burnt spots or blackened surface on the contact sectors prevent good
contact between roller and sector, sectors should show a bright, shining
metallic surface.

Sometimes the insulation warps or swells above the contacts so that the
roller jumps over the contacts without touching them, or if for any
reason that contact is made under these conditions, it is of a short
period and results in a poor spark.

Timers often make good contact when starting, or at low speed, and
misfire badly at high speed. This will be caused generally by the
contact sectors or insulation projecting beyond one another, the roller
has time to make good contact at low speed but jumps over the sector at
high.

The roller I may become rough or develop a flat stop which will cause it
to jump over the contact occasionally, or it may become loose on its
bearing pin J, causing intermittent misfiring.

The wearing or loosening of pins J and X result in poor contact. Should
pin J fall out of the lever H, the roller would drop out of the fork and
cause serious damage. This has happened in two cases to my knowledge.

Should the spring G weaken or break, contact will be made intermittently
at high speed, and no contact at low. In this case it would probably be
impossible to start the engine. In case the spring breaks, a rubber band
may be used temporarily. Wire connections to the timer should be
examined frequently as the continual back and forth movement tends to
twist and loosen the wire. Use stranded or flexible wire for these
connections, if possible.

Before removing the timer mark the hub and the shaft so that the hub can
be properly replaced. If this is not done the engine will be out of time
with the usual results of hammering or power loss.

Should the gears which drive timer shaft be removed, be sure and mark
the teeth of both gears in such a manner that there will be no mistake
possible in reassembling them. Mark a tooth on the small gear by
scratching or with a center punch (the tooth selected should be in mesh
with the large gear). Then mark the two teeth of the large gear that lay
on either side of the marked tooth of the small gear. Thus it will be
easy to locate the proper relative position of the two gears at any
time.

(95) High Tension Spark Plug.

The high tension spark plug is a device that introduces the spark gap
and spark into the combustion chamber, and at the same time insulates
the current carrying conductor from the cylinder walls. Since the
voltage of the jump spark current is very high it is evident that the
insulation of the plugs must be of a very high order and that this
insulation must be capable of withstanding the high temperature of the
combustion chamber. A cross-section of a typical plug is shown by Fig.
98, together with its connections and the course of the current, the
latter being shown by the arrow heads.

The electrode B through which the current enters the cylinder is
thoroughly insulated from the walls by the porcelain rod C.

The porcelain forms a gas tight joint with the threaded metal bushing F
at the point P, the tension caused by the electrode B and the nut I
holds the porcelain firmly on its seat at P.

The nut is supported by the porcelain shell H which rests in the top of
the metal bushing F. A washer L is inserted between H and F to insure
against the leakage of gas from the plug should a leak develop at P. L
being a soft washer (usually asbestos) allows the porcelains C and H to
expand and contract without breaking. A packing washer or gasket is also
placed at the point where the electrode B passes through the porcelain
H. This is the washer Q, held in position by the nut I. This washer is
elastic and reduces strain on porcelain caused by the expansion.

The cylinder wall G has a threaded opening R into which the plug is
screwed, the threads of the opening corresponding with the threads on
the metal sleeve E. The plug may be removed from the cylinder for
examination without disturbing the adjustment of the electrode and
porcelains by unscrewing it at R.

Allowing the current to jump from the electrode to the cylinder wall via
the metal sleeve saves one wire and connection, the cylinder and the
frame of the engine serving as a return path for the current. This
simplifies the wiring and minimizes the danger of high tension short
circuits.

[Illustration:

Fig. 98. Cross-Section of Typical Spark Plug.
]

By unscrewing the threaded metal bushing F it is possible to examine the
condition of the porcelain rod C at the point where it is exposed to the
heat of the cylinder. This inspection can be made without disturbing the
packed joints at L or Q.

In the high tension, or jump spark system, the spark gap D-K is of fixed
length, hence there are no moving parts or contacts within the cylinder
to wear, to cause leakage of gas, or to cause a change in the timing.
This advantage is offset to some degree by the difficulty experienced in
maintaining the insulation of the high tension current.

The high tension current leaves the spark coil M at the binding screw N,
flows along the wire J, and enters the spark plug at the binding screw
A. From the binding post the current follows the central electrode B to
its terminal at D. At D a break in the circuit occurs which is called
the spark gap. It is at this point that the spark occurs, the current
jumping from D to point K through the air. Point K is fastened in the
threaded metal sleeve E which is in turn screwed into the cylinder wall
G or ground. From the ground the current returns to its source through
binding post O to the coil. The spark therefore occurs inside of the
cylinder wall and in contact with the combustible charge, at the point
marked “spark” in the cut.

[Illustration:

Fig. 99. Bosch Spark Plugs.
]

If the fuel, lubricating oil, and air are not supplied in proper
proportions, soot will be deposited on the lower surface of the
porcelain, and as soot is an excellent conductor of high tension
current, the current will follow the soot rather than the high
resistance of the spark gap, a condition that will result in misfiring
or a complete stoppage of the motor. Carbonized lubricating oil or
moisture have the same effect.

Preventing the deposits of soot, moisture and carbonized oil is the
chief object of plug manufacturers, many of whom have brought out
designs of merit. In fact the problem of elimination of soot is the
principal cause of the many types of plugs now on the market.

While many plugs differ in minor refinement of detail from the typical
plug shown, the connections and general construction are the same in all
types, the spark being produced in a gap of fixed length which is
insulated from the cylinder.

A well known form of plug, the Bosch, is shown by Fig. 99 a-b. In this
plug a special material known as Steatite is used instead of the usual
porcelain. The three external electrodes surrounding the center
electrode is a particularly efficient arrangement, especially for
magnetos. A peculiar form of pocket minimizes the soot problem.

As porcelain is brittle and is easily broken by the effects of heat or
blows, mica insulation is often used in place of the porcelain. The
central core of a mica plug is formed by a stack of mica washers, which
are held in place by the central electrode and the upper lock nuts.

A poorly constructed mica plug is easily destroyed by a weak,
stretching, electrode, or by an overheated cylinder. The latter causing
the washers to shrink and admit oil between the layers of mica washers
causes a short circuit. As soon as the mica washers loosen and separate,
they should be forced together by means of the mica lock nuts on the top
of the plug.

If by any reason the mica core becomes saturated with oil, it is best to
obtain a new one, as it is almost impossible to remove the oil by simple
means open to the average operator.

The chief value of a mica plug lies in its toughness and mechanical
strength, a good mica plug being practically indestructible.

When heated, porcelain does not expand at the same rate as the metal
sleeves, hence in poorly designed or imperfect plugs, heavy strains are
thrown on the delicate porcelains which causes them to crack. When a
crack develops it provides a lodging place for soot and carbon which of
course causes a short circuit. Should a compression leak occur through
faulty packing between the porcelain and sleeve, it should be
immediately tightened up for eventually it will leak enough to destroy
the plug or reduce the output of the engine.

When ordering a plug be sure that you know the size and type required by
your engine. Some engines require a longer plug to reach the combustion
chamber than others. Never install a shorter plug than that originally
furnished with the engine. Be sure that the plug is not too long as it
may interfere with the action of the valves or may be damaged by them.
Plugs are furnished with several threads and taps, i. e.:

½ inch pipe thread (Generally used on stationary engines).
Metric Thread (Generally used on imported autos).
⅞ inch A. L. A. M. Standard (Used on Domestic automobiles).

Using a plug in a hole tapped with the wrong thread will destroy the
thread in the cylinder casting and cause compression leaks.

(96) Care of Spark Plug.

Porcelains are often broken by screwing the plug too tightly in a cold
cylinder, as the cylinder expands when heated and crushes the frail
plug. A plug installed in this manner is difficult to remove as the
expanded walls grip the thread. The plug should be screwed in just
enough to prevent the leakage of gas. A short thin wrench should be used
in screwing the plug home such as a bicycle wrench. A wrench of this
type is so short that it will be almost impossible to exert too much
force, and will be thin enough to avoid any possible injury to the
packing nut. Bad leaks may be detected by a hissing sound that is in
step with the speed of the engine, small leaks may be detected by
pouring a few drops of water around the joint. If a leak exists bubbles
will pass up through the water and show its location.

Plugs are more easily removed from a cold cylinder than a hot. If the
plug sticks when the engine is cold and is impossible to remove with a
moderate pressure on the wrench squirt a few drops of kerosene around
the threads. Never exert any force on the porcelain or insulation. The
high tension cables should be connected to the plugs by means of some
type of “Snap Terminal,” such terminals may be had from automobile
dealers.

These terminals make a firm contact with the plug and do not jar loose
from the plug by the vibration of the engine. They are easily
disconnected when the inspection of the plug becomes necessary, and are
generally a most desirable attachment.

The high tension cable should be firmly connected to the plug terminal
under all circumstances. A loose connection will cause misfiring or will
bring the engine to an abrupt halt. If snap terminals are not used the
plug binding screw should be screwed down tightly on the wire. When
making connections see that the wire is bright and clean, and that
frayed ends of the wire do not project beyond the plug and make contact
with other parts of the engine.

A large percentage of high tension ignition troubles are due to short
circuits in the spark plug which are generally caused by deposits on the
surface of the plug insulation. Soot or oil may be removed from the plug
by scrubbing the porcelain and the interior of the chamber with gasoline
applied by a tooth brush. Examine the plug for cracks, and if any are
found, replace the porcelain or throw the plug away. A cracked porcelain
is always a cause of trouble.

To test a plug for short circuits, remove it from the cylinder,
reconnect the wire, and lay the sleeve of the plug on some bright metal
part of the engine in such a way that only the threaded portion is in
contact with the metal of the engine. Close the switch and see if sparks
pass through the gap. If no sparks appear, and if the coil is operating
properly, clean the plug. As an additional test for the condition of the
coil, hold the end of the high tension cable about ¼ inch from the metal
of the engine while the coil is operating. If a heavy discharge of
sparks takes place between the end of the cable and the metal of the
engine, the coil is in good condition.

If a partial short circuit exists, the spark at the gap will be weak and
without heat; the result will be intermittent, or misfiring with a loss
of power. Moisture in the cylinder is a common cause of plug short
circuits, the moisture coming from leaks in the water jacket or from the
condensation of gases in a cold cylinder. A drop of water may bridge the
spark gap, allowing the current to flow from one electrode to the other
without causing a spark.

If a cloud of bluish white smoke has been issuing from the exhaust pipe
before the misfiring started, you will probably find that the trouble is
due to sooted or short circuited plug.

The remedy is to decrease the amount of lubricating oil fed to the
cylinder.

When a magneto is used the intense heat of the spark causes minute
particles of metal to be torn from the electrodes and deposited on the
insulation as a fine metallic dust. This will of course cause a short
circuit and must be removed. Short circuits are sometimes caused by the
magneto current melting the electrodes and dropping small beads of the
metal between the conductors. All metallic particles should be removed
from the plug.

While a spark plug may show a fair spark in the open air test, it will
not always produce a satisfactory spark in the cylinder on account of
the increased resistance of the spark gap due to compression.

Compression increases the resistance of the spark gap enormously and
thin, highly resisting carbon films that would cause very little leakage
in the open air will entirely short circuit the gap under high pressure,
the current taking the easiest path which in the latter case is the
carbon deposit.

In order to produce conditions in the open air test similar to those in
the cylinder we must devise some method of increasing the resistance of
the spark gap in the open air above any possible resistance that could
be offered by the carbon film.

Placing a sheet of mica or hard rubber between the electrodes, or in the
spark gap, will increase the resistance to the required degree. If the
spark plug is in good condition the spark will jump from the insulated
terminal to the shell when the mica is in the spark gap, but if a short
circuit exists the current will go through it without causing a spark.
It is assumed that the battery and coil are in good condition when
making the above test.

If the electrodes or spark points are dirty they should be cleaned with
fine sand paper, special attention being paid to the surfaces from which
the spark issues. When reassembling the plug, see that all of the
washers and gaskets are replaced and that the length of the spark gap is
unchanged. A little change in the spark gap may make a great change in
the spark. A good spark is blue white with a faint reddish flame
surrounding it. When the discharge is intermittent or sputters in all
directions, either the coil or the plug are partially short circuited.
Always have a spare plug on hand.

Ordinarily the length of the gap or the distance between the electrodes
should be about 1/32 inch for batteries, and a trifle less for magnetos.
A silver dime is a good gauge for the gap. If the engine misfires with
the coil and batteries in good condition, try the effects of shortening
the gap a trifle, usually this will remedy the difficulty. Exhausted
batteries may be made operative temporarily by closing up the plug gap
to 1/64 inch or even less. Shortening the gap increases the heat of the
spark and nothing is gained by having it over 1/32 inch.

Almost all high tension magnetos have visible safety spark gaps that
show instantly the presence of an open circuit in the secondary or high
tension circuit. If an open circuit exists, a stream of sparks will flow
across the safety spark gap at low speed.

To determine the cylinder that is misfiring in a four cylinder engine
proceed as follows:

Remove cover on spark coil, and hold down one vibrator spring firmly
against the core while the engine is running.

If the engine speed is not decreased by cutting this coil out of action,
it is probable that this is the coil connected to the misfiring
cylinder. Now release this vibrator and proceed to the next coil, and
hold its vibrator down. If this decreases the speed of the engine you
may be sure that the first coil is in the defective circuit. If the
vibrator buzzes on the coil under inspection the trouble will be found
in the plug.

Cutting out a coil connected to an active cylinder decreases the speed
of the engine. Cutting out the coil connected with a dead cylinder makes
no difference.

(97) Magnetos.

A magneto is a device that converts the mechanical energy received from
the engine into electrical energy, the electricity thus produced being
used to ignite the charge in the engine. This appliance does away with
all of the troubles incident to a rapidly deteriorating chemical battery
and produces a much hotter and uniform spark. A magneto is especially
desirable with multiple cylinder engines where the demand for current is
almost continuous, as the amount of current delivered by the magneto has
no effect on its life or upon the quality of the spark.

The principal parts of the generating system of the magneto are the
magnets, the armature, the armature winding, and the current collecting
device, of which the armature and its windings are the rotating parts.
The production of current in the magneto is the result of moving or
rotating the armature coil in the magnetic field of force of the
magnets. When any conductor is moved in a space that is under the
influence of a magnet a current is generated in the conductor which
flows in a direction perpendicular to the direction of motion. The value
of the current thus generated depends on the strength of the magnetic
field, the speed with which it is cut, and the number of conductors
cutting it that are connected in series. Roughly, the voltage is
doubled, with an increase of twice the former speed, and with all other
things equal, the voltage is doubled by doubling the number of
conductors connected in series.

By employing powerful magnets, and a large number of conductors (turns
of wire) on the armature it is possible to obtain sufficient voltage for
the ignition system at a comparatively low speed. The number of amperes
delivered depends principally upon the internal resistance of the
armature and the external circuit, and not on the number of conductors,
nor directly upon the strength of the field. For this reason, low
voltage machines that are intended to deliver a great amperage have only
a few conductors of large cross section, while high tension machines
have a great number of conductors of small size. In all cases the
magneto, or ignition dynamo must be considered simply as a generator of
current in the same way that a battery is a source of current since the
current generated by them is utilized in precisely the same way.

The class of ignition system on which the magneto is used determines the
class of the magneto. The low tension magneto is used principally for
the make and break system, although it is sometimes used in connection
with a high tension spark coil or transformed in the same way that a
battery is used with a vibrator coil. The high tension magneto is used
exclusively with the jump spark system and high tension spark plug.

These classes are again subdivided into the direct and alternating
current divisions, depending on the character of the current furnished
by the magneto. Briefly a continuous current is one that flows
continually in one direction while an alternating current periodically
reverses its direction of flow. As the alternating current magneto is
the most commonly used type, we will confine our description to this
class of magneto. The alternating current magneto is much the simplest
form of machine as it has no commutator, complicated armature winding,
nor field magnet coils, and in some types the brushes and revolving wire
are eliminated.

As the magnetic flux of an alternating magneto is changed in value, that
is increased and decreased, twice per revolution, it follows that the
current changes its direction twice for every revolution of the
armature. Each change in the direction of current flow is called an
alternation.

The voltage developed in each alternation or period of flow is not
uniform, the voltage being low at the start of the alternation, rapidly
increasing in voltage until it is a maximum at the middle, and then
rapidly decreasing to zero, from which point the current reverses in
direction. As we have two such alternations, in a shuttle type magneto,
per revolution we have two points at which the maximum voltage occurs;
that is in the center of each alternation. These high voltage points are
called the peak of the wave and consequently the sparking devices should
operate at the peak of the wave or at the point of highest voltage. The
spark therefore should occur when the shuttle or inductors are at a
certain fixed point in the revolution at which point the peak of the
wave occurs. The peak of the wave occurs when the shuttle is being
pulled or turned away from the magnets.

In what is known as the “shuttle type” alternating current magneto, the
generating coil is wound in the opening of an “H” type armature. This
iron armature core is fastened rigidly to the driving shaft and revolves
with it. As the armature revolves, it is necessary to collect the
current that is generated by means of a brush that slides on a contact
button B, the button being connected to one end of the winding.

(98) Low Tension Magneto.

The winding of the low tension magneto consists of a few turns of very
heavy wire or copper strip, one end of which is grounded to the armature
shaft and the other passing through the hollow shaft from which it is
insulated. The end of the insulated wire is connected to the contact
button (B) on which the current collecting brush presses. As one end of
the winding is grounded, one brush, and one connecting wire is saved as
the current returns to the magneto through the frame of the magneto. As
the shuttle revolves between the magnet poles the magnetism is caused to
alternate through the iron of the armature, thus causing the current to
alternate in direction and fluctuate in value.

Since there are only two points at which the maximum current can be
collected during a revolution with the alternating current magneto, it
is necessary to drive it positively through gears, or a direct
connection to the shaft so that this maximum point of voltage will
always occur at the same point in regard to the piston position. If it
is driven by belt without regard to the position of the piston, it is
likely that there will be many times that the voltage is zero or too low
in value when the spark is required in the cylinder. Alternating current
magnetos must be positively driven, and the armature must be connected
to the engine so that the peak of the wave occurs at, or a little before
the end of the compression stroke.

With this type of magneto the only point that is likely to give trouble
is the point at which the brush makes contact with the contact button.
If the brush should stick or not make contact, or if the button is dirty
or rusty, the current will not flow; this point should always be given
attention. Outside of this the only attention necessary is to keep the
bearings oiled.

[Illustration:

Fig. 101. Sumter Magneto Advanced.
]

[Illustration:

Fig. 102. Sumter Magneto Retarded.
]

[Illustration:

Fig. 103. Sumter Magneto on Horizontal Engine.
]

Fig. 101 and Fig. 102 show the Sumter low tension magneto as arranged
for make and break ignition. The armature and its connections are of
exactly the same type as that shown in the previous diagram. The magnets
and frame are arranged to tilt back and forth so that the peak of the
wave will occur at the advanced and retarded positions of the igniter.
This arrangement allows the full voltage of the magneto to be obtained
at any point within the range of the ignitor, an important item when
starting the engine or running at low speed. When mounted on the engine,
as shown by Fig. 103, the magnets are provided with an operating rod
that is marked “start” and “run.” When the pin on the engine bed is
engaged under “start,” the magneto is retarded, when the pin is under
“run” it is advanced. A number of intermediate points are provided at
which the operating arm is held fast by tooth engagements as shown in
the slotted handle. As shown in the illustration the magneto is fully
advanced. The gears by which the magneto is driven are clearly shown in
the cut, the ratio between the gear on the crank shaft and that on the
magneto shaft being exactly 2 to 1. One lead is carried to the make and
break igniter in the cylinder head, the current being returned through
the bed of the engine. The same make of magneto is shown mounted on a
vertical engine in Fig. 104. In this case the magneto is positively
driven from the crank shaft of the engine by a chain. The single
conductor running from the magneto to the cylinder heads is clearly
shown. To start the engine, the igniter is set in the usual manner and
the magneto tilted to starting position, as shown in the illustration.
The engine is then started in the usual manner and, when running, the
igniter is changed to running position, and the magneto is tilted
outwardly. It is not important which is changed first, the magneto or
the igniter. It is easy to remember the “starting” and running
“position” of the magneto, the running position always being that in
which the magnetos are tilted in the direction opposite to that in which
the engine runs.

(99) Care of Low Tension Magnetos.

(1) Avoid setting a magneto on an iron or steel plate, unless stated
otherwise in the manufacturer’s directions, as in some makes the
magnetism will be short circuit by iron or steel and will reduce the
output.

(2) Do not jar magnets or magneto unnecessarily, for this tends to
weaken the magnets.

(3) Never remove the magnets if it can possibly be avoided. If this must
be done, mark the magnets and gears so that they may be replaced in
exactly the same position. If your magneto refuses to generate after
reassembling it is probable that they are reversed in position or that
the magnetism has been knocked out of them while off of the magneto.

(4) As soon as the magnets are removed, or better before, place a plate
of iron or steel across both ends of the magnet. Don’t leave the magnets
without this keeper for any length of time or they will lose their
magnetism. The best plan is to leave the magnets alone.

(5) Remember that the running clearance between the magnets and armature
is very small, only a few thousandths of an inch, and that any error in
replacing the bearings in their proper position will cause the armature
to bind in the tunnel. Handle armature carefully and do not lay it in a
dirty place as a bent shaft or grit in the armature tunnel will fix it
permanently.

(6) Most all magnetos are practically water proof, but don’t experiment
with the hose.

(7) Make all connections firmly and have the wire clean under the
binding posts.

(8) Only a few drops of oil are needed at long intervals, don’t neglect
to oil them, but above all do not drown them with oil.

(9) Examine the brush occasionally and clean off all oil and dirt.

(10) When replacing the magneto on the engine after its removal see that
the gears are meshed in the former position. Best to mark the teeth
before removal.

(100) High Tension Magnetos.

The “true” high tension type magneto is complete in itself, requiring no
jump spark coil nor timer, the high tension current being generated
directly in the coils carried by the armature. This arrangement reduces
the wiring problem to a minimum, as the only wires required are those
leading directly to the spark plugs, and one low tension wire connecting
the cutout switch used for stopping the engine.

[Illustration:

Fig. 105. Single Cylinder High Tension Bosch Magneto.
]

The armature of this type of magneto carries two independent windings,
one of a few turns of coarse wire called the primary coil, and the other
consisting of thousands of turns of extremely fine wire called the
secondary coil. It is in the latter coil that the high tension current
is generated. The timer is connected directly to the armature shaft, and
is an integral part of the magneto. All primary connections are
therefore made within the magneto.

Belts or friction drives cannot be used with this type of magneto.

As there are no vibrators or independent coils used, the spark occurs
exactly at the instant that the timer operates or breaks the primary
circuit. It will be noted that the spark is produced with this magneto
when the primary circuit is broken by the timer, instead of made as is
the case with battery coils, or coils used with low tension magnetos.
There is no lag and consequently the time of ignition is not affected by
variations in the engine speed, which requires an advance and retard of
the spark with batteries and vibrator coils.

When used with multiple cylinder engines the high tension magneto is
provided with a distributor, which connects the high tension current
with the different cylinders in their proper firing order. The timer
determines the time at which the spark is to occur and the distributor
determines the cylinder in which the spark is to take place.

[Illustration:

Fig. 106. Connecticut High Tension Magneto.
]

The sparks delivered by the high tension magneto are true flames or arcs
of intense heat, and exist in the spark gap for an appreciable length of
time. It is evident that such flames possess a much greater igniting
value than instantaneous static spark delivered by the high tension
spark coil used with the battery or operated by the low tension magneto,
and are capable of firing much weaker mixtures.

Like low tension magnetos, the true high tension type may be of either
the inductor or shuttle wound class. All high tension magnetos are
positively connected or geared to the engine in such a manner that there
is a fixed relation between time of the current impulse produced by the
magneto and the firing position of the engine piston.

The current is generated on the same principle as in the low tension
shuttle type; that is, by a coil of wire revolving in the magnetic field
established by permanent magnets.

During each revolution of the armature, two sparks are produced at an
angle of 180° from each other.

The advance and retard of the spark is obtained by means of the timing
lever which shifts the timer housing back and forth which results in the
primary current being interrupted earlier or later in the revolution of
the armature.

[Illustration:

Fig. 107. Longitudinal Section Through Bosch High Tension Magneto.
]

The timing lever can turn through an angle of 40° measured on the
armature spindle, and the angle of advance for multiple engines is as
follows:

Advance for 1 cylinder 40°
Advance for 2 cylinders 40°
Advance for 3 cylinders 50°
Advance for 4 cylinders 40°
Advance for 6 cylinders 27°

A timer is used with the magneto on a “jump spark” system in the same
way as with a battery, providing a vibrating coil is used.

In one type of magneto the Connecticut, the coil is part of the magneto,
and is fastened to the magneto frame. This type of magneto uses a
non-vibrating coil, and produces but a single spark each time the
primary circuit is broken by the magneto timer. As the timer on this
type is driven by the magneto shaft, it is evident that the magneto must
be “timed” with the engine, or must have its armature shaft connected to
the shaft of the engine in such a manner that the timer contact is
broken, and the single spark produced at the instant that ignition is
required in the cylinder.

Unlike the dynamo, the alternating current magneto cannot be used with a
storage battery, the alternating current producing no chemical change in
the electrodes of the battery.

[Illustration:

Four Cylinder “D4” High Tension Bosch Magneto Showing Distributor.
]

The Bosch high tension magneto is a typical high tension magneto having
the primary and secondary windings wound directly on the armature shaft,
there being no external secondary coil. The end of the primary winding
is connected to the plate (1) Fig. 107, which conducts the current to
the platinum screw of the circuit breaker (3). Parts (2) and (3) are
insulated from the breaker disc (4), which is in electrical contact with
the armature core and frame. When the circuit breaker contacts are
together the primary winding is short circuited, and when they are
separated the current is broken and the spark occurs. The breaker
contacts are simply two platinum pointed levers that are separated and
brought together by the action of a cam as they revolve. A condenser (8)
is provided for the circuit breaker to suppress the spark and to
increase the rapidity of the “break.”

The secondary winding of fine wire is a continuation of the primary
winding, and the secondary is wound directly over the primary. The outer
end of the secondary connects with the slip ring (9) on which slides the
carbon brush (10), which conducts the high tension current from the
armature. This brush is insulated from the frame by the insulation (11).
From (10) the current is led through the bridge (12) through the carbon
brush (13) to the distributor brush (15). Metal segments are imbedded in
the distributor (16), the number of which corresponds to the number of
cylinders. As the brush rotates, it makes consecutive contact with each
of the segments in turn and therefore leads the current to the cylinders
in their firing order. Wires from the cylinders are connected to sockets
that in turn connect with the segments. The disc driving the distributor
brush (15) is geared from the armature shaft in such a way that the
armature turns twice for every revolution of the distributor, when four
cylinders are fired, and three times for the distributors once when six
cylinders are fired.

[Illustration:

Fig. 108. Bosch High Tension Circuit.
]

The voltage of the current generated in the secondary coil by the
rotation of the armature is increased by the interruption of the primary
circuit caused by the opening of the contact breaker.

At the instant of interruption of the primary circuit the high tension
spark is produced at the spark plug.

As the spark must occur in the cylinder of the engine at a certain
position of the piston, it is necessary that the interrupter act at a
point corresponding to a definite position of the piston, consequently
this type of magneto must be driven positively from the motor by means
of gears, or directly from the shaft.

These magnetos run in only one direction. This running direction should
be given when magneto is ordered, as being “clockwise” or
“counter-clockwise” when looking at the driving end of the magneto.

The magneto for the single and double cylinder engines has no
distributor, the high tension current being led directly from the
armature.

The circuit diagram of the Bosch four cylinder magneto is shown by Fig.
108, the winding and plug connections being clearly shown. When
connecting the magneto care should be taken to have the distributor and
plug connections arranged so that the cylinders will fire in the proper
order.

(101) Bosch Oscillating High Tension Magneto.

The oscillating type of magneto is used on slow speed heavy duty engines
that move too slowly for the ordinary type of magneto. In the
oscillating type the armature is given a short angular swing by the
action of a tripping device operated by the engine which results in an
intense spark at the lowest speeds.

Magneto type “29” is constructed with two powerful steel magnets, while
magneto type “30” is provided with three; an armature of the shuttle
type is arranged to oscillate between their pole-shoes.

The magneto is actuated by a rotating cam or other suitable device,
which moves the armature 30° from its normal position whenever ignition
is required. To permit this movement, a trip lever is mounted upon the
tapered end of the armature shaft, this trip lever being held in a
definite position by the tension of the spring or springs 1. The trip
lever is only supplied when specially ordered, but each magneto is
provided with the necessary springs and spring bolts.

When the trip lever is moved from its normal position by the operating
mechanism, the springs are extended, and when the operating mechanism
releases the trip lever, the later returns the trip lever and armature
to their normal position, this movement resulting in the production of a
sparking current in the armature winding.

The winding of the armature is composed of two parts, one being the
primary winding, which consists of a few turns of heavy wire, and the
other the secondary winding, which consists of many turns of fine wire.

The tension of the current produced by the oscillation of the armature
is increased by closing the primary circuit at a certain position in its
movement, and then interrupting it by means of the breaker. At the
moment of the interruption, an arc-like spark is formed at the spark
plug and ignition occurs.

[Illustration:

Fig. 109. Elevation of Bosch Oscillating Magneto for Slow Speed
Engines. High Tension Type.
]

On cam shaft (c) two cams are mounted side by side. One of these cams
(a) is to be used for starting the motor, or for the retarded spark
position, while the second (b) is to be used for operation, or for the
full advance position. These cams are mounted on a sleeve, which may be
moved longitudinally on the shaft, so that the trip lever may be
operated by cam (a) or cam (b) as desired. The sleeve is caused to
rotate with the shaft by a key. Between the cam (b) and a fixed collar
(f) a spiral spring is arranged, which tends to maintain the sleeves in
the position when the cam (b) is in operation. A stop collar is also
provided to limit the movement of the sleeve beyond this full advance
position. Over this collar is fitted a hand wheel, which, in the
position illustrated in the diagram, acts together with the collar as a
stop. Around the collar is a circular key-way, and a brass bolt is
located in the hand wheel to lock into this key-way when the hand wheel
is pushed into the position indicated by the dotted lines. This movement
of the wheel forces the cam sleeve forward, and brings the retarded cam
(a) into the operating position to permit the engine to be started.

(102) The Mea High Tension Magneto.

[Illustration:

Fig. 110. Diagram of Oscillating Magneto, Showing Cam and Trigger
Arrangement.
]

The low tension winding of the ordinary type of magneto is
short-circuited by a breaker which opens at certain points of each
revolution with the result that a high voltage is generated across the
high tension winding at the moment of the break, and a spark produced
across the spark gap in the cylinder to which it is connected. The
quality of this spark, or in other words the heat value, depends among
other factors upon the particular position of the armature in relation
to the magnetic field at the moment the spark is produced. As the
armature in this type of magneto is in a favorable position for
obtaining a spark twice every revolution, two sparks can be obtained per
revolution. The timing of the spark is accomplished by opening the
breaker earlier or later, by shifting the breaker housing naturally with
the unavoidable result that if the position of the magnetic field
remains stationary, the relative position between armature and field at
the moment of the break must vary. Since, however, as explained above,
the quality of the spark depends upon this relative position, it is
apparent that a good spark, can, with a stationary magnetic field, be
produced only at one particular timing.

[Illustration:

Fig. 111. Side Elevation of “Mea” Magneto, Showing the Magnets, and
Cradle in Which the Magneto Swings When Advanced and Retarded.
]

[Illustration:

Fig. 112. Longitudinal Section of “Mea” High Tension Magneto.
]

The result of these conditions are known to everybody familiar with
automobiles. They are the difficulty of cranking a motor on one of the
average high tension magnetos, if the spark is fully retarded, and of
operating the motor on the magneto at very low speed, particularly when
it is overloaded, as for example, in hill climbing. Attempts have
therefore been made to obtain the spark, independent of the timing,
always at the same favorable position of the armature.

The distinct innovation and improvement incorporated in the Mea magneto
consists in bell shaped magnets (Fig. 111) placed horizontally and in
the same axis with the armature, instead of the customary horse-shoe
magnets placed at right angle to the armature.

This at once makes possible and practicable the simultaneous advance and
retard of magnets and breaker instead of the advance and retard of the
breaker alone as the magnets may be moved to and fro with the breaker
housing. It will be seen that as a result of this new departure the
relative position of armature and field at the moment of sparking is
absolutely maintained, and the same quality of spark is therefore
produced, no matter what the timing may be. Furthermore, the range of
timing, which with the horse-shoe type of magneto is limited to 10° or
15° at low speeds (i. e. at speeds at which a retarded spark is of
value) becomes limited only by the necessity of supplying a suitable
support for the magnets. With the standard types of Mea magnetos
described in the following, this range varies from about 45° to 70°, but
if necessary this range can be increased to any amount desired.

The bell-shaped magnets are fixed to the casing which is mounted on a
base supplied with the magneto. The timing is altered by turning the
casing and magnets together on the base.

Fig. 112 shows a longitudinal section of a four cylinder Mea magneto.
The armature F with the ball bearings 17–18 rotates in the bell-shaped
magnets 100, the poles of the magnets being on a horizontal line
opposite the armature 1. The armature is of the ordinary H type iron
core wound with a double winding of heavy primary and fine secondary
wire. On the armature are mounted the condenser 12, the high tension
collector ring 4, and the low tension circuit breaker 26–39.

The circuit breaker consists of a disc 27 on which are mounted the short
platinum 33, the other contact point 34 is movable and is supported by a
spring 30 which is fastened to the insulated plate 28 mounted on disc
27. Fiber roller 31 in connection with cam disc 40 which is provided
with two cams is located inside the breaker. Revolving with the armature
the roller presses against the spring supported part of the breaker
whenever it rolls over the two cams which of course is twice per
revolution.

[Illustration:

Magneto of Roberts Motor in Advanced Position.
]

[Illustration:

112-a. Advance and Retard Mechanism Used in the Roberts Motors. The
Magneto is Driven by a Helical Gear from the Small Pinion. By
Shifting the Gear Back and Forth on the Pinion, the Armature of the
Magneto is Advanced or Retarded in Regard to the Piston Position.
The Reason for this Change Will be Seen from the Cuts by Noting the
Position of the Lower Helix.
]

Inspection of the breaker points is made easy by an opening in the side
of the breaker box. The box is closed by a cover 74 supporting at its
centre the carbon holder 47 by means of which the carbon 46 is pressed
against screw 24. This latter screw connects with one end of the low
tension winding while the other end is connected to the core of the
armature. It will, therefore, be seen that the breaker ordinarily
short-circuits the low tension winding and that this short-circuit is
broken only when the breaker opens; it will also be apparent that when
the screw 24 is grounded through terminal 50 and the low-tension switch
to which it is connected, the low-tension winding remains permanently
short-circuited, so that the magneto will not spark. The entire breaker
can be removed by loosening screw 24.

The high tension current is collected from collector ring 4 by means of
brush 77 and brush holder 76, which are supported by a removable cover
91 which also supports the low tension grounding brush 78 provided to
relieve the ball bearings of all current which might be injurious. Cover
91 also carries the safety gap 89 which protects the armature from
excessive voltages in case the magneto becomes disconnected from the
spark plugs.

The distributor consists of the stationary part 70 and the rotating part
60 which is driven from the armature shaft through steel and bronze
gears 7 and 72. The current reaches this distributor from carbon 77
through bridge 84 and carbon 69. It is conducted to brushes 68 placed at
right angles to each other and making contact alternately with four
contact plates embedded in part 70. These plates are connected to
contact holes in the top of the distributor, into which the terminals of
cables leading to the different cylinders are placed.

In the front plate of the magneto is provided a small window, behind
which appear numbers engraved on the distributor gear which correspond
to the number of the cylinder the magneto is firing. This indicator is
of great value as it allows a setting or resetting after taking out,
without the necessity of opening up the magneto to find out where the
distributor makes contact.

The magneto proper is mounted in the base 53 which is bolted to the
motor frame and the arrangement is such that the magneto can be removed
from its base by removing the top parts 60a and 60b of the two bearings.
The variation in timing is affected by turning the magneto proper in the
stationary base which is accomplished by the spark lever connections
attached to one of the side lugs 88. The spark is advanced by turning
the magneto opposite to rotation and is retarded by turning it with
rotation. One cylinder magnetos are similar to the four cylinder except
that the distributor and gears are omitted.

(103) The Wico High Tension Igniter.

The Wico igniter produces a spark similar to that of the conventional
high tension magneto except that the heat of the spark is independent of
the engine speed. In other respects it is very different from the types
described in the preceding pages for its motion is reciprocating instead
of being rotary, and because all of the wire is stationary, the only
movement being that of the iron core that passes through the center of
the fields. The fact that the spark is of the same intensity at all
speeds makes this device particularly desirable in starting the engine
at which time the mixture is always of the poorest quality.

[Illustration:

Fig. 113. Wico Igniter. High Tension Reciprocating Type.
]

It is very simple, and is without condensers, contact points or primary
windings, and has no parts that require adjustment.

The current is generated by the reciprocating movement of two soft iron
armatures shown as a bar across the bottom of the two coils, which move
alternately into and out of contact with the ends of the soft iron
cores. The movement of these armatures in the upward direction is
produced by the motion of the engine and the speed of this movement is,
of course, proportional to the speed of the engine. The downward
movement, which produces the spark, is caused by the action of a spring,
is much more rapid than the upward movement and entirely independent of
the speed of the engine.

The magnets are made of tungsten steel, shown as two bars across the top
of the coils, hardened and magnetized and are fastened by machine screws
to the cast iron pole pieces, which serve to carry the magnetic lines of
force from the poles of the magnets to the soft iron cores. The cores,
which fit into slots milled in the pole pieces, are laminated or built
up of thin sheets of soft iron, each sheet being a continuous piece, the
full length of the core. Each core, extends from just below the top
armature, down through the pole piece, and coil to just above the bottom
armature.

Each armature consists of a number of laminations or sheets of soft iron
mounted on a spool shaped bushing, which, in turn, is loosely fitted
onto the squared end of the armature bar. The armature bar is supported
with a sliding fit in a box shaped guide which is fastened in the case.

On the outer ends of the armature bar are spiral springs held in place
by cup shaped washers and retaining pins, the combination making a
self-locking fastening similar to the familiar valve spring fastening
used almost universally on gas engines. These springs bear against the
armatures and tend to force them against the shoulders of the armature
bar.

The coils each have a simple high tension winding of many turns,
thoroughly insulated and protected against mechanical injury. They are
connected together in series by means of a metal strip, thus making one
continuous winding. In the single cylinder igniter, one end of the
winding is grounded to the case of the igniter, while the other end is
connected to the heavily insulated lead wire. This lead wire passes out
through a stuffing box, packed with wicking and thoroughly water tight,
direct to the spark plug in the cylinder.

In the two cylinder machine no ground connection is used, but both ends
of the winding are connected to lead wires passing out of the case to
the spark plugs.

The action of the igniter is as follows:—As the driving bar, through its
connection with the engine, is moved downward to its limit of travel,
carrying the latch with it, the shoulder on the side of the latch snaps
under the head of the latch block. As the motion reverses the latch
carries the latch block and armature bar upward. The lower armature,
being in contact with the stationary cores, cannot rise with the
armature bar, but the lower armature spring is compressed between its
retaining washer and the armature, while the bar rises and carries with
it the upper armature, which bears against the upper shoulders on the
bar.

As the driving bar continues its upward motion the upper end of the
latch meets the lower end of the timing wedge and, as the wedge is held
stationary by the timing quadrant, a further movement of the latch
causes it to be pushed aside until the shoulder on the latch clears the
latch block and releases it.

As the lower armature spring is at this time exerting a pressure between
the armature bar and cores through the medium of the lower armature, the
instant the latch block is released, the armature bar is quickly pulled
downward, carrying the upper armature with it. Just before the motion of
the upper armature is stopped by its coming in contact with the cores,
the lower shoulders on the armature bar come in contact with the lower
armature, and, as the bar has acquired considerable velocity, its
momentum carries the lower armature away from the cores against the
pressure of the upper armature spring, which thus acts as a buffer to
gradually stop the movement of the armature bar. The armature bar
finally settles in a central position.

The timing of the spark is accomplished by releasing the armature bar
earlier or later in the stroke. This is done by shifting the position of
the eccentric timing quadrant, which in turn varies the position of the
wedge so that the latch strikes it earlier or later in the stroke. The
timing quadrant is furnished with several notches into one of which the
top of the wedge rests, thus holding the quadrant in the desired
position.

The motion should preferably be taken from an eccentric on the cam shaft
of a single cylinder four cycle engine, or the crank shaft of a single
cylinder two cycle or a two cylinder four cycle engine. On a two
cylinder four cycle engine, it is sometimes more convenient to drive the
igniter from the cam shaft, using a two throw cam to produce the
required number of sparks. In this case the shape of the cam should be
such as to duplicate the motion of the eccentric. That is, it should
start the driving bar slowly from its lower position, move it most
rapidly at mid stroke and bring it to rest gradually at the upper end of
the stroke, exactly as is done by the eccentric motion.

When an eccentric is already on the engine the motion may be taken from
it to an igniter with a driving bar through a properly proportioned
lever that will give the required length of stroke. Where a plunger pump
is used on the engine the motion can usually be taken from the pump rod.
Where an eccentric has to be provided especially for the igniter, the
driving bar is generally used with its roller running on the eccentric.

(104) Starting On Magneto Spark.

A four-cylinder engine in good condition will come to rest with the
pistons approximately midway on the stroke and balanced between the
compression of the compressing cylinder and of the power cylinder. When
the cylinders of such an engine are charged with a proper mixture, the
engine will start by the ignition of the mixture contained in the
compressing cylinder, for the pressure produced by the ignited gas will
be sufficient to rotate the crankshaft.

[Illustration:

Fig. 114. Bosch Dual System.
]

It is essential, for the ignition system to be so arranged that a spark
can be produced at any point in the piston travel, and in this the Bosch
dual, duplex and two independent systems are successful.

The Bosch dual system, Fig. 114, is part of the equipment of many of the
cars and engines marketed, and is composed of two separate and distinct
ignition systems, one supplying ignition by direct high-tension magneto,
and the other by a battery and high-tension coil. These two systems
consist in reality of but two main parts; the dual magneto,
incorporating a separate battery timer, and the single unit dual coil
with its battery. The sparking current from either battery or magneto is
brought to the magneto distributor, so that the only parts used in
common are the distributor and the spark plugs; the common use of the
latter for both magneto and battery systems is cause for the popularity
of the dual system for motors having provision for only one set of
plugs.

In both the magneto and the battery sides the spark is produced on the
breaking of the circuit, and the coil is so arranged that by pressing a
button when the switch is in the battery position, an intense vibrator
spark is produced in the cylinder during that period when the circuit
breaker is open, which will be the case during the first three-fourths
of the power stroke. The current is transmitted to the distributor and
passes through the spark plug of the cylinder that is on the power
stroke.

[Illustration:

Fig. 115. Bosch Duplex Breaker.
]

Should the engine come to a stop in such a position that the battery
timer is closed, it will not be possible to produce a vibrator spark by
the pressing of the button, but the releasing of the button will produce
a single contact spark that will ignite the mixture and thus start the
engine.

Thus if the engine should stop in some odd position, and the spark is
produced when the piston is slightly before top center, for instance,
there will be a slight reverse impulse which will bring another cylinder
on the power stroke and into the ignition circuit. The engine will
thereupon take up its cycle in the proper direction.

In the Bosch duplex system the coil is in series with the magneto
armature, but the spark is produced under the same condition, that is,
on the breaking of the circuit. In consequence the Bosch duplex system
will permit the production of a spark during the first three-quarters of
the power stroke by the pressing of the push button set on the switch
plate.

[Illustration:

The Herz High Tension Magneto in Which the Magnets are Built up of
Thin Steel Plates Without Pole Pieces (Four Cylinder Type).
]

The Bosch two independent system is composed of a separate Bosch battery
system and a separate Bosch magneto. Although the operation of the coil
is somewhat similar to that of the dual system, the nature of the
battery system is such as to require arrangements for two separate sets
of spark plugs. The coil is not unlike that supplied with the dual
system in that by pressing a button located on the switch plate a series
of intense sparks may be produced in the cylinder at all advantageous
points of the power stroke.

CHAPTER IX
CARBURETORS

(105) Principles of Carburetion.

The carburetor is a device for converting volatile liquid fuels, such as
gasoline, alcohol, kerosene, etc., into an explosive vapor. Besides
vaporizing the liquid, the carburetor also controls the proportion of
the fuel to the air required for its combustion. The mixture produced by
the carburetor must be a uniform gas and not a simple spray to
accomplish the best results for complete and instantaneous combustion.
Proper combustion cannot be attained with any of the fuel in a liquid
state as all of the fuel contained in a liquid particle cannot come into
contact with the consuming air. It is of the utmost importance to have
the air and fuel in correct proportions so that the fuel may be
completely consumed without danger of interfering with the ignition by
an excess of air.

With few exceptions modern gasoline carburetors are of the nozzle type
in which the liquid is broken up into an extremely fine subdivided state
by the suction of the engine piston. This fine spray is then fully
vaporized or gasified by the heat drawn from the surrounding intake air
that is drawn through the carburetor and into the cylinder on the
suction stroke. Owing to the low grade fuels now on the market and to
the constantly varying atmospheric conditions it is seldom possible to
obtain a perfect vapor in the correct proportions, and for this reason
much heat is lost that would be available were the mixture perfect.

Carburetors for automobiles and boats vary in detail from those used on
stationary engines due principally to the difference in matters of
speed. A stationary engine runs at a constant speed which makes
adjustment comparatively easy, while automobile engines have a wide
range of speeds and loads making it very difficult to maintain the
correct mixture at all points in the range. The difference in the fuel
and air adjustments for varying of speeds marks the principal difference
between stationary and automobile carburetors. There are many types of
successful carburetors on the market, so many in fact that we have room
for the description of only three or four of the most prominent, but we
will say that the well known carburetors are based on the same
principles and differ only in matters of detail.

A cross-sectional view of the well known Schebler Type D carburetor is
shown by Fig. 116, and is of the type commonly used on automobile motors
and boats.

[Illustration:

MODEL “D”

Fig. 116. Cross-Section Through Type “D” Schebler Carburetor.
]

(106) Schebler Carburetor.

The carburetor is connected to the intake of the engine by pipe screwed
into the opening =R=, the gas passing from the carburetor to the engine
through this opening.

=D= is the spray nozzle which opens into the float chamber =B=, the
opening of the nozzle being regulated by needle valve =E= which controls
the quantity of gasoline flowing into the mixing chamber =C=.

On the suction stroke of the engine, air is drawn through the upper left
hand opening, past the partially open auxiliary air valve =A=, past the
needle valve =D=, through the mixing chamber =C=, and into the engine
through =R=.

The suction of the engine produces a partial vacuum in the mixing
chamber =C= which causes the gasoline to issue from the nozzle =D=, in
the form of a fine spray which is taken up by the air passing through
the passage =H=, and is taken into the engine through =R=, thoroughly
mixed. The amount of mixture entering the engine, and consequently the
engine speed is regulated by the throttle valve =K=, operated by the
lever =P=.

In order that the amount of spray given by the nozzle =D= be constant it
is necessary that the level, or height of the gasoline in the nozzle be
constant. The level is maintained by means of the float =F=, which
opens, or closes the gasoline supply valve =H=, opening it and allowing
gasoline to enter when the level is low, and closing the valve when the
level is high.

The carburetor is connected to the gasoline supply tank, by pipe
connected to the inlet =G=, through which the gasoline flows into the
float chamber =B=. The float chamber carries a small amount of gasoline
on which the float =F= rests. The richness of the mixture is controlled
by opening or closing the nozzle needle valve =E=, which passes through
the center of the nozzle =D=.

The float =F= surrounds the nozzle in order to keep the level of the
liquid constant when the carburetor is tilted out of the horizontal by
climbing hills, or by the rocking of the boat when used on a marine
engine.

A drain cock =T= is placed at the bottom of the float chamber for the
purpose of removing any water, or sediment that may collect in the
bottom of the float chamber.

At low speeds, the auxiliary air valve =A= lies tight on its seat,
allowing a constant opening for the incoming air through the space shown
at the bottom of the valve.

When the speed of the engine is much increased, the vacuum is increased
in the mixing chamber =C=, which overcomes the tension of the air valve
spring =O= and allows the valve to open and admit more air to the mixing
chamber. The action of the auxiliary air valve keeps the mixture uniform
at different engine speeds, as it tends to keep the vacuum constant in
the mixing chamber.

When the engine speed increases, the flow of gasoline is greater, and
consequently more air will be required to burn it; this additional air
is furnished by the automatic action of the valve, and when once
adjusted, compensates accurately for the different engine speeds.

The gasoline is generally supplied by a tank elevated at least six
inches above the level of the fluid in the float chamber; although in
some cases the gasoline is supplied by air pressure on a tank situated
below the level of the carburetor.

In some types of Schebler carburetors, the float chamber =B= is
surrounded by a water jacket that is supplied with hot water from the
cylinder jackets of the engine. This keeps the gasoline warm so that it
evaporates readily under any atmospheric conditions.

The quantity of air admitted to the carburetor is controlled by an air
valve shown in the air intake by the dotted lines. This is adjusted by
hand for a particular engine and is seldom touched afterward.

When starting the engine it is necessary to have a very rich mixture for
the first few revolutions, this mixture being obtained by “flooding” the
carburetor.

On the Schebler carburetor the mixing chamber is flooded by depressing
the “tickler” or flushing pin =V=.

(107) Two Cycle Carburetors.

Nearly any type of carburetor can be used on a two port, two stroke,
cycle engine providing a check valve is placed between the crank case
and carburetor to prevent the crank-case compression from forcing its
contents back through the inlet passages. A great many manufacturers
make special carburetors for two stroke motors that have the check valve
built into the carburetor itself. With three port two stroke cycle
engines a check valve is not necessary as the piston in this type of
engine performs this duty.

In that class of vaporizers known as mixing valves, the valve that
controls the flow of gasoline blocks the air passage in such a way that
an additional check valve is not necessary.

(108) Kingston Carburetors.

The Kingston Carburetor shown by Fig. 117 differs from the Schebler in
many details, the principal difference being in the construction of the
spray nozzle and the construction of the auxiliary air valve. The
throttle valve E controls the exit of the mixture through the engine
connection C which is an extension of the mixing chamber. The spray
nozzle J which is surrounded by a hood or tube is controlled by the
needle valve A which is threaded into the top of the mixing chamber,
this latter adjustment being locked into place by a button head screw
and a slot in the casting.

[Illustration:

Fig. 117. Cross-Section Through Kingston Carburetor Showing Balls Used
for Auxiliary Air Valves.
]

Surrounding the nozzle tube or hood is a curved restriction in the air
intake passage, is known as a Venturi tube, which insures a constant
relation between the air and fuel supplies. As the action of the Venturi
tube is rather complicated, it will not be taken up in detail. Air is
supplied to the Venturi passage through the intake (D). An annular float
(K) surrounds the mixing chamber that acts on the gasoline supply valve
(I) through a short lever arm. This valve is accessible for cleaning on
the removal of the cap H that covers the valve chamber. Gasoline enters
the float chamber through the fuel pipe G, and enters the spray nozzle
through the two ports in the base of the mixing chamber.

The auxiliary air valve is a particularly novel feature of this
carburetor, as no springs nor disc valves are used in its construction.
Five balls (M) of different weights and sizes act as air valves, the
balls covering the inlet ports (L) under normal operation. As the speed
increases, the balls are lifted off their seats in order of their weight
or size by the increase in suction. With a slight increase of suction,
the lightest ball covering the smallest hole is lifted first, a further
increase in suction lifts the next largest ball which still further
increases the auxiliary air intake, and so on until at the highest speed
all of the balls are off their seats. Access to the ball valves is had
through the valve caps (N). The constant supply inlet is circular and
may be set at any desired angle, as can the float chamber and gasoline
supply connection. Control and adjustment are entirely by the needle
valve.

(109) The Feps Carburetor.

The Feps carburetor has the main needle valve surrounded by a Venturi
chamber as in the preceding case, the needle valve adjustment being made
through a lever on the left of the mixing chamber. An auxiliary nozzle
directly under the auxiliary air valve at the right, connects with the
float chamber and furnishes an additional mixture of gasoline and air
for hill climbing and high speed work when the leather faced auxiliary
air valve lifts from its seat. The adjustment for this auxiliary jet is
shown at the right of the air valve chamber.

For intermediate speeds, the air valve alone is in action. No
controlling springs are used on the air valve which insures positive
action and sensitive control of the air. A float surrounding the Venturi
tube controls the fuel valve through the usual lever arm. A wire gauze
strainer placed in the fuel chamber to the left prevents dirt and water
from being drawn into the nozzle, and as this strainer easily removed it
is a simple matter to clean and prevent the troubles due to dirty fuel.

By closing the upper valve in the vertical engine connection the vacuum
is increased in the manifold when starting the engine. This increase of
vacuum draws gasoline from the float chamber and primes the engine
making the engine easy to start in cold weather. The tube through which
the gasoline is drawn for priming is the small crooked tube bending over
the float and terminating above the starting valve. Below this valve is
the throttle valve which controls the mixture in the ordinary manner.
The adjustment for intermediate speeds is made by the center knurled
thumb-screw shown over the air valve chamber which controls the travel
of auxiliary air valve. In effect this is a double carburetor, one jet
for high speed and one for low.

(111) Gasoline Strainers.

Much trouble is caused in carburetors by dirt, water and sediment,
collecting in the small passages and obstructing the flow of the
gasoline.

[Illustration:

Fig. 119. The Excelsior Carburetor in Which the Air is Regulated by a
Ball which Lies in the Tapering Venturi Tube. An Increase of Suction
Lifts the Ball and Allows More Air to Pass.
]

The purpose of the gasoline strainer is to prevent any water or foreign
matter from being carried into the carburetor, and this device should be
used on every engine if the owner wishes to be free from carburetor
troubles.

(112) Installing Gasoline Carburetors.

(1) Use brass or copper pipe from the tank to carburetor if possible to
avoid trouble from dirt and flakes of rust.

(2) When installing a gasoline tank be sure that the bottom of the tank
is at least six inches above the carburetor to insure a good flow.

(3) The tank should be provided with an air vent hole, or the gasoline
will not flow because of the vacuum in the top of the tank.

(4) All tanks should be provided with a drain cock at the lowest point
so that water and dirt may be easily removed.

(5) Clean out the tank thoroughly before filling with gasoline to avoid
clogged carburetors.

(6) Pipes from the tank to carburetor should never be placed near
exhaust pipes or hot surfaces for the gasoline vapor may prevent the
feeding of gasoline.

(7) Clean out pipes before using.

(8) If common threaded pipe joints are used on the gasoline piping, use
common soap in place of red lead.

(113) Installing the Carburetor.

The carburetor should be placed as near to the cylinder as possible, the
shorter the pipe, the less the amount of vapor condensed in the
manifold. With multi-cylinder engines the carburetor should be so
situated, that is, an equal distance from each cylinder, so that each
cylinder will inhale an equal amount of vapor.

The intake opening of the pipe should be placed near one of the
cylinders, or draw warm air off the surface of the exhaust pipe in order
that gasoline will evaporate readily in cold weather, and form a uniform
mixture at varying temperatures.

Great care should be taken to prevent any air leaks in the carburetor,
or intake manifold connections, as a small leak will greatly reduce the
strength of the mixture and cause irregular running. Always use a gasket
between the valves of a flanged connection and keep the bolts tight. If
a brazed sheet brass manifold is used, look out for cracks in the
brazing.

Leaks may be detected in the connections by spurting a little water on
the joints, and turning the engine over on the suction stroke. If the
water is sucked in the leaks should be repaired at once. Make sure when
placing gaskets, that the gasket does not obstruct the opening in the
pipe, and that it is securely fastened so that it is not drawn in by the
suction.

Never allow the carburetor to support any weight, as the shell is easily
sprung which will result in leaking needle valves.

=CARBURETOR ADJUSTMENT.= When adjusting the carburetor of multiple
cylinder engine, it is advisable to open the muffler cutout in order
that the character of the exhaust may be seen or heard. With the muffler
open, the color of the exhaust should be noted. With a =PURPLE= flame
you may be sure that the adjustment is nearly correct for that load and
speed; a yellow flame indicates too much air; a thin blue flame too much
gasoline, and is not the best for power.

Before starting for the adjustment test, try the compression, and the
spark. If the compression is poor, try the effects of a little oil on
the piston, which may be introduced into the cylinder through the
priming cup. It will be well to dilute the oil to about one-half with
kerosene. After all trouble with all the parts are clear, you may start
the engine.

Turn on the gasoline at the tank, and after standing a moment see
whether there is any dripping at the carburetor, if there is, the
trouble will probably be due to a leaky float, dirt in the float valve,
or to poor float adjustment. Locate the leak and remedy it before
proceeding further. Dirt on the seat of the needle valve may sometimes
be removed by “flooding” the carburetor, which is done by holding down
the “tickler” lever for a few seconds, causing the gasoline to overflow,
and wash out the dirt.

If the motor has been standing for a time it would be well to “prime”
the motor by admitting a little gasoline into the cylinder through the
priming cup, or by pushing the tickler a couple of times so as to
slightly flood the carburetor.

Now turn on the spark and turn over the engine for the start, taking
care that the throttle is just a little farther open than its fully
closed position. If the engine takes a few explosions and stops, you
will find the nozzle, or that some part of the fuel piping is clogged
which will stop the engine. If the motor gradually slows down, and
stops, with =BLACK SMOKE= issuing from the end of the exhaust pipe, or
=MISFIRES= badly, the mixture is =TOO RICH=, and should be reduced by
cutting down the gasoline supply by means of the needle valve adjusting
screw. If it stops quickly, with a =BACKFIRE=, or explosion at the
supply of gasoline should be =INCREASED= by adjusting the mouth of the
carburetor, the mixture is =TOO LEAN=, and the needle valve.

In all cases be sure that the auxiliary valves are closed when the
engine is running slowly, with the throttle closed, as in the above
test. If they are open at low speed, the mixture will be weakened and
the test will be of no avail.

After adjusting the needle valve as above until the engine is running
(with throttle in the same partially closed position), turn the valve
slowly in one direction or the other until the motor seems to be running
at its best. During the above tests the spark should be left retarded
throughout the adjustment, and the throttle should not be moved.

The carburetor should now be tested for high speed adjustment, by
opening the throttle wide (spark ¼ advanced), and observing the action
of the motor. If the engine back-fires through the carburetor at high
speed, it indicates that the mixture is too weak which may be due to the
auxiliary air valve spring tension being too weak and allowing an excess
of air to be admitted. Increase the tension of the spring, and if this
does not remedy matters, admit a little more fuel to strengthen the
mixture by means of the needle valve adjustment. Do not touch the needle
valve if you can possibly avoid it, or the high-speed adjustment, as the
fuel adjustment will be disturbed for low speed.

If the engine misfires, with loud reports at the exhaust, does not run
smoothly, or emits clouds of black smoke at high speed, the engine is
not receiving enough air in the auxiliary air valve, consequently the
tension of the spring should be reduced.

Back firing through the carburetor denotes a weak mixture.

Trouble in cold weather may be caused either by slow evaporation of the
gasoline, or by water in the fuel that freezes and obstructs the piping
or nozzle. In cold weather a higher gravity of gasoline should be used
than in summer, as it evaporates more readily, and therefore forms a
combustible gas the rate at lower temperatures.

To increase the rate of evaporation of the gasoline, it should be placed
in a bottle and held in hot water for a time before pouring it into the
carburetor or tank, or the air inlet warmed with a torch.

The cylinder water jacket should always be filled with hot water before
trying to start the engine, and will prevent the gas from condensing on
the cold walls of the cylinder. Often good results may be had by
wrapping a cloth or towel around the carburetor, that has been dipped in
hot water.

The cylinder of an air-cooled engine may be warmed by =gently= applying
the heat of a torch to the ribs, or by wrapping hot cloths about it.

The tank, piping, and carburetor should be drained more frequently in
cold weather than in hot, to prevent any accumulation of water from
freezing, and stopping the fuel supply. A gasoline strainer should
always be supplied on the fuel line, and should be regularly drained.

The motor may often be made to start in cold weather by cutting out the
spark, and cranking the engine two or three revolutions with the
throttle wide open. The throttle should now be closed within ⅛ of its
fully closed position, the ignition current turned on, and the engine
cranked for starting. This system will very seldom fail of success at
the first attempt.

Carburetor flooding is shown by the dripping of gasoline from the
carburetor, and which results in too much gasoline in the mixture.
Flooding may be caused by dirt accumulating under float valve, by a
leaking float (Copper Float), by Water Logged Float (Shellac worn off
Cork Float), by float adjustment causing too high a level of gasoline,
by leaking float valve, by cutting out ignition when engine is running
full speed, by rust or corrosion sticking float valve lever, by float
binding in chamber, by float being out of the horizontal, by float valve
binding in guide, by excessive pressure on gasoline, or by tickler lever
held against float continuously.

Dirt accumulated under float valve may sometimes be flushed out by
depressing tickler lever several times; if this does not suffice, the
cap over the valve must be removed, and the orifice cleaned by wiping
with a cloth.

=LEAKING FLOAT VALVES= should be reground with ground glass or very fine
sand; never use emery as the particles will become imbedded in the
metal, which will be the cause of worse leaks.

Should the shellac be worn off of a cork float allowing the gasoline to
penetrate the pores of the cork, a new float should be installed, as it
is a doubtful policy for owner to give the float an additional coat of
shellac.

=MISFIRING AT LOW SPEED.= If the carburetor cannot be adjusted to run
evenly on low speed after making all possible adjustments with the
needle valve, the trouble is probably due to air leaks between the
carburetor and engine, caused by broken gaskets, cracked brazing in the
intake manifold, or by leaks around the valve stem diluting the mixture.

=INCORRECT VALVE TIMING= will cause missing, especially on multiple
cylinder engines, as the carburetor cannot furnish mixture to several
cylinders that have different individual timing. Look for air leaks
around the spark edge openings, and be sure that all valves seat gas
tight. Always be sure that the auxiliary air valve remains closed at low
speeds, as a valve that opens at too low a speed will surely cause
misfiring as it dilutes the mixture.

=MISSING= in one cylinder may be caused by an air leak in that cylinder.

=WATER= in gasoline will cause misfiring, especially in freezing
weather, as it obstructs the flow of fuel to the carburetor. The
carburetor and tank should be drained at regular intervals, and if
possible, a strainer should be introduced in the gasoline line.

=CLOGGED NOZZLE.= Particles of loose dirt in the nozzle will occasion an
intermittent flow of gasoline that will result in misfiring. The nozzle
should be cleaned with a small wire run back and forth throughout the
opening.

=CLOGGED AIR VENT= in the float chamber will change the level of the
fuel, and will either “starve” the engine, or flood the carburetor. The
air in the float chamber is a very small hole, and is likely to clog.

=HOT FUEL PIPE.= If the fuel pipe that connects the tank with the
carburetor, becomes hot, due to its proximity to the exhaust pipe of
cylinders, vapor will be formed in the pipe that will interfere with the
flow of fuel.

=DIRT UNDER AUXILIARY AIR VALVE= will prevent the valve from seating
properly, causing the engine to misfire at low speed.

=CRACKS OR LEAKS= in intake pipe or gaskets will cause intermittent
leaks of air and spasms of misfiring. Old cracks that have been brazed
will sometimes open and close alternately causing baffling cases of
spasmodic misfiring.

=DIRT IN AIR INTAKE= will change the air ratio, and the increased
suction will cause a greater flow of gasoline. Do not place the end of
the inlet pipe in a dusty place, nor where oil can be splashed into it
by the engine. Clean out periodically.

“=LOADING UP=” of the inlet piping in cold weather on light load is
caused by the mixture condensing in the intake pipe. The only remedy is
to keep the piping warm, or to heat the inlet air.

=CLOGGED OVERFLOW PIPE=, with engines equipped with pump supply will
cause flooding, as the fuel does not return rapidly enough to the tank.

(114) Kerosene Vaporizer for Motorcycles.

An ingenious vaporizing device has been designed for the use of kerosene
as a fuel for motorcycle engines, by the M. G. and G. Motor Patents
Syndicate, Ltd., England, is described in Motor Cycling. The device
consists of a comminuter, or vaporizer, which screws into the
sparkling-plug hole in the cylinder, the plug being transferred to an
aperture in the vaporizer, a feeder for regulating the supply of fuel to
the vaporizer, and a throttle and air barrel, or mixing chamber, for the
purpose of proportioning the amount of air and gas supplied to the
engine, and for controlling the speed of the machine as in an ordinary
carburetor.

The feeder receives the fuel—in this case kerosene—although any heavy
oil can be used with almost equally good results. The feeder answers a
purpose similar to the ordinary float chamber of the carburetor, i. e.,
to regulate the amount of kerosene it is required to pass through the
vaporizer. It consists of a small chamber mounted upon the end of a pipe
leading to the vaporizer. Kerosene is fed to this device by a copper
pipe from the tank, and enters at the lowest point through a 3/16-inch
hole or jet. This is covered by a small valve, operated by engine
suction. The lift of this valve can be adjusted by the insertion of
washers to suit any particular size of engine, just as one would use
various size jets to suit either a large or small engine. One of the
greatest advantages of the device lies in the size of this aperture or
jet, inasmuch as it cannot possibly choke up with grit, and even water
will pass through and not stop the operation of the carburetor. At the
top of the feeder is an air hole, which admits just sufficient air to
pass the kerosene through the vaporizer, the reason for this being that
the heat of the vaporizer shall only act upon the fuel, the mixture
afterwards being balanced by air being admitted through the mixing
chamber.

After the kerosene leaves the feeder it passes through a pipe to the
vaporizer. This consists of a gunmetal body with cooling ribs cast on
the outside, whilst through the center runs a thin copper tube of ⅝-inch
diameter and only 20 gauge, which would really melt during the heat of
combustion were it not for the fact of the fuel passing through it. The
heat derived from this formation of vaporizer is approximately 1,000
degrees Fahr. Inside the central tube is a strip-steel spiral, which
serves the double purpose of giving a centrifugal motion to the fuel,
and at the same time forming a supporter for the tube, preventing it
crushing under the force of the explosions. It is, of course, understood
that the inside of the feeding tube is entirely isolated from the
combustion chamber. The sparking plug is screwed into the wall of the
vaporizer, which is now really an extension of the combustion chamber.

Obviously this slightly reduces the compression of the engine, which,
however, is a necessary feature when kerosene is used as a fuel. After
passing through this device the kerosene is thoroughly vaporized, and
the vapor is led through a flexible pipe to the throttle chamber; this
taking the place of an ordinary carburetor and being fitted to the
induction pipe.

There are two slides, operated by Bowden levers from the handle-bar, one
being for the main air intake and the other for the gas.

[Illustration:

Fig. 121-a. The English Aster Electric Lighting Unit.
]

Undoubtedly the greatest claim for this vaporizer is the fact that
practically no carbon deposit forms upon the inside of the cylinder or
on the piston. What little deposit is formed takes the shape of small,
soft flakes, which, instead of adhering to the cylinder walls, break
away before they have attained any size and are blown through the
exhaust valve. Altogether, this device seems to have finally solved the
problem of using kerosene as a fuel on air-cooled engines, especially if
the carbon deposit difficulty has been finally overcome.

The device was fitted to a 3½ h.p. Matchless with a White and Poppe
engine. In order to start up, a small gasoline tank, holding about one
half-pint of gasoline, is fitted under the main tank and communicates
with the feeder. Half a minute is all that is necessary running on
gasoline, when the kerosene can be turned on. The machine would fire at
a walking pace, and could also be accelerated up to 55 m.p.h.

CHAPTER X
LUBRICATION

(116) General Notes on Lubrication.

No matter how carefully the surface of a shaft or bearing may be
finished, there always remains a slight roughness or burr of metal,
which although of microscopic proportions is productive of friction or
wear. Each minute projection of metal on a dry shaft acts exactly as a
lathe tool, when the shaft revolves in cutting a groove in the
stationary bearing. Since there are a multitude of these projections in
a journal, the wear would be very rapid, and would in a short time
completely destroy either the shaft or bearing, no matter how highly
finished in the beginning.

When lubricating oil is introduced into a bearing it immediately covers
the rubbing surface, and as the oil has a considerable resistance to
being deformed, or is “stiff,” it separates the surface of the shaft
from that of the bearing for a distance equal to the thickness of the
oil film. With ordinary lubricants this distance is more than enough to
raise the irregularities of the shaft out of engagement with those of
the bearing. This property of “stiffness” in the oil is known as
“viscosity.” The value of viscosity varies greatly with different grades
of oil, and also with the temperature with the result that the allowable
pressure on the oil per square inch also varies. With oils of low
viscosity a small pressure per square inch on the bearing will squeeze
it out, and allow the two metallic surfaces to come against into
contact, causing wear and friction, while an oil of greater viscosity
will successfully resist the pressure.

The life and satisfactory operation of the engine depends almost
entirely upon the lubricant and the devices that apply it to the
bearings. Excessive wear and change in the adjustments are nearly always
the result of defective lubricating devices or a poor lubricant. The
principal lubricants are:

(1) Solid lubricants such as graphite, soapstone, or mica.

(2) Semi-solid lubricants such as vaseline, tallow, and soap emulsions,
or greases compounded of animal fats, vegetable and mineral oils; and

(3) Liquid lubricants, such as sperm oil, or one of the products of
petroleum, the latter medium being the class of lubricant most suitable
for internal combustion engines, owing to its combining the qualities of
a high flash-point with a comparative freedom from either acidity or
causticity.

Oils of animal or vegetable origin should never be used with gas engine
as the high temperatures encountered will char and render them useless.
Tallow and lard oil are especially to be avoided, at least in a pure
state.

In the cylinder only the best grade of =GAS ENGINE= cylinder oil should
be used, which according to different makers has a flash point ranging
from 500 to 700 degrees. Using cheap oil in the cylinder is an expensive
luxury. In general, the oils having the highest flash points have also
the objectionable tendency of causing carbon deposits in the combustion
chamber and rings which is productive of preignition and compression
leakage. The lower flash oils have a tendency to vaporize and to carry
off with the exhaust which will leave the walls insufficiently
lubricated unless an excessive amount is fed to the cylinder. By
starting with samples of well known brands recommended by the builder of
the engine it will be an easy matter to find which is the cheapest and
gives the best results. In figuring the cost of oil do not take the cost
per gallon as a basis, but the cost for so many hours of running, or
better yet the number of horse-power hours. Unless you are fond of
buying replacements and new parts do not stint on the oil supply.

On the other hand, an excess of oil should be avoided as this means not
only a waste of oil through the exhaust pipe, but trouble with carbon
deposits and ignition troubles as well. Foul igniters, misfiring, and
stuck piston rings are the inevitable result of a flood of lubricating
oil. When a whitish yellow cloud of smoke appears at the end of the
exhaust pipe, cut down the oil feed. The exhaust should be colorless and
practically odorless.

Too much oil cannot be fed to the main bearings of the crank shaft if
the waste oil is caught, filtered and returned to the bearings by a
circulating system, for the flood of oil not only insures ample
lubrication but removes the heat generated as well. The bearings require
a much lighter oil, of a lower fire test than the cylinder oil. It is
evident that its viscosity is a most important element, as it determines
the allowable pressure on the shaft. The viscosity of an oil varies with
the temperature and is greatly reduced at cylinder heat. A comparative
test of the viscosity or load bearing qualities of an oil may be made by
making bubbles with it by means of a clay pipe; the larger the bubble,
the higher the viscosity of the oil.

Different sizes of bearings, and bearing pressures, call for oils of
different viscosities, and consequently an oil that would be suitable
for one engine would not answer for another; heavy bodied oils being
used for heavy bearing pressures, and light thin oil for small high
speed bearings. The best way to determine the value of an oil for a
particular shaft bearing is by experiment, attention being paid to its
adaptability for the feeding devices used.

The compression attained in a gas engine cylinder depends to a certain
extent upon the body of the cylinder oil, for many engines that leak
compression past the rings with thin oil will work satisfactorily with a
heavy viscous oil that clings tightly to the surfaces. An engine will
often lose compression when an oil of poor quality is used.

Air cooled engine cylinders require an oil of heavier body than water
cooled because of the higher temperature of the cylinder walls. Gum and
sticky residue are usually formed by animal oils or adulterants added to
the numeral oil base. Oils containing free acids should be avoided as
they not only corrode and etch the bearing, but also clog the oil pipes
or feeds with the products of the corrosion.

Free acid is left from the refining process, and may be determined by
means of litmus paper inserted into the oil. If the litmus paper turns
red after coming into contact with the oil, acid is present, and the oil
should be rejected.

The following are the characteristics of an oil suitable for use on an
engine:

(a) The oil must be viscous enough to properly support the bearings or
to prevent leakage past the piston rings.

(b) It should be thin enough so that it can be properly handled by the
oil pumps, or drip freely in the oil cups.

(d) It should contain no free acid.

Ordinarily a good grade of fairly heavy machine oil will be suitable for
use on the bearings of the average engine, such as the cam-shaft and
crank-shaft bearings.

Only very light clean oil, or vaseline should be used on ball-bearings,
as heavy greases and solid lubricants pack in the races and cause
binding or breakages.

Flake graphite is much used as lubricant, and too much cannot be said in
its favor, as it furnishes a smooth, even coat over the shaft, fills up
small scores and depressions, and makes the use of light oil possible
under heavy bearing pressures. With graphite, less oil is used, as the
graphite is practically permanent, and should the oil fail for a time,
the graphite coat will provide the necessary lubrication until the feed
is resumed without danger of a scoring or cutting. In fact, when
graphite is used, the oil simply acts as medium by which the graphite is
carried to the bearings.

If graphite is injected into the cylinder in small quantities it greatly
improves the compression, as it fills up all small cuts and abrasions in
the cylinder walls.

A good mixture to use for bearings is about 1½ teaspoonsful of graphite,
to a pint of light machine oil, thoroughly mixed.

Graphite can be placed in the crank chamber of a splash feed engine, by
means of an insect powder gun.

Trouble with oil cups is always in evidence during cold weather, as the
oil congeals, and does not drip properly into the bearings. The fluidity
of the oil can be increased in cold weather by the addition of about ten
per cent of kerosene to the oil.

If too much oil is fed to the cylinders, the piston rings will be
clogged with gum, and a loss of compression, or a tight piston will be
the result. An excess of oil will short-circuit the igniter or sharp
plugs, and will form a thick deposit in the combustion chamber that will
eventually result in preignition or back-firing. Deposits and gum formed
in the cylinder will cause leaky valves and a loss of compression. Feed
enough oil to insure perfect lubrication, but not enough to cause light
colored smoke at the exhaust.

Lubricating systems may be divided into three principal classes:
Sight-feed, splash system, and the force feed system. Sight feeding by
means of dripping oil cups is too common to require description, and is
used on many stationary engines, both large and small.

The splash system is in general use on small high speed engines both
stationary, and of the automobile type.

The force feed system in which oil is fed under pressure by a pump is by
far the most desirable as the amount of oil fed is given in positive
quantities proportional to the engine speed, and with sufficient
pressure to force it past any ordinary obstructions that may exist in
the oil pipe.

Another system that is half splash, and half force feed, is the pump
circulated system much used in automobiles.

=THE SPLASH FEED SYSTEM= is the simplest of all, as the bearings are
lubricated by the oil spray caused by the connecting rod end splashing
through an oil puddle located in the bottom of the closed crank case.
The piston and cylinder are lubricated by the spray, as well as the
bearings, as the lower end of the piston projects into the crank chamber
at the moment that the connecting rod end strikes the oil puddle.

To maintain constant lubrication, it is necessary that the oil in the
puddle be kept at a constant height, or as in some cases be varied in
such a way that the surface of the puddle is raised and lowered in
proportion to the load on the engine. In the average engine the oil
level is maintained by overflow pipes or openings that allow any excess
of oil over the fixed level to flow back to the pump. In the Knight
engine the puddles are formed in movable cups which are connected with
the throttle in such a way that the opening of the throttle raises the
oil level and supplies more oil to the engine at the greater load, or
speed.

Oil in splash systems is supplied by a low pressure pump, usually of the
rotary type, in the base of the engine. Oil from the pump passes to the
bearings, drops into the puddle, overflows through the overflow opening,
and returns to the pump through a filter, the same oil being used over
and over again until exhausted. This strainer should be removed
occasionally and the dirt removed, for should it be allowed to collect
it is likely to obstruct the oil supply. The oil should be replaced
before it becomes too black or foul, the crank case and bearings
thoroughly cleaned with kerosene, and new oil replaced. The supply may
be interrupted by the failure of the pump, caused by sheared keys or
leakage of air in the suction line due to cracks. It would be well to
run the engine for a few minutes with the kerosene in the crank case, in
order that all of the oil may be removed. See that the drain cock is
closed at the bottom of the cylinder or all of the oil will be lost.
Lock the valve handle carefully so that it cannot jar open. If light
colored smoke appears in intermittent puffs with a multiple cylinder
engine, it indicates that one cylinder is receiving too much oil.

(117) Force Feed Lubricating System.

The force feed system is by far the most reliable of all oiling systems,
as it feeds uniformly and continuously at almost any temperature, and
against the pressure of practically any obstruction in the pipe.

The oil is supplied by a small pump driven from the engine, the pump
being incased in the oil tank housing. Frequently a hand pump is used in
combination with the power pump when starting the engine, or at times
when the power pump is out of service. A single pump is used with any
number of leads, each lead, or feed, having an independent regulating
valve and sight feed, or a pump unit may be provided for each lead,
depending on the size of the engine.

(118) Bosch Force Feed Oiler.

The force feed of the Bosch Oiler is so positive in character, that the
flow of oil is not affected by heavy back-pressure due to elbows and the
diameter of the conducting pipes. Springs, valves and other devices,
which would check the flow of oil, are fundamentally eliminated. The
amount of oil fed may be accurately and permanently regulated. Glands
and other packings and bushings are eliminated. Connecting rods and all
links are eliminated by the direct application of the movements of the
oscillating cam disks to the pump plungers and piston valves.

Each feed of this oiler is provided with a separate pump element
consisting of a pump body plunger and a piston valve, the suction and
feed ducts connecting directly with the pump body of their respective
elements. With this construction, pump elements may be replaced or
added. The oiler requires no attention other than to be supplied with
oil; and the opening and closing of the valves, pet cocks, etc., on
starting and stopping the machine is rendered unnecessary. The correct
and regular operation of the elements may be verified by observation of
the reciprocating movements of the regulating screws.

Each pump plunger is provided with an adjusting screw through which the
feed may be regulated from 0 to 0.2 cubic centimeters for each stroke.

The Bosch Oiler (Fig. 121) being positively driven by the machine that
it supplies, the oil fed is in all cases proportional to the engine
speed; overloads are thus automatically taken care of.

The circular arrangement of the elements of the Bosch Oiler permits the
device to be driven by a single shaft, and the oil is forced through the
feeds from a single reservoir to the required points of application. A
pump element consists of a pump body 1, a pump plunger 2 and a piston
valve 3, and is supported on the base plate 13. The elements are
arranged concentrically about the drive shaft in such a manner that the
pump plungers form a circle around the circle formed by the piston
valves.

[Illustration:

Top View of Bosch Force Feed Oiler.
]

[Illustration:

Fig. 121. Cross-Section Bosch Oiler.
]

The pump cam disk 20 and the valve cam disk 22 are set on the drive
shaft at other than a right angle with its axis, and the rims of the
disks are gripped by slots formed in the heads of the pump plungers and
piston valves. The relation of these cam disks is such that the valve
cam disk is 90° in advance of the plunger cam disk. The valve cam disk
is solid on the drive shaft, but the pump cam shaft is loose and driven
through a lug on the valve cam disk. When the drive of the pump is
reversed, the lug on the valve cam disk frees itself and again takes up
the drive of the pump cam disk, after the drive shaft has made a half
revolution.

Regulating screws 4 are set in the slotted heads of the pump plunger,
and by means of this the back-lash or play of the cam disk may be
regulated. The regulating screws are provided with lock nuts, and
project through the cover of the oil tank housing, being exposed by the
removal of the filler cover 42. The filler opening is provided with a
removable strainer to prevent the entrance of foreign particles into the
oil tank.

Pump shaft 14 is driven through worm gear 23 which meshes with worm 24
on drive shaft 25; drive shaft 25 projects from the oiler housing, and
is coupled with the driving shaft of the machine to be lubricated.

Base plate 13 is attached to the oiler cover by three stud bolts, thus
permitting the removal of the entire oiler mechanism from the housing.

The quantity of oil in the oil tank is shown by gauge glass 44.

On the starting of the machine to which the oiler is attached, the pump
shaft and the cam disks that it supports are set in motion through worm
24 and worm gear 23. A direct reciprocating motion is given to the pump
plunger and to the piston valve by the rotation of the cam disks which
have a movement similar to that of the “wobble saw.” The relation of the
cam disk is such that the piston valve movements are 90° in advance of
the movements of the pump plungers. The pump will run in either
direction without alteration.

To secure this effect a play of 90° is provided between the cam disk.
When cam 22 is driven clockwise, cam disk 20 is driven by the lug which
meshes with a lug on disk 22. The cams are then in such a relation that
the cam valve disk is 90° in advance of the pump cam disk. When
reversed, cam 20 remains at rest until cam 22 catches the lug and cam
20, when the drive continues as before. The cams are then in the same
relation as previously for as the valve disk 22 has traveled through
180° it is evident that it is 90° in advance of the pump disk.

(119) Castor Oil for Aero Engines.

Castor oil is used almost exclusively in the Gnome and other rotary
engines of the same type, but has not been particularly successful on
stationary cylinders.

Chemically, castor oil differs from all other vegetable or animal oils
in containing neither palmitin or olein. It is soluble in absolute
alcohol, but practically insoluble in gasoline. On the other hand, the
castor oil is capable of dissolving small quantities of mineral oil, the
more fluid they are the less it absorbs of them. But the insolubility of
castor oil in mineral oil disappears completely when it is mixed with
even a very small quantity of another vegetable or animal oil, such as
colza or lard oil. An adulteration may thus result in a serious reversal
of the oil’s best qualities; in fact, in serious seizures, Castor oil
does not attack rubber, but it contains 1 to 2 per cent of acid fats;
sometimes more.

“In my opinion says a writer in ‘_Autocar_’ castor oil can only be used
in fixed cylinders with impunity for short distances and then with
repeated cleanings between runs, but on rotary engines of the Gnome type
cleaning is almost unnecessary. The reason is that one cannot
consistently use castor oil over and over again, for the fact is
indisputable that it has a far greater tendency than mineral oils to
absorb oxygen, and so gradually to increase in body and finally to gum.
When once it commences to gum the carbonization becomes more rapid,
because the thickened and pitch-like oil acts as an insulating covering
on the top of the pistons and of the cylinder, and cannot get away with
sufficient rapidity to avoid decomposition and baking to a coke.
Therefore if castor oil is to be used on the ordinary stationary
cylinder type of engine, it is necessary to wash out the crank chamber
and to replace with fresh oil at frequent intervals. On a rotary engine
such as the Gnome this cleaning is unnecessary, because there is a
continuous stream of fresh castor oil brought into the crank chamber and
then thrown by centrifugal force past the pistons and through the
cylinder into the exhaust. Thus the stream of oil never has sufficient
time to oxidize fully, gum or decompose. This action of centrifugal
force accounts for the large consumption of oil on the rotary engine,
and also for the fact that the pistons and cylinders keep comparatively
clean.

“In thus criticizing the use of castor oil I do not wish it to be
inferred that it is not an excellent lubricant. What I wish to suggest
is that in the case of an internal combustion engine it must be made
with discretion. A point in favor of castor oil is the fact that it
maintains its viscosity in a remarkable manner at high temperatures, and
that at those high temperatures it has a peculiar creeping or capillary
action which enables it to spread uniformly over the whole of the
metallic surfaces, whereas under the same conditions a similarly bodied
mineral oil would be unevenly distributed in patches. Another point is
that the specific heat of castor oil is considerably higher than that of
a pure mineral oil. This is in its favor, insomuch that it shows castor
oil to be a better heat remover than a mineral oil.

“Motorists and aviators have from time to time informed me that they are
using castor oil, but have apparently been under some misapprehension. I
find that they have been using a brand of prepared oil under the
impression that it is a specially refined castor oil, or that it is a
blend of castor oil.”

[Illustration:

Producer Gas Engine Plant at Göttingen, Germany, Consisting of Four
3,500 Horse-Power Units.
]

A simple method for testing the purity of castor oil is at the disposal
of all. It is known as the Finkener test. Ten cubic centimeters of
castor oil is placed in a graduate. Five times as much alcohol, 90 per
cent, is added and stirred in. The solution should remain clear and
brilliant at 15 to 20 degrees C. An admixture of foreign oils, even if
only 5 per cent, riles the solution at this temperature, though not
above it.

(120) Force Feed Troubles.

The most common trouble with force feed systems is the failure of the
operator to remove the dirt collected by the strainer. The oil piping
should be cleaned out at least once every year by means of a wire and
gasoline, to remove any gum that may have been deposited. Driving belts
should be kept tight to prevent slipping, and belts that are soaked with
oil should be cleaned with gasoline and readjusted.

Leaking pump valves generally of the ball type are a common cause of
failure. They may leak because of wear or by an accumulation of grit and
dirt on their seats, which prevents the valves from seating properly. If
the valves leak, the oil will be forced back into the tank, or will not
be drawn into the pump cylinder at all, depending on whether the inlet
or discharge valve is the offender. Plunger leakage which is rare will
cause oil failure.

If the oil pipes that lead to the bearings rub against any moving part,
or against a sharp edge, a hole will be worn in the pipe, a leak caused
which will prevent the oil from reaching the bearing. A dented or
“squashed” pipe will prevent the flow of oil.

The set screw or pin holding the pulley to the pump shaft may loosen and
cause it to run idly on the shaft without turning the pump. This will of
course, prevent the circulation of oil.

The worm and worm wheel may wear so that the pump is no longer driven by
the pulley shaft, or a poor pipe connection may leak all that the pump
delivers.

The amount of oil required by each lead or bearing should be carefully
determined by experiment, and kept constantly at the right number of
drops per minute.

The feed adjustments jar loose, and should be inspected frequently.

(121) Oil Cup Failure.

Oil cups should be cleaned out frequently with gasoline or kerosene, as
any gum or lint will interfere seriously with the feed. They should be
adjusted and filled frequently to prevent any possible chance of a hot
bearing.

Oil cups should be as large as possible in order that they may be left
for considerable periods without danger of a hot box.

Cold weather affects the oil feed to a considerable extent, especially
with small oil cups, and they should be kept as warm as possible. When
heavy oils are used a cold draft will stop the feed.

Oils may be made more fluid in cold weather by the addition of about ten
per cent of kerosene.

(122) Hot Bearings.

A hot bearing is almost a sure sign of insufficient oil, and the trouble
should be located and remedied immediately. Oil pumps stopping, clogged
oil pipes or holes, frozen oil, or oil leaks are common causes of hot
bearings.

Never allow an engine to run with a hot bearing for any length of time,
as the bearing or piston may seize tight and wreck the engine. Inspect
the journals frequently to see if they are above normal temperature. A
hot, binding bearing often causes the effect of an overload on the
engine, slowing it down, and increasing the governor and fuel feed, this
is followed in a short time by the bearing seizing.

(123) Cold Weather Lubrication.

It is by no means uncommon trouble in cold weather to find excessive
fluctuations in pressure as the engine speed and temperature of the oil
varies. Thus, if the pressure be set correctly with the engine running
fast, and when just started up, it will be found, after half-an-hour’s
running, that, with the engine turning slowly, the pressure is far too
low, owing to the oil having become thin. If the pressure be then reset,
it may be found on next starting up from cold that the gauge goes hard
over, and may very easily be burst if the engine is run fast.

The point is one to which many designers of engines pay far too little
attention, though the difficulty may be very easily gotten over. The
secret lies in having the by-pass outlet of most ample proportions, so
that the excess of oil, however thick, can get away quite easily. If
there is any throttling of the by-pass, back pressure must result with
consequent increase of the pressure at which the by-pass valve comes
into operation. In other words, the pressure of the main supply to the
bearings will be increased.

A writer to “The Motor,” London solved this problem in the following
manner:

“Originally, the by-passage was somewhat small, little larger than the
oil delivery pipe to the engine, which was about 3/16 inch bore, and the
result was that the pressure when starting with the oil cold rose to
about 25 pounds per square inch, and fell to about one pound per square
inch with the oil hot and the engine running slow. It was possible,
however, to bore out the by-pass passage and fit a larger pipe, about
three times the area of the main delivery pipe, with the result that the
oil, when cold, never rose above about 15 pounds per square inch,
however fast the engine run. When thoroughly heated, the normal running
pressure was about 6 pounds per square inch, falling to 2 pounds per
square inch with the engine only just turning over, which brings up the
question of the correct working pressure. This will vary very largely
with the design of the engine, but, broadly speaking, the higher the
pressure the better for the bearings. The limiting figure is determined
by the tendency of the engine to throw out oil at the end of crankshaft
bearings, and by the amount that gets past the piston rings. Obviously,
an engine with new, tight bearings and new piston rings will stand a
higher pressure without undue waste of oil or excess deposit in the
cylinder head than will an old engine with worn bearings and slack
rings. And, again, the question will be affected by the design of the
pistons. For instance, where the trunk of the piston is bored for
lightness, much more oil will get past the rings than in cases where a
‘solid’ trunk is employed. Roughly speaking, 8 to 15 pounds per square
inch is a good figure for a new, high-speed engine. An old and worn
engine, particularly if not of a high-speed type, may require no more
than 2 to 6 pounds per square inch.”

[Illustration:

Brookes Gasoline-Electric Generating Units for Operating Search
Lights. An Independent Unit is Used for Each Light.
]

The writer recently encountered a rather curious difficulty in
connection with obtaining a free by-pass. The return pipe from the
by-pass led into the case carrying the gearwheels of the camshaft and
magneto drive, and oil continually flooded out from the end of the
camshaft and other bearings. The waste and mess were sufficiently
serious to warrant investigation, and the cover plate over the gears was
accordingly taken off. It was then noticed that the oil delivered to the
gearwheel case had only two small holes by which to drain away to the
crankcase. The flow from the by-pass was beyond the proper capacity of
these holes, and so the whole gearwheel case became filled with oil
under considerable pressure, quite possibly 2 or 3 pounds per square
inch, and it was not surprising that oil exuded from the ends of the
bearing. A few extra limber-holes, if one may borrow a nautical
expression, were drilled through to the crankcase, and no further
trouble was experienced.

(124) Plug Oil Holes When Painting.

When the chassis of the car is repainted it is well to see that all
exposed oil holes are stuffed with waste to prevent them from being
choked. Failure to observe this precaution may result in the holes being
clogged with paint, which if not removed before the car is started, will
prevent oil reaching the bearings.

(125) Oiling the Magneto.

Never oil the circuit breaker or circuit breaker mechanism, unless for a
drop of sperm oil that may be applied to the cam roller by means of a
toothpick. If oil gets on the circuit breaker contact points, it will
cause them to spark badly, resulting in pitting or destruction of the
points. If the oil is occasionally applied to the cam roller or should
oil accumulate on breaker points, the breaker should be rinsed out with
gasoline to remove the surplus.

Pitted or carbonized contact points are capable of causing much trouble,
and gummy oil or dirt will develop this trouble quicker than any other
cause. Use only the best grade of thin sperm oil on the ball bearings.

In the course of time the circuit breaker contact points will wear or
burn, causing imperfect contact, and too great a separation between the
points. The contacts should be examined from time to time, and if rough
or pitted, should be dressed down to a flat even bearing by means of a
dead smooth file, and the distance readjusted. The contacts should not
bear on a corner or edge, but should bear evenly over their entire
surface to insure a maximum primary current and spark.

CHAPTER XI
COOLING SYSTEMS

The object of the cooling system is not to keep the cylinder cold, but
to prevent the heat of the successive explosions from heating the
cylinder walls to a degree that would vaporize the lubricating oil and
prevent satisfactory lubrication of the cylinder and piston. The hotter
the cylinder can be kept without interfering with the lubricating oil,
the higher will be the efficiency of the engine and the greater the
output of power.

To obtain the greatest power from an engine, the heat developed by the
combustion should be confined to the gas in order that the pressure and
expansion be at a maximum, it is evident that the pressure and power
will be reduced by over-cooling as the heat of the expanding gas will be
taken from the cylinder and transferred to the cooling medium. The
temperature of the cylinder, and therefore the efficiency of the engine
is determined principally by the vaporizing point of the lubricating
oil, and consequently the higher the grade of the oil, the higher the
allowable temperature of the cylinder.

If cold water from a hydrant or well be forced around the water jacket
rapidly, the power will be greatly reduced owing to the chilling effect
on the expanding gas. There is not much danger in keeping the cylinder
of an air cooled engine too cool, in fact the great difficulty with this
type of engine is to keep it cool enough to prevent an excessive loss of
lubricating oil.

The valves, particularly the exhaust valves, should be surrounded with
sufficient water to keep them cool as they are subjected to more heat
than any other part of the engine, and are liable to wrap or pit. The
water leaving the jacket of a gasoline engine should not exceed 160° F.,
as temperatures in excess of this amount cause deposits of lime scale.

When possible, a portion of the cooling water should be run into the
exhaust pipe immediately after it has completed its flow around the
valves and cylinders, as the water cools the gas so suddenly that the
exhaust to atmosphere is rendered almost noiseless, and the exhaust pipe
is kept much cooler and less liable to cause fire by coming into contact
with combustible objects.

On some engines the exhaust pipe is water jacketed for some distance to
prevent dirty rusty pipes in the vicinity of the engine mechanism and
also to prevent injury to the operator should he come into contact with
the pipe.

Small engines and medium size vertical engines usually have the water
jacket cast in one piece with the cylinder casting and others have a
separate head that is bolted to the cylinder.

In the latter type the water flows from the cylinder to the head through
ports or slots cut in the end of the cylinder water jacket that register
with similar slots in the jacket of the head.

Thus in this construction we have not only to pack the joint to prevent
leakage of gas from the cylinder, but also to prevent the leakage of
cooling water from the jacket into the cylinder, or outside. Thus there
is always a chance of water leaking into the cylinder bore and causing
trouble unless the packing is very carefully installed and looked after.

In large horizontal engines the gas and water joints are never made at
the same point, as it would be practically impossible to prevent leakage
into the cylinders of such engines.

When the cylinder and cylinder water jackets are cast in one piece
without a water joint at the junction of the cylinder and the head, the
water connection between the head and the cylinder being made by pipes
external to the castings.

Small, portable, stationary engines are sometimes “=HOPPER COOLED=,” or
cooled by means of the evaporation of the water contained in an open
water jacket that surrounds the cylinder.

The hopper is merely an extension of the water jacket such as used on
all water cooled engines, the only difference being that the top of the
hopper is open permitting the free escape of water vapor or steam to the
atmosphere. The water level should be carried within two inches from the
top of the hopper.

Water when converted into vapor or steam absorbs a great quantity of
heat, and of course the steam carries the heat of evaporization with it
when it escapes to the atmosphere.

As the hopper is open to the air, the temperature of the cylinder cannot
exceed 212° F. (temperature of boiling water) as long as there is
sufficient water left to cover the cylinder.

The hoppers contain sufficient water for runs of several hours’
duration, and as the water boils away or evaporates, it may be
replenished by simply pouring more water in the top of the hopper.
Hopper cooling is used principally for small portable engines where the
weight of a water tank or other cooling device would be objectionable
and also where there is danger of freezing the pipes and connections of
other systems.

The loss of water by evaporization is from .3 to .6 of a gallon per
horsepower hour; that is, for a 5 hp. engine the loss would be from 1.5
to 3 gals. for every hour that the engine was operated under full load.

The cylinder and the water jacket are cast in one integral piece, with
no joints of any kind in either the combustion chamber or in the water
jacket.

[Illustration:

Fig. 124. Air Cooled “Grey Eagle” Aeronautical Motor. Note the Depth
of Cooling Ribs.
]

A system of cooling by which the heat of the walls is radiated to the
air directly without the medium of water is often used on small high
speed engines, and is known as “=AIR COOLING=.”

This type of cylinder is surrounded with radiating ribs or spires which
increases the radiating surface of the cylinder to the extent that the
required amount of heat is lost to allow of economical lubrication. This
system is desirable where the weight of radiators and water would be a
drawback, where it would be inconvenient to obtain water, or where there
would be trouble from freezing. An air cooled motor generally is
provided with a fan that increases the efficiency of the radiating
surface by changing the air between the ribs. With aeronautical motors
such as the Gnome, and Gray Eagle, shown by Fig. 124, the circulation of
the air due to the propeller and the rush of the aeroplane is sufficient
to thoroughly cool the machine.

As a rule, the air cooled motor is made more efficient in fuel
consumption than the water cooled type because of the high temperature
of the cylinder walls. In fact all engines are air cooled eventually,
whether the heat is radiated at a high temperature by the fires, or at a
lower temperature through the circulating water and radiator.

When the engines are of the portable type, and likely to be used out of
convenient reach of water, the hopper or =EVAPORATOR TANK= system is
used, the tank system being used for the larger engines. In effect, the
tank system is the same as the hopper cooler, the heat being dissipated
principally by evaporation, although some heat is radiated from the
surface of the tank itself. The difference between the two systems is
merely one of size, the tank offering a greater area for the emission of
heat than the hopper.

A tank-cooled engine has one pipe running from the top of the cylinder
to a point near the top of the tank, the bottoms of the cylinder and
tank being connected together by another pipe.

When the water becomes heated in the cylinder, it expands and becomes
lighter than the cold water in the tank and consequently rises to the
surface of the water in the tank through the upper pipe. As the warm
water flows into the tank, it is immediately replaced by the heavier
cold water that flows into the cylinder from the bottom of the tank
through the lower pipe. This successive discharge of the heated water
from the cylinder to the tank sets up a continuous flow of water through
the water jacket of the cylinder, which transfers the excess heat of the
cylinder to the tank where it is dissipated to the atmosphere by
evaporation and radiation.

The circulation of the cooling water set up by the action of heat or the
expansion of the water is called Natural or Thermo Syphon circulation.

Cooling tanks may be used profitably with stationary engines if the tank
can be located so that vapor and steam produced will not be
objectionable. If the tank is used inside of a building, the vapor
should be conveyed to the outside air by means of a stack or chimney, or
by means of a small ventilating fan driven by the engine.

The water consumption of a cooling tank is from .3 to .6 gallons per
hour, the exact quantity varying with the atmospheric conditions and
temperature.

[Illustration:

Fig. 124-a. De Dion Bonton “V” Type, Air Cooled Aero Motor. The
Cooling Air is Furnished by a Blower Mounted on the Crank Shaft at
the Rear of the Motor. The Propeller is Driven from the Cam Shaft.
Courtesy of Aero.
]

For engines of from 10 to 50 horsepower a battery of cooling tanks may
be used, the number depending on the size of the engine. For natural
circulation, the tank should be installed so that bottom of the tank is
above the bottom of the cylinder for maximum results, if placed much
lower the engine should be provided with a circulating pump.

If water is used from the city mains from 10 to 15 gallons will be
required per horsepower hour, the exact quantity varies with the
temperature of the supply.

The water from very large stationary engines is cooled by allowing it to
trickle down through a cooling tower, which is built somewhat like the
screen cooler only on a larger scale. The object of the cooling tower is
to present the greatest possible surface of water to the air, this is
accomplished by screens or baffles that turn the water over and over as
it falls. The water, well cooled, finally collects in a cistern at the
base of the tower from which it is pumped back to the engine and thus is
used over and over again. This is an ideal system when water is
expensive and when engines of considerable power are used.

(126) Cooling System Troubles.

Overheating caused by deposits of scale or lime in the jacket is one of
the most common causes of an excessively hot cylinder. When hard water
containing much lime is heated, the lime is deposited as a solid on the
walls of the vessel forming a hard, dense, non-conducting sheet. When
scale is deposited on the outside of the cylinder walls it prevents the
transfer of the heat from the cylinder to the cooling water and
consequently is the cause of the cylinder overheating. Besides acting as
an insulator or heat, the deposit also causes trouble by obstructing the
pipes and water passages, diminishing the water supply and aggravating
the trouble.

Scale interferes with the action of the thermo syphon system more than
with a pump, as the pressure tending to circulate the water is much
lower. Whatever system is used, the scale should be removed as often as
possible, the number of removals depending, of course, on the “hardness”
of the water.

Large horizontal engines are usually provided with hand holes in the
jacket, through which access may be had to the interior surfaces on
which the scale collects. Under these conditions the scale may be
removed by means of a hammer and chisel.

The scale may be softened by emptying half the water from the jacket and
pouring in a quantity of kerosene oil, the inlet and outlet pipes being
stopped to prevent the escape of the oil. The engine should now be
started and run for a few minutes with the mixture of kerosene and water
in the jacket; no fresh water being admitted during this time. After the
mixture has become boiling hot, stop the engine and allow it to cool; it
will be found that the scale has softened to the consistency of mud, and
may easily be washed out of the jacket.

The work of removing the scale can be reduced to a minimum by filling
the jacket with a solution of 1 part of Sulphuric Acid and 10 parts of
water, allowing it to stand over night. The scale will be precipitated
to the bottom of the jacket in the form of a fine powder and may be
easily washed out in the morning.

If the jacket water is kept at a temperature above 185° F. the amount of
scale deposited will be nearly doubled over that deposited at 160° F.

Wash out sand and dirt occasionally, a strainer located in the pump line
will help to keep the jacket clear and free from foreign matter.

If a solution of carbonate of soda, or lye, and water are allowed to
stand in the cylinder over night, the deposit will be softened and the
work with the chisel will be made much easier.

If a radiator is used (automobile or aero engine) the deposit can be
removed with soda, never use acid, lye, or kerosene in a radiator or
with an engine with a sheet metal water jacket.

=Obstructions in Water Pipes.= Poor water circulation may be caused by
sand, particles of scale, etc., clogging the water pipes, or by the
deterioration of the inner walls of the rubber hose connections.
Sometimes a layer of the rubber, or fabric of the hose may loosen from
the rest and the ragged end may obstruct the passage.

A sharp bend in a rubber hose may result in a “kink” and entirely close
the opening.

The packing in a joint may swell, or a washer may not have the opening
cut large enough, either case will result in a poor circulation.

Sediment is particularly liable to collect or form in a pocket, pipe
elbow, or in the jacket opposite the pipe opening. Oil should be kept
off of rubber hose connections as it will cause them to deteriorate
rapidly, this may finally result in water circulation troubles. Rubber
pipe joints between the engine and the radiator or tanks are advisable
as they do not transmit the vibration of the engine, and hence reduce
the strain on the piping. A strainer should be provided in order to
reduce the amount of foreign material in the water.

=Radiators.= A clogged radiator will give the same results as a clogged
jacket with the exception that steam will issue from the radiator if the
circulation is not perfect.

If the radiator becomes warm over its entire surface it is evident that
the water is circulating, the temperature being a rough index of the
freedom of the water, or the interior condition of the surfaces. A
leaking radiator may be temporarily repaired with a piece of chewing
gum.

Should the radiator be hot and steaming at the top and remain cold at
the bottom for a time, it shows that the water is not circulating and
that the jackets on the cylinders are full of steam. Such a condition
usually is indicative of clogging between the bottom of the radiator and
pump, between the pump and bottom of cylinders, or of a defective pump.

[Illustration:

Natural Gas Plant at Independence, Kansas. Used for Pumping Gas From
the Wells to Various Distributing Points.
]

Thermo-syphon radiators are more susceptible to the effects of sediment
and clogging than those circulated by pumps.

A radiator may fail to cool an engine because of a slipping or broken
belt driving the fan, or on account of a loose pulley or defective belt
tension adjuster. Keep the belt tight. The fan may stick on account of
defective bearings.

Radiator may be =AIR BOUND=, due to pockets or bends in the piping
holding the air.

=Rotary Pump Defects.= A defective circulating pump will cause
overheating, as it will supply little if any water to the jackets.

Examine the clutch or coupling that drives the pump and see that the key
or pin that fastens it to the shaft is in place. Next see that the
driving pinion and gear are in mesh and properly keyed to their
respective shafts.

In some cases the shaft has been twisted off, or the coupling pin
sheared through by reason of the shaft rusting to the pump casing. Worn
gears or impellers =IN THE PUMP= reduce the output and cause heating, as
will a sheared driving pin in the impeller. Wear and bad impeller fits
reduce the capacity of the pump.

Scale or sediment collecting in the pump sometimes strips the pins or
impeller teeth. Note the condition of the gaskets or whether the pump
shaft is receiving the proper amount of grease. Put a strainer in pump
intake. See that no leak occurs on pump intake pipe.

To avoid the trouble and expense due to cracked water jackets, never
neglect to drain the cylinders and piping from all water in freezing
weather. Drain cocks should be provided at the lowest points in the
water circulating system for this purpose. It would be well to provide
an air cock at the highest point in the line in order that all of the
water can drain out as soon as the drain cock is opened.

With automobile or portable engines it is not always convenient or
possible to drain the engine every time that it is stopped and
consequently we must resort to a “non-freezing” mixture or at least a
solution that will not solidify under ordinary winter temperatures. Such
a solution should be chosen with care, as many will cause the corrosion
and destruction of the jackets and piping; =NEVER USE COMMON SALT= and
water under any conditions.

Wood alcohol and water in equal parts, is often used for automobiles,
but is rather expensive for portable engines having a comparatively
great amount of water in circulation.

Unless the circulating system is absolutely air tight, as it is when
radiators are used, alcohol will be lost by evaporation and must be
replaced frequently.

The most practical solution for the average engine used, is made up by
dissolving about five pounds of =CALCIUM CHLORIDE= in one gallon of
water. This mixture will stand a temperature of about 15° F below zero,
and if diluted to half the strength will not freeze above zero.

Use =CALCIUM CHLORIDE=, not ordinary Salt (Sodium Chloride).

CHAPTER XII
GOVERNORS AND VALVE GEAR

(127) Hit and Miss Governing.

When the speed of an engine is held constant for varying loads by
missing explosions on the light loads and increasing the number for
heavy loads, the governing system is said to be of the “hit and miss
type.” The mixture remains constant in quantity and quality in this type
of engine. A hit and miss governor allows only enough charges to be
fired to keep the speed constant.

When the load falls off, with a natural tendency on the part of the
engine to increase its speed, the governor cuts out the next explosion
by holding the exhaust valve open and the inlet closed, thus preventing
fresh mixture from being drawn into the cylinder. With an increase in
load, the governor allows the valves to follow their regular cycle with
the result that a greater or less number are fired in succession. Hit
and miss governing is very economical for only full charges of the most
perfect mixture are fired, and with short exhaust pipes the scavenging
is much better than with other forms of governing. The principal
difficulty with this system is that the regulation is not as perfect as
with some other types.

(128) The Throttling System.

Unlike the hit and miss system of governing, the throttling type of
governor allows the engine to take an explosion on every working stroke,
the speed being held constant by either regulating the quality or
quantity of the mixture, or both. Throttle governor permits of close
speed regulation as the impulses are more frequent and not so violent as
with the hit and miss system.

The governor acts directly on the throttle valve, and at no time is the
operating mechanism disengaged from the driving cam. The throttle
governor engine is particularly well adapted for driving dynamos, supply
electric light, as the uniform speed gives a smooth, steady light
without the objectionable flickering so likely with the hit and miss
engine. To obtain the best fuel economy with a throttling engine, it
should be run close to its rated capacity, as the poor and imperfect
mixture admitted at light loads considerably increases the fuel
consumption.

[Illustration:

Fig. 76-d. De La Vergne Governor.
]

Practically all motors of the variable speed type such as are used on
automobiles and motor boats are controlled manually by the throttle;
although marine motors are often fitted with governors to prevent racing
when the screw is lifted out of the water in a heavy sea.

(129) The Controlling Governor.

The governor proper depends upon centrifugal force for its action, and
generally consists of two weights which are pivoted at one end to a
rotating shaft driven by the engine. When these weights are rotated
rapidly the bottoms are thrown outwardly by the centrifugal force and
tend to assume a horizontal position. The faster the weights are
rotated, the greater will be the tendency for the bottoms of the weights
to come into the horizontal, and the greater will be the pressure
exerted by them on the controlling levers connected to the throttle. It
is evident that the centrifugal pull on the weights varies directly with
the speed of rotation and consequently with the speed of the engine. The
exact relation between the travel of the weights and the speed of the
engine is controlled by a spring that acts between arms cast on the
weights and the spindle. If a heavy spring is used, greater speed must
be attained to move the weights a given distance than with a weak
spring, as the centrifugal force must be greater.

[Illustration:

Fig. 124-d. Governor and Governor Mechanism of Fairbanks-Morse Type “R
E” Engine. The Fly-Balls, Springs, and Control Rods Are Shown on the
Governor Staff. The Upper End of the Bell Crank Goes to the
Throttle.
]

The throttle valve of the engine is connected by a rod to the governor
through a sliding collar in such a way that the movement of the governor
weights due to an =INCREASE= of speed partially closes the valve until
the speed of the engine is reduced. Should the speed of the engines
=DECREASE=, owing to a heavy load coming on, the spring will force the
balls to occupy a lower position which will increase the valve opening
until the engine again reaches the normal speed for which the tension of
the spring is adjusted.

Thus the speed of the engine is kept practically constant by the action
of the governor in opening and closing the throttle, which in turn,
varies the =QUANTITY= of mixture admitted to the cylinder. The =QUALITY=
of the mixture is varied by hand, in the engine by means of cocks in
both the air and gas pipes. The =GOVERNOR PROPER= is of practically the
same construction in the hit and miss engine, the difference of the two
types lying in the method of connecting it to the controlling system. In
one case (hit and miss) the governor controls the exhaust valve, and in
the other (throttling) it controls the quantity of gas admitted by the
throttle valve. The speed of the engine may be varied within certain
limits by a lever connected to the valve controlling rod.

(130) Types of Governors.

The types of governors used on the leading makes of engines will be
found described and illustrated in Chapter V which treats of each engine
in detail.

(131) Governor Troubles.

Hit and miss governor troubles may be due to the following defects:

=BINDING GOVERNOR COLLAR=, stuck with dirt or gummy oil, will cause the
engine to die under load, and overspeed on light load.

=INLET VALVE LOCK= may be worn in such a manner as to prevent the valve
from seating during the idle strokes and lose fuel, or cause
overspeeding.

=DETENT LEVER KNIFE EDGE= may be worn, or rounded off, so that the
exhaust valve is not held open for the idle stroke. This defect will
cause overspeeding.

=SPEED CHANGING LEVER= may work loose and cause the speed to vary
erratically.

=GOVERNOR WEIGHTS= may be stuck on pins with dirt or gummy oil causing
engine to overspeed.

=LOST MOTION IN GOVERNOR GEAR= such as loose pins and bushings, worn
rollers, or bearing surfaces will cause the speed to vary continuously.
=LOST MOTION= on portable engines will cause the engine to run normally
in one position, and overspeed in another.

=WEAK OR BROKEN SPRINGS ON GOVERNOR= will cause engine to lose speed or
die down altogether. Springs may be stiffened by pulling out the coils.

=DRY GOVERNOR BEARINGS= or joints will cause binding and cause governor
to act sluggishly. Use plenty of lubricant.

=WORN ROLLERS= may cause a speed variation. Keep the governor well
oiled, clean, and free from gum.

If the knife edges are allowed to slip over one another, much wear is
caused on the cams and if allowed to continue, sooner or later the
engine will run away. Springs will weaken with age and hard usage. With
belt driven governors see that the belt is tight and that the lacing is
in good condition for a slack belt may allow the engine to overspeed.

I advise that every purchaser of an agricultural motor read his
instruction book with care, that is, locate all oil holes and note the
action and purpose of every part. If in doubt as to any part of its use
write the manufacturer of the motor.

(132) Throttling Governor Troubles.

=STICKING GOVERNOR VALVE= will cause the engine to overspeed; remove the
gum and dirt.

=LOOSE PINS OR BUSHINGS=, or lost motion in any part of the governor
mechanism will cause irregular motion or running; be sure that the
bearings and joints are well oiled.

=STUCK PINS= will cause the engine to overspeed on light loads, and fall
down on the normal load, or cause racing.

=WEAK OR BROKEN SPRINGS= will cause the engine to lose speed or to lie
down altogether even on light loads.

=STIFF GOVERNOR SPRINGS= cause the engine to speed up.

=SLIDING COLLAR= stuck will cause racing or a fluctuation in the speed.
Keep the governor well oiled, clean, and free from gum.

The governing valve should be removed from its care frequently and
thoroughly cleaned with kerosene. Deposits of carbon and gummed oil at
this point are dangerous because of the likelihood of their causing
overspeeding.

(133) Valve Gear Arrangement.

The valve operating mechanism lay-out depends upon the cylinder and
valve arrangement, and consequently varies in detail with different
engines.

[Illustration:

Overhead Valve Arrangement of the Fairbanks-Morse “R E” Engine.
]

Fig. F-14–15 in Chapter V, shows the valve gear of an upright engine
having the inlet and the exhaust valves located in pockets placed at one
side of the cylinder. The inlet valve is operated by a valve rod that is
actuated by the cam. The exhaust valve stem is raised and lowered,
directly, through a cam on the same shaft. The method of driving the
valves in this engine is practically standard for all vertical engines
having the valves located in pockets. This system is used in a greater
proportion of automobile engines.

The opposed engine has the cylinders arranged on opposite side of the
crank case, and makes an exceedingly well balanced and quiet running
engine; as there is no point in the revolution where either the crank
throws or connecting rods have an unequal angularity, or differ in
velocity.

While this type of two cylinder engine is common in automobile practice,
it is not often met with in stationary work, the cam-box and the cam
being directly in the center of the crank case.

The opposed type of engine is particularly well adapted for aeroplane
service as a steady, quiet running engine is an absolute necessity
because of the frail construction of the aeroplane frame.

(134) Cam Shaft Speeds.

The valves of the gas engine are opened and closed by means of cams or
eccentrics, that are geared to the crankshaft, and which also control
the timing.

As a four stroke cycle engine performs all of the events, or a complete
cycle in two revolutions of the crankshaft, it is evident that the cam
must go through the routine in one revolution or must revolve at
=ONE-HALF OF THE CRANKSHAFT SPEED=.

Therefore the cam gear ratio must be as one is to two, the smaller gear
being placed on the crankshaft, the gears being known as the “half time
gears.”

As a two stroke cycle engine goes through the routine of events in every
revolution, the cam-shaft must run at crankshaft speed so that the cam
outline makes one revolution in the same time as the crank. The cam
shaft speeds given here apply to all engines of the corresponding cycle
no matter whether the valves are of the poppet, rotary or slide-sleeve
types.

(135) Valve Gear Troubles.

The valve gear mechanism causes trouble principally through the wear of
the various parts which results in a change in the valve timing, or in
the lift of the valves. Loss of power, =MISFIRING=, and overheating are
the result of such derangements.

Often trouble is caused in reassembling the valve mechanism after the
engine has been torn down for repairs, which trouble may generally be
traced to incorrect gear meshing.

The following list will give the principal defects due to the wear of
the valve mechanism.

(a) =WORN CAM GEARS= change timing because of play, or “back lash” in
the teeth, or cause a howling or grinding noise, that will cause the
owner to believe that the end of the engine is near. =MISFIRING= and
=LOSS= of power are probable results of a change in the timing. If any
of the teeth are stripped from the gear you may be sure that the timing
is changed. Replacement with a new gear is the only cure for a worn or
broken gear.

(b) =GEARS NOT IN PROPER MESH= due to an error in assembling the gears,
will prevent the engine from being started, or cause misfiring and loss
of power.

The maker of the engine generally marks the teeth that go together, but
if no such marks appear, the owner should center punch or scratch them
before taking down the engine.

(c) =A GEAR SLIPPING ON THE SHAFT=, due to a missing key in the gear, or
to a loose set-screw will cause all of the troubles due to a change in
the timing. Examine the key carefully, for dirt often collects in the
key-way to such an extent that it is liable to be mistaken for the key.
Keys and pins have sheared in two, allowing the shaft to slip in the
gear.

(d) =WORN CAM-SHAFT BEARINGS= are the cause of trouble, as they will
change both the timing and the lift of the valves. If much play exists
in the bearing, it will prevent the valves from lifting at the proper
time, and will also reduce the lift by the amount of the play, which
sometimes has a considerable effect on the free passage of the gases. If
the cam-shaft bearings are of the bushing type they should be replaced
with new paying attention at the same time to the condition of the
shaft. If rough or shouldered the shaft should be machined to a dead
smooth surface. If on a large engine and of the adjustable type, the
shims should be removed as required or the wedges adjusted.

(e) =LOOSE CAMS OR ECCENTRICS= will change the timing because of lost or
sheared keys. If your cams are not integral with the shaft, look them
over occasionally and be sure that the keys are tight. Loose cams will
produce thumping and grinding and may often be located by the sound. See
that the key-way is not worn when fitting keys.

If the cams are fitted with taper pins it would be well to ream the hole
before placing new pins, as there is a liability of the hole being worn
oval.

(f) =A TWISTED OR SPRUNG CAM-SHAFT= will change the positions of the
cams relative to one another, and not only will change the time of all
cylinders, but will change their time relatively causing the engine to
run out of balance, or produce an unusual vibration.

(g) =WORN CAMS= are causes of a change of timing on all types of
engines, and are the most frequent cause of reduced valve lift with its
consequent trouble of overheating.

If the outline or contour of a cam is changed with wear it should be
replaced, if keyed to the shaft, as it will be a constant source of
trouble. If the cams and cam-shaft are in one integral piece, it will be
necessary to replace the entire shaft.

(h) =WORN CAM ROLLERS AND ROLLER PINS= will reduce the lift of the
valves, and in the case of a broken or sheared pin will prevent the
valve from lifting at all. Always replace loose pins or loose rattling
roller.

(i) =PUSH ROD DEFECTS.= Too much clearance between the push rod and
valve stem will reduce the lift of the valves and change the timing. The
clearance for small engines should be equal to the thickness of a
visiting card, and for large engines is somewhat larger, say 1–16″. The
increase of clearance is due principally to wear.

Too small a clearance should be avoided for the reason that the valve
stems expand with the heat and will lift the valves too soon, or even
permanently until readjusted. Broken valve springs will cause trouble,
or lost keys that retain the valve spring washers. Loose adjusting
screws on the push rods or stripped threads will delay the valve
opening.

(j) =TAPPET LEVER DEFECTS= are generally caused by wear or poor
adjustment. Loose pins or bushings, too much clearance between the
tappet and valve stem or broken valve springs, or loose adjusting screws
will produce changes in the timing or valve lift.

(k) =BENT VALVE ROD.= A bent valve rod will shorten the travel of the
valves, and change the timing.

(l) =CAM LEVER OR PIN= will cause timing troubles if the pin or bushing
are loose or worn, by reducing the travel of the valves.

When occasion arises for the removal of valves, the opportunity should
be taken to clean the stems and guides, which may be more or less gummed
with ancient oil. Freedom of valve movement is of extreme importance,
and for this reason neither the cleaning nor the lubrication of the
stems and guides should be neglected. The occasional use of a little
kerosene will prevent gummy accumulations, but care should be taken not
to allow the kerosene to wash out all of the oil and thereby leave the
surfaces dry.

A broken valve spring, though not a common occurrence, is not an unknown
possibility. If no spare spring is at hand, a plan that can be
recommended is to turn the broken spring end for end, thus bringing the
finished ends up together; this will prevent the spring from shortening
by overlapping, and winding itself together.

(136) Valve Timing.

The exact time at which the valves of a four stroke cycle engine open
and close depends to a great extent upon the speed of the engine, the
fuel used, the compression pressure, and the relation of the bore to the
stroke.

As these items vary in nearly every make of engine there has appeared in
the technical press, a great mass of seemingly conflicting data. Engine
speed is the principal factor in determining the timing.

Correct valve timing plays a considerable part in the output and
efficiency of an engine, for if the inlet valve, for example, opens too
late, the cylinder will not receive a full charge. If it opens too early
the hot gases in the cylinder will ignite the gas in the carburetor and
cause back-firing. Should the exhaust open too late, the retention of
the hot gas in the cylinder is likely to cause overheating.

The timing of the valves is usually expressed in degrees of the circle
described by the crank-pin, or the angle formed by the crank with the
center line of the cylinder at the time the valve is to open or close.

(137) Valve Setting on Stationary Engines.

The exhaust should open when the crank lacks 30° of completing the outer
end of the power stroke, that is, the crank should make an angle of 30°
with the center line of the cylinder when the exhaust valve begins to
open, and should be inclined =AWAY= from the cylinder. Some makers have
the exhaust open a little later in the stroke, but little is to be
gained with a later opening as the retention of the charge beyond 30°
heats the cylinder and does very little towards developing power. The
only advantage of the late opening is that the valve opens against a
lower pressure and causes slightly less wear on the parts.

The exhaust valve should close 5° =AFTER= the crank has passed the
=INNER= dead center on the exhaust or scavenging stroke, although some
makers close the valve exactly on the dead center. The 5° should be
given to allow the gas all possible chance of escape. The piston is said
to be on the inner dead center when it is in the cylinder as far as it
will go, and on the outer dead center when it is on the center nearest
the crankshaft.

The =INTAKE= valve should open about 5° =AFTER= the exhaust valve
closes, or 10° after the crank passes the inner dead center. The inlet
valve should =NEVER= open before the exhaust valve closes on a low speed
engine. The above timing is for engines running 150–600 R.P.M. The
automatic type of inlet valve, of course, cannot be timed, but attention
should be paid to the strength and tension of the spring and the
condition of the valve stem guides.

The inlet valve should close 10° =AFTER= the crank passes the outer dead
center in order that the cylinder be filled to the fullest possible
extent. If the valve closed exactly on the dead center a partial vacuum
will exist and the charge retained in the cylinder will be comparatively
small, but if the valve remains open past this point the air would have
time to completely fill the cylinder and develop the capacity of the
engine. The longer the inlet pipe, the longer the inlet valve opening.

(138) High Speed Engine Valve Timing.

The faster a motor turns, all other things being equal, the greater the
amount of advance necessary with the valves, as the higher the speed the
less the time required to fill or empty the cylinder. In a short stroke
high speed motor the exhaust should close and the intake open as early
as possible in order to admit the full charge. The exhaust should open
early to allow of the full escape of the gases, as the time allowed for
expulsion is extremely short when an engine runs 1,000 R.P.M. and the
back pressure is liable to be considerable.

The inlet valve of high speed engines should remain open for a
considerable period after the crank passes the outer dead center on the
suction stroke, owing to the inertia of the gases which tends to fill
the cylinder. Lengthening the period of opening of the inlet valve in
multiple cylinder engines produces better carbureting conditions and
reduces the variations of pressure in the manifold.

=EXHAUST VALVES.= The exhaust valve should begin to open 40° =BEFORE=
the crank reaches the =OUTER= dead center on the working stroke, and
should close 10° =AFTER= the crank has passed the inner dead center.

=INLET VALVES.= The inlet valve should open 15° =AFTER= the crank passes
the inner dead center on the suction stroke, and should close 35° after
the crank passes the outer dead center.

The inlet valve should never open before the exhaust valve closes,
although this is done on several types of high speed aeronautical
engines. The makers of these engines claim that this practice scavenges
the combustion chamber more thoroughly and makes the mixture more
effective owing to the inertia of the burnt gases forming a partial
vacuum in the combustion chamber. The writer has never been able to get
satisfactory results with this timing and doubts whether it can be
accomplished successfully.

In timing an engine great care should be taken to get the crank exactly
on the dead center.

(139) Timing Offset Cylinders.

The only difference in timing engines with offset cylinders and timing
those with the center line of the cylinder in direct line with the crank
shaft, is in the locating of the dead center. With no offset, the center
of the cylinder, the crank pin and the crank shaft are all in one direct
line when the engine is on the dead center.

With offset cylinders the crank pin lies to one side of the cylinder
center line when on the dead center, on either the inner, or the outer
center. To find the center on an offset engine proceed as follows:

Turn the engine over slowly until the crank-pin reaches either the
extreme top or bottom point of the crank circle, depending on which
center is to be determined, and then turn very slowly until the centers
of the piston-pin, crank-pin, and crank-shaft are in line. With the
average engine this will be found a difficult and tedious job, and it
will be well to mark the dead center on the flywheel or other convenient
point to prevent a repetition of the job. The quickest method of
accomplishing the feat is to remove the spark plug or relief cock to
gain access to the piston, and insert a rod or pointer in the opening
thus provided.

Draw the piston back a short distance from the end of the stroke with
the pointer resting on the head of the piston, and mark this position of
the piston both on the pointer, and on the flywheel, using some
stationary part of the engine as a reference point.

Now turn the crank over the center line until the piston is moving in
the opposite direction, and is the same distance from the end of the
stroke as shown by the mark on the pointer. Mark this position on the
flywheel using the same reference mark as before. We now have two marks
on the flywheel, and will bisect the distance between them, using the
dividing mark to obtain the center.

Place the bisection mark even with the reference point used for
obtaining the two previous marks on the flywheel, and the engine will be
on the true dead center, as the flywheel is now midway between two
points of equal stroke.

(140) Auxiliary Exhaust Ports.

To decrease the amount of hot gas and flame passing over the exhaust
valve some makers provide their engines with auxiliary exhaust ports,
which are similar to the exhaust ports used on two stroke cycle engines.

The auxiliary exhaust consists of a series of holes drilled or cored
through a rib on the cylinder wall, the holes being so situated that
they are covered by the piston until it is at the extreme end of its
outward stroke. The holes are not uncovered until the burning charge has
been expanded and cooled to the greatest extent possible in the
cylinder. As soon as the piston uncovers the ports the greater portion
of the dead gas escapes instantly to the atmosphere, carrying with them
the greater percentage of the heat and flame. The small amount of
residual gas that remains is forced out through the exhaust valve in the
usual manner, thus no flame ever reaches the exhaust valve.

The use of auxiliary exhaust ports produces a cooler cylinder as the gas
passes over the cylinder wall only once, and consequently is in contact
with the walls only one-half of the time usual with the ordinary system.
The cool cylinder lessens the liability of =PREIGNITION= and decreases
the consumption of cooling water and lubricating oil. Auxiliary exhaust
ports are particularly desirable on air cooled engines.

(141) Valves and Compression Leaks—Misfiring.

Owing to the intense heat in the cylinder, and the action of the gases
on the valves the seating surfaces become =ROUGH= and =PITTED= which
causes leakage and loss of compression. Exhaust valves cause the most
trouble in this respect as they are surrounded by the hot gases during
the exhaust stroke and are much hotter than the inlet valves.

To determine the value of the compression, turn the engine over slowly
by hand.

Leaking inlet valves usually are productive of =BACK FIRING= or
=EXPLOSIONS IN THE CARBURETOR= intake passages, or in the mixing valves,
as flame from the cylinder leaks through the valve and fires the fresh
gas in the intake.

=MISFIRING OR LOUD EXPLOSIONS= at the end of the =EXHAUST PIPE= are
indicative of leaky exhaust valves, if the mixture is correct and the
ignition system above suspicion. Misfiring caused by leaky exhaust
valves is due to combustible mixture escaping from the cylinder to the
exhaust pipe and being ignited by the succeeding exhaust of the engine.

If the engine has more than one cylinder, test one cylinder at a time,
opening the relief valves on the other cylinders. Now take a wrench and
=ROTATE= the inlet valve on its seat, for it may be that some particles
of carbon or dirt have been deposited on surface of the valve seat which
prevents the valve from closing properly. Rotating the valve will
usually dislodge the deposit.

Try the compression again; if there is no improvement, rotate the
exhaust valve on its seat in the same manner, and repeat the test for
compression. =ROTATING THE VALVES IN THIS MANNER WILL OFTEN MAKE THE
REMOVAL OF THE VALVES UNNECESSARY.= When the valves are closed the end
of the valve stem should =NOT= be in contact with the =PUSH ROD=, or cam
lever. Suitable =CLEARANCE= should be allowed between the end of the
valve stem and the operating mechanism when the valve is closed; this
clearance varies from the thickness of a visiting card on small engines
to ⅛ of an inch on the large. If the valve stem is continually in
contact with the push rod it cannot seat properly and consequently will
leak. Wear on the valve seats and regrinding reduces this clearance,
wear on the ends of valve stems and push rods from continuous thumping
increases it. Keep the clearance constant and equal to that when the
engine was new. On many engines this clearance is adjustable to allow
for wear by lock nuts on the ends of the valve stems or push rods.

If the above attempts have proved unsuccessful remove the exhaust valve
from the cylinder, if the valve is in a cage, remove the entire cage;
this may easily be done on most types of engines. Always remove the
exhaust valve first as the inlet valve rarely requires attention. With
small engines, and engines having the valves mounted directly in the
cylinder head it will be necessary to remove the cylinder head to gain
access to the valves. In such a case use care when opening the packed
joint between the cylinder and head, to avoid damaging the gasket.

The exhaust valves should be lubricated with Gas Engine Cylinder Oil,
never with common machine oil on account of gumming and sticking, or
with gas engine cylinder oil thickened with =FLAKE GRAPHITE=. Powdered
graphite may be used with success without the addition of oil, but oil
makes the application of the graphite much easier.

A cracked valve seat, due to expansion strains or to the hammering of
the valve, is a common cause of compression leakage, and is rather
difficult to locate as the leakage only occurs under comparatively high
pressure. Leakage may also occur between the valve cage and the cylinder
casting unless pains are taken to thoroughly clean the cage and the bore
before fastening into place.

Warped valves are caused by overheating, the head of pallet of the valve
becoming out of square with the stem, or by twisting on the valve seat.
If warped valves are suspected the high point of the seat may be
determined by means of the following test and should be carefully filed
down until it is close to a bearing after which it may be ground down as
described under pitted valves.

If the stems are now in good condition examine the seating surfaces of
the valve pallets and cage or rings.

The seats should be bright and free from pits, depressions, or streaky
blue discolorations. If the seats are deeply grooved from long continued
leaks it is best to discard them and replace with new.

Pitted valves, and those slightly grooved or streaked should be reground
by the use of a little emery flour and tripoli which operation is
performed as follows:

Lift the valve from its seat and apply lubricating oil to the seating
surface, then sprinkle a little flour or emery on the oiled surface and
drop the valve back on the seat. Do not use coarse emery nor too much of
the abrasive, a pinch is enough and will grind as rapidly as a pound.
Take care to drop the emery only where required, do not sprinkle it over
the engine or working parts as it will cause cutting and the destruction
of the bearings.

Now turn the valve around in one direction for about a half dozen turns
and then in the other direction for the same length of time,
alternately, at the same time applying a moderate pressure on the valve.
Small valves may be rotated with a large screw driver entered in the
slot found on the valve plate, but the handiest method is with a
carpenter’s brace in which is inserted a screw-driver bit.

Never turn the valve around and around in one direction continuously as
this movement is liable to cause grooving, alternate the direction of
rotation frequently with occasional back and forth movements made in a
semi-circle.

Do not press heavily on the valve, use only enough pressure to insure
contact between the two seating surfaces.

The valve should be lifted occasionally from the seat to prevent
grooving, and to redistribute the abrasive, and then dropped back, after
which the grinding should proceed as before. Remove the valve after it
turns without friction, wipe it clean, apply fresh oil and emery and
grind once more. When the grinding has removed all pits and ridges, and
presents a smooth even surface, the grinding is complete. To test for
accuracy of grinding place a little Prussian Blue on the seat, if the
valve is ground to a perfect surface the blue will show uniformly spread
over the seat, if the grinding is incomplete bare places showing high
spots will be seen. It is a good plan to finish the grinding by using a
little Tripoli with oil after the emery has removed the pits and high
spots, as Tripoli is finer than emery and will smooth down scratches
made by the emery.

After the grinding has been performed to your satisfaction, wash the
valve, valve stem, and guides thoroughly with gasoline and kerosene to
remove the smaller traces of emery, to prevent wear and cutting.

When the valves are ground in place on the engine stuff up all openings
or parts of the cylinder to prevent the emery from gaining access to the
bore. After grinding is complete wipe off surfaces thoroughly and remove
waste used for stuffing.

CHAPTER XIII
TRACTORS AND FARM POWER

Because of our increased population, which results in a greater planted
acreage, and the scarcity and increased cost of farm labor, farming has
rapidly developed into an industrial science. Where formerly the farmer
was content to perform certain parts of his work by hand, he today
employs machinery for the same task, and is far more particular as to
the working of his soil and the cost of production per acre. By the use
of machinery his crop is marketed at less expense, in a shorter time,
and he has more time in which to enjoy life than ever before.

The modern gasoline and oil engine has been the greatest factor
contributing to the farmer’s ease and prosperity for it has eliminated
the terrors and drudgery of plowing, churning, watering stock, sawing
wood, threshing, and has besides given him many of the conveniences of
city life, such as running water and electric light. The benefits of
power are not only conferred on the farmer but his wife as well for the
small domestic engines have saved the back of the house wife during the
strenuous period of harvest time.

One of the difficulties of farming is the necessity of doing certain
work in a limited time or else suffering a heavy loss. The breaking, the
plowing, the harvesting, and the threshing each must be done at a
certain time, often within a few days of each other in order to obtain
the benefits of the best weather conditions. Threshing starts as soon as
the grain is ready, and if rain interferes with the threshing, the
farmer can start plowing immediately if provided with a tractor and
thereby gain the undoubted benefits of fall plowing. Plowing at harvest
time has much to do with eliminating weed seeds for the weeds are turned
under while green, the seeds sprout and commence their growth and are
winter killed before they reach maturity. In this way the field is
practically freed from weeds in the spring. When the weather again
becomes suitable, the threshing may be resumed and when completed he can
again turn to his plowing.

[Illustration:

Operator’s View of the “Big Four” Tractor, Showing the Four Cylinder
Engine in Place.
]

Gas power is not to be considered merely as a substitute for animal
power for the engine not only performs the work of the horses but also
performs work that no horse can do, and does it with far less expense.
In the hottest weather when horses are dropping in the broiling sun, the
tractor moves tirelessly through the fields. Every farmer knows the
expense attached to keeping a horse in the idle winter period for it
must be fed, watered, and cared for, work or no work. When the engine is
idle it costs nothing except for the interest on the investment, while
animals grow old and are subject to disease whether they work or not.

The time of plowing and harvest is short and requires quick work, and
continuous work. Horses cannot be driven at plow faster than one mile
per hour, and cannot be worked more than 10 hours per day, while the
tractor under suitable conditions can travel 2 to 3 miles per hour, and
keep at it twenty-four hours per day. An ordinary tractor can break from
20 to 40 acres of ordinary loam per day and will plow in cultivated land
from 40 to 50 acres per day.

The same factors govern the fuel consumption of a tractor that govern
the rate of plowing, that is, the character of the soil and the depth of
plowing. On an average, 1½ to 2½ gallons of gasoline will be used in
breaking an acre of sod, and 1 to 1½ gallons of gasoline in plowing
stubble. As kerosene contains about 18 per cent more heat per gallon
than gasoline, the quantity of fuel used by an oil tractor is
correspondingly less. When used for pulling wagons on the road at about
3 miles per hour the fuel consumption will approximate 4 gallons per
hour, this consumption varying of course with grades, etc.

Thirty horse-power, at the speed given above represents a draw bar pull
of about 9,000 pounds, which is equivalent to the tractive effort of
from 30 to 40 horses, were it possible to concentrate the pull of so
many horses at a single point, at one time. It would of course be
impossible for the horses to maintain this effort for as long a time as
the tractor. On a level road it will take about 100 pounds tractive
effort for each 2,000 pounds of weight in the form of road wagons
(including the weight of the wagon). The number of wagons that can be
drawn with a given draw bar pull can be easily figured. When pulling on
a grade, the effective draw bar pull will be reduced in proportion to
the extent of the grade. While no fixed rule can be given regarding the
number of plows that can be handled by a tractor, the average machine
can pull six to eight breaking plows and from eight to twelve stubble
plows, depending on the character of the soil and the depth of plowing.
When the conditions permit the use of a greater number of plows, than
specified above the amount of work done will of course be greater.

A tractor can haul four ten foot seeders and two twenty foot harrows and
cover 7 or 8 acres per hour at a cost of from 12 to 15 cents per acre.
At harvest time the tractor will also effect a great saving in time and
expense for the average machine will handle five or six eight foot
binders, making a cut of nearly 50 feet wide, and this can be kept up
for 24 hours at a stretch.

A tractor of the average output can handle any separator, and with a 44″
cylinder machine can turn out from 2,000 to 3,000 bushels of wheat and
5,000 bushels of oats in a ten hour run. It will also handle any of the
largest shredders. For irrigation work, silo filling, and wood cutting
it is equally efficient.

(142) The Gas Tractor.

The tractor of the internal combustion type using gasoline or oil as a
fuel is much more successful than the steam machine, both from the
standpoints of convenience and cost of operation. There is absolutely no
danger of fire whatever around a gas tractor for this reason the engine
can be placed in any position regardless of the direction of the wind,
which would be impracticable with a steam engine. This is a great
advantage for if the wind is allowed to blow directly from the engine to
the separator, it will be of great assistance to the pitchers who feed
the separator.

When threshing or plowing in a remote field considerable difficulty is
always experienced in supplying the steam tractor with the enormous
amount of water that it consumes. To supply the water requires a team,
tank wagon and drivers which is a considerable item in the running
expense. The small amount of water used for cooling the gas engine is
renewed once, or at the most, twice a day. Steam coal is bulky and
requires the continuous service of a man and team to keep things moving,
and this expense is greatly increased by the expense of the coal.

A gas tractor can be started in a very few moments while the engineer of
a steam rig has to start in an hour or more before the crew to get steam
up, etc. In addition to this there is the usual tedious routine of
“oiling up,” cleaning the flues, etc. There is absolutely no danger of
explosions with the gas engine which have proved so disastrous in the
past with steam threshing engines.

With the gasoline, the operator is left free to work on the separator as
he has no firing to do and does not have to concentrate his attention on
keeping the water level at the correct point in the gauge glass. The
engine is automatically lubricated in all cases so no attention is
demanded on this score for it will run smoothly hour after hour without
the least attention. This feature eliminates one high priced man from
the job. On heavy loads the problem of keeping up the steam pressure is
often a vexatious one, especially if a poor grade of coal is used. With
a lower priced man as operator tending both the separator and the gas
engine the crew need only consist of two pitchers to feed the machine,
with a man and team for each pitcher. This small crew is easily
accommodated at the farmers house, and does not require the services of
a separate cook and camp equipment.

With a gasoline rig the expenses will be approximately as follows:

Engineer, wages and expenses $ 5.00
Two pitchers, at $3.00 6.00
Four men and teams 20.00
60 gallons of gasoline at 15c 9.00
Lubricating oil 1.00
——————
Cost per day $41.00

Taking 1,500 bushels (wheat) as a day’s work, the cost of threshing
figures out at 2¾ cents per bushel.

According to data furnished by the M. Rumely Company, which is based on
an actual test, the total cost of plowing, seeding, cutting and
threshing, including ground rental and depreciation, amounted to $8.65
with horses and $6.55 with their oil tractor. These figures will of
course vary in individual cases, but are principally of interest in
showing the comparative cost of horse and tractor operation.

With a gasoline or oil tractor equipped with engine plows one man can
tend to both the plows and the engine, although some operators prefer to
have two men, one relieving the other consequently plowing more acres
per day and reducing the cost per acre. In some cases one man is placed
on the plows and the other on the engine. By running the tractor
twenty-four hours per day, with two shifts of men, a much better showing
is made by the tractor when compared with horse plowing, for with the
latter method it would be necessary to supply twice the number of
horses.

To show the relative merits of various grades of fuel we will print the
data kindly furnished by Fairbanks Morse for a ten hour day.

═════════════════════╤════════╤════════╤════════
ITEM │Fuel Oil│Kerosene│Gasoline
│ 3c │ 6½c │ 15c
─────────────────────┼────────┼────────┼────────
60 Gallons Fuel │ $1.80│ $3.90│ $ 9.00
Lubricants │ .40│ .40│ .40
Engineer │ 3.50│ 3.50│ 3.50
Plowman │ 2.00│ 2.00│ 2.00
Repairs │ .12│ .12│ .12
Cost to Plow 24 Acres│ 7.82│ 9.92│ 15.02
Cost per Acre │ .32│ .41│ .63
─────────────────────┴────────┴────────┴────────

Plowing at the rate of 20 acres per day, and kerosene at 6⅔ cents per
gallon, the Rumely Company obtain the cost of plowing one acre as $0.66.
In the latter figure the interest and depreciation are included which
will increase the figures over those given by Fairbanks Morse. It should
be understood that these costs are approximate and will vary
considerably in different localities and under various conditions.

Oil Injection Engines.

Engines using low grade fuels such as kerosene, usually experience much
trouble in obtaining a proper mixture when the fuel is vaporized in an
external carbureter even when the carbureter is specially designed for
the heavy oil. This leads to fuel waste, starting troubles and cylinder
carbonization, to say nothing of the objections of an odorous, dirty
exhaust. To overcome the objections of carbureting the heavy oils it has
been common practice to inject or aspirate a small amount of water, the
water vapor tending to prevent the fuel from cracking and to distribute
the temperature more uniformly through the stroke. The injection of
water is not a particularly desirable feature, since its use involves
one more adjustment and possible source of trouble when running on
variable loads.

In the semi-Diesel engine the fuel is sprayed directly into the
combustion chamber by mechanical means, thus making the fuel supply to a
certain extent independent of atmospheric and temperature conditions.
After the injection the spray is vaporized both by the hot walls of the
combustion chamber and the heat of compression, the latter being
principally instrumental in causing the ignition of the gas. In this
case no electrical ignition devices are required, thus at one stroke
overcoming one of the principal objections to a gas engine.

Until recently the semi-Diesel engines were confined to units of rather
large size, the smallest being much larger than the engines usually used
on the farm. It is now possible, however, to obtain oil engines of the
fuel injection type in very small sizes, built especially for portable
or semi-portable service. Not only is it possible to use a cheaper grade
of fuel with this type of engine, but the fuel consumption is also less
than with the carbureting type. To this may be added the advantages of
an engine free from the troubles incident to the ignition and
carbureting systems.

Good results may be obtained with small injection engines on oils
running from kerosene (48 gravity) down to 28 gravity, the combustion in
all cases being complete and without excessive carbon deposits. Little
trouble is caused by variable loads as long as the speed is kept
constant. Compared with gasoline, the heavier fuels are much safer to
store and handle, owing to their high flash points.

The compression of the injection engine is much higher than the old
carbureting kerosene engine as the compression heat is used in a great
part to ignite the oil vapor. Usually the pressure is in excess of 150
pounds per square inch, the exact value being determined by the form of
the combustion chamber, whether a hot bulb is used, etc. The high
compression assists in increasing the economy of the engine.

Usually the piston either draws in a complete volume of pure air or
draws in pure air through the greater part of the induction stroke, the
spray either starting near the end of the suction stroke or during the
early part of the compression. When a hot bulb is used the oil spray
strikes the bulb forming vapor, the increasing compression caused by the
advancing piston furnishing the air for combustion and forces the
mixture into contact with the hot walls. Another type has no hot bulb,
the lighter constituents of the fuel being vaporized and ignited by the
compression alone, their inflammation serving to kindle the main, heavy
body of the oil. In some engines, the combustion of the light
constituents serves to spray the heavy oil through the valve and into
the combustion chamber. Details of several of the most prominent makes
of oil engines are described in an early chapter of this book.

As a rule, this class of oil engine does not run well when the speed is
varied through any great range, nor when governed by a throttling type
governor, since both of these conditions affect the compression. They
may be either of the two or four stroke cycle type, and when of the
latter they are much more successful than a two stroke cycle engine
using a carbureter.

On small engines the fuel consumption will run about 0.7 pint per brake
horsepower hour, this consumption decreasing on large engines to about
0.6 pint per brake horsepower hour or even less.

[Illustration:

Oil Injection Type. Injection pump P driven by eccentric E through
rods G-H draws oil from tank K through M-N and sprays it into
combustion chamber R through O-Q. Amount of oil sprayed is
controlled by fly-wheel governor W-W shifting E on shaft S, thus
varying stroke of P. Engine is started by heating R with torch U and
injecting first oil with hand lever I. A second pump supplies
constant level of oil to K, level being observed in glass L. C-C is
the cylinder, and F is the fly-wheel.
]

The accompanying diagram shows a diagram of a typical oil engine of the
injection type, a pump P supplying the oil from auxiliary tank to the
hot, extended combustion chamber R, this chamber being an extension of
the cylinder C-C. Oil is kept at a constant level in K by an overflow
pipe, the oil entering from the supply pump through pipe J, and entering
the pump through M at N. By gauge glass L, the operator can tell whether
he has a sufficient supply of oil.

The injection pump P is driven from the eccentric E (mounted on the main
shaft S) through the eccentric rod G and the rod H. The governor weights
W-W alter the amount of fuel supplied by changing the stroke of the
pump, thus keeping the speed constant under varying loads. The governor
acts by shifting E in relation to the shaft S, a spring T controlling
the throw of the governor. The entire governor mechanism is contained in
the fly-wheel F.

To start, the combustion chamber R is heated by the torch U, and after
thoroughly heated, the starting fuel is injected by means of the hand
lever I. This engine is of the two cycle type with scavenging air
furnished by crank-case compression.

(143) Construction of Gas Tractors.

A gas tractor may be considered as being simply a special application of
the gasoline or oil engine in which the engine drives the road wheels
through a train of gearing instead of driving its load by a belt from
the pulley. Four intermediate mechanisms must be provided between the
engine and the road wheels in order that the tractor may properly
perform its work. These devices are known as the “clutch,” the driving
gears, reverse gear and the “differential” gear. It should be understood
that these mechanisms do not change the construction or operation of the
engine in the slightest, and that the principles that apply to the
engines described in the previous chapters apply also to the engine of
the tractor. The following will briefly describe the functions of the
intermediate trains in their proper order, starting at the engine.

The Clutch.

A tractor is arranged to pull its load in two different ways, first by
the draw bar, as when pulling plows, and secondly by a belt from the
engine pulley as in driving a threshing machine or circular saw. In the
first case it is necessary to drive the road wheels through the gear
train, and in the second case it is necessary to disconnect the road
wheels while driving the thresher or saw. As the engine cannot be
started while under load it is also necessary to disconnect the road
wheels to free the engine while turning it over to get the first
explosion.

The device that connects and disconnects the engine from the road wheels
is known as the =CLUTCH=. This usually consists of two or more friction
surfaces that form a part of the driving gear, which may be brought into
frictional contact with the engine pulley, when it is necessary to drive
the road wheels. When the two members of the clutch are brought into
contact they revolve together, thus connecting the engine with the
driving gear.

Reverse Gears.

[Illustration:

The Reverse Gear of the “Big Four” Tractor.
]

As it is not practicable to reverse the direction of rotation of the gas
engine, the rotation of the road wheels is reversed by means of gears
contained in the driving train. In some tractors the reverse gears are
similar to those in an automobile, being located in the transmission. In
other tractors two bevel pinions are provided that fit loosely on the
engine shaft and engage with a large bevel wheel that forms part of the
driving gear. A sliding jaw clutch that revolves on the engine shaft is
arranged so that it can connect with either of the bevel pinions causing
them to rotate with the engine shaft and drive the main wheel. As the
two pinions are on opposite sides of the large bevel wheel, they run in
opposite directions in regard to it, so that it is possible to reverse
the large wheel by engaging the clutch with either one or the other of
the bevel pinions.

The Differential Gear.

The differential gear makes it possible to apply the same amount of
power to each of the road wheels, and also allows one wheel to rotate
faster than the other when turning around a corner. If both road wheels
were rigidly fastened to a single rotating axle it would be practically
impossible to turn a corner for it would be necessary for the engine to
slip one or the other of the wheels because of their difference in
speed, as the outer wheels turn faster than the inner.

[Illustration:

Differential Gear of the “Big Four” Tractor.
]

The Driving Gear.

The driving gear consists of a series of spur gears arranged for the
purpose of reducing the high speed and small “pull” of the motor into
the low speed and heavy pull of the road wheels. This reduction in speed
is generally brought about by a double system of shafts, the second
shaft from the motor carrying the differential gear and meshes directly
with the master gear on the bull wheel. The first shaft is an idler.

[Illustration:

Fig. 125. Fairbanks-Morse Oil Tractor, Showing General Layout.
]

[Illustration:

Fig. 126. Two Cylinder Engine of Fairbanks-Morse Oil Tractor.
]

(144) Fairbanks-Morse Oil Tractor.

The Fairbanks-Morse 30–60 Horse-power Oil Tractor gives an effective
draw bar pull of 9,000 pounds and develops over 60 horse-power at the
belt pulley which is more than sufficient to drive any farm machinery.
It will operate equally well on kerosene, distillate oils, and gasoline,
any of which will develop the rated horse-power. Two forward speeds and
one reverse are obtained by a gear transmission of the automobile type,
the forward speeds being 1¾ and 2½ miles per hour and the reverse 1¾
miles. Combined with the governor variation, it is possible to get the
proper speed for any kind of work.

The fuel is sprayed directly into the cylinder with a spray of water,
the proportion of water to oil being nearly equal at full load. As
explained in Chapter VII, the water spray aids in the combustion of the
heavier oils, eliminates soot and tarry deposits, and makes the engine
run more smoothly because of the reduction of the explosion pressure.
The spray also reduces the temperature of the cylinder and minimizes the
dangers of preignition. The engine is of the slow speed type running at
a normal speed of 375 revolutions per minute, and the two cylinders have
a bore and stroke of 10½ × 12 inches. The speed regulator supplied with
the engine gives an extreme variation of 300 to 375 R.P.M.

[Illustration:

Fig. 127. Fairbanks-Morse Tractor Transmission with Two Forward Speeds
and One Reverse.
]

The cylinders are cast two in a block which arrangement permits of the
bores being brought close together and gives an easy circulation of
cooling water. The value of this practice has been proved in automobile
work where a simple and rigid structure is absolutely necessary.

All of the valves are in the heads of the cylinder which eliminates heat
radiating pockets in the combustion chamber. Both the inlet and exhaust
valve are mechanically operated through substantial push rods and valve
rockers, and are completely surrounded by water. Large clean out holes
are provided in the separately cast cylinder head making it accessible
for the removal of scale and sediment. A single cylinder head serves for
both cylinders which contributes to easy cooling passages and a single
arrangement of exhaust and inlet piping. The valves are in cages bolted
to the cylinder head in such a way that they are easily removed for
inspection without disturbing the piping or connections.

The pistons are easily removed without taking the heads out of the
cylinder or taking down any shafting. The valve rocker arms are provided
with easily renewed bushings and grease cups. As the engine is of the
four stroke cycle type with both cylinders on the same side of the
crank-shaft, only a single throw crank shaft is used, which is without
intermediate bearings.

Dual ignition is used, the high tension magneto and the two unit spark
coils shown in Fig. 126 being independent of one another so that either
the magneto or battery can be used for starting or for continuous
operation. The magneto is mounted directly on the engine bed and is gear
driven from the crank shaft. The ignition advance and retard lever and
ignition switch are mounted on the engine in an accessible position. As
the coil is mounted on the engine the leads are short and the vibrators
are directly under the supervision of the operator.

Close speed regulation is maintained by a throttling type governor. The
voluntary speed variation used to slow the engine down to meet certain
conditions encountered in plowing is accomplished by a small lever
located at the end of the cylinders. The cooling water is circulated
through the cylinders by a gear driven centrifugal pump. From the
cylinders the water enters a closed radiator of the automobile type
located at the front of the traction where it is cooled without loss. A
nine feed, forced type oiler is used which supplies oil to the cylinders
and bearings, and also to the transmission gears. External bearings
which are subjected to dust are equipped with grease cups. The fuel pump
which takes its supply from an 80 gallon tank is in an accessible
position near the operator and is provided with a handle by which it is
operated when starting the engine.

The clutch which is located in the flywheel at the right of the engine
is operated by a lever on the footboard. All of the friction faces and
levers are arranged inside of the pulley so that they are not only
protected from injury but are prevented from tearing the belt should it
slip from the pulley face.

A powerful foot with a drum on the differential gear will hold the
outfit on a grade independent of the engine.

The transmission is of the shifting gear type with hardened steel gears.
The transmission gears are enclosed in a practically dust proof case,
this being connected with enclosed crank case and better providing for
air displacement of the pistons. Power is transmitted to the truck
through the clutch on the left hand side of the engine, which is
operated by combined clutch and shifting lever on the footboard. This
lever has an interlocking device, arranged so that it is impossible for
the operator to shift the gears before the clutch is disengaged, or to
engage the clutch until the gears are completely in mesh. It is also
impossible to get two sets of gearing in mesh at one time and prevents
any possibility of stripping gears by applying the load on the corners
of the teeth.

The drive wheels are 78″ diameter, 30″ face. These give a very large
bearing on the ground which is particularly desirable when using the
engine for cultivating or seeding on plowed ground. The front wheels are
48″ in diameter, 14″ face. The wheel base is long and engine is easy to
guide. The drive wheels are covered by a metal housing which protects
the operator and the working parts of the engine from dust and mud.

This engine gives a drawbar pull on low gear of 9,000 lbs., which will
haul from 8 to 12–14″ plows, according to the character of the plowing.
The hitch is placed about 18″ above the ground and consists of a heavy
bar extending approximately to the middle of the bull wheels on each
side, thus providing for hitching the load most satisfactorily.

(145) The Rumely “Oil Pull” Tractor.

The Rumely oil-pull tractor is driven by a two cylinder, four stroke
cycle oil engine, having a bore and stroke of 10 × 12 inches giving 30
tractive horse-power and 60 horse-power at the pulley. The cylinders are
cast single and are provided with independent heads. The pistons are
easily removed by unbolting the cylinder heads and the crank end of the
connecting rod, after which operation they may be pulled out upon the
platform. The exhaust and inlet valves are in easily removable cages
placed on either side of the cylinder. The stems of the valves are at
right angles to the bore of the cylinder and open directly into the
combustion chamber without pockets or extensions to the chamber.

A bell crank rocker arm acts on the valve stems which in turn is
actuated through a push rod that extends from the cam-shaft in the crank
chamber. The cam-shaft, rocker arms, valves, and half time gears are
clearly shown by Fig. 128. The housings of the inlet valves connect
directly with the special kerosene carburetor made by the Rumely
Company. The Higgins carburetor used on these engines is very simple and
effective in vaporizing the heavier fuels and has no springs nor
internal mechanism to get out of order. The carburetor is controlled
directly from the governor which regulates the air, water and kerosene
required for the combustion, and has no manual adjustments that need
attention from the operator. A constant flow of kerosene and water is
maintained through the carburetor by means of force pumps, the level in
the device being kept constant by overflow pipes through which the
excess returns to the supply tanks.

[Illustration:

Fig. 128. Phantom View of the Rumely “Oil Pull” Engine.
]

As in nearly all types of low compression, or carbureting oil engines,
the Rumely engine receives an injection of water in the cylinder to aid
the combustion and cooling, and to reduce the initial pressure of the
explosion. While the initial pressure is reduced by the water vapor, and
with it the strain on the engine, the mean effective pressure is
increased because of the absorption of heat from the walls and the more
perfect combustion. The only moving part in the carburetor is a single
plate controlled by the governor which is produced with one or more air
passages. The governor that operates this valve is driven by gears and
regulates the speed by throttling the charge. The speed of the engine
can be varied from 300 to 400 revolutions per minute while the engine is
running.

[Illustration:

Fig. 129. Higgins Oil Carburetor.
]

In this engine it is a very simple matter to remove the crank-case cover
and the cylinder heads and expose the whole of the working mechanism of
the engine.

After removing the cylinder heads and without changing his position, the
operator can examine, clean, and, if necessary, regrind the valves. Also
without changing position the operator can control his reverse
transmission gears, friction clutch for starting the tractor. He is also
in reach of the ignition apparatus, governor carburetor and oiler.

The crank case is cast in one piece. The bearings are cast integral with
the crank case, and are fitted with interchangeable, adjustable,
babbitted shells. Binder caps hold the bearings together and keep the
babbitted shells securely in position. The design permits removal of
binder caps for examination of crank shaft bearings without distributing
the adjustment. The crank case is secured to tractor frame by well
fitted bolts, thereby avoiding annoyance from loose bolts and nuts.

The crank case is covered with a sheet steel lid that shuts out all dust
and dirt. This cover can easily be removed at any time by simply
unscrewing the bolts that hold it in place. It is constructed with this
cover on top instead of on the side or end, which permits of easy access
to any working parts in the crank case.

[Illustration:

Fig. 130. Rumely Oil Pull Tractor.
]

To further facilitate the accessibility to working parts in the crank
case, a secondary cover is provided which can be removed in a couple of
minutes. This opening is large enough to allow the operator to reach any
point within the crank case.

All cams are key-seated upon the cam shaft with double key-seats, which
absolutely prevent any possibility of slipping or alteration in the
timing of the engine. The exhaust and intake valves are mechanically
operated. The valves are constructed with steel stem, nickel-steel
heads, the whole being highly finished.

Valve cages are oil cooled, thereby eliminating all possibility of the
valves overheating or warping. The valves themselves can be removed by
simply unscrewing the connection. The engine is provided with a set of
relief cams by which the compression can be relieved—this greatly
facilitates the starting of the engine.

The piston is equipped with five self-expanding rings. Connecting rod is
of drop-forged steel construction. Crank-pin bearings are made in halves
and lined with shells of special metal.

A combination of mechanical force feed and splash lubrication is
employed. Six force feed tubes enter the crank case, on to each bearing,
and two tubes force oil into the cylinder. The crank case contains two
gallons of oil and is arranged so that any surplus may be drawn off
immediately. The lubricator has a gauge glass that shows the quantity of
oil supplied at all times, and which is always in view of the operator.

A make and break system (low tension) furnishes the ignition spark,
which is supplied with current by a Bosch low tension magneto under
normal running conditions, and a battery for starting and for use when
the magneto fails. The magneto is of course gear driven so that its
armature has a fixed relation with the piston position. The igniters of
either cylinder may be easily removed for examination by simply
unscrewing two nuts.

Oil is used as a medium for carrying heat from the cylinder walls to the
radiator. In the construction of the cooler the company have followed
new principles, thus accomplishing the desired result with a minimum
amount of metal and liquid. There is no surplus of liquid, just enough
oil being used to fill the cylinder jackets, radiator and circulation
pipes. The oil is kept in a constant flow from the cylinders to the
radiator and back to the cylinders by a large pump which is driven by a
chain direct from the crank shaft. The radiator is self-contained and
will hold the oil for an indefinite period.

The radiator is composed of a number of sections of pressed galvanized
steel. Oil circulates freely within the sections and the air is drawn
round the outside. There is a constant flow of oil inside and a constant
current of air outside.

The engine is provided with a smooth-working, efficient friction clutch,
which is easily handled by a platform lever and with little exertion on
the part of the operator. The toggle bolts are adjustable so that any
wear in the blocks can be taken up.

The clutch and brake are so connected that when the clutch is thrown out
the brake is immediately applied and when thrown in the brake is
released.

The various movements of the valves and the ignition mechanism on the
face of the flywheel, are marked so that one can check up the timing of
the engine. By bringing any one of these marks to coincide with the
stationary pointer attached to the side of the crank case, one can
easily ascertain whether the adjustments and the timing are exact.

The crank shaft is supported by two end, and one intermediate bearing,
the latter bearing being placed between the two throws of the crank
shaft. As the two cylinders are placed on the same side of the crank
shaft, the two throws are also on the same side of the shaft and to
balance these throws cast iron counter weights are bolted on the bottom
of the crank arms. The bearings are exceptionally long, the total length
of the three bearings amounting to more than half the length between the
outer ends of the bearings.

The frame of the tractor consists of four twelve inch “I” beams securely
riveted together with intermediate channel stiffeners. The cast steel
bearings are riveted to the frame so that the whole construction is one
unyielding mass. The bearings are in halves which makes the removal of
the shafts an easy task.

With the exception of the differential and master gears all of the gears
are cut out of semi steel blanks. The fly wheel has a face of 11 inches,
and a diameter of 36 inches.

(146) The “Big Four” Tractor.

The Big Four tractor differs from the majority of tractors in having a
four cylinder vertical type motor of 30 tractive and 60 brake
horse-power capacity. The cylinders have a bore of 6½ inches and a
stroke of 8 inches. The engine runs at the comparatively high speed of
450 revolutions per minute. Gasoline is used for fuel, and is vaporized
in a conventional type of jet carburetor.

Both the inlet and the exhaust valves are placed in a pocket at one side
of the cylinder making what is known as an “L” engine. The cylinders and
the heads are cast in one piece, doing away with points between the
cylinders and heads. The pistons and connecting rods may be removed
without disturbing the cylinders or their connections by pulling them
out through hand holes in the base of the crank case.

The four throw crank shaft is provided with five bearings, these
intermediate bearings between the throws and two end bearings in the
case. The interior working parts of the motor are lubricated by the
splash system with a positive forced feed oiler. The splash pools can be
adjusted at a minute’s notice so that any desired oil level can be
obtained. Grease cups provide the lubrication for all bearings outside
of the motor.

Water is circulated by a direct driven centrifugal pump, and as the
cooling water is in a closed system the same water is used over and over
again without much loss, a bucketful or so a day being an ample supply.
The tubular radiator situated in the front of the tractor is provided
with a cooling fan that is driven from the engine in a manner similar to
automobile practice. A high tension magneto is gear driven from the cam
shaft, and is mounted on a rocking bracket so that the armature is
advanced and retarded as well as the circuit breaker.

[Illustration:

Fig. 131. Views of the Four Cylinder Motor of the “Big Four” Tractor.
Note the Massive Construction Compared with Automobile Practice.
]

An internal expanding clutch connects the motor with the driving gear by
operating on the inner run of the fly-wheel. The motion of the engine is
transmitted to an intermediate reversing device through bevel gears,
this being necessary for the reason that the crank-shaft runs “fore and
aft,” or parallel to the length of the tractor. A double acting jaw
clutch engages with either one or the other of a pair of bevel pinions
that run in opposite directions. Motion from the reverse gear is
transmitted directly to the different shaft, and from there it is
transmitted to the master gears on the bull wheels. The differential
shaft is in one piece.

[Illustration:

“Big Four,” Four Cylinder Tractor Motor.
]

[Illustration:

Showing the Position of Engine on “Big Four” Tractor.
]

The main driving wheels are very large when compared with the wheels of
an ordinary tractor, for they are eight feet in diameter and are
proportionately broad. This no doubt gives splendid tractive effect in
soft and uneven fields and must save the machine from “stalling” under
adverse conditions. Another unusual feature is the automatic steering
device used in plowing. This device consists of a long tubular boom that
is fastened to the swiveled front axle of the tractor and a small wheel
fastened to the outer end of the boom. The small wheel rolls in the next
furrow and compels the tractor to plow in a line parallel to it. This
steers the tractor more accurately than would be possible by hand and at
the same time enables one man to operate both the engine and the plows.

[Illustration:

The “Case” Gas Tractor.
]

Cost of Gas Engine Operation (American).

═══════════════════════════╤═════════════════════╤═════════════════════
│ GAS PRODUCER PLANT. │ NATURAL-GAS ENGINE.
│ │
│ Three- Half │ Three- Half
│Load. quarter Load. │Load. quarter Load.
│ Load. │ Load.
───────────────────────────┼─────────────────────┼─────────────────────
1 Fuel per hp-hour │ 1.25 1.5 1.8 │10 cu. 12 cu. 15 cu
│ lb. lb. │ ft. ft. ft.
2 Fuel per hp-year (4,500 │ 2.5 3.6 │45,000 54,000 67,500
hours) │ tons 3 tons tons │ cu. cu. ft. cu.
│ │ ft. ft.
3 Cost of fuel │ $4.00 per ton │ 30 cents per 1,000
│ │ cu. ft.
4 Cost of fuel per year │$10.00 $12.00 $14.40│$13.50 $16.26 $20.25
5 Cost of attendance per │ 0.40 cent │ 0.25 cent
hp-hour │ │
6 Cost of attendance per │ $18.00 │ $11.25
year │ │
7 Lubricating oil per │ 0.006 pint │ 0.006 pint
hp-hour │ │
8 Cost of oil per year at │ $0.84 │ $0.84
25 cents per gal. │ │
9 Scrubber and cooling │ 8 gals. │ 5 gals.
water per hp-hour │ │
10 Cost of water per year │ │
at 30 cents per 1,000 │ $1.44 │ 0.90
cubic feet │ │
11 Operating expenses; │$30.28 $32.28 $34.68│$26.49 $29.19 $34.24
items, 4, 6, 8 and 10 │ │
12 Saving by Diesel engine │ 5.43 6.47 7.90 │ 1.64 3.39 6.56
13 Interest, depreciation │ │
and maintenance │ 6 + 7 + 2 = 15% │ 6 + 7 + 2 = 15%
respectively in per │ │
cent of investment │ │
14 Assuming $80 initial │ │
cost per hp. the │ $12.00 │ $12.00
yearly fixed charges │ │
will be │ │
───────────────────────────┴─────────────────────┴─────────────────────

═══════════════════════════╤═════════════════════╤═════════════════════
│ LOW-PRESSURE OIL │ DIESEL ENGINE.
│ ENGINE. │
│ Three- Half │ Three- Half
│Load. quarter Load. │Load. quarter Load.
│ Load. │ Load.
───────────────────────────┼─────────────────────┼─────────────────────
1 Fuel per hp-hour │1 lb. 1.25 1.60 │ 0.50 0.55 0.60
│ lb. lb. │ lb. lb. lb.
2 Fuel per hp-year (4,500 │ 643 803.5 1028.5│321.5 353.5 386
hours) │gals. gals. gals. │gals. gals. gals.
│ │
3 Cost of fuel │ 3 cents per gallon │ 3 cents per gallon
│ │
4 Cost of fuel per year │$19.30 $24.10 $30.85│$9.65 $10.60 $11.58
5 Cost of attendance per │ 0.25 cent │ 0.30 cent
hp-hour │ │
6 Cost of attendance per │ $11.25 │ $13.50
year │ │
7 Lubricating oil per │ 0.006 pint │ 0.007 pint
hp-hour │ │
8 Cost of oil per year at │ $0.84 │ $0.98
25 cents per gal. │ │
9 Scrubber and cooling │ 5 gals. │ 4 gals.
water per hp-hour │ │
10 Cost of water per year │ │
at 30 cents per 1,000 │ 0.90 │ 0.72
cubic feet │ │
11 Operating expenses; │$32.29 $37.09 $43.84│$24.85 $25.80 $26.78
items, 4, 6, 8 and 10 │ │
12 Saving by Diesel engine │ 7.44 11.29 17.06 │ ... ... ...
13 Interest, depreciation │ │
and maintenance │ 6 + 7 + 2 = 15% │ 6 + 10 + 3 = 19%
respectively in per │ │
cent of investment │ │
14 Assuming $80 initial │ │
cost per hp. the │ $12.00 │ $15.00
yearly fixed charges │ │
will be │ │
───────────────────────────┴─────────────────────┴─────────────────────

From a Paper Read Before the American Institute of Electrical Engineers.

CHAPTER XIV
THE STEAM TRACTOR

(147) The Steam Tractor.

The steam tractor consists of the following elements, which will take up
in detail under separate headings.

(1) Engine proper, consisting of the cylinder, piston, valve motion,
guides, crank, fly wheel, etc.

(2) Boiler—with the grates, burners, etc.

(3) Feed pump or injector.

(4) Feed water heater.

(5) Driving gear, differential, clutch, etc.

As in the case of the gas tractor, the machine consists simply of a
steam engine and its boiler that drive the road wheels of the tractor
through a gear train. With the steam tractor the gearing is simplified
as the reverse is performed by the engine’s valve motion, and not
through gearing. There is no need of speed changing transmission gears
in the steam tractor as the engine is sufficiently flexible to provide
an innumerable number of speeds by simple throttle control.

While the fuel most commonly used is coal, straw and wood, crude oil is
often used, the fuel being determined principally by the location of the
engine, and by its cost on the job. The matter of fuel should be taken
into consideration when the engine is purchased as the different grades
demand different fire box and boiler construction. When it is possible
to obtain crude oil at a reasonable figure, it certainly should be used
in preference to all others as liquid fuel is the most compact, most
easily controlled, and efficient of any. The subject of oil burners is
taken up later in this chapter, a number of types of which are clearly
illustrated.

(148) The Cylinder and Slide Valve.

The steam engine cylinder consists essentially of a smoothly bored iron
casting in which a plunger called the “piston” slides to and fro, the
cylinder acting not only as a container for the steam acting on the
piston but as a guide and support as well. Needless to say, the contact
or fit between the piston and cylinder walls must be as perfect as
possible, tight enough to prevent steam passing the piston, and free
enough to allow the piston to slide without unnecessary friction. The
reciprocating piston is connected to the crank through a connecting rod
by which the pressure on the piston is communicated to the crank arm.

The pressure exerted on the crank pin by the piston depends on the area
of the piston (in square inches) and the pressure of the steam on each
square inch of the area. With a given steam pressure, the greater the
area, the greater the force tending to turn the crank. As power is the
rate or distance through which the force acts in a unit of time it is
obvious that the power developed by the engine is equal (in foot pounds)
to the force in pounds multiplied by the velocity of the piston in feet
per minute. Since there are 33,000 foot pound minutes in a horse-power,
the power developed by such a cylinder is equal to the force multiplied
by the piston velocity, divided by 33,000.

[Illustration]

As the cylinder is necessarily limited in length it is evident that the
piston cannot travel in one direction continuously but must be reversed
in direction when it travels the length of the cylinder bore thereby
traveling the next distance in the opposite direction. This reversal of
the piston is accomplished by admitting the steam in one end of the
cylinder and then into the other, this causing the steam to act on the
opposite sides of the piston alternately. To establish a difference of
pressure on the two piston forces, the steam pressure is relieved on one
side while the steam acts on the other.

A typical cylinder furnished with the ordinary steam tractor is shown by
Fig. 133, in which T is the cylinder, P the piston and R is the piston
rod. When the steam in the cylinder end E acts in the direction shown by
arrow E, the piston pulls the rod R in the direction shown by arrow S,
the pressure in the cylinder end D being relieved to atmospheric at this
time. The steam is admitted and relieved by the valve L which slides
back and forth on its seat actuated by the valve rod VR.

In the position shown, the valve L is moving to the left as shown by
arrow O. The edge of the valve N is just opening the steam port G
through which the cylinder end F is placed in communication with the
steam filled valve chest A. Steam at boiler pressure fills the space A,
which flows into E past N and through G when the valve opens and
establishes pressure against P, which, through the piston and connecting
rods turns the crank.

The steam is exhausted from the cylinder end D, through the port F,
through the exhaust port U, and out of the exhaust pipe X. As will be
seen from the figure, the inside valve edge Y has moved to the left so
that the port F is fully opened. When the piston reaches the left hand
end of the cylinder, the valve L moves to the right so that the end of
the cylinder E is connected to the exhaust port V through the cylinder
port G, thus allowing the steam in the space E to pass out of the
exhaust pipe X. A further movement of the valve to the right causes the
left edge Z of the valve to uncover the cylinder port F which allows the
steam to flow into the cylinder space D and push the piston to the
right. This motion is carried on continuously, the valve moving in a
fixed relation to the piston, and admits the steam and releases it first
on one side of the piston and then on the other. The valve shown is
known as a “D” valve and is one of a variety of valves furnished with
steam engines, which, however perform exactly the same functions as the
valve shown.

An “eccentric” which is really a form of crank, drives the valve to and
fro, the eccentric being fastened to the crankshaft. The full pressure
of the steam forces the D valve down on its seat, and as the valve is of
considerable size, this pressure causes much friction and power loss. In
some engines a “balanced” valve is used in which the pressure on the
valve is balanced by an equal pressure that acts on the under side of
the valve face. Balanced or unbalanced, the function of the slide is to
alternate the flow of steam in the two ends of the cylinder.

Steam is prevented from passing the piston into the opposite end of the
cylinder by elastic rings placed in grooves on the piston which are
known as “piston rings.” Being thin and elastic these rings instantly
conform with any irregularity of the piston bore and effectually stop
the flow of steam past them. At the point where the reciprocating piston
rod R passes through the cylinder, a steam tight joint is made by the
“stuffing box” or gland H. The space between the inner walls of the
stuffing box and the piston rod are either filled with some description
of fibrous packing or a metallic packing that fits around the rod in the
same manner that the piston rings fit in the bore of the cylinder. The
packing is arranged around the valve rod VR in the same manner.

As the piston, piston rod, and valve slide on their respective surfaces
with considerable pressure it is absolutely necessary that these parts
receive ample lubrication. In practically all engines the oil is taken
into the cylinder with the steam in the form of drops, the oil being
measured out by a sight feed lubricator that is tapped into the steam
supply pipe. In this device, the oil from the lubricator reservoir is
fed through a regulating needle valve, drop by drop, up through a gauge
glass so that the engineer can tell the amount of oil that he is
feeding. The body of the lubricator is filled with condensed water up to
the level of the outlet through which the oil passes into the cylinder,
and the entire lubricator, reservoir and all is under boiler pressure at
all points. The oil regulating valve is placed at the bottom of the
lubricator, and as oil is lighter than water, it floats up from the
valve to the level of the outlet, through the gauge glass, and from the
outlet level floats out into the steam pipe and mixes with the steam. By
floating the oil in this manner, the engineer can see every drop that is
fed.

(149) Expansion of Steam.

In order to reduce the amount of steam used, the valve does not allow
the steam to follow the piston at full boiler pressure through the
entire stroke, but cuts it off at a certain point after the piston has
started on its travel. As the volume of the steam is increased by the
further travel of the piston after the point of cut-off, the steam
expands in volume until the end of the stroke is reached, at which point
the pressure is naturally much below the initial or boiler pressure.
This reduction in temperature and pressure results in a wider working
temperature range than would be the case with the steam following the
piston throughout the stroke, and as the steam is exhausted to
atmosphere at a temperature much lower than that of the boiler steam,
much less heat is carried out through the exhaust. As a general rule,
the most economical point of cut-off is at ¼ of the stroke. Engines
requiring more steam than is supplied at ¼ cut-off in order to carry the
load, are too highly taxed for efficient results. Since the most
efficient point of cut-off is only ¼ of the possible steam travel it is
evident that an engine can carry a load much greater than that for which
it is rated, but it is also evident that this increased capacity is
gained at the expense operating economy. Wear and tear on the engine
parts are also duly increased.

[Illustration:

Fig. 134. Case Steam Tractor.
]

(150) Speed Regulation.

On steam tractors a constant speed is maintained by “throttling” the
steam, to meet the demands of the load by partially restricting the flow
of steam at light loads and opening the inlet at full load. The valve
that controls the steam for the different loads is controlled by a
“governor” which depends on the centrifugal force exerted by two
fly-balls. The balls, or weights are hinged to a revolving spindle,
driven by the engine, in such manner that an increase of speed tends to
straighten out and revolve in a more nearly horizontal plane. The amount
of travel of the balls for a given speed increase, is governed by a
spring, which returns them to a vertical position when the speed
decreases. By means of a simple system of levers, the valve is closed
when the balls fly out, due to an increase of speed, and is opened when
the speed decreases, so that the engine will receive the steam at a
higher pressure and again build up its speed to normal. As the load
fluctuates, the balls are constantly moving up and down, seeking a valve
position that will keep the engine at a constant speed.

Speed variation is generally accomplished by increasing or decreasing
the tension of the spring that controls the travel of the governor fly
balls, and in the majority of engines this may be done without stopping
the engine.

Another form of governor used extensively on stationary engines controls
the speed by increasing or decreasing the cut-off. Thus with a heavy
load the cut-off may occur at ½ the stroke while with a very light load
it may be at 1/10 stroke. This is by far the most sensitive and
economical form of governor, but on account of the reverse gear it is
difficult to apply it on a tractor.

(151) Reverse Gear.

As explained under “Cylinders” the travel of the valve bears a definite
relation to the piston position so that the ports may be opened and
closed at the proper times. It may be shown by a rather complicated
diagram that this relation of the valve together with that of the
eccentric that drives it is only correct for one direction of rotation.
For any other direction of rotation the relation of the valve and piston
position must be changed. This may be done in several ways but the most
common types are the Stevenson Link and the Wolff slotted yoke.

The Stevenson link motion used on the majority of engines, consists of
two independent eccentrics, one being fixed in the relation for forward
motion and the other for the reverse direction. The ends of the
eccentric rods leading from these eccentrics are connected by a slotted
bar or link, in which a block is placed that is connected with the valve
rod. The block is free to slide in the slot of the links, that is, it
may be moved from one end of the slot to the other. When it is desired
to have the engine rotate in a right handed direction, for example, the
link is lowered so that the rod from the forward eccentric is brought
directly in line with the block so that this eccentric alone acts
directly on the valve through the valve stem. When the reverse is
desired the link is raised until the rod from the reverse eccentric is
brought in line with the block and valve stem, drive being by the
reverse eccentric.

When the block is on the link in a position between the two points
mentioned, the valve has less travel and it cuts off earlier in the
stroke than when driven directly by one eccentric, for the motion at an
intermediate point on the link is much different than at the ends of the
slots. This fact is taken advantage of in operating engines with the
idea of economy in view, and is known commonly as “hooking up” the
engine. The best point at which to “hook up” the engine is best
determined by experiment, and is equivalent in many respects to the
problem of advancing and retarding the spark of a gas engine. We
earnestly advise an engineer of a traction engine to take up this
subject and determine the best point of cut-off for different loads as
he will find that different positions make a considerable difference in
his coal bill. Of course the proper way is to determine this point with
a steam engine indicator, but as few engineers have such an appliance,
the work is generally of the cut and try order. Wear and varying
adjustment soon change the points marked on the reverse sector, and for
economy’s sake these points should be checked occasionally.

In the Wolff motion, a single eccentric is used for both directions of
rotation, in connection with a slotted link. A single eccentric is
securely keyed to the crank shaft. The eccentric strap has an extended
arm which is pivoted to a block that slides back and forth in a curved
guide. The angle at which the guide stands with the horizontal
determines the direction of rotation, the angle being changed by the
reverse lever. The degree of the angle made by the block also determines
the point of cut-off. This is a very efficient and simple valve gear.

Guides and Cross-Head.

The outer end of the piston rod is supported by a sliding block known as
the “cross-head” which in turn is supported by the guides. An
oscillating rod called the “connecting rod” connects the reciprocating
cross-head with the crank pin, this rod is used in the same way as the
connecting rod of the gas engine except that it is connected to the
cross-head instead of the piston.

Clutch.

The clutch affords a means of connecting and disconnecting the driving
wheels and engine shaft. It is usually of the friction type described
under “Gas Tractors.” By releasing the clutch the engine is disconnected
from the driving gear so that the tractor remains stationary while the
engine is driving a load through the belt.

Use of the Exhaust Steam.

The exhaust from the cylinders is used in two ways, first to create a
draft for the fire, and second to heat the feed water pumped into the
boiler. The draft is increased by exhausting a portion of the steam into
a nozzle placed directly under the stack. The friction of the steam on
the surrounding air, draws the air with it, forming a partial vacuum
over the grate at each puff, and in this way it causes additional air to
rush through the fuel and increases the temperature of the combustion.
As the load increases the “puffs” increase in intensity due to the
greater terminal pressure and the fire is accelerated in proportion.
This is a simple but rather expensive way of increasing the draft.

A considerable proportion of the heat in the exhaust steam is saved by
using it to heat the feed water supplied to the boiler. Besides the
saving in fuel, affected by heating the water from steam that would
otherwise be thrown away, the strains on the boiler due to the injection
of cold water are greatly decreased as the difference between the
temperatures of the boiling water in the boiler and the hot feed water
are much less than in the former case.

The feed water heater consists essentially of a series of tubes in a
cylindrical shell. The tubes are surrounded on the outside by the feed
water, and are filled with the exhaust steam which passes from end to
end through the tubes. The hot water is pumped from the heater into the
boiler. An efficient feed water heater adds greatly to the steaming
capacity of the boiler.

(152) Feed Pump.

A small steam pump is furnished for pumping the water into the boiler.
This device consists of a small steam cylinder connected directly with
the pump plunger and is absolutely independent of the main engine so
that it can be used whether the engine is running or not. The exhaust of
the pump should be turned into the feed water heater when the engine is
not running so as to heat the water, but should be directed to
atmosphere when the main exhaust is passing through the heater. An
injector is usually supplied with the engine for feeding the boiler in
emergencies.

The injector forces water into the boiler by means of a steam jet which
is arranged so that a high velocity is imparted to the water in the
injector nozzle by the condensation of the steam furnished by the jet.
In this way water is pumped into the boiler against a pressure that is
equal to the pressure of the steam acting on the water. Except for a
check valve there are no moving parts. No feed water heater connection
is made with the injector for this device raises the temperature of the
feed to a considerable temperature. The temperature is not as high,
however, as the temperature of the water from the feed water heater and
pump, and because of the comparatively low temperature coupled with the
fact that live steam is used in heating the injector water, it is not an
economical method of pumping.

(153) The Boiler.

As the boilers of traction engines sustain the pull and vibration of the
engine as well as the stresses due to traveling over rough roads in
addition to the steam pressure strains, they must be made very
substantially and of the best materials. The service of the boiler on a
traction engine is very different from that met with in stationary or
locomotive practice for the tractor seldom receives the attention that
is given to the other types and as it goes bumping over the fields with
the water whacking at every joint and the engine rushing and surging at
every little grade, it receives an “endurance” test every moment of its
existence.

A boiler should show an inspection pressure considerably in excess of
that which it is intended to carry. It should be well stayed and braced,
and should be suspended from the road wheels in such a way as to be
relieved from as much strain as possible. No transverse seams should be
permitted, and the barrel should be well reinforced at the point where
the front bolster is attached as well as at points where pipe
connections are tapped into the shell. No large bolts should be tapped
into the steam or water space. The tubes should be placed so that they
may be easily withdrawn or cleaned. The location of the hand holes and
washout holes is also an important item, for inaccessible hand-holes are
an abomination.

Boiler lagging or covering is intended to reduce the heat loss by
radiation, and for this reason it should be of a good insulating
material and should be thick enough to be effective. The cost of
jacketing is more than covered by the saving in coal, especially in cold
weather.

A straw-burning fire box differs from a coal burner in having a fire
brick arch and a shorter grate, and in having a special chute on the
fire door for feeding the straw into the furnace. After a short time,
the fire brick arch becomes incandescent, keeping the firebox
temperature constant and producing perfect combustion of the tarry
vapors distilled from the straw. A trap door is provided on the straw
chute which automatically keeps the outside air from chilling the fire.

(154) Oil-Burning Steam Tractors.

As with the straw-burning furnace, a brick arch is used in burning oil
for the purpose of preventing fractional distillation of the oil during
the combustion. In some forms of oil furnaces a brick checker-work is
used that provides a much greater surface to the gases than the ordinary
firebrick arch and therefore keeps a steadier temperature and pressure.
Broken firebrick in the furnace placed in heaps with a rather porous
formation is also an aid to combustion. With very heavy oils a jet of
steam in the firebox is of great assistance in consuming the free carbon
of the fuel (soot).

The oil in practically all cases is atomized or is broken up into a very
finely subdivided state by the action of a jet of steam. The finer this
subdivision the better will be the combustion for the oil particles will
be brought into more intimate contact with the air. Provision is also
made in the burner for either whirling or stirring the oil vapor with
the air so that a rapidly burning mixture is formed. In other respects
the oil burning engine is the same as the coal or wood burner.

(155) Care of the Steam Tractor.

During the idle season, the engine should be well housed, all bright
parts slushed with grease and the whole engine carefully covered with
tarpaulins. A tractor is an expensive machine and should be given care,
or it will rapidly depreciate and start giving trouble. When one
considers the abuse and neglect given farm machinery it is remarkable
that it will work at all, let alone give efficient service.

[Illustration:

Small Fairbanks-Morse Motor Driving Binder.
]

Before starting a new engine or one that has been idle for a
considerable time, all of the bearings and lubricating should be
thoroughly cleaned with kerosene oil, removing all grit or gum. After
cleaning, they should be thoroughly oiled with the proper grade of
lubricant and then adjusted for the correct running fit, taking care
that the bearings and wedges are not taken up too tight, nor too many
shims are taken out. Be sure that the openings in the lubricating cups
and oil pipes are not clogged and that oil holes in the bearing bushings
register with those in the bearing caps. At points where there are sight
feed gauge glasses, the glasses should be cleaned with gasoline and all
of the joints repacked with new packing.

Careful attention should be paid to the piston rod and valve rod packing
taking care that it is only tight enough to prevent the leakage of steam
and no greater. Excessively tight packing burns out rapidly, scores and
shoulders the piston rod, making it impossible to keep the joint tight.
When rods are badly scored they should be trued up in the lathe taking
care not to take off too much metal on the finishing cut. When renewing
fibrous packing be sure that all of the old packing is removed before
placing the new packing in the box. Keep the packing well lubricated at
all times to prevent wear, and in some cases it will be advisable to add
an oil cup to the stuffing box to insure sufficient lubrication.

Go over the valve gear and make sure that there is no looseness or play
in the eccentrics or pins, and that all of the bolts and keys are tight
and in place. Loose connections in the valve gear are not only
productive of knocks and wear but also tend to increase the fuel
consumption of the engine. When possible, indicator cards should be
taken at intervals to make sure that the valves are correctly set. In a
test recently made by the author, the indicator cards showed a defective
setting due to wear, that when corrected saved the owner of the engine
about 600 pounds of coal per day, and as the coal cost $9.50 per ton
delivered in the field, the saving soon paid for the expense of the
test. Points of adjustment are provided on all valve gears, and as they
differ in detail for each engine we cannot give explicit directions for
settling the valves, but will leave this point for the direction book of
the maker.

The governor and governor belt should now receive attention making sure
that there are no loose points or nuts in the mechanism and that the
governor belt is in good condition. Defective governor belts are
dangerous through the possibility of over speeding. Slipping or oily
belts not only increase the chances of fly-wheel explosions, but also
cause a fluctuation in the speed which is not desirable especially in
threshing, where good results are obtained only by a constant speed.
Make sure that the safety lever works properly and shuts off the steam
with a loose or broken belt. Test the governor valve stem for sticking
or for rough shots that are likely to cause uneven running. Keep the
governor well lubricated with light oil, and keep the oil off the belt
as much as possible. Governor valve should be carefully tested for
tightness and freedom.

The throttle valve must be absolutely steam tight for a leaking valve is
a dangerous proposition especially in stopping the engine. It is
generally arranged so that it can be reground with pumice stone or
crocus powder and oil. If the valve is of bronze or brass do not use
emery or carborundum for the particles will become imbedded in the soft
metal and put it in a worse condition than ever. Pack the valve stem.

A leaking slide valve is the cause of much loss of power, and waste of
coal, and as the leakage mingles directly with the exhaust, it often
remains unknown until it has thrown away a considerable quantity of
fuel. It is best detected by blocking the engine with the piston at
mid-stroke and opening the throttle valve slightly. If the cylinder
drain cocks are now opened, the leaking steam that escapes into the
cylinder will be seen issuing from the drains. The leakage that passes
into the exhaust will be seen escaping from the stack while it is
practically impossible to have the valves absolutely tight at all times,
the steam should not escape so rapidly that it roars through the
openings. Leakage past the piston is another source of loss that can be
detected by blocking the engine so that the piston is very near, one end
of the stroke, with the valve opening one of the cylinder ports. Any
steam that passes the piston will pass out of the exhaust. With an old
engine it is likely that the cylinder is worn oval, or that the valve
seat is grooved or uneven, in which case it will be necessary to rebore
the cylinder and fit new piston rings or reface the valve seat. Broken
piston rings are often the source of leakage, and if not replaced with
new at an early date, are likely to destroy the cylinder bore as well.
Broken rings generally make themselves known by a wheezing click when
the engine is running.

The steam feed pump should be well lubricated with a good grade of
cylinder oil and should be well packed around the piston rod especially
at the water end. To guard against pump troubles a good strainer should
be provided on the water suction line to prevent the entrance of sticks
and dirt into the cylinder. Great care should be exercised in keeping
the suction line air tight, for if any air escapes into this line no
water will be lifted. Dirt under the valves is the cause of much pump
trouble, as a very small particle of dirt will allow the water to pass
in both directions through the valves. Leaking packing will also destroy
the vacuum in one end of the cylinder. For the best results the pump
should be run slowly but continuously, feeding a small amount of water
at one time. This method of feeding allows the feed water heater to
bring the water up to the highest possible temperature which reduces the
fuel consumption and reduces the strains on the boiler. It is a bad
policy to let the water get low in the boiler and then “ram” full of
cold water in a couple of minutes. Attention should be paid to the check
valve that is located between the pump and boiler. It should be kept
clean and the valve kept tight and in good condition.

When the feed water is hard a boiler compound should be used to reduce
the amount of scale in the boiler or soften it and make its removal
easier. Scale of 1/16 inch thickness will decrease the efficiency of the
boiler by 12%, and this loss increases rapidly with a further increase
in the thickness of the scale because of its insulating effect on the
tubes. Soft sludges such as mud and clay may be removed by-blowing off
or by the filtration of the water before it is pumped into the boiled.
Lime and magnesia which form flint-hard deposits, require chemical
treatment such as the addition of sodium phosphate, etc. In any case,
the deposits waste heat and increase the liability of burning out tubes
or bagging the sheets.

[Illustration:

Buffalo Marine Motor.
]

A solution that has given good results with waters containing lime,
consists of 50 pounds of Sal Soda and 35 pounds of japonica, dissolved
in 50 gallons of boiling water. About 1/40 quart is fed into the boiler
for every horse-power in 10 hours, the solution being mixed with the
feed water. Kerosene has been used a great deal to soften scale, and
gives good results if not fed in quantities to exceed 0.01 quart per
horse-power day of 10 hours. An excess of kerosene is to be guarded
against for it is likely to accumulate in spots and cause bagged sheets
or burn outs.

CHAPTER XV.
OIL BURNERS.

(156) Combustion.

To obtain the full heat value of a liquid fuel it must be provided with
sufficient air to complete the combustion, it must be in a very finely
subdivided state, or in the form of a vapor at the time of ignition, and
it must be thoroughly mixed with the air so that every part of the oil
is in contact which its chemical equivalent of oxygen. Failure to comply
with any of these conditions will not only result in a waste of fuel but
will also be the cause of troublesome carbon deposits and soot, which
eventually will interfere with the operation of the burner.

Complete combustion is much more easily attained with the lighter
hydrocarbons such as gasoline or naptha than with crude oil or the
heavier distillates, for they are more readily vaporized and mix more
thoroughly with the oxygen. Only a slight degree of heat and pressure is
required with gasoline while with crude oil a high atomizing pressure
and high temperature are required to obtain a satisfactory flame. In the
majority of cases where heavy oils are used the fuel is not even
completely vaporized but enters the combustion chamber in the form of a
more or less finely atomized spray. The methods by which the liquid fuel
is broken up divides the burners into three primary classes.

(1) LOW PRESSURE BURNERS in which the fuel is atomized by a blast of low
pressure air which also supplies a considerable percentage of the air
required for combustion.

(2) HIGH PRESSURE BURNER in which a small jet of high pressure air or
steam is used to atomize the oil, the air for combustion being supplied
from a source external to the burner.

(3) COMBINED HIGH AND LOW PRESSURE BURNER in which the fuel is atomized
by high pressure air or steam, and the greater part of the air for
combustion is furnished by a blower at a comparatively low pressure.

In class (1) the oil is supplied to the burner under pressure and by
means of a specially designed jet is thrown against hot baffle plates or
gauze screens where the partially broken up liquid is caught by the high
velocity air and reduced to a still finer spray by its impact against
other screens or baffles further on in the burner. This system is
applicable only to the light and intermediate grades of oils, such as
gasoline, naptha or kerosene, unless heat is applied to the external
casing to aid in the vaporization. In some cases the projection of the
burner into the furnace gives satisfactory results, but with such an
arrangement there is a tendency to deposit carbon in the burner and for
the flame to “strike back” should the velocity of the air fall below a
certain critical point. Better results were had with this type of
burner, by the author when the air blast was preheated by passing
several long lengths of the intake air pipe over a hot part of the
furnace, instead of entering the burner nozzle into the combustion
chamber proper.

A well known modification of this type is the gasoline torch used by
electricians and plumbers in which the gasoline is sprayed into a
perforated hot tube by air pressure in the tank. When the spray formed
at the needle valve strikes the surrounding hot tube it is instantly
vaporized and is mixed with the air passing through the perforations in
the tube. While the air entering the tube is not forced through the
openings by external pressure it attains sufficient velocity to aid in
the vaporization because of the vacuum established by the jet. This
however is only enough for the more volatile fuels—such as gasoline or
benzine.

The high pressure which is by far the most commonly used with low grade
fuels may be divided into five principal types (a) =ATOMIZER= burner,
(b) The =INJECTOR= burner, (c) =DRIP= feed burner, (d) =CHAMBER OR
INTERNAL= burner, (e) =EXTERNAL BLAST= burner. All of these burners
break up the fuel by high pressure air or steam, the types given being
different only in the way that the pressure is applied to the fuel.

The atomizer acts on the same principle as the medical or perfumery
atomizer, the high pressure jet playing directly across the open end of
the oil passage as shown by Fig. A. As the vacuum created by the blast
is very low, and has little effect in lifting the fuel to the burner,
the oil either is made to flow by gravity or by a pump. In the figure
the oil in the upper passage is shown pouring down in front of the air
or steam jet issuing from the lower port. Both ports are supplied by the
pipes shown by the circular openings at the right. The steam and oil are
controlled by independent valves placed in the two passages.

In practice the oil and steam openings at the end of the burner may be
either single or multiple round openings or long thin slots, the former
style being the most common. Since only a small amount of air is
admitted through the blast nozzle, far too little to completely consume
the oil, the air for the combustion is admitted through openings in the
combustion chamber proper, this air being supplied by natural draft or
by blower. In some cases the burner is entered into the furnace through
an opening that is much larger than the burner itself. The atmospheric
air enters through baffle plates in this opening which impart a whirling
motion to the air that passes over the burner. This is of considerable
aid in maintaining complete combustion in the furnace, and also tends to
prevent deposits in the burner.

[Illustration:

Fig. 135. Showing the Different Classes of Oil Burners.
]

[Illustration:

Fig. F. Mixed Pressure Burner, Using Both Steam and Low Pressure Air.
]

[Illustration:

Fig. G. Burner Used by the Pennsylvania Railroad Under Locomotives.
]

In the injector type of burner shown by Fig. B the air or steam nozzle
terminates inside of a shell and is completely surrounded by the oil. A
mixture of air and oil issues from main nozzle shown by (2). When the
air or steam blows through the inner opening, a partial vacuum is formed
in the space (1) which draws the oil into the burner from the supply
pipe. On entering this vacuous space the oil comes into contact with the
jet and is blown out through the opening (2) in the form of a spray.
This vacuum is high enough to lift the fuel for a considerable distance
without the aid of a pump and for this reason is the type most commonly
met with in practice. A boiler or furnace equipped with this burner will
lift the oil directly to the furnace from the reservoir in the same way
that a feed water injector will lift water into the boiler. With the
commercial injector, the position of the steam jet is made adjustable in
relation to the main jet to meet different feed conditions. The steam
enters the inner port through the end of the pipe shown at the right.
The oil enters the outer port at the right through a port not shown.

[Illustration:

Fig. H. Lassoe-Lovelsin Burner.
]

Fig. C shows a drip feed or “dribbling” burner in which the oil pours
out of the upper port and over the lower port through which the steam or
air issues. As would be expected, the atomization is not as perfect with
this burner as with the atomizer or injector type.

[Illustration:

Fig. I. Sheedy Oil Burner, Used for Locomotives.
]

A burner in which the oil and steam mix before passing out into the
furnace through the final opening is known as a “Chamber burner,” and is
shown by Fig. D. In some respects, at least in construction, it is
similar to the injector burner, but it does not possess the lifting
abilities of the latter because of the open space in front of the steam
nozzle. The atomization takes place largely within the burner because of
the eddy currents of air and oil vapor created both by the vapor
striking the walls of the outer tube and by the large space in which it
has to circulate before passing out of the orifice.

An external blast burner as shown by Fig. E, in which the oil is forced
out of the openings (3–3) at the extreme end of the burner atomizes by
blowing the oil off of the tube by jets of steam directed by a series of
annular openings in a disc. This is really a type of atomizer burner as
will be seen by close inspection. This type must be very carefully
constructed and the steam jets must be kept very clean in order to have
good results for a little variation in the pressure or a small particle
of dirt in the openings will deflect the steam and prevent a perfect oil
spray. It’s one advantage lies in the fact that the oil and air are
always separate and therefore minimize the danger of carbonization.

[Illustration]

It should be noted that the figures just shown in the illustration of
the various classes of burners are diagrammatic only, and that many
modifications in detail are made in the practical burner such as
regulating valves, sliding steam nozzles, etc.

A burner much used in stationary engine practice and with heating
furnaces, where air at two or three ounces pressure is available, is the
mixed pressure burner shown by Fig. F. In this burned steam or air
compressed, to say 80 pounds per square inch is used for breaking up the
fuel oil. A blast of air at low pressure but with considerable volume is
used to support combustion in the furnace. The steam or compressed air
enters the burner at (5) and meets the oil at the nozzle (8) where it is
sprayed into the chamber (9). The oil enters the burner by the pipe (4),
flows into the annular passage around the steam nozzle and meets the
steam at (8). It will be noted that the steam nozzle (5) is free to
slide back and forth in its casing so that the relation between the
steam nozzle and spray nozzle may be adjusted to meet different
operating conditions. This adjustment is affected by the levers (10) at
the end of the burner.

The low pressure air entering through opening (6) from the blower
passes around the chamber (9) and mixes with the oil spray from (8) in
the mixing chamber (7). This causes a violent swirl in (7) with the
result that a comparatively intimate mixture of oil vapor and air is
formed before they issue into the furnace. In many burners of this type
a gauze screen (11) is placed over the mouth of the final orifice so
that back fires are prevented and a still better mixture is formed. Many
burners of this type have been built by the author with very
satisfactory results, and he knows of only one weak point in the type.
This is due to the fact that if a sufficient volume of air is not kept
flowing through the low pressure pipe (6), the oil vapor may collect in
the piping with the result a back fire will wreck all of the low
pressure connections. To prevent this trouble a light galvanized iron
weighted damper was placed beneath (6) which closed the pipe when the
pressure fell below a certain amount. Since this check valve was placed
there were no more pipe fires.

In all cases a sliding damper should be placed in the opening so that
the blast can be regulated to suit the amount of oil injected.

As these burners were used in a closed building continuously without
smoke or smell and with indifferent grade of oil it will be seen that
the combustion was as nearly perfect as could be expected with any type
of oil burner.

Several of these burners were made from ordinary steam pipe fittings
without steam nozzle adjustment.

While the burners shown are arranged to give a flat flame (with the
exception of burner F) they may all be built for a circular flame by
surrounding the injection nozzle with a suitable nozzle. A =ROSE= or
circular flame is particularly desirable for a vertical boiler where it
can be made to conform with the circular shell and apply the heat
directly to the tube sheet through suitable fire brick baffles.

A burner of the injector type shown by Fig. G, has been used by the
Pennsylvania Railroad with a considerable degree of success. The steam
enters the steam nozzle at (12) through the circular openings from which
point it passes through the nozzle (13) and carries the oil from the air
port (14). The mixture or spray of steam and oil passes out of the
nozzle (15) into the furnace. The steam nozzle is threaded into the
casing at (16), and is keyed to the bevel gear (17). Meshing with (17)
is the bevel mounted on the vertical stem which terminates in a
hand-wheel in the engineer’s cab. By turning the bevels, the nozzle
turns in the casing threads causing it to move back and forth for the
adjustment.

In many types of burners having a nozzle similar to (15) a twisted form
of rifling is placed in the bore that gives the escaping gas a rotary
motion. This is very effective in mixing the air and oil vapor and
spreads the flame very close to the orifice. In burners of the chamber
type a spiral vane is sometimes used to gain the same effect, and in one
make a rotating fan, is placed near the opening of the outer nozzle
which gives a sudden whirl to the gases. While this latter attachment
does all that is claimed for it while it is in good repair, it is very
likely to stick and put the burner out of commission.

The Lassoe-Lovelsin locomotive burner is shown by Fig. H in which the
gas exits through a series of holes in the end of the nozzle (22). The
steam enters the outside casing, and unlike the burners just described,
entirely surrounds the central oil nozzle, (20). The steam in passing
through the openings 21–22 draws the oil through the central opening
(23), this oil nozzle being controlled by the needle valve (24) which
terminates in the handle (25). Oil enters the oil nozzle through the
inlet pipe (26).

The Sheedy oil burner shown by Fig. I has a rectangular nozzle for a
flat flame, and has no steam nozzle adjustment. Oil surrounds the steam
nozzle and enters the casing through the upper connection. Air enters
the lower port through the lower opening as shown in the cross-section
of the burner. As the oil flows over the trough formed by the steam
nozzle it meets the jet of steam at (30) and is atomized. The air from
the lower port aids in bringing the combustion near the tip of the
nozzle and therefore prevents carbon deposits from being formed in the
burner as well as spreading the flame at a wide angle.

------------------------------------------------------------------------

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engines—Three port, two-stroke cycle engines—Mixing
valves—Carburetors—Manifolds for multi-cylinder engines—Mufflers—Exhaust
pots, etc.—Cooling systems—Purpose of cooling systems—The radiator—Air
cooling—Tank, hopper and trays—Circulating pumps—Thermo—Syphon—Water vs.
oil—Anti-freezing solutions—Lubrication—Splash, force feed, exhaust
feed, properties of lubricating oils, grease, pumps, strainers, filters,
cups, connections, etc.—Details of approved systems—Construction
details—Engines for various purposes—Electric lighting
engines—Dynamos—Storage batteries—Wiring—Switch
Board—Installation—Engine room
arrangement—Foundations—Piping—Shafting—Hangers, etc.—Operation—_Trouble
Chart_ for location of troubles—Remedies for trouble—Shop
rules—Formulas—Automobile, motor boat and aero motors, _Trouble
Chart_—Accessories—Operation, etc., etc.

Price, FLEXIBLE LEATHER $1.50
CLOTH BINDING 1.00

THE PRACTICAL HANDBOOK OF GAS, OIL, AND STEAM ENGINES

[Illustration]

BY JOHN B. RATHBUN.

Author of “Gas Engine Troubles and Installation,” Editor
“Ignition”—Instructor Chicago Technical College.

370 Pages, 150 Line Drawings and Illustrations.

This book is the most complete and up-to-the-minute book for the
practical man on the subjects of gas, gasoline, oil, and steam engines.
Oil burners for use in steam engines in a useful feature. Special
emphasis is placed on farm tractors and their operation, both oil and
steam driven. The engines described are the latest types, and include
the Diesel, Semi-Diesel Gnome, Low and Turbine types.

CONTENTS

=Heat and Power.=—=Fuels=—Calorific Values of Fuels—Solid,
Liquid and Gaseous Fuels—Kerosene—Gasoline—Crude Oil—Producer
Gas—Illuminating Gas—Coal—Benzol. =Working Cycles=—Definitions
of =Cycles Indicator Diagrams=—Practical Use of the Indicator—=Typical
Four Stroke Cycle Engines=—=Single Cylinder=—=Four
Cylinder=—=Automobile=—=Opposed Type=—V Type—Tandem—Twin Tandem—Rotary
Cylinder—Radial—Diesel—Knight—Argyle—Rotary Valve. =Typical Two
Stroke Cycle Engines=—Two Port—Three Port—Marine—Controlled
Port—Aeronautic—Oechehauser—Gnome Rotary Two Stroke. =Oil
Engines=—Elyria—Marine Diesel—Installation—Aspiration Types—Fairbanks
Morse—Kerosene—Carburetion—Semi-Diesel—Combustion of Heavy Oils.
=Ignition Systems=—Hot Tube System—Low Tension System—High Tension
System—Details of Make-and-Break Batteries—Low Tension Magnetos—High
Tension Magnetos—Coils—Adjustment—Troubles. Carburetors—Principles of
Carburetion—Jet Carburetors—Water Jacketing—Fuel Supply—Different Types
of Auto Carburetors—Adjustment—Carburetor Troubles. =Lubrication=—Forced
Speed—Splash System—=Oil Pumps=—Lubrication Troubles. Cooling
Systems—Evaporation Systems—Radiators—Air Cooling. =Speed
Governors=—Automobiles—Stationary—Adjustment—Mixture—Control Hit and
Miss—Mixed Systems. =Tractors and Various Farm Engines=—Gasoline and Oil
Tractors—Mechanism of Various Types—Steam Tractors—Plowing and Threshing
Costs—Plowing Contests Data—Two Speed Mechanisms—Draw Bar Pole—Oil
Carburetors, etc. Oil Burners—Combustion—High Pressure System—Low
Pressure System—Mixed System—Burners for Furnaces, Locomotives,
Pennsylvania Type, Sheedy Burner, Kirchoff Burner, etc.

Price, FLEXIBLE LEATHER $1.50
SILK CLOTH 1.00

Questions and Answers

For Automobile Students and Mechanics

[Illustration]

—By—

Thomas H. Russell, A.M., M.E.

Author of “Automobile Driving Self-Taught,” “Automobile Motors and
Mechanism.” “Ignition, Timing and Valve Setting,” “Motor Boats:
Construction and Operation,” etc., etc.

A book of 600 Questions and Answers, adapted for teaching School,
the Machine-shop or before the Board of Examining Engineers. This is
the largest, the latest and most authentic book of its kind upon the
market. Prepared especially for Home Study. 150 pages. Bound in
Cloth, Stiff Covers—In fact it is a regular text book.

The Questions and Answers in this book will be found useful by every
Student and Mechanic of Motor Cars and Motoring, as a handy means of
reviewing systematic study or in daily work.

It has long been recognized that the Question and Answer method is most
effective in fixing in the memory facts gained by study or problems that
confront the Mechanic in his daily work; hence it is adapted for the
purpose.

The more important subjects connected with Motor Cars, are treated
individually, there being a separate set of Questions and Answers for
each. For the greater convenience of the reader, the Questions and the
Answers in each set appear on separate pages; the Questions can thus be
used alone for self-instruction, while the Answers if needed are close
at hand for reference.

Minor subjects are covered in a special Catechism, which deals with all
the factors which go to make up the power plant of a Modern Motor Car.

Price, CLOTH $1.00
LEATHER $1.50

AUTOMOBILE MOTORS AND MECHANISM.

[Illustration]

By THOMAS H. RUSSELL, M. E., LL. B. Author of “Automobile Driving
Self-Taught.” “Ignition, Timing and Valve Setting.” “Motor Boats:
Construction and Operation,” etc

Pocket size, 265 pages, Blue flexible leather, round corners, red edges,
fully illustrated

CONTENTS

=The Internal Combustion Engine=—Principles and Construction—Production
of the fuel mixture—Function of the carbureter—The cycle of
operations—Cylinders, piston and rings—Shafts and bearings—Ignition
apparatus—Single and multi-cylinder engines—The two cycle engine—Valves
and their functions—Silencing the exhaust—Engine hints and tips—=A
Typical Modern Motor=—Detailed description of construction—=Governing
and Governors=—The centrifugal governor—Throttle valves—Governing and
control—The hit-or-miss governor—=Carbureters=—The float-feed
principle—The float chamber and jet—Various types of modern
construction—Quality of mixture—Flooding the carbureter—Carbureter
troubles and adjustments, etc.—=Transmission Mechanism=—=The
Clutch=—Various forms in use—Positive and friction clutches—Plate or
disk clutches—The combined disk and cone type—Expanding clutches—Clutch
troubles, etc.—=Gear or Gearing=—Belt and chain gearing—Friction
gear—Spur or tooth gearing—Spiral, helical, worm and bevel
gearing—Epicyclic gear—Infinitely variable gear—=Differential or
Balance Gear=—Its functions—=Shafts and their Functions=—The
crankshaft, half-speed shaft, countershaft, etc.—=Lubrication and
Lubricators=—=Pumps and their Purposes=—=Motor Misfiring, Causes and
Remedies=—=Noises in the Motor, Causes and Remedies=—=Motor Overheating,
Causes and Remedies=—=Electric Motors=—Principles and operation—=Steam
Cars=—The engine, generator, reverse gear, etc.

Price, FLEXIBLE LEATHER $1.50
CLOTH BINDING 1.00

A B C of the MOTORCYCLE

[Illustration]

By W. J. JACKMAN. M. E. Author of “Facts for Motorist,” “Crushed
Stone and Its Uses,” and Similar Books.

Pocket Size, 250 pages, fully Illustrated, Leather and Cloth, Round
Corners, Red Edges. A “Show How” Book for Owners and Operators of
Motorcycles.

CONTENTS

Inception and Evolution of the Motorcycle—Modern Machines and their
Vital Parts—How to Master the Mechanism—Production and Application of
Motive Power—Construction and Operation of the Carbureter—What the
Carbureter Does—Ignition Systems—Batteries and Magnetos—Practical
Methods of Handling—Various Types of Motors—Theory and Effect of
Internal Combustion—Troubles of all Kinds and How to Avoid or Overcome
Them—Lubrication Methods—Transmission or Drive Systems—How to Compute
Horse Power—Relation of Power and Speed—Weather Effects on Gasolene
Engines—Cost of Maintenance on Basis of Mileage—Some Dont’s that will
save Time and Money—Selecting a Motorcycle—Hints for the Buyer—What an
Owner should do on receiving a New Machine—The First Ride.

Price, FLEXIBLE LEATHER $1.50
CLOTH BINDING 1.00

DUSTMAN’S PLAN BOOK

and

COMPLETE MODERN ESTIMATOR of GENERAL BUILDING CONSTRUCTION

By U. M. Dustman, Licensed Architect,
Editor of “The Progressive Builder.”

250 pages, 9×13 inches, Several Books Combined in One.
Invaluable to the Contractor, Builder or Layman.

[Illustration]

Cloth Binding, White Foil Stamping,
Price $2.00

CONTENTS

Designs and Suggestions—Geometrical Problems Illustrated—Roof Trusses
Illustrated—Rafter Diagrams—Construction Diagrams—Stair Work
Diagrams—Stair and Handrailing Tables—Window Frame Work and
Diagrams—Store Front Problems Illustrated—Brick Work Construction and
Tables—Window Frames for Brick Walls—General Construction Problems,
Concrete Work, Arches, Brick Work, Mill Construction, Beams, Columns
and Splices, Framing, Drafting, Properties of Woods and
Metals—Plastering—Painting—Roofs—Tables of Mensuration—Engineering
Tables of Beams, Columns, Channels, etc.—Tables of Rafters—Building
Terms—Builders’ Arithmetic—How to Read Plans—Detailed Estimates of
various mechanical departments—Complete Detailed Specifications
Form—Concrete Mixing, Construction of Houses, Barns, Garages, Silos,
Sidewalks, etc.—Photographs, Plans and Elevations of Many Houses,
Barns. Public Buildings, Out-buildings, etc.

------------------------------------------------------------------------

TRANSCRIBER’S NOTES

1. “Baumé” was consistently misspelled as “Beaumé”. Did not correct.
2. The spelling of words such as “distributor/distributer” and
“carburetor/carbureter” was inconsistent.
3. The section and paragraph numbers are not always sequential.
4. Changed “may read” to “may be read” on p. 22.
5. Changed “engine is instrument” to “engine is an instrument” on p.
27.
6. Changed “use in temperature” to “rise in temperature” on p. 32.
7. Changed “air the same temperature” to “air at the same temperature”
on p. 52.
8. Changed “alcohol than for in the neighborhood” to “alcohol in the
neighborhood” on p. 55.
9. Changed “fuel heated” to “fuel is heated” on p. 56.
10. Changed “moving ports.” to“moving parts.” on p. 64.
11. Changed “reading for the succeeding suction stroke” to “ready for
the succeeding suction stroke” on p. 76.
12. Changed “inlet shots” to “inlet slots” on p. 124.
13. Silently corrected typographical errors.
14. Retained anachronistic and non-standard spellings as printed.
15. Enclosed italics font in _underscores_.
16. Enclosed bold font in =equals=.
17. Superscripts are denoted by a caret before a single superscript
character or a series of superscripted characters enclosed in
curly braces, e.g. M^r. or M^{ister}.
18. Subscripts are denoted by an underscore before a series of
subscripted characters enclosed in curly braces, e.g. H_{2}O.

*** End of this LibraryBlog Digital Book "Practical Hand Book of Gas, Oil and Steam Engines - Stationary, Marine, Traction Gas Burners, Oil Burners, - Etc. Farm, Traction, Automobile, Locomotive A simple, - practical and comprehensive book on the construction, - operation and repair of all kinds of engines. Dealing with - the various parts in detail and the various types of engines - and also the use of different kinds of fuel." ***

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