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Title: Shafting, Pulleys, Belting and Rope Transmission - The Power Handbooks Library
Author: Collins, Hubert E. (Hubert Edwin)
Language: English
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SHAFTING, PULLEYS, BELTING
AND ROPE TRANSMISSION
THE POWER HANDBOOKS
The best library for the engineer and the man who hopes
to be one.
This book is one of them. They are all good--and
they cost
=$1.00 postpaid per volume. (English price 4/6 postpaid.)=
_SOLD SEPARATELY OR IN SETS_
BY PROF. AUGUSTUS H. GILL
OF THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY
ENGINE ROOM CHEMISTRY
BY HUBERT E. COLLINS
BOILERS KNOCKS AND KINKS
SHAFT GOVERNORS PUMPS
ERECTING WORK
PIPES AND PIPING SHAFTING, PULLEYS AND
BELTING
BY F. E. MATTHEWS
REFRIGERATION. (In Preparation.)
HILL PUBLISHING COMPANY
505 PEARL STREET, NEW YORK
6 BOUVERIE STREET, LONDON, E. C.
THE POWER HANDBOOKS
Shafting, Pulleys, Belting
AND
Rope Transmission
COMPILED AND WRITTEN
BY
HUBERT E. COLLINS
Published by the
McGraw-Hill Book Company
New York
Successors to the Book Departments of the
McGraw Publishing Company Hill Publishing Company
Publishers of Books for
Electrical World The Engineering and Mining Journal
The Engineering Record Power and The Engineer
Electric Railway Journal American Machinist
_Copyright, 1908_, BY THE HILL PUBLISHING COMPANY
_All rights reserved_
_Hill Publishing Company, New York, U.S.A._
INTRODUCTION
THIS handbook is intended to furnish the reader with practical help
for the every-day handling of shafting, pulleys and belting. These are
allied in the operation of plants and it is a pretty generally conceded
fact that all three are much neglected by many operators.
A close perusal of these pages will enable the reader to determine
the best course to pursue in the most common instances and in various
troubles, and in all articles there are suggestions for similar cases
which may arise.
For instance, the need of belt dressing as a preservative, now
generally conceded by most authorities, is fully covered in Chapter
XI and the result of a test made by disinterested parties to find the
degree of efficiency of four of the best known dressings is given. The
results are of importance to all belt users.
A portion of the book is also given to rope transmission which is in
more general use to-day than ever before, and in this connection some
advice is offered by experts as to the selection and care of the rope.
Rope splices and how to make them will also prove valuable to many
engineers.
The author wishes to make acknowledgment to various contributors
to _Power_ whose articles are used herein, and to some special
contributors, from whose articles small portions have been taken.
Acknowledgment is also made to Stanley H. Moore, the author of
"Mechanical Engineering and Machine Shop Practice" for the section on
splicing.
HUBERT E. COLLINS.
NEW YORK, _November_, 1908.
CONTENTS
CHAP. PAGE
I SHAFTING HINTS 1
II SHAFTING HINTS 21
III SHAFTING HINTS 32
IV TRUING UP LINE SHAFTING 49
V APPARATUS FOR LEVELING AND LINING SHAFTING 54
VI SOME PRACTICAL KINKS 61
VII PRACTICAL METHODS OF LOOSENING PULLEYS 65
VIII SPLICING LEATHER BELTS 72
IX CARE AND MANAGEMENT OF LEATHER BELTS 89
X BELTING--ITS USE AND ABUSE 99
XI A COMPARATIVE TEST OF FOUR BELT DRESSINGS 102
XII BELT CREEP 106
XIII ROPE DRIVES 108
XIV A NEW SCHEME IN ROPE TRANSMISSION 115
XV HOW TO ORDER TRANSMISSION ROPE 122
XVI A BELTING AND PULLEY CHART 129
XVII SPLICING ROPE 135
XVIII WIRE ROPE TRANSMISSION 143
I
SHAFTING HINTS[1]
IN the installation, maintenance and repair of shafting, as in all
other things, there is a right and a wrong way; and though the wrong
way ranges in its defects from matters causing trivial inconvenience
to absolute danger, the right too often--owing to lack of knowledge or
discernment--finds but scant appreciation.
[1] Contributed to Power by Chas. Herrman.
Where, as is often the case, the end of a shaft is journaled to admit
of the use of an odd, small-bore pillow block or wall-box hanger, the
journaled part should equal in length twice the length of the hanger
bearing plus the length of the collar. The hanger can thus readily be
slid out of the wall box, and the necessity of uncoupling this shaft
length and removing it before access to the bearing for purposes of
cleaning or repair is done away with.
A plank or board _A_ (Fig. 1), about 1/4 to 1/2 inch longer than the
distance from the bottom of the shaft to the floor, can be used to good
advantage at such times to free the hanger of the shaft's weight, and
to prevent the shaft's springing from its own weight and the pulleys it
may be carrying.
Should it become necessary to place a pulley with half the hub on and
half off the journaled part, this can readily be done by the use of a
split bushing, as shown in sectional view of Fig. 1.
[Illustration: FIG. 1.]
Very often a small-sized bearing is used and the shaft journaled off
to act as a collar. Of this procedure it can only be said that if done
with the idea of making a "good job" it signally fails of its object;
if of necessity (a collar being insufficient), then the shaft is
heavily overloaded and serious trouble will result, because of it.
It is advisable to center punch, or otherwise mark, the ends of both
shafts held by a compression coupling close up against the coupling,
and both edges of the coupling hub should have a punch mark just
opposite and close to the shaft punch marks. These marks will serve
at all times to show at a moment's glance any end or circumferential
slippage of the shafts within the coupling. The same method can be
resorted to for proof of pulley slippage.
When a new line of shafting is put up, the foot position of each hanger
should be clearly marked out on their respective timbers _after_ the
shaft has been brought into alinement. Hangers can thus be easily
put back into their proper place should timber shrinkage or heavy
strains cause them to shift out of line. This idea can be applied to
good advantage on old lines also, but before marking out the hanger
positions the shaft should be tried and brought into perfect alinement.
Hangers that do not allow of any vertical adjustment should not be used
in old buildings that are liable to settle. Shafting so run pretty
nearly always gets out and keeps out of level.
In flanged bolt couplings (Fig. 1) no part of the bolt should project
beyond the flanges. And where a belt runs in close proximity to such
a coupling, split wood collars should be used to cover in the exposed
coupling flanges, bolt heads and nuts. Countershafts have been torn out
of place times innumerable by belts getting caught and winding up on
the main line.
Whenever possible a space of 8 to 10 inches should be left between the
end of a shaft line and the wall. A solid pulley or a new coupling can
thus readily be put on by simply uncoupling and pushing the two shaft
lengths apart without taking either down. Ten inches does not represent
the full scope of pulleys admissible, for so long as the pulley hub
does not exceed a 10-inch length the pulley face (the more readily in
proportion to the larger pulley diameter) can be edged in between the
shafts.
Fig. 2 is an instance of bad judgment in locating the bearings. In one
case this bearing overheated; the remedy is either to re-babbitt the
old box or replace it with a new one.
Both pulleys were solid and the keys--headless ones--had been driven
home to stay. The rims of both pulleys almost touched the wall, and the
circumferential position on the shaft of both these pulleys was such as
to preclude the possibility (owing to an arm of _a_ being in a direct
line with key _B_^1 and arm of _b_ with key _a_^1) of using anything
but a side offset key starting drift.
[Illustration: FIG. 2.]
An effort was made to loosen _b_ (which was farthest from the wall)
by sledge-driving it toward the wall, hoping that the pulley might
move off the key. The key, as was afterward found out, not having been
oiled when originally driven home had rusted in place badly; though
the pulley was moved by sledging, the key, secure in the pulley hub,
remained there.
Ultimately one of us had to get into pulley _b_, and, removing cap _c_,
hold the improvised side offset, long, starting drift _D_ in place
against _B_^1 at _b_^2 while the other swung the hand sledge at _a_.
The entering end of the key, not having been file chamfered off, as it
should have been (see _E_), our starting drift burred it up; so, after
having started it, we had the pleasure of getting into _b_ to file the
key end _b_^2 into shape so as to admit of getting it out.
The solid pulley _b_ has since been replaced with a split pulley.
By the arrangement, as shown in Fig. 3, of the rim-friction
clutch on the driven main shaft _B_ and the driving pulley on the
engine-connected driving main shaft _A_, no matter whether _B_
shaft is in use or not--_i.e._, whether the clutch be in or out of
engagement--so long as _A_ shaft is in motion the belt _C_ is working.
[Illustration: FIG. 3.]
Main line belts come high, and the more they are used the sooner will
they wear out. By changing the clutch from shaft _B_ to _A_ and the
pulley _D_ from _A_ to _B_, belt _C_ will be at rest whenever _B_ is
not in use. Where, however, these shafts are each in a separate room or
on a different floor (the belt running through the wall or floor and
ceiling, as the case may be) the clutch, despite belt wear, should be
placed directly on the driven shaft (as _B_), so as to provide a ready
means for shutting off the power in cases of emergency.
Figs. 4, 5 and 6 represent a dangerous mode, much in vogue, of driving
an overhead floor. An extremely slack belt connects the driving shaft
_A_ and the driven shaft _B_; when it is desired to impart motion to
the driven shaft the belt tightener _C_ is let down and belt contact is
thus secured.
[Illustration: FIG. 4.]
[Illustration: FIG. 5.]
[Illustration: FIG. 6.]
This tightener system is called dangerous advisedly, for few are
the shops employing it but that some employee has good cause to
remember it. Unlike a clutch--where control of the power is positive,
instantaneous and simple--the tightener cannot be handled, as in
emergency cases it has to be.
In any but straight up and down drives with the driven pulley equal to
or larger (diametrically) than the driver, unless the belt have special
leading idlers there is more or less of a constant belt contact with
its resultant liability to start the driven shaft up unexpectedly. When
the tightener is completely off, the belt, owing to heat, weight or
belt fault, may at any time continue to cling and transmit power for a
short space, despite this fact.
These tighteners are usually pretty heavy--in fact, much heavier than
the unfamiliar imagines when on the spur of emergency he grapples them,
and trouble results.
Tightener (in Fig. 5) _A_ is held in place by two threaded rods _B_--as
shown by slot _a_ in _A_^1--and regulated and tightened by ring-nuts
_C_ working along the threaded portion of _B_. _C_ (of Fig. 4) is also
a poor arrangement. Fig. 6 is the best of them all.
Apropos of clutches, great care must be exercised in tightening them
up while the shafting is in motion, for if the least bit overdone the
clutch may start up or, on being locked for trial (according to the
clutches' structure), continue running without possibility of release
until the main source of power be cut off. Nothing can exceed the
danger of a clutch on a sprung shaft.
Heavily loaded shafting runs to much better advantage when center
driven than when end driven, and what often constitutes an overload
for an end drive is but a full load for a center drive. To illustrate,
here is one case of many: The main shaft--end driven--was so overloaded
that it could be alined and leveled one week and be found out one
way or the other, frequently both ways, the next week. Being tired
of the ceaseless tinkering that the condition under which that shaft
was working necessitated, the proprietors were given the ultimatum: A
heavier line of shafting which would be sure to work, or a try of the
center drive which, owing to the extreme severity of this case, might
or might not work.
[Illustration: FIG. 7.]
[Illustration: FIG. 8.]
A center drive, being the cheapest, was decided upon. Pulley _A_,
Fig. 7, which happened to be a solid, set-screw and key-held pulley,
was removed from the end of the shaft. The split, tight-clamping-fit
pulley _B_, Fig. 8, was put in the middle of the shaft length; the gas
engine was shifted to accommodate the new drive, and hanger _C_^1 was
put up as a reinforcement to hanger _C_ and as a preventive of shaft
springing. After these changes the shaft gave no trouble, so that, as
had been hoped, the torsional strain that had formerly all been at
point 1 must evidently have been divided up between points 2 and 3.
When a main shaft is belted to the engine and to a countershaft,
as shown in Fig. 9, the pulley _A_^1 gets all the load of main and
countershafts. In the arrangement shown in Fig. 10 point 1 gets _A's_
load and 2 gets _B's_ load and is the better arrangement.
[Illustration: FIG. 9.]
[Illustration: FIG. 10.]
Where a machine is situated close to one of the columns or timber
uprights of the building it is very customary to carry the belt shifter
device upon the column, as in Fig. 11. The sudden stoppage of a machine
seldom does any damage, whereas an unexpected starting may cause
irreparable damage and often even endanger the limb and life of the
machine operative.
[Illustration: FIG. 11.]
To avoid the possibility of some passing person brushing up against
the shifting lever and thus starting the machine, the tight and loose
pulleys of the countershaft should be so placed that when _A_ is
exposed--that is, away from the column--its accidental shifting shall
stop the machine. Fig 12 makes this point clear.
[Illustration: FIG. 12.]
This arrangement is often used to save a collar (at _A_). The oil
runs out between the loose pulley and the bearing, especially if the
latter be a split bearing; the loose pulley, instead of being totally
free when the belt is on the tight pulley, acts more or less, in
proportion to the end play of the shaft, as a buffer between the tight
pulley and the bearing; finally, the tight pulley is deprived of the
support (which, when under load, it can use to good advantage) a nearer
proximity to the hanger would give it.
The shafts of light-working counters should not be needlessly marred
with spotting or flats for collar set-screws, nor should cup or pointed
set-screws (which mar a shaft) be used. If the collar be sharply tapped
with a hammer, diametrically opposite the set-screw, while it is being
tightened up, all slack is taken out of the collar; and the hold is
such that, without resource to the same expedient when loosening the
collar, a screwdriver will scarcely avail against a slotted set-screw.
When required to sink the head of a bolt into a timber to admit of the
timbers lying snug in or against some spot, if allowable, the bolt's
future turning can be guarded against by cutting the hole square to
fit the bolt head. But where a washer must be used, the only positive
and practical way to prevent the bolt from turning is to drive a nail
(as shown) into _A_ (Fig. 13) far enough for the nail head to flush
_B_; now bend the head down behind the bolt toward _c_. It is evident
that if the bolt tries to turn in the direction of 3 the nail end
(wood held) will prevent it; if toward 4, the nail head will be forced
against the wood and catch hold of the bolt head.
[Illustration: FIG. 13.]
Large belts of engines, dynamos, motors, etc., when in need of
taking-up are usually attended to when the plant is shut down; that
is, nights, Sundays or legal holidays. At such times power is not to
be had; and if the spliced part of the belt, which must be opened,
shortened, scraped, re-cemented and hammered, happens to be resting
against the face of one of the pulleys, is up between some beams or
down in a pit, the chances of the job, if done at all, being any good
are very slim.
The spliced part of a large belt should be clearly marked in some
permanent and easily recognizable way (a rivet, or where the belt is
rivet-held at all its joints some odd arrangement of rivets is as good
a way as any). This marking will minimize the possibility of mistake
and enable the engineer to place the belt splice in the position most
favorable for the belt-maker's taking-up.
In wire-lacing a belt, very often, despite all efforts and care, the
edges of the belt (_A_, _B_) get out of line, as shown in Fig. 14,
and make the best of jobs look poor. By securing the belt in proper
position by two small pieces of wire passed through and fastened at 1,
2, 3 and 4, Fig. 15, the lacing can be more conveniently accomplished
and the edge projection is avoided. When the lacing has progressed far
enough to necessitate the removal of wires _c_ _d_, the lacing already
in place will keep the belt in its original position.
[Illustration: FIG. 14.]
[Illustration: FIG. 15.]
A wire lacing under certain conditions will run a certain length of
time to a day. On expensive machinery whose time really is money it
pays to renew the lacing at regular intervals so as to avoid the loss
of time occasioned by a sudden giving out of the lace.
Never throw a belt on to a rim-friction or other kind of clutch while
the shaft is in full motion. Belts, when being thrown on, have a knack,
peculiarly their own, of jumping off on the other side of the pulley.
And should a belt jump over and off on the wrong side and get caught
in the clutch mechanism, as the saying goes, "there will be something
doing" and the show usually comes high. It pays to slow down.
A mule belt (transmitting in the neighborhood of or considerably over
25 horse-power) that runs amuck through the breaking down of the mule
can make enough trouble in a short time to keep the most able repairing
for a long while.
[Illustration: FIG. 16.]
No matter what the pulley shafts holding arrangement and adjusting
contrivance may be, all of the strain due to belt weight, tension, and
the power transmitted falls mainly at points _A_, _A_^1, Fig. 16; and
it is here that, sooner or later, a pin, set-screw or bolt gives way
and the belt either gets badly torn up, rips something out of place,
or a fold of it sweeping to the floor slams things around generally
until the power is shut off.
The remedy is obvious: Reinforce _A_, _A'_ by securing _B_, _B'_ to
the supporting shaft _c_ at _c_^1, _c_^2. The yoke _x_ is a reliable
and practical means to this end. Straps _a_ held by the nuts _b_ hold
the yoke securely on the supporting shaft _c_, while the pulley-shaft
ends _B_, _B'_ are held in the _U_ of the yoke at _w'_ at any desired
distance from _c_ by means of the adjustment provided by the nuts _b_.
[Illustration: FIG. 17.]
The end of a hanger bearing was badly worn (Fig. 17). The cap could
be lifted out by removing bridge _A_, but the shaft interfered with
the lifting of the bottom out, owing to its being held in the hanger
slides. It had to be removed and we were called upon to put it into
shape by re-babbitting.
Being a newspaper plant, money was no object; the time limit, however,
was three hours, or hands off. Opening the 30-inch engine belt and
removing the interfering shaft length was out of the question in so
short a time. So the job was done as follows: The shaft was braced
against down sag and engine pull along the line _B_ _C_ by a piece of
timber at _A_, and against pull on _B_ _D_ by timber arrangement _X_;
timber _y_'s points _y_^1 and _y_^2 resting against the uprights at 1
and 2, timber _z_ wedged in between _y_ at _y_^3 and the shaft at 4,
thus acting as the stay along line _B_ _D_. The nuts and washers _a_,
_a_ were removed; the bolts driven back out of the bracket; the end
of a rope was thrown over the shaft at _b_, passed through the pulley
and tied to the bracket and hanger which, as one piece, were then
slid endways off the shaft and lowered to the floor. The bearing was
cleaned, re-babbitted and scraped, everything put back, stays removed
and the shaft running on time with a half-hour to the good.
[Illustration: TIMBER ARRANGEMENT X]
When desirable to keep a shaft from turning while chipping and filing
flats, spotting in set screws or moving pulleys on it, it can be done
by inserting a _narrow_ strip of cardboard, soft wood or several
thicknesses of paper between the bearing cap and the top of the shaft
and then tightening the cap down.
The packing, 1-16 to 3-16 inch thick and about as long as the bearing,
must be narrow; otherwise, as may be deduced from Fig. 18 (which shows
the right way), by the use of a wide strip in the cap the shaft is
turned into a wedge, endangering the safety of the cap when forced
down. At point 3 packing does no harm, but at 1 and 2 there is just
enough space to allow the shaft diameter to fit exactly, with no room
to spare, into the cap bore diameter.
[Illustration: FIG. 18.]
As a very little clamping will do a good deal of holding the clamping
need not be overdone. A shaft can also be held from turning, or turned
as may be desired, by holding it with a screw (monkey) wrench at any
flat or keyway, as shown in sectional view, Fig. 19.
When a shaft breaks it is either owing to torsional strain caused by
overload, springing through lack of hanger support at the proper
interval of shaft length, the strain of imperfect alinement or level,
or a flaw.
An immediate temporary repair may be effected by taking some split
pulley that can best be spared from another part of the shaft and
clamping it over the broken part of the shaft, thus converting it, as
it were, into a compression coupling. The longer the pulley hub the
better the hold; spotting the set-screws--that is, chipping out about
1/8-inch holes for their accommodation into the shaft--is also a great
help.
[Illustration: FIG. 19.]
If when the shaft breaks it has not been sprung by the sudden dropping
of itself and the pulleys that were on it, a permanent repair can be
effected, after correcting the cause of the break, by the use of a
regular key-less compression coupling.
If it has been sprung, a new length comes cheapest in the wind-up; and
if overload was the original cause of the trouble, only a heavier shaft
or a considerable lightening of the load will prevent a repetition.
In Fig. 20 _A_ shows how to drive to make belt weight count in securing
extra contact. In _B_ this weight causes a loss of contact. Bearing
in mind that _B_ is not only a loss from the normal contact but
also a loss of the extra contact that _A_ gives, it will readily be
seen how important a power-saving factor the right sort of a drive
is--especially on high-speed small-pulley machines, such as dynamos,
motors, fans, blowers, etc.
[Illustration: FIG. 20.]
A good many electrical concerns mount some of their styles of dynamos
and motors (especially the light duty, small size) upon two _V_-shaped
rails, Fig. 21 (the bottom of the motor or dynamo base being V-grooved
for the purpose). The machine's weight and the screws _A_ are counted
on to keep it in place. If the machine be properly mounted on these
rails, as regards screws _A_ in relation to its drive, the screws
reinforce the machine's weight in holding it down and also permit a
surer adjustment through this steady holding of the machine.
[Illustration: FIG. 21.]
Fig. 22 shows the machine properly mounted. The belt tension and pull
tend to draw _B_ corner of the machine toward the shaft _C_; and screw
_B_^1 is there to resist this pull. Owing to this resistance and
the pull along line _D_, _E_ tends to lift and slew around in _E_^1
direction; screw _E_^2 is, however, in a position to overcome both
these tendencies. If the screws are both in front, there is nothing
but the machine's weight to keep the back of it from tilting up. The
absurdity of placing the screws at _F_ and _G_, though even this is
thoughtlessly done, needs no demonstration.
[Illustration: FIG. 22.]
When putting a new belt on a motor or dynamo, both the driver and the
driven are often needlessly strained by the use of belt-clamps, in the
attempt to take as much stretch out of the belt as possible. On being
loosely endlessed it soon requires taking up; and if only laced, when
the time for endlessing comes the belt is botched by the splicing in
of the piece which, owing to the insufficiency of the original belt
length, must now be added to supply enough belt to go around, plus the
splice.
The proper mode of procedure is: Place the motor on its rails or slides
5 inches away from its nearest possible approach to the driven shaft
or machine and wire-lace it (wire-lacing is a very close second to an
endless belt). Let it run for a few days, moving the motor back from
the driven shaft as the belt stretches. When all reasonable stretch is
out, move the motor back as close to the driven shaft as possible.
The 5 inches forward motion will give 10 inches of belting, which will
be amply sufficient for a good splice; and, further, the machine will
be in position to allow of tightening the belt up, by simply forcing
the motor back, for probably the belt's lifetime.
II
SHAFTING HINTS[2]
THE bolts, set-screws, pulleys, bearings, shafting and clutches of
a plant, although among the foremost factors in its efficiency, are
very often neglected until they reach the stage where their condition
absolutely compels attention.
[2] Contributed to Power by Chas. Herrman.
Very often this lack of proper attention is due to surrounding
difficulties of an almost insurmountable and most discouraging nature.
At other times it is due to a lack of proper appreciation of the damage
resultant from seemingly insignificant neglects. How to overcome some
of these difficulties is the object of this chapter.
Fig. 23 shows a case of a turning bolt. The head is inaccessible and
the bolt's turning with the nut, owing to burrs or rust, prevents
either the tightening or the loosening of the nut. One to three
fair-sized nails driven through the timber as at _C_, hard up against,
or, better still, forced into a tangent with the bolt, will often
suffice to hold it while the nut is being turned. In iron girders,
beams, etc., the nail method being impossible, a slot _E_ can easily be
cut with a hack-saw through the lower end of both the nut and bolt, so
that the bolt may be held by a screwdriver while the nut is turned with
a wrench.
Where an extra strong screwdriver must be used, the use of two blades
at the same time in the hack-saw frame will give a slot of the
requisite width. Where the bolt's end projects beyond the nut and it
is desired to tighten the nut, a Stillson wrench is often, though
inadvisedly, called into service. This tends to spoil the lower threads
of the bolt and thus prevents any future loosening, except by the
cutting off of the projecting end.
[Illustration: FIG. 23.]
As the alinement and level of shafting depend on the power of their
hold, bolts, lag-bolts and set-screws should, when they are tightened,
be so in fact and not in fancy.
The proper way to use a wrench, especially a screw wrench, so as to
avail yourself of every ounce of power, not of your biceps only but
of your whole body, is as follows: Place your shoulders on a level
with the object to be tightened, secure the wrench jaws well upon it,
grasp the jaws with the left hand and the wrench handle with the right,
holding both arms straight and tense; swing the upper part of the body
to the right from the hip, backing the force of your swing up with
the full force of your legs, steadying yourself the while with your
left-hand grip on the wrench jaws, which are the center of your swing.
Several such half turns, at the wind-up, will cause an extremely hard
jam with comparative ease.
In tightening up a split-pulley, the expedient of hammering the bolts
tight, by means of an open-ended bolt-wrench and a small sledge, is
often resorted to. If the head of the bolt be lightly tapped while the
nut is being tightened, even a light hammering, except in the extremest
cases, becomes unnecessary.
Split-pulleys are invariably better held in place by a good clamping
fit than by set-screws. It must also be borne in mind that, for good
holding, set-screws must be spotted into the shaft, and this defaces
and often materially weakens the shaft. Split-pulleys, like solid
ones, are sometimes subject to stoppage, owing to excessive strain.
Set-screws, at such times, cut a shaft up pretty badly; whereas, if
clamped, only a few slight scratches would result.
Where packing with paper, cardboard, emery cloth or tin becomes
necessary to secure a good clamping fit, care should be taken to put an
equal thickness of packing into both halves of the pulley; otherwise it
will wabble and jump when running.
Emery cloth, on account of its grittiness, is preferable for packing
where the duty done by the pulley is light. When the duty done is
extra heavy, emery cloth, despite its grittiness, will not do; tin or
sheet iron, owing to body, must be used.
The following is the most practical way of packing a split-pulley to a
good clamping fit, assuming that emery cloth is to be used:
The thickness of the emery cloth to be used, and whether to use one
or more folds, can readily be ascertained by calipering the shaft
diameter and pulley bore, or by trial-clamping the pulley by hand. In
both of these instances, however, due allowance must be made for the
compressiveness of the packing used. If the packing be too thin, the
pulley will not clamp strongly enough; if too thick, the chances of
breaking the lugs when drawing the bolts up are to be apprehended.
Having determined the proper thickness of emery cloth to be used, place
the pulley on the shaft, as shown in Fig. 24. Into the lower half _C_,
in space _A_, which is out of contact with the shaft, place a sheet of
emery with the emery side toward the hub and the smooth side toward the
shaft. The width of the emery should be a little less than half of the
shaft's circumference, and it should be long enough to project about
one-half of an inch to an inch on each side of the hub.
Now turn the pulley on the shaft so that the position of the halves
shall become reversed (Fig. 25), _C_ on top, _B_ on bottom. See that
the emery cloth remains in its proper position in half-hub, the smooth
side being toward the shaft; the projecting length beyond the pulley
hub will help you to do this.
Into half-hub _B_ (space _D_) insert a similar sized piece of emery
cloth, smooth side toward the hub and the emery side toward the shaft.
Draw up on your bolts to clamp the pulley into position. Be sure,
however, that no emery cloth gets in between the half-hubs or lugs at
points 1 and 2, Fig. 25, as this would prevent their coming properly
together; the width of the emery being less than half of the shaft's
circumference will be a help to this end.
[Illustration: FIG. 24.]
It often happens, owing to downright neglect or unwitting neglect,
through the oil hole or oiler being blocked up, that a loose pulley,
running unlubricated, cuts, heats, and finally, through heat expansion,
seizes. It then becomes necessary to take the countershaft down, force
the loose pulley off and file and polish the shaft up before it can be
put back into place.
[Illustration: FIG. 25.]
The following method avoids the taking down and putting back, provides
an easy means for loosening up the pulley that has seized, and
improvises, as it were, a lathe for filing and polishing the shaft.
[Illustration: FIG. 26.]
In Fig. 26, _A_ is the loose pulley that has seized. Throw off both
the belt that leads from the main shaft to pulleys _A_, _B_ and the
belt that leads to the driven machine from the driving pulley _C_.
Tie, or get somebody to hold, an iron bar in pulley _A_ at side _a_,
as shown in Fig. 27, over an arm of the pulley, under the shaft, and
resting against the timber, ceiling, wall or floor, in such a way as
to prevent the pulley from turning in one direction, as shown in Fig.
27. Now, with another bar, of a sufficient length to give you a good
leverage, take the grip under a pulley arm and over the shaft in the
tight pulley _B_ at _b_, which will enable you to work against the
resistance of the bar in the loose pulley _A_.
[Illustration: FIG. 27.]
With enough leverage, this kind of persuasion will loosen the worst
of cases. Take the bars out and move _B_ sufficiently to the right
to allow _A_ to take _B_'s former position. Secure _B_ by means of
its set-screws in its new position and, by means of a piece of cord,
fasten an arm of _A_ to one of _B_'s. It is evident that by throwing
the main-shaft belt on to _A_ it will, through _A_'s cord connection
with _B_, which is screwed to the shaft, cause the shaft to revolve,
thus enabling you to file up and polish that portion of it formerly
occupied by _A_. To prevent the countershaft from side-slipping out
of hanger-bearing _D_^1, get somebody to hold something against
hanger-bearing _D_^2 at _E_; or fasten a piece of wire or cord on
the countershaft at _F_ and the hanger _D_^1, so as to prevent
side-slipping while not interfering with revolution.
Filing, polishing, a cleaning out of the oil hole or oiler, and the
taking of proper precaution against future failure of lubrication will
put everything into first-class order. When the loose pulley is, as it
is best for it to be, farthest away from the bearing, held in its place
by the tight pulley and a collar, not only is the tight pulley better
adapted for carrying its load, owing to additional support resultant
from its proximity to the bearing, but such matters of small repair as
come up are much simplified.
[Illustration: FIG. 28.]
Fig. 28 in some degree, aside from the cutting up and heating of the
bearings, illustrates the breaking strain, in addition to the usual
torsional strain, which becomes enhanced in direct proportion with the
increase of breaking strain, to which an out-of-line or out-of-level
shaft is subject. The bends are exaggerated for illustration.
In this instance, the fact of one hanger-bearing being out of line
or level subjects the shaft to a severe breaking strain. The shaft
being both out of line and level does not, if both at the same point,
aggravate matters, as might at first be supposed.
It is true that the full torsional strength of a shaft is only equal
to the weakest portion of it, so that three weak spots more or less
can, theoretically, make no difference one way or the other. But,
practically, there is the undue strain and wear of the bearings at
these points, and if a pulley transmitting any considerable amount of
power is situated anywhere along the length _A B_ it is sure to be
unpleasantly in evidence at all times.
Only an eighth or a quarter out, but oh, what shaft-breaking stories
that fraction could tell!
The following is a simple method for testing the alinement and level of
a line of shafting that is already up.
[Illustration: FIG. 29.]
As in Fig. 29, stretch a line _C_ so that it is exactly opposite the
shafting. Set it equidistant from the shaft end centers _G_ and _F_ and
free from all contact along its entire length except at its retaining
ends _A_ and _B_. Now, it is self-evident, as line _C_ is straight and
set equidistant from the shaft end centers _G_ and _F_, that if you set
the entire center line of the shafting at the same distance from line
_C_, as _G_ and _F_, you are bound to get your shafting into perfect
alinement.
In leveling a line of shafting that is already up, you can, by the use
of a level and perseverance, get it right.
Placing the level at _A_, you are just as likely to raise the first
hanger as to lower the middle one. Look before you jump, even if
compelled to climb to the top of the fence to do so. When you find a
length of shafting out of level, try the two adjacent lengths before
acting, and your action will be the more intelligent for it.
On exceptionally long lines of shafting the following method, in
which the level and a line constitute a check upon and a guide for
each other, can be used to great advantage. Stretch a line so that it
is exactly above, or, if more convenient, below the shafting to be
leveled. With the level find a length of shafting that is level and
adjust your line exactly parallel with this length. Your line now,
free of contact except at its retaining ends, and level owing to its
parallelism to the level shaft length, constitutes a safe _hight level_
guide while the level itself can serve to verify the accuracy of the
finished job.
In lining, whether for level or alinement, unless the shafting line
consists of the same diameter of shafting throughout its entire length,
though of necessity measuring from the shaft circumference to the line,
always base your calculations on the shaft centers. The figures in
Fig. 29 will make this point clear.
The manner of securing the ends of the line under different
circumstances must be left to individual ingenuity. Only be sure that
the line is so placed that the shafting adjustment shall not affect its
original position with reference to the end shaft centers.
Coupling clutches, _i.e._, those joining two lengths of shafting into
one at option, will fail, utterly or partially, if the respective
shafts which bear them are out of line or level with each other. Such a
condition should not be tolerated on account of the danger entailed by
the inability to shut off the power in cases of emergency.
As a general rule, it is most advisable to set a clutch to take as hard
a grip as it can without interfering with its releasing power. Where
a clutch grips weakly, it is subject to undue wear owing to slippage,
whereas a strongly regulated clutch absolutely prevents slippage wear.
III
SHAFTING HINTS[3]
ENGINEERS, machinists and general mechanics are often called upon
to turn their hands to a shafting job. We recognize that all of the
following cannot prove new or even suggestive to most of our readers;
still, some of it for all, and, mayhap, all for some, may not come
amiss.
[3] Contributed to Power by Chas. Herrman.
We all know that to have belting run rightly on pulleys located upon
parallel lines of shafting the shafting must be in absolutely correct
parallel. The slightest deviation, even to a 1-16 inch, often imparts a
marring effect, through poorly running belts, to an otherwise faultless
job.
[Illustration: FIG. 30.]
Fig. 30 shows how to line a countershaft as regards parallelism with
the driving shaft when the countershaft's end-centers are availably
situated for thus measuring. _A_ is the countershaft, _B_ the main
shaft, _C_ is a stick of proper length about 1-1/2 inches in thickness
and width, _D_ a heavy nail--about 20-penny will do--driven into _C_
far enough from its end _E_ to allow of _C_'s resting squarely upon the
top of the shaft _B_.
Rest the measuring rod upon the main shaft, keeping the nail in touch
with the shaft, so that when the _F_ end is in contact with the end of
the countershaft the stick shall be at right angles to the main shaft,
and then mark the exact location _a_ of the countershaft's end-center
on the stick. Do the same at the other end of the countershaft. If
both marks come at the same spot, your counter is parallel; if not,
space between these two marks will show you how much and which way the
counter is out.
It may only be necessary to shift one end in or out a little; and then,
again, it may be that to get into line you will have to throw one end
all the way in one direction and the other all or some in the opposite
direction. But, whichever it be, do not rest content until you have
verified the correctness of your adjustment by a re-measurement.
The nail should be well driven into _C_, so that its position will not
readily change, and it should, preferably, be slant driven (as shown in
Fig. 30), as it thus helps to keep the stick down in contact with the
shaft.
Where an end-center is not available or where there is no clear space
on the main shaft, opposite a center, the method shown in Fig. 31 can
generally be used.
Rest _C_ on top of both shafts and at right angles to the driving shaft
_B_. With _D_ pressed against _B_, place a square on stick _C_, as
shown (stock in full contact with the top of the rod, and the tongue
running down the side of it). Slide along _C_ toward _A_ until the
side of the tongue touches the shaft the other side of _A_. Now mark
a line on the stick down tongue. Do the same at the other end of
your countershaft and the two resultant marks will be your parallel
adjustment guides.
[Illustration: FIG. 31.]
It often happens that a counter, or even line shaft, is end driven from
the extreme end of the main or jack driving shaft with its other end
running beyond the reach of the driving shaft, as shown in Fig. 32.
[Illustration: FIG. 32.]
It is evident that neither method 1 nor 2 can here be applied to solve
the alinement problem. If the driving pulley _B_ and the driven pulley
_A_ are both in place, the following method can be used to advantage.
Fasten, or let somebody hold, one end of a line against pulley _B_'s
rim at _B_^1; carry the line over to _A_ at _A_^2; now sweep the loose
_A_^2 end of the line toward pulley _A_ until the line just touches
pulley _B_'s rim at _B_^2. When the line so touches--and it must just
barely touch or the measurement is worthless--_A_^1 and _A_^2 of pulley
_A_ must be just touched by or (if _B_ and _A_ are not of a like face
width, as in Fig. 32) equidistant from the line.
A single, two-hanger-supported length of shafting thus lined is bound
to be in parallel; but where the so adjusted shaft line consists of two
or more coupling-joined lengths supported by more than two hangers,
only pulley _A_'s supporting portion of the shaft between its immediate
supporting hangers 1 and 2 is sure to be lined; the rest may be more or
less out.
To make a perfect job, fix a string in parallel with shaft length 1 and
2, stretching along the entire length of the adjusted shaft, and aline
the rest of the shaft length to it.
When there are no pulleys in place to go by, or when, as occasionally
happens, the wabbly motion of pulley _B_ (when running) indicates that,
having been inaccurately bored or bushed, or being located on a sprung
shaft length, its rim line is not at right angles to the shaft line,
the method shown in Fig. 33 can be resorted to.
Instead of the nail used in methods 1 and 2, use a board about 8 to
12 inches long and of a width equal to considerably more than half of
shaft _B_'s diameter. By nailing this board _x_ to the measuring rod
_c_ at any suitable angle, you will be enabled to reach from the end
_a_ well into the shaft _B_, as at _b_, and from _b′_ well into _A_, as
_a′_. By keeping the board _x_ along its entire length in full contact
with the shaft _B_ at both 1 and 2, the angular position of rod _C_ is
bound to be the same in both instances, and you will thus (by the use
of a square, as in Fig. 31) be enabled to aline _A_ parallel with _B_.
[Illustration: FIG. 33.]
In all instances of parallel adjustment here cited it is assumed that
both the alined and the alined-to shafts have been, as to secure
accuracy of result they must be, properly leveled before starting to
aline.
The above methods apply to cases where the shafting is already in
place. Where, however, shafting is being newly installed before the
work can be proceeded with, it is necessary, after determining on the
location for the shafting, to get a line on the ceiling in parallel
with the driving shaft to which to work to. Mark that point _A_ which
you intend to be the center line for the proposed shafting upon the
ceiling (Fig. 34).
Rest your measuring rod upon the driving shaft and at right angles to
it, with the nail against it. Hold your square with the stock below and
the tongue against the side of the measuring stick, so that its tongue
extremity touches the ceiling mark _A_, and then mark a line on the rod
along the tongue side _A_. Move your rod along the driving shaft to the
point where the other end of the proposed shafting line is to be, and,
squaring your stick to the driving shaft with the tongue side _A_ on
the marked line of the stick, mark your section point on the ceiling.
Draw a line or stretch a string between these points, and you have a
true parallel to work to.
[Illustration: FIG. 34.]
Owing to the supporting timber _B_'s interference, a square had to
be used; but where the ceiling is clear the rod can be cut to proper
length or the nail be so located as to allow of using the stick
extremity _C_ for a marking point.
When a pulley is handily situated on the driving shaft, the method
shown in Fig. 35 can be used to advantage.
Let somebody hold one end of a line at 1, and when you have got its
other end so located on the ceiling that the line just touches the
pulley rim at 2, mark that ceiling point (we will call it 3). In the
same way get your marks 4 and 5, each farther back than the other and,
for the better assurance of accuracy, as to just touching at 2, remove
and readjust the line separately each time. If now a straight line from
3 to 5 cuts 4, your line 3, 4, 5 is at right angles to the driving
shaft and a line at right angles to this will be parallel to the shaft.
[Illustration: FIG. 35.]
The plumb-bob method is so familiar and, where not familiar, so easily
thought out in its various applications, that we deem it useless to
touch upon it.
The stringers or supporting timbers of drop hangers should be equal in
thickness to about one-fifth of the hanger drop.
Where the stringers run with the hangers and crosswise of the shaft,
both feet of a hanger base are bolted to the same stringer, and this
should be from 1-1/4 to 1-1/2 times the width of the widest portion of
the hanger base. As the hanger is securely bolted to its stringer, this
extra width is in effect an enlargement of the hanger base, and thus
enables it the better to assist the shaft's end motion.
Where the stringers run with the shaft and crosswise of the hangers,
the two feet of the hanger base are each fastened to a separate timber,
and these should be equal in width to the length of one hanger foot,
plus twice the amount of adjustment (if there be any) the hanger's
supporting bolt slots will allow it. In reckoning hanger adjustment, be
sure to figure in the bolt's diameter and to bear in mind that to get
the utmost adjustment for the countershaft the bolts should originally
be centered in the slot; thus a 13/16 × 1-1/2-inch slot, as it calls
for a 3/4-inch bolt, leaves a 3/4-inch play, and this play, with the
bolt in the center of the slot, allows of 3/8-inch adjustment either
way. Without this extra width addition any lateral adjustment of the
hanger would result in leaving a part of the hanger's feet without
stringer support. Such jobs look poorly, and often run still more
poorly. Fig. 36, in its two views, will make the above points clear.
[Illustration: FIG. 36.]
In the stringing of countershafts whose hangers have no adjustment it
often happens, despite all care in the laying out, that they come 1/8
to 1/4 inch out of parallel. A very common and likewise very dangerous
practice at such times is to substitute a smaller diameter supporting
bolt instead of the larger size for which the hanger foot is cored or
drilled, and to make use of the play so gained for adjustment.
That shafting so carried does not come down oftener than it does is due
solely to the foresight of the hanger manufacturers. They, in figuring
the supporting bolt's diameter as against the strain and load to be
sustained, are careful to provide an ample safety margin for overload,
thus enabling the bolt substituted to just barely come within the
safety limit under easy working conditions.
The largest-sized bolt that a hanger will easily admit should
invariably be used, and for alinement purposes either of the following
slower but safer methods should be used.
Rebore the hanger-supporting bolt holes in the stringers to a larger
size, and use the play so gained for adjustment. It is not advisable,
however, to rebore these holes any larger than to one and three-quarter
times the diameter of the bolt to be used; and the diameter of the
washers to be used on top of the stringers should be diametrically
equal to at least twice the size of the rebored holes. That the washers
used, under such conditions, must be of a good proportionate thickness
goes without saying.
When the reboring method cannot be used--as when the hangers are
carried by lag screws, lag-bolts, bolts screwed directly into
supporting iron girders, etc.--it is evident that hanger adjustment
can be secured by packing down one foot of the hanger base, as shown in
Fig. 37.
[Illustration: FIG. 37.]
The piece of packing (necessarily wedge-shaped) between the hanger
foot _B_ and the stringer _A_ tilts the bottom of the hanger forward.
The size of the wedge regulates the amount of adjustment. Wedge-shaped
space _D_, at foot _C_, should also be packed out so as to avoid
throwing undue strain upon _C_'s extremity _c_. If now, the foot _c_
of the countershaft's other supporting hanger (No. 2) be similarly and
equally packed, as _B_ of No. 1 hanger, the shaft will have been thrown
forward at one end and back at the other, and thus into line. The equal
division of the adjusting wedge packing between the opposite feet of
the two hangers enables a limited packing to do considerable adjusting
without any undue marring effect; and, further, insures the shaft's
remaining level, which evidently would not be the case if only one
hanger were packed down.
After so adjusting, be sure to get your hangers squarely crosswise of
the shaft as readjusted, so that the hanger bearings will lie in a true
line with the shaft and not bind it. At all times be sure to have your
hangers hang or stand plumb up and down; as, if the bearings are not
so pivoted as to be horizontally self-adjusting, excessive friction
will be the lot of one end of the bearing with not even contact for the
rest of it. The bearing being self-adjusting all ways, square crossing
of the shaft line by the hanger line and plumb still remain eminently
desirable for appearance's sake.
Before a countershaft can be put up on a ceiling whose supporting
timbers are boarded over, or in a modern fireproof structure whose
girders and beams are so bricked and plastered in as not to show, it
is necessary to positively locate those of them which are to carry the
stringers.
It is in the earnest endeavor to properly locate these that the
unaccustomed hand turns a wood ceiling into a sieve and a brick one
into a wreck. To avoid kitchen and house razing effects, try the
following recipe:
We will assume that line _A B_, Fig. 38, laid out by one of the methods
previously described, is the center line of the proposed countershaft.
The hanger's base length, lateral adjustment and individual foot length
call for stringers 4-3/4 inches wide, placed 5-1/4 inches apart or
14-3/4 inches outside (as per sketch). The floor position of the machine
to be driven, or the driving point of the main shaft, is so located with
reference to the countershaft that one of the supporting hangers must
go at or very near _C_, and the countershaft's length brings the other
hanger at or very near _D_.
Now between points _C D_ and with due reference to the center line _A
B_, lay out the position which your stringers are to occupy. It is
self-evident that by confining your beam prospecting to the stringer
spaces _E_ and _F_, ultimately, when the countershaft is in place, all
the cut-up portions of the ceiling will be hidden from view.
[Illustration: FIG. 38.]
Generally the necessary supporting beams will not all be found within
the shaft's length distance _C D_; in such cases continue your cutting
in the same parallel line to _A B_, as at _E_ or _F_, going from _C D_
outwardly until you strike the sought-for beams. Having located beams,
say 1 and 2, we find by measurement that they are 5 feet apart, and, as
beams are generally uniformly spaced, we may start 4 feet 6 inches (go
4 feet 6 inches and not 5 feet, to make sure not to skip beam 3 and
thus make a cut that will not be covered by the stringers) from 1 to
cut outwardly for the location of beam 3.
Where the building's beams run parallel to the shaft, Fig. 39, mark the
counter's-center line _A B_, and then mark the spaces--as determined by
the countershaft length, floor position of the driven machine or the
driving point on the main shaft--to be occupied by the stringers _C D_,
and, starting from the center line _A B_, cut outwardly each way to the
desired beams 1 and 2.
[Illustration: FIG. 39.]
Where the center line as laid out (before the position of the ceiling
beams was known) brings it close to or directly under a supporting
beam, it is generally advisable where possible to step the counter back
or forward to a central position between the beams.
Where shafting is already in place in a building, no matter on what
floor, valuable measurements as to beam location can thus be had
from the plainly in sight and the reasonably deducible. Lacking
in-place-shafting to go by, the walls, columns and main girders always
clearly indicate the crosswise or parallel run of the ceiling beams to
the proposed shafting line.
In the usual method of locating the timbers of a boarded-over ceiling,
a brace and bit, or a nail, can be used for the purpose. If shy of an
awl, and in preference the other two ways, force or drive a chisel
(cold chisel or wood) in between a tongue and groove of the ceiling
boards in stringer space (Fig. 38) _E_ or _F_, and thus spring the
boards sufficiently apart to insert a compass saw. With the extremity
of a 12-inch saw a very little cutting (along the tongue and groove,
as this shows least) will enable you to locate a beam, since they
generally run 8, 12, 16, 20, 24 and 30 inches apart.
Always, on locating your beam, run the point of your compass saw down
the whole of the timber's width, so that any nailed-on pieces will not
lead you into a false estimate of the beam's thickness.
[Illustration: FIG. 40.]
[Illustration: FIG. 41.]
Figs. 40 and 41 make this point and its object clear. The saw, in Fig.
40, being stopped by _A_, naturally leads to the inference that _A
B_ is the timber's thickness. By running down the timber, as in Fig.
41, the saw's point sticking at _a_ acts as a sure detector. This
precaution should be taken on both sides (_B_ and _A_) of the timber,
and then, when the lags are screwed in, they can be sent home safe and
true in the center of the timber.
It often happens that in boring for the lag screws the bit strikes a
nail and further progress at that point seems out of the question. When
so situated, take your bit out, and running the lag screw up as far as
it will go, by sheer force swing it three or four turns up further than
the point where your bit struck. Removing the lag and replacing the
bit, it will be found that the nail has been forced aside and the way
is now clear.
[Illustration: FIG. 42.]
Hook bolts (Fig. 42) or--as our across-the-sea cousins call
them--"elbow bolts," despite all assertions to the contrary, are an
easy, safe and economical stringer fastener or suspending device.
Figs. 43 and 44 illustrate two very common abuses of the hook bolt. In
the one (Fig. 43), instead of the bolt proper lying snug up against the
beam flange with the whole of its hook resting squarely upon the beam's
flange, its supporting countershaft is turned into a menace to limb and
life by this "chance it" kind of erection. In the other (Fig. 44),
though the bolts do lie snug against the flange, the hook being out of
sight and no means being provided for telling whether the hook lies,
as it should, at right angles to the web of the beam, even if properly
placed at installation, timber shrinkage, vibration or a slight turn
of the bolt when tightening the nut, all constitute dangerous factors
tending to loosen or entirely loosen the hook's grip upon the beam
flange.
[Illustration: FIG. 43.]
[Illustration: FIG. 44.]
Fig. 43 suggests its own remedy. As to Fig. 44, a screwdriver slot
(made by a hacksaw) at the nut end of the hook bolt and running in
the same direction as the hook, Fig. 45, will at all times serve to
indicate the hook's position and, allowing as it does of a combined use
of screwdriver and wrench, it can be used to prevent the bolt's turning
when being tightened.
[Illustration: FIG. 45.]
[Illustration: FIG. 46.]
Where two or more hook bolts are placed close together on the same beam
flange, a plate, preferably wrought iron with properly spaced confining
pins for the hooks, may be placed between the beam flange and the hooks
as in Fig. 46. Its benefits are obvious and so likewise is the use of a
small, square, wrought-iron plate with a bolt hole through its center
instead of hook bolts.
The various styles of beam clamps carried by the hardware and supply
trade all have their good points, and though the _C_ of their cost may
seem to loom large, it is not a whit more emphatic, taken all in all,
than the _W_ of their worth.
IV
TRUING UP LINE SHAFTING
IT is assumed, for the purposes of this description, that the modern
style of shafting, increasing in diameter by the 1/2 inch, is used, and
that all pulleys and belts are in place. We will take a line composed
of sizes ranging between 3-15/16 and 2-7/16 inches. This gives us four
sizes, 3-15/16, 3-7/16, 2-15/16 and 2-7/16 inches in the line.
We will first consider the plumb-bob. The accompanying sketch, Fig. 47,
illustrates a good one.
The ball is 1-1/2 inches diameter, and the large end of the tapered stem
1/2 inch in diameter, turned parallel for a short distance at the lower
end. The two thin sheet-steel disks, 1 and 2 inches in diameter, are
drilled to fit snugly when pushed on to the 1/2-inch part of the stem,
and stay there until pulled off. These disks are turned true. This
arrangement of plumb-bob and disks enables us to deal with five sizes
on one line, and there are not many lines that contain more.
Now having our plumb-bob ready, we will stretch the line. The
stretchers should be set horizontally by nailing a strip of wood, say 1
× 1-1/2 × 12 inches, with a piece at each end to form a space between it
and the wall, or place of location in line with the edge of the shaft,
as in Fig. 48. The top of this stretcher should be low enough to clear
the largest pulley, and high enough to clear the hat of your tallest
man. You would perhaps find it convenient to go between the spokes of a
large pulley.
[Illustration: FIG. 47.]
Now having located your stretcher, find approximately the position of
your line, and drive a nail a foot or more below it in a vertical line,
and another nail anywhere for convenient winding. The advantage of this
plan is that the line can be easily adjusted as it merely passes over
the stretcher, and is free to respond to movement either way; then when
the final adjustment is made, and is ready for its final stretch, it is
only necessary to pinch the line to the nail with one hand, while the
other is at liberty to unwind, stretch and rewind the line without fear
of its shifting.
[Illustration: FIG. 48.]
The line being adjusted over the stretchers, we will now proceed to
set it. Begin at the 2-7/16-inch end, by throwing your plumb line over
the shaft and setting your line at that end, right with the _center
point_ of your bob. Having done so, go to the other or 3-15/16 end of
your line, and set the line so that the edge of the _ball_ of your
bob just touches it. Now go back to the 2-7/16 end and see that the
necessary adjustment did not alter it. Having proved this, give your
line the final stretch and try if it is right at both ends. You now
have a center line (though the edge instead of the center of the shaft
is used) that may remain up for days if necessary without fear of
disturbance.
It is best to go over the whole line first, before disturbing anything;
so starting at the first hanger at the 2-7/16-inch end, throw your
plumb line over the shaft, and record on the floor in chalk beneath
it whether it is O. K. or wants to go either way, and how much; then
go to the next hanger, and so on to the end. A short study of the
conditions enables one to correct the faults, with a knowledge of the
requirements, and consequently in the least time and with the least
trouble.
Now suppose we start at the 2-7/16-inch end to inspect the line, we
use the center point of the bob on the line so long as we are testing
2-7/16 inches.
When we get to the 2-15/16-inch part, which is 1/2 inch larger, we use
the half diameter of the stem, the edge of which should just touch the
line.
When we come to the 3-7/16-inch part, 1 inch larger than 2-7/16, we use
the 1-inch disk, slip it on to the stem, and when it just touches the
line with its edge it is O. K.
The 3-15/16-inch, being 1-1/2 inches larger than the 2-7/16-inch, will
be right when the ball of the bob is in light contact with the line.
The 2-inch disk would be suitable for the next size, and other disks or
modifications of the bob proper might be made to suit circumstances.
Now having straightened the line, the next process is to level it.
As in some cases your pulleys will be too close to place your level
where you want, make a light iron frame as per Fig. 49, making the
suspending members of sufficient length to admit of your reading the
level conveniently when standing on the floor. Hang your frame on
the shaft, and put your level on the straight-edge below; in this
way travel along the shaft, placing your frame where convenient. Be
sure that one end of your frame does not rest on a shaft of different
diameter, a key, keyseat, or anything to distort the reading.
[Illustration: FIG. 49.]
Never be content with trying your level, especially an adjusting level,
one way; always reverse it and try again; for if it is out of truth at
the start, you might want to go through the roof or down cellar at the
finish. Get into a habit of reversing your level, and so prove your
work as you proceed.
V
APPARATUS FOR LEVELING AND LINING SHAFTING
THE first apparatus explained in this chapter was designed by the late
Chas. A. Bauer, and is a highly perfected instrument.
For those who have lined and leveled shafting with an engineer's
transit and level it is unnecessary to say anything of the advantages
of that method over the cruder methods usually employed. It is not only
done much more rapidly and economically, but the greater accuracy with
which the work is done goes on paying dividends in decreased friction
and loss of power and in lessening of wear.
[Illustration: FIG. 50.]
The apparatus we now illustrate (Fig. 50) has at the top a hook, which
is passed over the shaft, as indicated; on the straight portion of
this hook are two sliding jaws which are so set that the shaft will
just pass between them. Set into the face of this hook is a commercial
6-inch steel rule which facilitates the setting of the jaws, and
they are of course so set that the tubular portion of the hook or
leveling rod is centered vertically under the shaft. Within the outer
tube, which is about 1 inch outside diameter and nicely japanned, is
another tube, and inside this a third tube, these being arranged _à
la_ telescope slide, and clamps being provided so that the length or
distance from the shafting to the target may be anything desired from
4 to about 10 feet. At the lower end of the third or inner tube is a
swiveling head to which the target is attached, and nurled nuts at this
point give means of adjusting the sighting point of the target to the
exact hight of the transit or level sighting line.
The target is a brass plate 5-1/2 inches diameter, on the face of which
is a recess milled for the reception of a second commercial steel rule,
which in this case is vertical and can be moved vertically and clamped
in any desired position with reference to a line drawn upon the target.
At the center of this scale is a very small hole through which the
light of a hand flash lamp may shine to form the sighting point. The
slot through the target at the right of the scale is provided with a
single thickness of white cloth, which permits enough light to pass
through it to help in finding the target in the field of the telescope.
The object of providing a vertical adjustment for the rule on the
target is so that when passing from one diameter of shafting to another
in the same line, as sometimes happens, the scale can be moved up or
down just half the difference of diameter and the sighting point thus
be kept at a constant hight.
[Illustration: FIG. 51.]
The target is readily detached from the rod, and may then be placed
upon the small standard (Fig. 51) which has at its base a V adapted
to go over the shaft. The standard is tubular and the wire (about 1/8
inch diameter) may be adjusted and clamped at the desired hight. The
target fits over the wire as shown (rear view of target) for leveling
lines of shafting that may be near the floor, or, with the target
removed, the V and wire form a sort of length gage or caliper with
which the shaft may be made parallel to a line or wire stretched at the
side of it. Two different lengths of wire are provided for this purpose.
The plumb-bob shown is part of the equipment and is a very superior
article. A new feature it possesses is in having its larger portion
hexagonal instead of round, so when laid down upon a plank or
scaffolding it will lie there instead of promptly rolling off and
falling to the floor. The entire apparatus is, we think, very well
designed for its purpose.
TOOL FOR LEVELING SHAFTING
The instrument shown in Fig. 52 is a good one for use in leveling up
shafting. It can be made to fit several sizes of shaft, or all the
sizes ordinarily found in a factory.
When the instrument is placed on any piece of shaft and leveled up with
the attached level, the plumb line will hang exactly the same distance
from the shaft center every time. In this case the distance of line
from center is 6 inches.
A handy apparatus for use in leveling up long lines of shaft can be
made as follows.
[Illustration: FIG. 52.]
[Illustration: FIG. 53.]
[Illustration: FIG. 54.]
Take two pieces of finished material, fasten together as in Fig. 53 and
cut out as shown at _A_ and _B_ in Fig. 54. The opening _A_ is made so
that the piece can be hung over the shaft, and the opening _B_ is made
for the reception of a wooden straight-edge.
Make the straight-edge out of 1-1/4-inch stuff. Be sure that the edges
are parallel, the width just enough less than the width of opening _B_,
Fig. 55, to enter it, and the length 6 or 8 feet, to suit convenience.
Use the apparatus with a level, as in Fig. 55, taking care that the
suspension pieces are always on the same size shaft.
[Illustration: FIG. 55.]
VI
SOME PRACTICAL KINKS[4]
[Illustration: FIG. 56.]
A PULLEY on one of the motors at a certain plant had been giving some
trouble by becoming loose and working its way along the shaft toward
the motor bearing. Each time the pulley became loose, the set-screw
was loosened, the pulley put back in position, the set-screw made
tight and the motor started. After a few trials it was found that this
would not prevent the pulley from working its way along the shaft. In
order to overcome this difficulty the pulley was placed in its proper
position, a line was drawn around the shaft close to the hub and, after
the line was scribed, the pulley was removed and the shaft was burred
upon the line as shown at _B_, Fig. 56. The pulley was then put back
and driven close up to the burred line, the set-screw made tight and
the pulley is now running without any apparent tendency to travel from
its proper position. It will be seen that the position of the set-screw
as indicated by the line at _A_ is a poor one and calculated to give
plenty of trouble at the most inopportune time.
[4] Contributed to Power by Wm. Kavanagh.
Not long ago a cast-iron pulley had to move along a countershaft in
order to make room for a pulley of another diameter. The pulley had
not been on the shaft long, so it was thought that little work would
be required to move it. A heavy bar was placed against the hub and a
sledge hammer was used to strike the bar. After an hour and a half of
heavy work the pulley was not moved over 1 inch (it had to be moved
16 inches), so it was suggested that a Bunsen burner be attached to a
gas pipe by means of a hose and placed beneath the hub. The plan was
immediately adopted. The burner was placed beneath the hub, the gas lit
and allowed to heat the hub. After about twenty-five minutes it was
found that a blow from the bar was sufficient to move the pulley. The
pulley was moved the 16 inches inside of twenty minutes.
[Illustration: FIG. 57.]
A very handy arrangement for moving pulleys is a bolt and nut. Fig. 57
shows the bolt and nut with a piece of pipe attached. A piece of pipe
can be cut to suit the distance between the nut and hub of one pulley
while the bolt head is against the other hub. The nut is screwed back
upon the bolt as far as possible. A washer is then placed against the
nut, and a piece of pipe cut to suit. Of course, the pipe must be large
enough in diameter to fit over the bolt. If we screw back upon the nut,
a powerful strain can be brought to bear between the hubs and in all
probability the pulley will move.
[Illustration: FIG. 58.]
In taking down solid pulleys from main or counter shafting it sometimes
happens that a hanger must be removed to permit the pulley to be taken
off. A first-rate plan is to make a couple of long bolts hooked at
the end as shown in Fig 58; pass the hook around the shaft and the
threaded end through a hole in the stringer. By screwing up the nut
as shown, the shaft and remaining pulleys can be kept in position,
obviating the use of tackle, not to mention the labor required to hoist
back the shaft into position. The application of this contrivance is
especially valuable where heavy cone pulleys are required to be lowered
or changed. It will be seen that if we employ a pipe thread we will be
enabled to suit almost any condition of length that may arise between
the shaft and stringer.
VII
PRACTICAL METHODS OF LOOSENING PULLEYS
WHEN a solid pulley is to be removed from a piece of shaft for any
reason, it is not good policy to use sledge hammers on the spokes or
hub to do it. Cast iron in pulleys is too liable to break or crack
under repeated blows.
[Illustration: FIG. 59.]
In Fig. 59 one ready method is illustrated by which the pulley may be
removed. When a place between two walls can be found that will admit
of this arrangement, proceed as shown to force the shaft through the
pulley, substituting longer pieces of pipe as the shaft is forced
through farther.
In one case where a large pulley was stuck on a 7-inch shaft and its
removal was imperative, the shaft was sawed off (with large hack-saws)
close up to the pulley hub and two 5/8-inch holes were drilled into
the shaft parallel to its axis, as shown in Fig. 60. These holes were
drilled so that they were 90 degrees apart and came within 1/16-inch of
the hub of the pulley. The hub was 14 inches through and these holes
were 8 inches deep; but that was enough to loosen up the shaft so
that when the pulley was laid over on beams with the shaft hanging
through, a sledge hammer applied on the shaft end soon drove it out.
Another way to remove a pulley is shown in Fig. 61, where a ram is
used. The ram is another piece of old shaft. To prevent its damaging
the pulley hub and also to have its force applied most advantageously,
it should be used in a direct line with the direction of removal. To do
this, the method shown in Fig. 61 is self-explanatory.
[Illustration: FIG. 60.]
Another good method of removing an obdurate pulley is illustrated in
Fig. 62, where the bolts _W_, _W_ must have long threads and the work
is done by pulling up on the nuts _A_, _A_. This method can be used
only when the end of the shaft can be reached and used as shown. In
using this method, care must be exercised in the pulling up on the
bolts _W_, _W_, keeping the strain equally divided between the two by
pulling a little at a time on each.
[Illustration: FIG. 61.]
[Illustration: FIG. 62.]
If the pulley comes extra hard, it can be assisted when the strain is
on the bolts by striking at _X_ with a sledge.
A good device for removing motor and generator pulleys that are near
the shaft end is shown in Fig. 63. The arms _Z_, _Z_ are adjustable to
take hold of hub or arms, and the screw applied to the shaft center
will do the rest.
To run a pulley off a shaft without injury to the hands, use a monkey
wrench on the rim of each pulley, as shown in Fig. 64. One pulley on
the shaft can be selected for a hold-back; one monkey wrench there will
hold the shaft from turning, while the other will turn around the shaft
the pulley which it is intended to remove.
[Illustration: FIG. 63.]
[Illustration: FIG. 64.]
VIII
SPLICING LEATHER BELTS[5]
THE first thing is the tools for the different kinds of work. These may
be usually changed somewhat to suit the taste of the user, but in the
main the style and kind herein shown in attached drawings cannot be
very much improved upon.
[5] Contributed to Power by Walter E. Dixon, M. E.
[Illustration: FIG. 65.]
[Illustration: FIG. 66.]
Figs. 65 and 66 show a splice opener for heavy belts. It is made of
1/2-inch tool steel with the point spread out about 2 inches wide and
well tempered, after which it is ground to a good sharp edge, and then
an oil stone run over the edge until it has been dulled so that it will
not cut. The right kind of an edge can only be secured by trying; it is
one of the tools that is very hard to get just right. You will notice
that the manner in which this splitter is built may seem to be rather
too much work to bestow on such a simple tool, but the reasons for so
doing are as follows: in opening a 36-inch belt an old splice opener
that was driven into the handle like an ordinary file was used and the
handle split; that sharp point came back through the handle, and when
it finally stopped it had gone about 2 inches into the palm of the
operator's hand. Some 1/2-inch hexagon steel was turned down 6 inches,
just enough to round it up; then a solid brass washer was turned out
1-1/4 inches in diameter and 1 inch thick, a hole bored through it that
was a driving fit on the piece of steel and was driven down to the
shoulder. Washers were cut out of old pieces of belt and put on with a
liberal coat of glue on both sides; when the handle was filled, a steel
washer which was 1/2 inch thick was screwed down hard on the leather
washers, and when it had dried well the whole was turned down to size
shown in the sketch. Two of these tools were made, one for belts up
to 18 inches, and another that will reach through a 40-inch belt. The
tool shown in Fig. 67 is an ordinary heavy screwdriver with the point
rounded nicely, and it is used to raise the thin points that the larger
tool will sometimes tear.
[Illustration: FIG. 67.]
[Illustration: FIG. 68.]
Fig. 68 shows a handle made almost like the one in Fig. 65, with the
exception that the brass washer referred to in Fig. 65 is here turned
down to 3/4 inch, commencing 1/2 inch from the large end, which is 1
inch in diameter. The leather washers are slipped on over the small part
until it is filled, and then a washer is screwed on the small end and
the whole turned as shown in the sketch. A hole that will tap out 3/8
inch is bored in the large end of the brass center, and then tools made
with threaded ends on them that will fit into it. These tools are made
of 3/8-inch tool steel with scraping ends, as shown. These scrapers
are used only for removing glue that is too hard and too thick to be
removed by the scraper shown in Fig. 69.
[Illustration: FIG. 69.]
[Illustration: FIG. 69a.]
[Illustration: FIG. 69b.]
Figs. 69, 69a and 69b show views of the only tool that is hardly worth
being referred to as a leather-cutting tool. It is made of a thin piece
of steel, about 18 gage, or any old hand-saw will make the very best
scrapers that can be secured. They should be about 4 inches square,
perhaps a little smaller, and fixed in a hardwood handle (usually of
hard maple), simply by sawing about 2-1/2 inches into the handle and
then driving the blade in. The saw cut should be just a trifle thinner
than the piece of steel. Should they get loose from use, a piece of
paper folded over the back of the blade and forced back into the handle
with the blade will usually tighten it all right.
This is the tool that will ordinarily worry the novice more than all
the rest to keep in proper condition. Fig. 70 shows an exaggerated view
of how the blade should look when properly finished. It should be
hooked considerably.
[Illustration: FIG. 70.]
Fig. 71 shows a small steel for sharpening the scraper after it is
turned, and it should be absolutely smooth.
[Illustration: FIG. 71.]
[Illustration: FIG. 72.]
Fig. 72 shows the equipment for turning the edge of the scrapers. A
large three-cornered file, about 12 inches long, which has all the
teeth ground carefully off of it and then nicely polished, is fastened
to a piece of good clean belt leather by means of the staples shown.
[Illustration: FIG. 73.]
Fig. 73 shows the method employed in turning the edge of the scraper,
which is as follows: After the blade has been set firmly in the handle,
grind the edge rounding, as is shown in Fig. 69; then grind sharp with
a good long taper of about 3/8, and grind from both sides just as you
would an ordinary axe. After you have a good smooth edge on it, put
it on an oil or water stone and put as fine an edge as possible on
it, then put on a smooth piece of leather and hone it down until it
would shave you. You will then have a tool that will do a world of
work for you, "if you will turn it right." The method shown in Fig.
73, if properly carried out, will do the trick for you; the thing to
be remembered is that at no time in the turning of the scraper must
the cutting edge bear on the smooth file. The first position is not
shown right; the handle should be allowed to touch the file the first
few times it is passed over, and then gradually raise the handle and
keep on passing the blade from side to side, as is shown in Fig. 74;
allowing it to slip off on the leather every time you cross the file;
this is to keep the corners in proper shape. Another thing to remember
is to bear down on the blade as it is passed over the file; you can't
bear too hard; the only thing to look out for is not to raise the
handle too fast. An ordinary blade can be turned in about fifty strokes
across the file. The edge turned over should be at least 1/16 inch long
and should be well hooked, as is shown in Fig. 73.
[Illustration: FIG. 74.]
It is well to keep on hand about six of these scrapers, and as they
get too dull to cut leather use them on glue. With one good scraper
that is not too sharp all the glue can be cleaned off of both points
of a 36-inch belt in from five to ten minutes. When the edge gets a
trifle dull, use the small steel on both sides of the edge; first wet
the steel with the lips, it makes a much better edge. For the benefit
of beginners who may attempt to splice a belt for the first time, do
not use a glue that will not allow you to remove the clamps and put on
the full load in forty-five minutes after the glue has been applied and
well rubbed down. The time given here applies only to clean belts that
are absolutely free from all oils, and does not include old oil-soaked
leather that no glue will ever dry on.
Fig. 75 shows the equipment necessary to do a good, quick job on a
belt, and most of them are required to be done quickly and well. With
such an outfit and half-dozen sharp scrapers a joint in a 36-inch belt
can be made and run again in four hours after the engine is stopped.
This includes all the time consumed in putting on and taking off the
clamps, etc.
[Illustration: FIG. 75.]
The top of the platform, 76d, is level with the bottom of the belt
and is held in position by the hooks, 76b, which are shown in Figs.
75 and 76. These hooks slip over the 2×4-inch pieces that project
outside the platform to which they are attached, and should be made
of three-quarter iron and not too long, or some difficulty may be
experienced in getting them on the two-by-fours.
[Illustration: FIG. 76.]
The rods should be long enough to take care of the longest possible
splice and still give plenty of room to work. There should be about
2-1/2 feet between the inside ends of the threads and the threaded end
should be 3 feet long. This will make the rod 8 feet 6 inches long,
and it will be none too long at that. For instance, in removing the
glue from the splice, if the last end point is very close to the clamp,
there will be great difficulty in cleaning it and also in fitting the
leather after the belt has been shortened. What is meant by the head
end splice is the one that is on the pulley first--the arrows in Figs.
77 and 78 will make this clear: they indicate the direction in which
the belt should run; therefore that end of the piece of leather that
is on the pulley first is the head end (or first end) and the end that
leaves the pulley last is the last end. If the two belts shown in the
sketch were reversed, the points would be turned up by everything
that touched them; whereas, running in the direction that they do,
everything that touches them has a tendency to rub them down.
[Illustration: FIG. 77.]
[Illustration: FIG. 78.]
We will suppose that the belt shown in Fig. 75 had a "first end" point
that opened on the top of the belt instead of the bottom as this one
does (see left-hand end of belt between the clamps, on the lower side);
one can easily see how hard it would be to work if the clamp were near
the point. There should always be enough room between the clamps to
allow the splicer to take the last end (which is always the forked
end), carry it entirely over the clamp toward the left in Fig. 75, lay
it down on that part of the belt that is outside the clamp and slip an
extra splicing board under it. Fasten the two belts and splicing board
all together by means of a couple of 8-inch hand-screws (of which every
belt splicer should have at least six or eight); then clean and shape
it to suit the other end. It can be passed back over the clamp from
time to time and tried for a fit.
[Illustration: FIG. 79.]
The proper mode of procedure in splicing a belt on the pulleys is as
follows: Decide on where the belt is to be opened, and always open it
in the worst place in the belt for that is the place you certainly want
to fix. Pay no attention whatever to any former splicing place that
may be in the belt, but take it apart at any place where you are sure
repairs are actually necessary. First put in the most convenient place
possible the point that you have decided to open and then put the
clamps in position. If you are sure that it is going to require very
hard pulling to get it as tight as you wish, take a damp cloth, moisten
the inside of the clamps and then sprinkle powdered resin on both upper
and lower clamp. Put the "first end" clamp on first, as this is always
the easiest point to clean and fit; decide how much you will have to
take out, or as near as possible, measure off this amount on the belt
and place the clamp this distance plus about 10 inches from the "first
end" point. This extra 10 inches will give you plenty of room to clean
the glue off and also to shorten up the belt the right amount, for all
the shortening must be done on the "first end" point on account of the
ease with which the new scarf can be made.
Should you try to shorten up from the "last end" point, by referring
to Fig. 78, you can easily see the amount of work you would be in
for. There would be two thin ends to scarf, and outside ends at that;
whereas if you shorten up from the "first end" you make only one thin
end and that one in the inside of the belt.
The first clamp, with the center mark of the clamp coinciding with
the center of the belt, should be very tight; for should it slip when
the load is put on, it will very probably slip in the middle of the
belt and may not slip on the edges at all. Should you glue it in this
condition, the chances are very much in favor of the outside edges
giving away on a heavy load, due to the middle being too long. After
the first clamp is in position and tightened, put on the second one and
leave the bolts loose, so that it can be slipped easily. Then put the
belt rods in position with just a "full nut" on each end and tighten
the clamp. Tighten the rods enough to take most of the load, then get
the large splitter shown in Figs. 65 and 66 and open the joint. The
place to commence is between _X X_ in Fig. 75; this inclined point
is about 4 inches long and must be opened at both ends of the splice
before the middle is touched.
The tool should be entered at _O_, in Fig. 78, and worked gradually
toward _A_; when the point is raised to _A_ clear across the belt, open
on down to _C_. After both ends of the splice have been opened up in
this way, proceed to open the middle, which is now an easy task, there
being no thin stock that a separating tool will pass through easily.
After the belt is entirely apart tighten up on the rods until the belt
is the proper tension and hang the hooks (76b, Fig. 75) on the belt
rods. Throw the two ends of the belt back over the clamp and put the
splicing board in position. After this is in place, throw the two ends
of the belt back on the board and proceed to lay off the scarfs. To
do this, first take a square and get the two thin points perfectly
square, then put the "first end" point in between them. This is shown
very clearly in Fig. 77, the shaded end being the last end. Of course
the "first end" point at _C_, Fig. 77, will have to be cut off before
the belt will lie down properly; the amount to cut off of this end will
be just as much as you have shortened the distance between the clamps.
After the point has been cut to the right length, take the square and
make a mark across the belt, using the end of the thin point as your
measure for length; then without moving the belt make a mark on the
edge of the belt, showing just where the lower thin point came on the
bottom. Throw the "last end" over the left-hand clamp out of the way
and scarf down the top of the "first end" point, letting the scarf be
about 4 inches long. Be careful not to gouge a hole in the belt where
the scarf is started, but try to make the inclined plane from _X_ to
_X_ perfect; try to keep the whole surface of this incline true and
straight. After the short 4-inch scarf is finished, clean the glue off
of the inside of the "first end"; lap up to where it enters the "last
end"; then turn it over by bringing it over the right-hand clamp, place
a scarfing board under it and make the scarf shown at _T_, Fig. 75.
Now clean all glue off the "last end" lap and take a sharp scraper
like the one shown in Fig. 69 or 69b, place a piece of glass under the
points that have been previously squared up, and scarf them down to a
knife-edge.
After the thin points are properly scarfed, lay the whole splice back
on the splicing board just as it will be when it is glued, and do any
fitting that may be necessary. Be very careful to get it thin enough,
or it will make a hammering noise when going over the pulleys. When
scarfing down the thin points with the scrapers, be sure that they
are very sharp; if not, they will tear the point off when it gets
down to an edge; also give the blade a drawing motion in order to
facilitate cutting. It may seem to the novice that to use a piece of
glass to scarf on, when one is using a tool with a razor edge, is a
trifle inconsistent, but it is not so in the least; if the blade is
held well back at the top and a considerable pressure applied to it,
there will be no danger in the edge actually touching the glass; the
edge is turned past a right-angular position, or hooked, and the heel
is all that touches the glass. A good piece of plate glass about 12 ×
18 inches is large enough for any width of belt, although a piece much
smaller will do all right. Do not attempt to do any scarfing on the
board 76d, for if you do it will be so full of holes that have been
gouged by the scraper that it will be ruined for any purpose.
This board must be kept smooth in order to be able to do a good job of
rubbing down when gluing. Never hammer a glue joint in order to set
it; it is just that much unnecessary work and does absolutely no good;
simply get a smooth block of wood 2 × 6 × 8 inches and rub hard and
fast as soon as the glue is applied. Do not try to glue more than 6
inches in length at one time. Use a heavy brush--a high-priced paint
brush is the best; the regular glue brush is about the only thing in
existence that will not put on any glue at all--about a 3-inch brush
is the thing; have the glue just as hot as it is possible to get it.
Keep the brush in the pot all the time the glue is heating; also have a
strong stick made somewhat like a three-cornered file, only larger, in
the glue--this last is used to scrape off the brush all the glue that
it is possible to get off without allowing the glue to get too cold.
When you take the brush out of the pot, work fast; get all the glue
possible off the brush and get the rest on the belt at once. Make two
or three fast strokes across the belt and close down the splice and rub
for dear life. After the first brushful has been applied (and rubbed
for about two minutes), have an assistant raise the point up until
you can see the glue breaking all across the whole width of the belt.
Then have a second brush ready and repeat the former process, with the
exception that you need not apply the glue to both sides of the leather
as in the first case; for if you will keep the brush down in the fork
between the two laps you will give both sides a coat, and in addition
to the time saved by using this method you will get the joint closed
while the glue is hot. As fast as you go across the belt with the
brush, have the assistant roll the belt together after you; when you
have used all the glue out of the brush, the joint is closed and ready
to rub. You will keep the glue much hotter by immediately closing the
splice after the brush, and there is nothing else so important as using
hot glue; as soon as it commences to get shiny on the surface the thing
is all off and it will not hold anything.
You cannot do any quick work with water in your glue--that is, unless
it is old and has been heated up several times. If this is the case,
it will have to be thinned with water. The proper consistency is about
that of a very heavy grade of cylinder oil; if it is too thin, it will
not dry in any reasonable time and it will also cause pockets in the
splice by opening up after the joint has been rubbed, and the air in
the pockets will open the whole splice. In important work never use
a glue that will not stick so tightly between every application belt
that after rubbing down you can give it a good, hard pull without its
opening up. In all statements regarding the time necessary for the
joint to dry, the belts are considered absolutely clean, dry and free
from all oils.
The most disagreeable portion of the belt repairer's work is the
splicing and repairing of oil-soaked belts. It is a well-known fact
that the action of oil and that of glue are in direct opposition to
each other: the oil prevents sticking and the glue sticks, if it has
a chance. Such being the case, the first thing to do is to eliminate
the oil completely, and the efficiency of your joint will be in direct
proportion to your success in getting rid of the oil. To this end
secure a large gasoline blow torch, such as painters use to burn off
old paint. If you are not used to it, be very careful; at all events,
have a bucket of dry sand to use in case of trouble. Just throw the
sand on the fire and the fire will go out--that is, if you can get the
sand in the right place.
The torch is to be used after the splice has been all completed except
the thin points. The flame will burn them if finished, so leave them
tolerably thick until after the oil has been removed; then finish them
as directed before. When the scarfs have been made and the old glue
has been removed, turn the flame (which should be an almost invisible
blue if the torch is working properly) directly on the leather and
move it over all the surface of the splice until the leather has
become thoroughly heated; never allow the flame to remain directed
at any point long enough to make the oil in the leather boil. If you
do, the belt is burned. Continue to move the flame over the surface
of the belt until the leather is so hot that the hand can scarcely
be held on it. With one of the scrapers shown in Figs. 69 and 69b
(69b preferred) scrape the oil off as the heat raises it up. Turn the
cutting edge of the scraper up and wipe the oil off after every stroke;
keep the scraping process going right on after the torch; never allow
the leather to cool off until you can get practically no oil and the
leather begins to turn brown. By heating the leather and bringing the
oil to the surface you do just what the glue does when you put it on
an oil-soaked belt without removing the oil. By means of the heat
contained in it, it brings up all the oil near the surface to which it
is applied and in consequence does not take any hold on the leather.
It will take two men with all the necessary tools and appliances at
least six hours of good hard work to remove the oil from a well-soaked
36-inch belt--that is, to remove it to an extent sufficient to warrant
the gluing of it.
In case of overflows in which the wheel pits are liable to be filled
with water, pour cylinder oil on all belts that are liable to get wet
and then remove them from pulleys if they will be covered for more than
twenty-four hours, clean them with gasoline and they will be found to
be all right and dry.
Hold a clean piece of waste against all belts at least twice every
twenty hours, and wipe them clean.
IX
THE CARE AND MANAGEMENT OF LEATHER BELTS[6]
OUTSIDE of the direct care and management of high-pressure boilers and
the steam lines pertaining thereto, there is no other part of a power
or lighting plant, mill or factory in which a large number of indirect
connected machines are used that is of such vital importance as leather
belting and rope drives. The subject under discussion in this chapter
will be the former, and the selection, care and management thereof.
[6] Contributed to Power by Walter E. Dixon. M. E.
The first thing in order will be the selection of a leather belt, and
when we consider that all makers make good belts, that there are no
particular secrets in the belt-making business, and that in order to
get the very best we must take every advantage of all small details in
construction, it stands every engineer and belt user in hand to get all
the information available; for we must remember that the percentage of
good hides does not run very high, that all that are bought go into
belt stock of some kind or other, and that some one must buy the goods
that are not quite up to the standard of belt excellence. It is very
evident that no man wants anything but the best when he is paying for
the best, and it is also evident that no maker is going to say that he
makes inferior goods; so therefore we must read the quality by what is
in sight, and in the judging of leather that is already made up, the
proposition resolves itself into a very hard one.
The two principal things left for an opinion to be based upon as to
quality are the relation the pieces that constitute the laps bear to
the hide from which they were cut. They should, in belts running from
18 to 36 inches, be cut from the center of the hides, or should be
what is known as "center stock." Of course all belts should be "center
stock," but where they are very narrow or so wide that one hide will
not be wide enough to make a lap, then there is always a lot of narrow
stock worked in that cannot always be strictly center. The next thing
to look out for is brands that are so deep that they destroy the life
of the leather and will cause it to break after being used. Then look
out for the length of lap. If this is too long, you will know that it
runs into the neck, for about all that it is possible to get out of
average hides and still leave nothing in that is not first class is
54 or 56 inches. Ordinarily, you can tell if a lap is "center stock"
by the marks that run down either side of the back bone; they will
be usually a little darker than the rest of the belt. These marks or
streaks should be in the center of the belt. The principal objection to
neck leather is that it is liable to stretch excessively, and on this
account it will put too much load on the piece immediately opposite it
in a double-ply belt; for the point of one side is in the middle of the
lap on the other side. Next look out for holes, which will usually be
found so nicely plugged as to escape detection unless subjected to the
most careful examination.
Next in importance is to buy a belt that has already been filled with
some good waterproof dressing. It is quite likely that to buy a belt
that has been filled means to buy one that perhaps has some bad leather
in it that would be seen in a dry oak tan belt, and also that the
adhesive power of the filled belt is not quite equal to the dry one;
but the points that the filled one possesses over the one not filled
are, first and mainly, "it is filled when you buy it with a preparation
that does not injure the leather in the least," and the preparation
you will fill it with, for it will be filled, will be engine oil and
water, a combination that will ruin any belt made and also get it in
six months into a condition that will make a permanent repair with glue
impossible, for machine oil and moisture are strangers to glue and will
ever be. More good belts are ruined by being soaked with engine oil
until the points come loose and then pulled out of shape than from any
other cause. Of course you may be able to keep a main engine belt that
runs through a damp wheel pit and basement, and through a long damp
tunnel to a main driven pulley that has two big boxes that are just as
close to the pulley as a first-class machine designer could put them,
and never get a drop of oil or water on it. But this is not likely.
One very common cause of trouble with engine belts is the fact that
such belts usually run under the floor, where there is considerable
moisture. Then the oil table under the average large Corliss engine
will leak around dash-pots and rocker-arm shafts, and some oil will
fly from the eccentric oil cups, get into the wheel, run around the
rim and get to the belt; if the belt is not filled a very few drops of
oil will make a large spot on it. Then, if an engine does not run the
whole twenty-four hours, while it is off, watch. A few drops of water
from a leaky valve stem whose bonnet drain is stopped up, as it will
sometimes be, has a way of getting through the floor and falling on to
the belt and running down the inclined inside of it until it finally
comes to the flywheel, which, with the assistance of its crowning face,
very kindly makes a nice pocket for said water and proceeds to drink
it up. Result: the glue is loosened and the belt may come apart in
consequence. Should there chance to be a point just at the bottom of
this pocket, it will get the glue soft enough to slip but may not open
up, which is much worse than if it did open up; for it may slip away
from the shoulder of the splice for half an inch, and when the engine
is put to work it may close down by running under the wheel and stick.
If it does, the result is that at no very distant day you will find a
break at that particular place, right across the face of the belt. The
reason is that the load was all taken off the inside half of the belt
by point slipping, thereby making the inside of the belt too long and
putting all the load on the outside. The outside will continue to do
all the work until it stretches enough to bring the inside back into
service again. During this week or month you have been pulling your
load with a single belt, not a double one, and after a short time
you will find the break referred to above in the shape of a clean,
well-defined crack extending across the belt parallel with the points
of the laps. Now of course you are going to send for the man who sold
you the belt and ask him to fix it. If he is a wise man and understands
his business, he won't do a thing but show you right under that crack
a point that does not come up to where it should come. Then the thing
for you to do is to say to him that the belt is examined every time it
is put into service and that you have noticed that the points he refers
to all come loose during a "run," that any one knows that a few drops
of water would not take any belt to pieces while it was running, and if
it was water, why did it not take it apart everywhere, etc? And finally
crush him completely by telling him that your men have no time to put a
pair of clamps on a belt in order to pull back into its proper position
every point that comes loose; that if they did do it they would have no
time for anything else, especially in the present case, and that if his
people had made the belt right the glue would have held, anyway.
After he has given you a new belt or repaired your old one, just take
my advice and box that flywheel up above the top of the eccentric oil
cup, at least 12 inches, and get some good, heavy tin or zinc and put a
tight roof over the belt, under the floor.
First put in a ridge pole out of 1-1/2-inch pipe, starting at the face
of the wheel and running in the direction of the main driven pulley,
holding it firmly in place at each end with a strong iron clamp. Then
solder into each edge of the strip of tin, which should be long enough
to reach beyond any possible leak through the floor or oil table, a
piece of 1/2-inch pipe, and put the tin over the ridge pole with a piece
of small pipe on either side. Ordinarily the belt goes out past the
cylinder; if it runs through a bricked-up runway on its route to the
main driven pulley, just fasten the two pieces of 1/2-inch pipe to
either wall and have the ridge about 6 inches higher than the outside
ones. Then every drop of oil or water that comes through the floor will
fall on to the roof and run down to the walls and be carried down to
the floor of the pit and have no chance to touch the belt.
One of the most difficult things in the operation of large stations
where a large number of belts are used is to keep them thoroughly
clean and free from moisture and machine oil, the latter especially.
One very hard problem that confronts all designers of machinery is the
prevention of oil leakage from boxes. In several plants with as many as
six dynamos of the same kind and the same design, at least four of the
six have leaked oil every time they were run. The others did not leak
as a usual thing, and all were equipped with the most modern methods of
holding oil.
[Illustration: FIG. 80.]
Now we come to the building of the belt, and we will notice only such
points as interest the engineer or buyer. The first thing is to see
that the laps are of uniform thickness, so that the belt will run
quietly; and it should be absolutely straight when unrolled on the
floor. If it has a long, graceful curve in it, look out; for it will
not run straight on the pulleys until it has stretched straight, and
by that time one of its edges may be ruined by coming in contact with
the floor or some other obstacle. Next notice how long the leather is
from which it is made. It should not show more than 52 inches, and
then there will be 4 inches hidden by the point that is out of sight.
Then see that the joints are broken properly. For instance, find the
center of any piece of leather on one side of the belt, and then look
on the opposite side and see if the joint is right under your center
mark. It should be by all means, for right here lies the most important
thing about the construction of leather belts. A belt whose laps are
all the same length, and which has all its joints broken correctly,
will put the same load on the glue throughout, and that is what must
be done in order to get the best results. See Fig. 80. Here we have a
belt that is 36 inches in width and a double ply. Now suppose there
is a draft of 9360 pounds on this belt, that from point _A_ to point
_B_ is 26 inches, and that the points are 4 inches long. Now we have
26 inches plus 4 inches plus 4 inches times 36 inches for the number
of square inches in the glued joint. This equals 1224 square inches;
the total pull on the belt divided by 1224 will equal the load on each
square inch of glued joint, and will equal in this case 7.65 pounds.
Now instead of assuming distance _A--B_ in Fig. 80 to be 26 inches, let
the lower joint get out of step with the upper ones, and conditions get
vastly different. We will suppose that the dimensions are as given in
Fig. 81, as was the case with a new belt that was measured less than
one month before the observation was made and we have the following:
Joint _A B_ is now only 10 inches, and we have 10 inches plus 4 inches
plus 4 inches times 36 inches which equals 648 square inches, and the
lead on the joint is now 14.44 pounds. You will readily perceive what
an important part in the life of the belt, and the life of everything
around the belt as far as that goes, the proper breaking of the upper
and lower joints is. Of course the belt maker will tell you that his
glue is just as strong as the leather itself, and he is about right
as long as you keep the belt free from oil and water; but when the
belt becomes filled with oil the glue rots and loses its strength much
faster than does the leather.
[Illustration: FIG. 81.]
No good belt needs any posts along the sides to make it run straight
and stay on the pulleys. If the pulleys are in line and the belt
straight, it will run straight. All belts should be made to run
perfectly straight on pulleys, first on account of the local
advertisement that it gives to the man who has charge of them; second,
if they do not run true, they will be on the floor or wrapped around
the shaft in a very few minutes, should they ever slip. Another very
important thing in the care of belts that carry heavy loads is that if
any of the points do come loose so far back that they will not return
to place without putting on the clamps, put them on by all means; as
the restoring of this point to place means that you will still retain
in service all of your belt, as you will not do if you glue it down
where it is and thereby cut one side completely out of service.
HOW TO CLEAN BELTING
We submit the following as the best and proper way of cleaning a
leather belt. It may seem simple, but it is safe and effective, as has
been proved by many people who have thus restored old and dirty belting
which had become almost or quite unfit for use.
Coil the belt loosely and place it on edge in a tank in which it may
be covered with naphtha; a half barrel makes a good receptacle, but
something with a tight cover would save the loss by evaporation. Put
in enough naphtha to cover the belt completely and allow it to remain
for ten or twelve hours; then turn the belt over, standing it upon the
other edge. The vertical position of the belt surfaces allows the dirt
to settle to the bottom of the receptacle as it is washed out, and
permits naphtha to get at all the parts.
After the belt has remained in the naphtha another ten or twelve hours,
or until sufficiently clean, raise it and allow the naphtha to drip
back into the tank. Then lay the belt flat, stretching or shaking it
until almost dry. You will find that the naphtha will not affect the
leather nor the cement in the center of the belt, but may open the
joints at the edges; in which case the old cement should be scraped off
and the edges recemented. Your belt man will know how to do this. The
belt will now be somewhat hard, and should be treated with a reliable
belt dressing before being replaced on the pulleys.
X
BELTING, ITS USE AND ABUSE[7]
THERE is no class of appliances so little understood by the ordinary
steam engineer and steam user as belts, which may be seen by the
quantity of belting sold annually. Where one can point to a belt that
has been in continuous use for twenty years, you can find hundreds that
do not last one-fourth as long. Why? Not always because the buyer has
tried to get something for nothing, but as a rule, when they do, they
get nothing for something.
[7] Contributed to Power by Wm. H. McBarnes.
The average belt is a poor one, and the average buyer will not find it
out till he has used it for some time. If you weigh the belt dealer up
as a man who is trying to rob you, beat him down in price, then get him
to give from 5 to 40 per cent. off, he will enter a protest, and, after
some explanation, will come to some terms with you. Have you gained
anything by your cleverness? Well, hardly. Belt dealers and makers,
like almost all other dealers in supplies, aim to get nothing but
first-class goods; but second and third, and even fourth-class goods,
are made, and you get the quality you pay for. In the second place,
belts wear out quickly because they do not get proper care. To let a
belt run one moment after it gets too slack is bad practice, for it is
apt to slip and burn all the staying qualities out of it. Another good
reason why it should not be run slack is that the engineer or belt man,
to save work, would be tempted to put on a dressing or, worse yet, put
on resin to make it pull, and, in the language of Rex, "the man who
will put resin on his belts is either a fool or a knave," for it is
sure to spoil his belt if continued for any length of time.
In an emergency, as when some unforeseen substance has found its way
to the belt, it may be necessary, to keep from shutting down between
hours, to use some of the so-called dressing. We know from experience
that engineers will go to almost any extreme to get out of a tight
place--circumstances sometimes make it necessary to keep a belt running
when it should not--but this should not be allowed to any extent. To
allow a belt to run too tight is just as bad, for it will make short
life for the belt, hot boxes and scored shafting. There is not one
in twenty who takes the time or can splice a belt properly; it is
generally done in a hurry, any way to make it hold together, with the
understanding that it cannot talk; but it does. How often we see boards
nailed up or rims tacked on to keep belts from getting off the pulleys.
All of this is good for the belt dealers.
This is not all the fault of the engineer or the belt manufacturer.
Often belts are made uneven, and soon get out of shape, even with the
best of care. We sometimes find a belt that ordinarily runs easy on
the pulleys and does its work with ease suddenly inclined to run to
either one side or the other of the driven pulley. This is caused by
one of two things--either the belt has been too slack, or the load
increased for want of lubrication, or other causes. In either case it
will run off if you insist on applying the power. The remedy would be
to take up the belt, thoroughly oil the journals, or take off the extra
load--maybe a combination of all. Still a little extra work making the
belt tighter will enable it to run well and do the extra work just
as long as the extra tension can be maintained. Then it may appear
perplexing and run to one side of the driven pulley when the driven
shaft gets out of line with the driving shaft. In a case of this kind
the belt does not run to what is called the high side of the pulley,
but to the low side. Another peculiar indication: If two shafts are
parallel and there is a high place on the pulley, then a belt will run
to the high place; but if the shafts are out of line, or, in other
words, are not parallel, and the face of the pulley straight, then the
belt will run to the low side or that closest to the driving shaft. The
remedy would be to line up your shafting.
The object of this chapter is not to say how belts are made, but to
impress upon the minds of belt users that to get the best results,
belts, like all good servants, must be well cared for, and all
responsibility should rest with one man, just as with your engine or
any high-priced machine.
XI
A COMPARATIVE TEST OF FOUR BELT DRESSINGS[8]
DURING January, 1905, a comparative test of the working efficiency
of four belt dressings and preservatives was made by T. Farmer, Jr.,
and the writer. The test was made on the regular belt-testing machine
of Sibley College, Cornell University, a full description of which
appeared on pages 705-707 of Vol. 12, _Trans. A. S. M. E._ This machine
tests the belt under actual running conditions, though our belts were
in somewhat better than average condition. The four belts were new
4-inch Alexander No. 1 oak-tanned single-ply, and were 30 feet long.
Particular care was taken to keep them free from oil and dirt. The
belts were first tested as received from the manufacturer, after which
each belt was treated with one of the dressings and again tested.
[8] Contributed to Power by William Evans.
The dressings were two semi-solids, designated No. 1 and No. 2; a bar,
No. 3, and neatsfoot oil, No. 4. As the first three are proprietary
articles, it was not thought best to give their names, though any one
familiar with the actions of belt dressings will readily recognize No.
1 from its peculiar curve. In applying the dressings, we followed
directions carefully, and in the case of Nos. 2 and 3 exceeded
them. The belt was given a five-hour run, during which two or three
applications of the dressing were given, and then it was set aside in
a warm place to allow it to absorb the applied dressing. After thus
"soaking" for at least forty-eight hours, the belt was again run, this
time for three hours, with one more application of the dressing. As
No. 3 was a bar of sticky dressing, it will readily be seen that this
precaution was not really necessary. No. 4, the neatsfoot oil, was not
applied during the last run, as we were afraid of getting too much
oil in the belt. As this oil is so extensively used by engineers for
dressing belts, special care was taken to get the best possible results
with it.
[Illustration: FIG. 82.]
In Fig. 82, the result of the test with the neatsfoot oil is shown
graphically. This curve is platted to show the relation between initial
tension per inch of width and horse-power per inch of width. One reason
for the drop in horse-power in the treated belt is that the slip was
materially increased; in the lowest tension at which any power at all
was transmitted, about 15 pounds per inch of width, the slip ran up as
high as 25 per cent.
[Illustration: FIG. 83.]
In Fig. 83, which shows the comparative value of the four dressings,
the highest horse-power delivered to the belt was taken as the
standard. The horse-power delivered by the belt was divided by this
standard, and the result, expressed in percentage, was used as the
percentage of available horse-power transmitted. This comparison shows
the great superiority of dressing No. 1 at all times, and especially at
low tensions. In looking at this chart, it is well to remember that No.
3 is a sticky dressing.
As the time of the test was so short, we were unable to determine the
ultimate effect of the dressings on the leather of the belts. We could
only approximate this by a chemical test and a close examination of the
belts at the end of each test. The chemical analysis showed no ammonia
or rosin in any of the dressings; No. 2 had a trace of mineral acid,
and all had oleic acid as follows: No. 1, 0.27 per cent; No. 2, 29.85
per cent; No. 3, 3.5 per cent; No. 4, 0.7 per cent.
The practical test showed no ill effects except from No. 3, the sticky
dressing, which ripped and tore the surface of the belt. The high
initial tensions caused overheating of the journals, even though we
kept them flooded with oil. On the low initial tensions there was
no tendency to heat, even when the maximum horse-power was being
transmitted by dressing No. 1. In the latter case we oiled the bearings
once in every two or three runs (a "run" comprised all the readings
for one initial tension), while in the former we oiled the bearings
after each reading and sometimes between them; even then we were afraid
that the babbitt would get hot enough to run. The readings for each
run varied in number from two to a dozen, but only the one giving the
maximum horse-power was used in drawing the curves. The belt speeds
during the tests varied between 2000 and 2500 feet per minute, most of
the tests being made at about 2200 feet per minute.
XII
BELT CREEP
THE question of the minimum amount of slip of a belt in transmitting
power from one pulley to another reduces itself to a question of creep,
for it is possible to have belts large enough so that with proper
tensions there will be no regular slip. With a difference in tension on
the two sides and of elasticity in the belt, creep, however, is bound
to take place. What does it amount to and what allowance should be made
for it? asks Prof. Wm. W. Bird of the Worcester Polytechnic Institute
in his paper under the above title.
[Illustration: FIG. 84.]
In Fig. 84 let _A_ be the driver and _B_ the driven, _T__{1} the
tension in the tight side of the belt and _T__{2} in the slack side,
the pulleys and belt running in the direction indicated. One inch of
slack belt goes on to the pulley _B_ at _o_; at or before the point
_p_ it feels the effect of increased tension and stretches to 1 + _s_
inches. It now travels from _p_ to _m_ and goes on to pulley _A_
while stretched. At or before reaching the point _n_, as the tension
decreases, it contracts to one inch and so completes the cycle.
With a light load the belt creeps ahead of the pulley _B_ at or near
the point _p_. If the load is heavy, the creep works towards the point
_o_ and the belt may slip; this also takes place when the belt tensions
are too light even with small loads.
The point may be easily appreciated by imagining the belt to be of
elastic rubber. Professor Bird gives formulas for calculating the
creep, and tests made at the Polytechnic to determine the modulus of
elasticity. He concludes that the answer to his opening question is
that for the common leather belt running under ordinary conditions the
creep should not exceed one per cent. While this is sometimes called
legitimate slip, it is an actual loss of power and cannot be avoided by
belt tighteners or patent pulley coverings.
The smooth or finished side should go next to the pulley because
the actual area of contact is greater than when the rough side is
in contact; consequently, the adhesion due to friction is greater.
Moreover, the smooth side has less tensile strength than the rough
side, so that any wear on that side will weaken the belt less than wear
on the other side would.
XIII
ROPE DRIVES[9]
THERE seems to be considerable difference in opinion regarding the
various ways of applying rope to the sheaves in rope driving, viz.,
multiple- or separate-rope system, continuous-wrap or single-rope
system with the rope from one of the grooves running on a traveling
take-up device, continuous-wrap or single-rope system with the take-up
working directly on all the wraps.
[9] Contributed to Power by R. Hoyt.
[Illustration: FIG. 85.]
The multiple- or separate-rope system on a horizontal drive where the
distance between centers is great enough so that the weight of the
rope will give the required tension, having the tight or pulling part
on the lower side and the sheaves of the same diameter, as in Fig. 85,
should be very satisfactory, as old or worn ropes may be replaced by
new ones of larger diameter, or some of the ropes may be tighter than
others and still not alter the efficiency of the drive. It will be
noticed in this case that a larger rope does not alter the proportional
pitch diameters of the rope on the driving and driven sheaves; but if
one of the sheaves is larger than the other, as in Figs. 86 and 87, and
a new or larger rope is substituted for a worn or smaller one, or if
some of the ropes are a great deal tighter than others, a differential
action will be produced on the ropes owing to the fact that the larger
or slack rope will not go as deeply into its grooves as the smaller or
tight one. Consequently the proportionate pitch diameter on the rope
on the driver and driven sheave will be changed. The action will depend
upon whether the large or the small sheave is the driver. If the driver
is the larger, and of course assuming that the slack or large rope is
weaker than the combined tight or smaller ones, then it will have less
strain on the pulling side; but if the driver is smaller, then the new
or large rope will have greater strain on the pulling side. Whether the
driver is larger or smaller, a large or slack rope affects the action
oppositely to a small or tight rope. Fig. 87 shows how the action is
reversed from Fig. 86.
[Illustration: FIG. 86.]
[Illustration: FIG. 87.]
For clearness we will exaggerate the differences in diameter in the
sketches and figure the speeds that the different size ropes would
produce. We will take _A_ as normal, _B_ 1 inch farther out of the
groove, producing a difference in diameter of 2 inches; _C_ 1 inch
deeper in the groove, producing a difference in diameter of 2 inches.
In Fig. 85 assume for the normal diameter of driver and driven 40
inches, 42 inches for _B_ and 38 inches for _C_, with a speed of 200
revolutions per minute for the driver. Either _A_, _B_ or _C_ will give
200 revolutions per minute for the driven sheave, omitting slippage,
of course. In Fig. 86 say the normal diameter of the driver for rope
_A_ is 60 inches and of the driven 30 inches, a speed of the driver of
200 revolutions per minute will give the driven sheave a speed of 400
revolutions per minute; _B_, with the driver 62 inches and the driven
sheave 32 inches diameter, will give the latter a velocity of 387-1/2
revolutions per minute. With _C_ the driver is 58 inches, the driven 28
inches, and the speed given the latter 414-2/7 revolutions per minute.
In Fig. 87, the normal diameter of the driving sheave being 30 inches
and the driven 60 inches, a speed of the driver of 200 revolutions per
minute will give a speed of the driven member of 100 revolutions per
minute. With _B_, if the driver is 32 and the driven 62 inches, the
driven sheave will have a speed of 103-7/31 revolutions per minute;
_C_, with the driver 28 inches and the driven sheave 58 inches, will
give the latter a speed of 96-16/29 revolutions per minute. So it will
be readily seen what effect a large or a small rope would have.
[Illustration: FIG. 88.]
There are some who claim that slack ropes will transmit more power
owing to more wrap on the sheaves, while others claim that tight ropes
are better. If a drive with all the ropes slack gave trouble by the
ropes slipping, the first remedy tried would be tightening the ropes.
But if the conditions were like Fig. 87, it would not be particularly
harmful to have some of the ropes longer than others; in fact, it might
be well, as the longer ropes would not make a complete circuit as
quickly as the shorter ones; consequently the position of the splices
would be continually changing. However, it seems more natural to have
about the same pull on all the ropes, that is, not have them as shown
in Fig. 88. In conclusion for the system, it should be noted that
it has no means of tightening the ropes except by resplicing; it is
not as well adapted to various conditions as the other forms; it is
the cheapest form to install and in some cases should give excellent
satisfaction.
With the continuous-wrap system having the rope from one of the grooves
pass over a traveling take-up, the latter has a tendency to produce
an unequal strain in the rope. In taking up, or letting out, the
rope must either slide around the grooves, or the strands having the
greatest pull will wedge themselves deeper into the grooves, producing
a smaller pitch diameter than the ones having less pull, making a
differential action on the ropes. It is therefore probable that it
is the differential action that takes up or lets out the ropes, the
take-up merely acting in a sense as an automatic adjustable idler. In
tightening, when the rope stretches or dries out, or even in running
normal, the greatest pull will be near the take-up, but if the drive is
exposed to moisture, and the rope shortens, it will be farthest from
the take-up, depending proportionately on the number of grooves the
take-up controls; so in large drives it is best to have more than one
take-up.
If one should use an unyieldable substance, as, for experiment, a
plain wire on two drums wrapped a number of times around and also over
a take-up, and the drums were moved together or apart, he would find
that the wire would have to slide around the drum; but, of course,
with a rope in a groove it is different. The rope will yield some.
It will also go deeper into the groove. This system costs more than
the preceding form, owing to extra expense for the traveling take-up,
but may be applied readily to different conditions and will be quite
satisfactory in general, if properly designed and installed.
The continuous-wrap system with a take-up or tightener acting directly
on all the wraps has practically none of the objectionable features
mentioned in the other two forms, and is quick in action, making it
applicable where power is suddenly thrown on or off. If the tightener
is made automatic, it may be controlled in numerous ways, as with a
weight or weight and lever or tackle blocks and weight, etc. It also
may be fitted with a cylinder and piston, with a valve to prevent too
quick action if power is suddenly thrown off or on. There is ordinarily
practically no unequal strain on the rope. This system may be applied
to different conditions as readily as the preceding form. Its cost is
more than that of either of the others, as the tightener must have as
many grooves as there are wraps. It must also have a winder to return
the last wrap to the first groove, and to give its highest efficiency
it must be properly designed and installed.
In either of the continuous-wrap systems, if a portion of larger rope
is used, it will produce a greater strain directly behind the large
rope, owing to its traveling around the sheave quicker. In angle work
there is always extra wear on the rope in the side of the groove, as
only the center or one rope may be accurately lined; so it is not
advisable to crowd the centers in angular drives, as the shorter the
centers and wider the sheaves the greater the wearing angle. It must
be remembered that the foregoing applies to ordinary simple drives
as shown in the sketches; where the drive is complicated, it may be
necessary to make other allowances.
XIV
A NEW SCHEME IN ROPE TRANSMISSION[10]
THE use of manila rope for transmitting power is becoming so common as
to attract no comment, and it possesses so many advantages in its own
field over any other method of conveying power that some objections
really existing are overlooked. When a rope drive is installed
according to modern practice, it is generally so successful and
furnishes such an agreeable and smooth running drive that any possible
objection is silenced by the many good qualities it evidently has. But,
as a matter of fact, the American continuous method of installing a
rope drive has a few serious drawbacks.
[10] Contributed to Power by Geo. F. Willis.
Were it possible to install a drive of say thirty ropes in such a
manner that each one of the ropes had exactly the same strain on it
that each other rope had, and this under varying conditions of speed
and load, it is evident that the thirty ropes would work exactly as a
belt of proper width to carry the load would, that the ropes would be
running with exactly the same tension clear across the width of the
drive, like the belt. But according to the best authorities on rope
transmission, this ideal condition is impossible to obtain.
It is given as desirable, by writers on rope transmission problems, to
use a take-up sheave for every twelve ropes, while ten is considered
even better. The best results have been secured by using a take-up
sheave for not more than eight ropes. But in any case the evil of
differential driving still exists.
In truth, the only drive in which perfect conditions can exist,
according to present practice, is one using but a single rope.
It is evident that when the load comes on the ropes, the entire number
of ropes in use are only able to ultimately reach the same tension from
the elasticity of the ropes themselves, as slipping in the grooves
rarely occurs. But there is a continued and uneven strain on the ropes
until the load becomes divided between them, and where ropes are used
to drive a varying load, this strain must and does reduce the life of
the ropes materially.
Many rope transmissions have been unsatisfactory because of this, and
when these drives have been so badly designed as to use one take-up
sheave for more than ten ropes, they are apt to be more expensive and
troublesome than could have been anticipated.
One rope drive is known where thirty ropes are used, with only one
take-up sheave. It has been a source of continual trouble and expense,
and has been replaced by the English system of multiple ropes. The
inherent troubles of this system have made the changed drive even
worse than the original. It will now be replaced by the system here
illustrated.
[Illustration: FIG. 89.]
In Fig. 89 is shown a plan view of the tighteners for a thirty-one
rope drive. As the ropes shown are 1-1/2 inches in diameter the main
tightener sheave is shown 60 inches in diameter or forty times the
diameter of the rope used. Mounted above the thirty-two groove sheave,
and in the same frame, is a single groove sheave of the right diameter
to reach the two outside ropes as shown, in this case 86 inches in
diameter. Further details are shown in the end elevation, Fig. 90, and
in the side elevation, Fig. 91. Allowing a working strain of say 250
pounds to each strand of the thirty-one ropes, we have a total weight
of 15,500 pounds which these two idler sheaves should weigh, including
the frame holding them.
These sheaves and the frame are mounted directly upon the ropes, on the
slack side of course, and just as a tightener is mounted on a belt. The
first rope passes around the thirty-two-groove sheave, on up over the
single-groove sheave, and back under the multiple-groove sheave again,
and is thus crossed over.
[Illustration: FIG. 90.]
It is evident that a rope threaded on this drive would, by the time
it had run ten minutes or so, have every strand in exactly the same
tension every other strand was in, and that the ropes would remain in
this condition in spite of variation of load and speed, as long as they
lasted.
The initial expense, including the erection, would probably be no
more than that for the necessary six or eight single-groove idlers,
with their shafts and boxes, tracks, etc., which would be necessary
according to established practice. The room taken up would evidently be
much less.
[Illustration: FIG. 91.]
In Fig. 92 an assembled drive of this character is shown. In Fig. 93
is shown a reverse drive, common in sawmill practice, where the two
sheaves described would preferably be mounted on a car, with the proper
weight to give the desired tension.
[Illustration: FIG. 92.]
[Illustration: FIG. 93.]
In a recent design is shown a cylinder with about 6 feet of piston
travel, provided with a reducing valve, so that the steam pressure
would remain constant at about 40 pounds. The cylinder is bolted to the
mill frame, while the piston rod is connected to the car carrying the
tightener sheaves. The cylinder is of the proper area, when furnished
with steam at 40 pounds pressure, to put the correct strain on the
ropes. A small steam trap is part of the equipment. This should give a
very elastic tension, and so long as steam pressure was at 40 pounds
or over, the tension would remain constant. With 6 feet piston travel,
it is evident that 372 feet of stretch could be taken out of the rope,
an amount entirely out of the question. A dog, or buffer, can be so
located as to prevent excessive back travel of the piston and car when
steam pressure is taken off.
It is evident that this method can be applied to a drive using any
number of ropes.
XV
HOW TO ORDER TRANSMISSION ROPE[11]
IT is probable that more different and erroneous terms are used by
purchasing agents and engineers when writing orders for transmission
rope than are used to describe any other article needed about a mill.
A knowledge of how to order clearly just the kind of rope wanted
would prevent delays and expense to many plants. Manufacturers of
transmission rope constantly receive orders so peculiar in their
wording that they dare not venture an immediate shipment, but must
first resort to the mails, telegraph or telephone to find out what is
really desired, and, of course, these mistakes, following the law of
"the general cussedness of things," usually occur after a breakdown at
the very time when every minute's delay means a considerable sum of
money lost.
[11] Contributed to Power by F. S. Greene.
There are in this country two manufacturers of cordage who make a
specialty of transmission rope, and the names under which their
rope is sold are fairly well known to all users of rope drives. In
addition to these two concerns, there are, perhaps, three or four other
cordage mills which make this grade of rope to some extent. From this
comparatively small source many different brands have sprung which,
rechristened, find their way to the market under a variety of names,
both poetic and classic. These many names lead to frequent delays in
ordering. The man who does the splicing at the mill has, at one time
or another, heard of a rope glorying in the possession of some fancy
title. It is more than probable that some salesman has told him most
wonderful stories of what this particular rope can do; consequently
when the time comes for a new rope, the splicer goes to the office
and asks that so many feet of such and such a rope be ordered. The
purchasing agent makes out the order, using this name, and sends it to
the manufacturer, who in all probability has never heard of the rope
and knows for a fact that it is not the brand under which any of his
fellow manufacturers are selling rope. Before the order can be filled,
two or more letters or telegrams must be sent and received.
It frequently occurs that manufacturers receive orders specifying
brands which never had existence at all, so far as their knowledge
goes. One firm recently found in the same mail requests for "Fern,"
"Juno," and "Elephant" transmission rope, though no such brands have
ever been on the market.
Another familiar mistake is the ordering of a certain color yarn
in the rope, as if this decoration possessed some peculiar virtue.
These colored yarns are simply a question of dye, and the rope in all
probability would be better and stronger were they left out.
Then again, we find peculiar wording as to the lubrication of a rope.
Some people insist that the rope shall be "tallow inlaid"; others
call for an "absolutely dry" rope or for a "water-laid" rope. All
transmission rope, to be of any service whatsoever, must be lubricated
and such a thing as a "dry" transmission rope or a "water-laid" one,
whatever that term might mean, would be of but small service to the
user. Each manufacturer has his own method or formula for lubricating,
and if this be a plumbago or graphite-laid rope, and he is asked for
an old-fashioned tallow-laid rope, he cannot fill orders directly from
stock.
It is unnecessary to name the number of strands, unless you wish a
three- or six-strand rope, for a four-strand transmission rope is
always sent, unless otherwise specified. It is also unnecessary to say
anything about the core, as the rope is always supplied with one, and
generally it is lubricated. Frequently five-strand rope is ordered.
This is very confusing, as there is such a thing as a five-strand rope,
but it is very rarely made. Ordering a five-strand rope is usually
brought about through the error of considering the core as a fifth
strand.
It is better, though not necessary, to order by the diameter instead of
the circumference, as transmission rope is made and usually sold upon
diameter specification.
By far the most frequent specifications received call for "long-fiber,
four-strand rope with core," and having done this, the purchaser
considers he has named all necessary requirements. At the present
price of manila hemp, which varies from 7 cents per pound for the
poorer grades to 12-1/2 cents per pound for the best, he may be quoted
for such a rope, with entire honesty, anywhere from 11 to 17 cents
per pound. To procure long-fiber manila hemp, and twist it into four
strands about a core, does not make a proper transmission rope. As
the rope will probably be required to run at a speed of from 3000 to
5000 feet per minute and be subjected to rapid and constant bending
throughout its entire length, the fiber should not only be long, but
the rope should be soft and pliable. Further than this, as the fiber,
yarns and strands must slip one upon another during the bending, the
rope should be so lubricated as to reduce to a minimum the frictional
wear from such slipping and rubbing, which is a much larger factor than
is generally supposed. Again, the unusual strength of manila fiber is
shown only when subjected to a longitudinal strain. Transversely, owing
to the cellular formation, the fiber is relatively weak; therefore,
in manufacturing transmission rope, the greatest care is necessary to
secure such proportion of twist in both yarns and strand as to render
the rope least vulnerable to crosswise strain. Nor will the term "long
fiber" insure the purchaser obtaining the proper material in his rope,
for the longest manila fiber, contrary to general belief, is not always
the best from which to make a transmission rope. Some of the extremely
long variety is coarse and brittle. The best fiber for transmission
rope is a particular grade of manila hemp known as Zebu, Fig. 94,
which is light in color, silky to the touch and exceedingly strong and
flexible.
[Illustration: FIG. 94.]
[Illustration: FIG. 95.]
[Illustration: FIG. 96.]
The accompanying illustration, Fig. 95, shows a close view of two
grades of hemp, that on the left being known in the trade as
"Superior 2ds," while the fiber to the right of the cut is "Zebu."
Fig. 96 shows a more distant view of the same two "heads" of hemp,
and the reader will see that in both the fiber is exceeding long,
and if anything, that of the Superior 2ds is longer than in the Zebu.
A transmission rope made from the latter, however, will cost the
manufacturer from 3-1/2 to 4 cents more per pound than if he had used
Superior 2ds, and will outlast two ropes made from the longer though
coarser fiber.
The reader, if he has perused this chapter to the present point, is
doubtless now asking himself: "How shall I word my order when I want
a first-class driving rope?" The safest road to follow is to write
to some manufacturer or firm whom you know to be reliable, and ask
for so many feet of their transmission rope, giving the name, if you
are certain on that point, and, of course, being sure to mention the
diameter. In case you do not know the name of his rope, word your order
as simply and briefly as possible; for example: "One thousand feet
1-1/2 inches diameter first quality manila transmission rope," and if
the concern to which you write is a reputable one, you will receive a
four-strand rope, made from Zebu manila hemp, put together with proper
twist and lay for the service required.
XVI
A BELTING AND PULLEY CHART[12]
RULE 1. _Pulley Speed._--When the diameter of both pulleys and the
speed of one is given, to find the speed of the other: Place the points
of spacing dividers upon the two given diameters in inches upon the
scale (Fig. 97); then raise the dividers, keeping the space obtained,
and place one point on the given speed and the other _above_ it for
speed of _S_, or _below_ it for speed of _L_ (_S_ and _L_ meaning
smaller and larger pulley, respectively). This point will fall upon the
required speed.
[12] Contributed to Power by A. G. Holman, M. E.
Example: If the two pulley diameters are 10 and 25 inches and speed of
larger pulley is 120 revolutions per minute, what is speed of small
pulley?
Place the points of dividers on 10 and 25 on scale _A_, then lift the
dividers and place one point on 120 and the other above it upon the
scale; the other point now rests on 300 as the speed of _S_. If the
speed of _S_ had been given, one point would have been placed at 300
and the other _below_ it, falling upon 120, the required speed of _L_.
Note.--In applying this rule, if the speed comes beyond the range
of scale _A_, the result may be read by carrying the space to the
revolution scale on scale _B_, and proceeding in the same way.
[Illustration: FIG. 97.]
Example: Diameter of pulleys 12 and 36 inches and speed of _L_ 500,
what is speed of _S_? Place points of dividers on 12 and 36. Now, if
dividers are raised and one point placed on 500 and the other above it
on scale _A_, it will come beyond the top of the scale. Hence go to
scale _B_, placing lower point on revolution scale at 500 and the other
point above, which will fall upon 1500, the answer.
RULE 2. _Pulley Diameters._--When the speed of both pulleys and the
diameter of one is given, to find diameter of the other: Place points
of dividers on the two speeds on scale _A_ or revolution scale _B_.
Then place one point of dividers on given diameter and the other above
it to find diameter of _L_, or below it for diameter of _S_. The figure
thus indicated is the required diameter.
Example: Speeds 180 and 450 and diameter of smaller pulley 20. What
must be diameter of _L_?
Place points of dividers on 180 and 450 on scale _A_. Then place one
point on 20 (the given diameter). The other point falls at 50, the
required diameter of _L_.
If the point falls between two graduations in any problem, the result
can be closely judged by the relative position.
The other and more labor-saving use for this chart is its application
to belting problems. It is generally conceded that there is no subject
of more general interest in practical mechanics and none on which there
is a greater difference of opinion than the proper allowance to be
made in the selection of belt sizes for given requirements. The general
formula for the horse-power transmitted by belting is
_HP_ = _WS_/_C_ in which _HP_ = horse-power,
_W_ = width of belt in inches, _S_ = speed of belt in feet per minute,
and _C_ = constant.
The proper values of this constant, or the feet per minute that each
inch of width must run to transmit a horse-power, under certain
conditions, is the point in question.
On the right-hand side of line _A_ on the chart is a series of lines
representing different values for this constant. The lower one,
marked 4, represents 400 feet belt speed per minute, the next above
is for 500, and so on. Against some of these values are suggestions
as to belts often recommended in connection with these constants. For
instance, 2 to 6 _S_ suggests the constant 1100 to be used for 2- to
6-inch single leather belt, 1000 for 6-1/2- to 10-inch single, 600 for
2- to 6-inch double, etc.
These suggestions practically agree with the advice of the Geo. V.
Cresson Company's catalog and the deductions of Kent's Handbook.
More power may be transmitted than these suggestions will allow, by
increasing the tension, but this is accompanied by the disadvantage of
requiring extra attention and undue pressure upon bearings.
The use of the chart for horse-power and width of belting is explained
by the following rules:
RULE 3. _Horse-power of Belting._--To find the horse-power that can
be transmitted when diameter and speed of pulley and width of belt
are given: Place one point of dividers on scale _A_ at the width of
belt in inches and the other point at the bottom of the line (at 1).
Next add this space to the hight representing diameter of pulley by
placing lower point of dividers upon the given diameter and allowing
the other point to rest upon the scale above. Then holding the upper
point stationary, open or close dividers until the other point falls
upon the proper constant on the scale at right-hand side of line _A_.
Now transfer this space last obtained to the scale _B_ by raising the
dividers, carrying them square across to _B_ and placing the point that
was on the constant upon the given speed on the revolution scale. Note
the location of the other point of dividers upon the horse-power scale,
which indicates the horse-power that can be transmitted under the given
conditions.
Example: What horse-power can be transmitted by an 8-inch double belt
running on a 40-inch pulley at 500 feet per minute? Place one point of
dividers on line _A_ at 8 (width of belt) and the other point at bottom
of line. Next raise dividers and place lower point on 40 (diameter of
pulley) and let the other point fall above upon the scale. Then close
dividers until lower point comes to the constant for 6-1/2 to 10 double.
Carry this space to scale _B_ with lower point on 500 on revolution
scale. Under point now falls upon 84 on horse-power scale, which is the
required horse-power.
RULE 4. _Width of Belting._--To find the necessary width of belting
when size and speed of pulley and the horse-power are given: Place one
point of dividers on scale _B_ upon the horse-power and the other point
upon the revolutions. Next transfer this space to scale _A_ by raising
the dividers, carrying them square across and placing the point that
was on revolutions upon the constant. Then holding the other point
stationary, raise the point that was on the constant and open dividers
until this point falls upon the given diameter. Now lift the dividers
and carry the lower point down to bottom of line (the point 1). The
upper point will now indicate the required width of belt.
Note.--If, in finding width of belt, there is doubt about the proper
constant to take, a medium value, say 6, may be assumed and a hasty
"cut and try" will show in what classification the required belt will
come.
Example: What width of belt for 100 horse-power with 40-inch pulley at
500 revolutions?
Place point of dividers on scale _B_ upon 100 on horse-power scale and
the other upon 500 on the revolution scale. Then carry the space to
scale _A_ with lower point on constant 5. Then resting dividers upon
upper point open them until lower point is at 40 (diameter). Finally,
raise dividers and place lower point at bottom of line. Upper point is
now at 9-1/2, indicating the nearest even width 10 as the answer.
A little practice will make one familiar with these rules, and it
will be seen that in the belting rules the four motions perform two
multiplications and a division.
XVII
SPLICING ROPE
THE splicing of a transmission rope is an important matter; the points
on which the success of the splice, and incidentally the drive, depend
being the length of the splice, which in turn depends upon the diameter
of the rope and which is given in the table (Fig. 97a); the diameter
of the splice, which should be the same as the diameter of the rope;
the securing of the ends of the strands of the splice, which must be
so fastened that they will not wear or whip out or cause the overlying
strands to wear unduly; and the workmanship of the splice, which should
be the best it is possible to secure. When splicing an old and a new
piece of rope, the new piece should be thoroughly stretched, for, at
best, it is an exceedingly difficult task on account of the stretch and
difference in diameter of the rope.
[Illustration: FIG. 97a. DATA RELATIVE TO MANILA TRANSMISSION ROPE AND
SHEAVES]
========+========+===========+=========+=========
| | | |
| | | |
| | | |
Diameter| Square |Approximate|Breaking | Maximum
of Rope| of |Weight per |Strength,|Allowable
in |Diameter| Foot, | Pounds |Tension,
Inches | | Pounds | | Pounds
--------+--------+-----------+---------+---------
1/2 | .25 | .12 | 1750 | 50
5/8 | .2906 | .16 | 2730 | 80
3/4 | .5625 | .20 | 3950 | 112
7/8 | .7656 | .26 | 5400 | 153
1 | 1. | .34 | 7000 | 200
1-1/8 | 1.2656 | .43 | 8900 | 253
1-1/4 | 1.5625 | .63 | 10,900 | 312
1-1/2 | 2.25 | .77 | 15,700 | 450
1-3/4 | 3.0625 | 1.04 | 21,400 | 612
2 | 4. | 1.36 | 28,000 | 800
2-1/4 | 5.0625 | 1.73 | 35,400 | 1012
2-1/2 | 6.25 | 2.13 | 43,700 | 1250
========+========+===========+=========+=========
+====================+========+==========
|LENGTH OF SPLICE | |
| IN FEET |Smallest| Maximum
+------+------+------+Diameter| Number
| 3- | 4- | 6- | of | of
|Strand|Strand|Strand|Sheaves |Revolutions
| | | | in |per Minute
| | | | Inches |
+------+------+------+--------+-----------
| 6 | | | 20 | 1060
| 6 | | | 24 | 970
| 6 | 8 | | 27 | 760
| 6 | 8 | | 32 | 650
| 7 | 10 | 14 | 36 | 570
| 7 | 10 | 16 | 40 | 510
| 7 | 10 | 16 | 45 | 460
| 8 | 12 | 18 | 54 | 380
| 8 | 12 | 18 | 63 | 330
| 9 | 14 | 20 | 72 | 290
| 9 | 14 | 20 | 81 | 255
| 10 | 16 | 22 | 90 | 230
+======+======+======+========+==========
The illustrations and instructions for making standard rope splices
are taken, by the courtesy of the American Manufacturing Company, from
their "Blue Book of Rope Transmission."
There are many different splices now in use, but the one that
experience has proved best is what is known as the English transmission
splice. In describing this we take for our example a four-strand rope,
1-3/4 inches in diameter, as spliced on sheaves in the multiple system.
The rope is first placed around sheaves, and, with a tackle, stretched
and hauled taut; the ends should pass each other from six to seven
feet, the passing point being marked with twine on each rope. The rope
is then slipped from the sheaves and allowed to rest on shafts, to give
sufficient slack for making the splice.
[Illustration: FIG. 98.]
Unlay the strands in pairs as far back as the twines _M_, _M′_, crotch
the four pairs of strands thus opened (Fig. 98), cores having been
drawn out together on the upper side. Then, having removed marking
twine _M_, unlay the two strands 6 and 8, still in pairs, back a
distance of two feet, to _A_; the strands 1 and 3, also in pairs,
being carefully laid in their place. Next unlay the strands 5 and 7 in
pairs, to _A′_, replacing them as before with 2 and 4. The rope is now
as shown in Fig. 99. The pair of strands 6 and 8 are now separated,
and 8 unlaid four feet back to _B_, a distance of six feet from
center, strand 6 being left at _A_. The pair of strands 1 and 3 having
been separated, 3 is left at _A_, as companion for 6, strand 1 being
carefully laid in place of strand 8 until they meet at point _B_. The
two pairs of strands 2-4 and 5-7 are now separated and laid in the same
manner, every care being taken, while thus putting the rope together,
that original twist and lay of strand is maintained. The protruding
cores are now cut off so that the ends, when pushed back in rope, butt
together.
[Illustration: FIG. 99.]
The rope now appears as shown in Fig. 100, and after the eight strands
have been cut to convenient working lengths (about two feet), the
companion strands are ready to be fastened together and "tucked"; this
operation is described for strands 2 and 7, the method being identical
for the other three pairs. Unlay 2 and 7 for about twelve to fourteen
inches, divide each strand in half by removing its cover yarns (see
Fig. 101), whip with twine the ends of interior yarns 2′ and 7′; then,
leaving cover 2, relay 2′ until near 7 and 7′, here join with simple
knot 2′ and 7′, Fig. 102. Divide cover yarns 7, and pass 2′ through
them, continuing on through the rope _under_ the two adjacent strands,
avoiding the core, thus locking 2′, Fig. 103. _In no event pass 2′
over these or any other strands._ Half-strand 7′ must now be taken
care of; at the right of the knot made with 2′ and 7′, 2′ is slightly
raised with a marlin spike, and 7′ passed or tucked around it two or
three times, these two half-strands forming in this way a whole strand.
Half-strand 7′ is tucked until cover 2 is reached, whose yarns are
divided and 7′ passed through them and drawn under the two adjacent
strands, forming again the lock. The strand ends at both locks are
now cut off, leaving about two inches, so that the yarns may draw
slightly without unlocking. This completes the joining of one pair of
strands, Fig. 104. The three remaining pairs of strands are joined in
the same manner.
[Illustration: FIG. 100.]
[Illustration: FIG. 101.]
[Illustration: FIG. 102.]
[Illustration: FIG. 103.]
[Illustration: FIG. 104.]
After the rope has been in service a few days, the projecting ends
at locks wear away, and if tucks have been carefully made, and the
original twist of yarns preserved, the diameter of the rope will not be
increased, nor can the splice be located when the rope is in motion.
XVIII
WIRE ROPE TRANSMISSION[13]
WIRE ropes are extensively and successfully used in the horizontal
and inclined transmission of great power of unlimited amount, the
advantages over hemp rope belting being: driving at very long
distances, comparatively small loss through slipping and the
possibility of driving in the open air.
[13] Contributed to Power by C. Boysen, M. E.
Vertical transmission of power, on account of the weight of the rope,
is excluded.
Formerly the material used in the manufacture of the wires was best
charcoal iron, but now almost exclusively tough crucible-steel wires
are used, as steel wire ropes are stronger, do not stretch as much, and
last longer than iron ropes.
The wire ropes consist of six strands of from six to twenty wires each,
and the strands to form the rope are woven in the opposite direction
to the wires in the strand. In the center of each strand and in the
center of the rope a cotton core is placed. These cores are of the
greatest importance, for by reducing the friction of the wires against
each other, they serve to increase the lifetime of the rope, which,
according to the strain on the rope and the size of the smallest
pulley, is from one to three years.
To prevent rusting, the wire ropes receive a coat of boiled linseed
oil, or a hot mixture consisting of three parts of drip oil and one
part of resin is applied. This latter mixture at the same time improves
the adhesion between the rope and the lining placed in the bottom
of the pulleys, thus reducing the loss caused by slipping of the
rope. Wire ropes used for the transmission of power should never be
galvanized.
The ends of the rope are spliced together, from 10 to 20 feet being
necessary for a good splice; great care should be taken that the splice
is made by experienced men, and that the rope is made long enough. A
rope stretches constantly from the time when placed on the pulleys,
the more so when placed on the pulleys tightly. Therefore it has to
be made long enough to transmit power without undue tension, and
for this reason the distance between the two pulleys has to be long
enough and the working strain per square inch of section low enough to
allow sufficient deflection in the rope. As a guidance to the amount
of deflection necessary, be it said that even in a short drive the
deflection of the rope, when not running, should not be less than
2 feet; and for a distance of 400 feet between pulley centers, the
deflection of the rope when running should be 5 feet in the driving
rope and 10 feet in the driven rope.
Either the top or the bottom rope may be the driving one, the former
being preferable; but the ropes should never be crossed.
Power can be transmitted to a distance of 6000 feet and more without
great loss; but as two pulleys should on no account be more than 500
feet apart, intermediate stations are placed along the road.
Precautions should be taken against the possibility of the rope
swaying. This may be caused either by the influence of the wind, by
a bad splice, by the rope wearing too much, by the pulleys not being
balanced well or by the pulleys not being in the same plane. It is of
importance that the pulleys be exactly in line, and careful attention
should be given to the construction and placing of the bearings.
Although the bearings are not strained excessively, the steps are
usually made long and movable. The connection between the shaft and the
pulley is best made by means of tangential keys.
Some engineers, when two ropes are found necessary for the transmission
of the power in question, use pulleys containing two grooves each,
and make the same kind of pulleys for the intermediate stations of
long-distance driving; whereas others advise a separate pulley for each
rope, both being connected with each other by a clutch.
The diameter of the smallest pulley has to be large enough in
comparison with the diameter of the rope or the thickness of the single
wires used to easily overcome the stiffness in the rope. The larger the
pulleys, the longer the rope will last.
The rim of the pulley is V-shaped, and the bottom of the groove is
dovetailed to receive a lining of wood, rubber or leather, on which
the rope rests. The lining increases the friction and reduces the loss
caused by slipping of the rope. Leather is the best lining and lasts
about three years. Either old belt leather, well saturated with oil,
or new leather, boiled in fish oil, can be taken. It is cut in pieces
of the same size as the dovetailed part of the groove, and then placed
on and pressed together in the latter. The pressing is done by means
of a piece of wood. The last remaining small space in the groove is
filled with soft rubber. If the lining has to consist of rubber, this
is softened and hammered into the groove. For wood lining, thin blocks
of the required size are placed into the groove through a hole provided
in the bottom of the rim. This slot is closed by a plate and fastened
to the bottom of the rim by means of screws after all blocks have been
inserted. The lining has to be turned absolutely true, for which reason
the filling is done while the pulley is still in the lathe.
Pulleys up to 3 feet in diameter are built with cast-iron arms; whereas
larger pulleys have wrought-iron arms made of round iron, cast in the
rim and boss. Pulleys under 8 feet 6 inches in diameter are made in one
piece, if for other reasons it is not necessary to have them in halves.
Guide pulleys are used for long ropes, especially if there is not
sufficient hight above the ground. The guide pulleys are of the same
construction as the main pulleys, and for the driving rope they are
also made of the same diameter. The diameter of the guide pulleys for
the driven rope can be made from 20 to 25 per cent. smaller.
The breaking strength of unannealed wires per square inch of section
and according to thickness and quality is: For iron wires from 70,000
to 110,000 pounds, and for steel wires from 110,000 to 130,000 pounds.
For thinner wires a higher value is taken than for thick ones.
The diameter of the wires used for making ropes for transmitting power
is from 0.02 to 0.1 inch, and on account of the stiffness, no wires
above the latter size should be used. A rope consisting of a greater
number of thin wires, besides being stronger is more pliable and lasts
longer than a rope of the same area consisting of a less number of
thicker wires.
INDEX
A
American Mfg. Co., 136
B
Bauer, Chas. A., 54
Beams to carry stringers, finding, 42
Bearings, locating, 3
Belt, building, 94
Belt creep, 106
dressing, 91, 100
comparative test, 102
running off, 101
shifter device upon column, 9
sizes, 132
Belt, leather, selection, 89
marking spliced part, 12
new, putting on, 19, 20
slack, 100
splicing on the pulleys, 81
throwing on, 12
tight, 100
wire-lacing, 12
Belt-clamps, use, 19
Belting and pulley chart, 129
Belting, cleaning, 97
horse-power transmitted, 132, 133
use and abuse, 99
width, 132
Belts, cleaning, 88
keeping clean, 94
leather, care and management, 89
splicing, 72
main line, 5
taking-up, 11
Bird, Prof. Wm. W., 106, 107
Blue Book of Rope Transmission, 136
Board for use in lining countershaft, 35, 36
Boiled linseed oil in wire rope, 144
Bolt and nut for moving pulleys, 62
for hanger, size, 40
Bolt, preventing turning, 11, 21
Boysen, C., M. E., 143
Brands, effect on leather, 90
Breaking strain on shaft, 28
strength of unannealed wires, 146
Bunsen burner, use in moving pulley, 62
Bushing, split, 2
C
Center drive for heavily loaded shaft, 7
stock, 90
Chart, belting and pulley, 129
Cleaning belting, 97
Clutch, rim-friction, arrangement, 5
Clutches, coupling, 31
tightening while shafting is in motion, 7
Collars, split wood, 3
Compass saw, use in locating beams, 45
Contact, extra, securing, 17
Continuous-wrap system of rope drive, 112
-wrap system with direct-acting tightener, 113
Core, cotton, of wire rope, 143
rope, 124
Countershaft, lining, 32, 33, 35, 36, 37
Couplings, flanged bolt, 3
Cresson Co., Geo. V., catalog, 132
D
Deflection of rope, 144
Diameter of splice, 136
rope, 124, 135
of wires for transmission rope, 147
Diameters, pulley, 131
Differential action on ropes, 109, 112, 116
Disks for plumb-bob, 49
Distance of power transmission by wire rope, 144
Dixon, Walter E., M. E. 72,, 89
Dressing, waterproof, for belts, 91
Driving an overhead floor, 6
E
Elbow bolts, 46
Emery cloth for packing, 23, 24
End drive compared with center drive, 7
English transmission splice, 136
Evans, William, 102
F
Farmer, T., Jr., 102
Fastening strands of splice, 136
Fiber, rope, 124
Filled belts, 91
Flanged bolt couplings, 3
G
Gasoline blow torch, use in getting oil out of belt, 88
Gluing a joint, 85
Greene, F. S., 122
Guide pulleys, 146
H
Hanger adjustment, securing, 40, 41
bearing, repairing worn end, 14
positions, marks, 3
Hanger, removing to take off pulley, 63
sliding out of wall box, 1
Hangers, crosswise of shaft, 42
Hangers not allowing vertical adjustment, 3
Heads of hemp, 127
Hemp, 125, 127
Herrman, Chas., 1, 21, 32
Holman, A. G., M. E., 129
Hook bolts, 46
Horse-power transmitted by belting, 132, 133
Hoyt, R., 108
J
Joints in leather belt, 95
Journaled end of shaft, proper length, 1
K
Kavanagh, Wm., 61
Kent's Handbook, 132
Kinks, practical, 61
L
Lag screws, boring for, 46
Laps of leather belt, length, 90
of leather belt, thickness, 94
Leather belts, care and management, 89
selection, 89
Leather-cutting tool, 75
Leather, length for belt, 90, 95
Length of splice, 135
Leveling shafting, 54, 58
Line, leveling, 52
setting, 51
Lining a countershaft, 32, 33, 35, 36, 37
of pulley, wire rope transmission, 145
shafting, 30, 54
Loosening pulley that has seized, 26
Lubrication of rope, 123
M
McBarnes, Wm. H., 99
Main shaft belted to engine and to countershaft, 8
Marks on ends of shafts, 2
to show hanger positions, 3
Mounting dynamos and motors, 18
Mule belt, 13
Multiple-rope system, 108
N
Neatsfoot oil as belt dressing, 103
O
Oil, boiled linseed, on wire rope, 144
effect on belt, 92
getting out of belt, 87
P
Packing to secure good clamping fit, 23, 24
Plank to use in sliding hanger out of wall box, 1
Plumb-bob, 49, 58
-bob method of lining countershaft, 38
Point slipping, 92
Power transmission by wire ropes, distance, 144
Practical kinks, 61
Pulley and belting chart, 129
diameters, 131, 145
lining, wire rope transmission, 145
shafts holding arrangement and adjusting contrivance, 13
speed, 129
Pulley, cast-iron, moving, 62
driving, location, 5
loose, 61
seized, loosening, 25, 26
Pulleys for wire rope transmission, 145, 147
Pulleys, guide, 146
loosening, 65, 67, 70
moving, 62
removing, 65, 67, 70
solid, 4
split, 5
R
Rope, core, 124
diameter, 124, 135
differential action, 109, 112, 116
drives, 108
fibers, 124
lubrication, 123
splicing, 135
strands, 124
transmission, 135
new scheme, 115
ordering, 122
Ropes, slack, 111
tight, 111
Rusting of wire rope, preventing, 144
S
Scrapers for removing glue, 74, 75
Scrapers, turning edge, 76, 77
Seizing of pulley, 25
Separate-rope system, 108
Set-screws, use, 23
Shaft, breaking strain, 28
causes of breaking, 16
preventing turning, 15, 16
repairing break, 17
journaled off to act as collar, 2
length of journaled part of end, 1
Shaft line, space between end and wall, 3
Shafting, apparatus for leveling and lining, 54
hints, 1, 21, 32
leveling, 58
line, turning up, 49
lining, 30
testing alinement and level, 29
Shafts of light-working counters, marring, 10
Sheaves, 135
Sheet iron for packing, 24
Sizes of belts, 132
of rope, effect, 110
Slack ropes, 111
Slip of belt, legitimate, 107
Space between end of shaft line and wall, 3
Speed, pulley, 129
Splice, diameter, 136
English transmission, 136
fastening strands, 136
length, 135
Splice opener for heavy belts, 72
Splice, wire rope, 144
workmanship, 136
Spliced part of belt, marking, 12
Splicing belt on the pulleys, 81
board, 78, 79
leather belts, 72
rope, 135
Split bushing, 2
Split-pulley, tightening, 23
Split wood collars, 3
Steel for sharpening scraper, 76
Stillson wrench, use, 22
Strands of rope, 124
Stretchers, position, 49
Stringers, locating beams to carry, 42
Stringers of drop hangers, thickness, 38
Superior 2ds hemp, 127
Swaying of rope, preventing, 145
T
Take-up for rope drive, 112
-up sheave for rope drive, 116
Testing alinement and level of shafting, 29
Tight ropes, 111
Tightener, automatic, for rope drive, 113
Tightener for 31-rope drive, 117
system, dangerous, 6
Tightening ropes, 112
Timbers of boarded-over ceiling, locating, 42, 45
Tin for packing, 24
Tool for leveling shafting, 58
Tools for splicing leather belts, 72
Transmission rope, 135
rope, ordering, 122
Transmission, wire rope, 143
rope, deflection of rope, 144
Traveling take-up for rope drive, 112
Tucking strands, 139
Turning edge of scrapers, 76, 77
up line shafting, 49
V
V-shaped rails, for mounting dynamos and motors, 18
Vertical adjustment for hangers, 3
W
Water, effect on belt, 92
Width of belting, 132, 133
Willis, Geo. F., 115
Wire diameter, for transmission rope, 147
Wire-lacing a belt, 12
Wire rope, splice, 144
transmission, 143
Wrench, proper way to use, 22
Z
Zebu manila hemp, 125, 127
Transcriber's Notes:
Obvious typos were silently corrected.
Archaic and variable spelling has been preserved.
Variations in hyphenation and compound words have been preserved.
Italics are shown thus: _sloping_.
Bold type is shown thus: =shout=.
Small capitals have been capitalised.
Punctuation has been preserved as it appears in the
original publication.
Due to space constraints the table on p135 has been split.
Subscript shown by underscore _, superscript by ^.
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