_ACCIDENTS TO THE VALVE-MOTION._
RUNNING WORN-OUT ENGINES.
Some of our most successful engineers, the men who pull our most
important trains daily on time, attribute their good fortune in
avoiding delays, to training they received in youth, while running
or firing worn-out engines that could only be kept going by constant
attention and labor. In such cases men must resort to innumerable
makeshifts to get over the road; they have frequently to dissect the
machinery to remedy defects; they learn in the impressive school of
experience how a broken-down engine can best be taken home, and how
breaking down can best be prevented. Firemen and young engineers,
generally feel aggrieved at being assigned to run on worn-out
engines,--the scrap heaps as they are called: but the man who has not
passed through this ordeal has missed a Golconda of experience; his
potentialities are petrified without reaching action.
CARE AND ENERGY DEFY DEFEAT.
Among a certain class of seafaring men, the captain of a ship who fails
from any cause to bring his vessel safely into port, is regarded as
disgraced; and, therefore, a true sailor will use superhuman efforts
to prevent his ship from becoming derelict, often preferring to follow
it to the bottom rather than abandon his trust. In many instances
the sentiments and traditions of seamen teach railroad men valuable
lessons. The sacrifice of life is not desired or expected of engineers
in their care of the vessel they command; but every engineer worthy of
the name will spare no personal exertion, will shrink from no hardship,
that will be necessary to prevent his charge from becoming derelict.
Once I heard a hoary engineer, who had become gray on the footboard,
make the proud boast, “My engine never was towed in.” His calm words
conveyed an eloquent sermon on care and perseverance. He had been in
many hard straits, he had been in collisions, he had been ditched with
engines, but had always managed to get them home without assistance.
WATCHING THE EXHAUST.
What the beating pulse is as an aid to the physician in diagnosing
diseases, the sound of the exhaust is to the engineer as a means of
enabling him to distinguish between perfective and defective working of
the locomotive. The ability to detect a slight derangement by the sound
of the exhaust, can only be acquired by practice in watching those
steam-notes day after day, as they play their tune of labor through the
smoke-stack. When the steam-ports are even, and the valves correctly
set, with tight piston-packing, and valves free from leaks, the notes
of the exhaust will sound forth in regular succession in sharp,
ringing, clear tones, every puff seeming to cut the steam clean off at
the top of the stack. There is a long array of defects represented in
the journey from this case of apparently perfect steam performance, to
that where the exhaust steam escapes as an unbroken roar mixed with
uncertain, wheezy coughs.
THE ATTENTIVE EAR DETECTS DETERIORATION OF VALVES.
The deterioration of piston-packing, and the rounding of valve-seats,
which produce an asthmatic exhaust, may be followed in their downward
course if the engineer gets into the habit of listening to the exhaust,
and marking its changes. It is very important that he should do so. The
man whose ear from long practice has become sensitive to a false tone
of the exhaust, needs not to make experiments, by applying steam to the
engine while it stands in various positions, in order to find out where
a blow comes from,--whether it is in the pistons or in the valves.
LOCATING THE FOUR EXHAUST SOUNDS.
Leaning out of the cab-window, he watches the crank as it revolves,
and compares the noise made by the blowing steam with the crank
position. When pulling on a heavy grade is an excellent time for
noting imperfections in the working of valves and pistons; for the
movements are comparatively slow, while the pressure of steam on the
working-parts is so heavy that any leak sounds prominently forth. The
observing engineer perceives that the four sounds of the exhaust, due
to each revolution of the drivers, occur a few inches before the crank
reaches, first, the forward center, second, the bottom quarter, third,
the back center, fourth, the top quarter. The first and third position
exhausts emit the steam from the forward and back strokes of the
right-hand piston: the second and fourth exhausts are due to discharges
of the steam that has been propelling the left-hand piston. With
these facts impressed upon his mind, he will understand, that if an
intermittent blow occurs during the periods when the crank is traveling
from the forward center to the bottom quarter, or from the back center
to the top quarter, the chances will be that the right-hand piston
needs to be examined. For the greatest pressure of steam follows the
piston just after the beginning of each stroke, and that is the time
a blow will assert itself. Should the blow occur while the right-hand
crank is moving from the bottom quarter to the back center, or from the
top quarter to the forward center, it will indicate that the left-hand
piston is at fault. For at these periods the left-hand cylinder is
receiving its greatest pressure of steam.
IDENTIFYING DEFECTS BY SOUND OF THE STEAM.
It is generally understood that an intermittent or recurring blow
belongs to the pistons, and that a constant blow comes from the valves.
But sometimes the valves blow intermittently, being tight at certain
points of the travel, and leaky at other points. To distinguish
between the character of these blows is sometimes a little difficult
except to the thoroughly practiced ear. The sound of the blow can
be heard best when the door is open, and the novice should not fail
to listen for it under that condition. The valve blow is a sort of
wheeze, with the suggestion of a whistle in it: the piston makes a
clean, honest blow, which would break into a distinct roar if enough
steam could get through. But a whistling sound in the exhaust is, by
no means, a certain indication of the valves blowing through; for
sometimes the nozzles get clogged up with a gummy substance from the
lubricating oils, and a distinct whistling exhaust results therefrom.
With a watchful ear, the progress of degeneration in the valves can be
noted day after day; for it is a decay which goes on by degrees,--the
inevitable slow destruction that friction inflicts upon rubbing
surfaces. Pistons are more erratic in their calls for attention. With
them it is quite common for a stalwart blow to start out without any
warning, the cause generally being broken packing-rings. The various
kinds of steam packing seem more liable to have broken rings than the
old-fashioned spring packing, but they generally run longer with less
attention.
ACCIDENTS PREVENTED BY ATTENDING TO THE NOTE OF WARNING FROM THE
EXHAUST.
The habit of closely watching the exhaust is likely to prove
serviceable in more ways than in keeping the engineer posted on the
condition of the steam-distribution gear. Its sound often acts as
a danger alarm, which should never go unheeded. Many an engine has
gone home on one side, and not a few have been towed in cold, through
accidents to the valve-gear, which could have been prevented had the
engineer attended to the warning voice of a false exhaust. The nuts
work off an eccentric-strap bolt; and it drops out, letting the strap
open far enough to cause an uneven valve-travel. If the engineer hears
this, and stops immediately to examine the machinery, he is likely to
detect the defect before the strap breaks. Again, one side of a valve
yoke may have snapped, leaving the other side to bear the load; or
bolts belonging to different parts of the links or eccentric-straps
may be working out,--so that the uniformity of the valve-travel is
affected; and the same result may be produced by the eccentrics getting
loose. Young engineers, to whom these pages are addressed, should make
up their minds that an engine never exhausts an irregular note without
something being the matter which does not admit of running to a station
before being examined. It may only be an eccentric slipped a little
way, a mishap that is not calculated to result disastrously; but, on
the other hand, it is probably something of a more dangerous character.
NEGLECTING A WARNING.
Engineer Joy of the D. & E. road went in with a broken eccentric-strap.
Questioning him about the accident brought out the fact, that, in
starting from a station, he heard the engine make two or three curious
exhausts; but he was running on a time-order, and did not wish to cause
delay by stopping to examine the engine. But he had not gone half a
mile when he found it necessary to stop and disconnect the engine, and
by doing so held an express train forty minutes.
HOW AN ECCENTRIC-STRAP PUNCHED A HOLE IN A FIRE-BOX.
A representative case of neglecting a plain warning happened on an
Illinois road some time ago. John Thomas was pulling a freight train
up a grade, when, to use his own words, “The engine began to exhaust
in the funniest way you ever heard. She would get on to three legs for
an engine length or so, then she would work as square and true as she
ever did, but only for a few turns, when she got to limping again.”
This runner knew that something was wrong, and he determined to examine
the engine at the next stopping-point. But delays in such a case are
full of peril. When he got over the grade, and shut off steam, there
was a tumultuous rattling of the reverse-lever, succeeded by a fearful
pounding about the machinery; a tearing up of road-bed sent a shower
of sand and gravel over the train; then a scream from escaping steam
and water drowned all other noises, and the engine was enveloped in a
cloud of blinding vapor. The forward bolt of one of the eccentric-strap
rods had worked out, and allowed the end of the rod to drop on the
track. Then it doubled up, and tore away the whole side of the motion;
and part of a broken eccentric-strap knocked a hole in the fire-box.
Here was the progress towards destruction. A small pin got lost, which
permitted the nut of an important bolt to unscrew itself; then this
bolt, with many a warning jar and jerk, escaped from its place in the
link; and the conditions for a first-class break-down had come round.
INTEREST IN THE VALVE-MOTION AMONG ENGINEERS.
Whenever locomotive engineers congregate in the round-house, in the
lodge or division room, a fruitful theme of conversation and discussion
is the valve-motion. Curious opinions are often heard expressed upon
this complex subject. There are comparatively few men who understand it
properly: but it has a fascination which attracts all alike, the wise
and the ignorant; and the man who is altogether uncertain about the
true meaning of lap and lead, expansion and compression, is generally
more loquacious on valve-motion than the engineer who has made the
subject an industrious study.
TROUBLE WITH THE VALVE-MOTION.
However well each may understand his business, in one respect all
engineers are in perfect harmony; that is, in hating to encounter
trouble with the valve-gear on the road. The valves being the lungs
of the machine, any injury or defect to their connections strikes at
a vital organ. With a good valve-motion, and valves properly set,
the steam is distributed so that nearly an equal amount is admitted
through each part in regular rotation; the release taking place in even
succession. This makes the exhaust notes uniform in pitch and period. A
sudden departure from this uniformity indicates that something is wrong
with the valve-motion. It should be the signal to stop, and institute
a searching examination. In doing so, avoid jumping at conclusions
regarding the cause of the irregularity, and coolly examine,
separately, each part whose motion influences the valve-travel.
A WRONG CONCLUSION.
Fred Bemis missed his luck by jumping too readily at conclusions.
Something happened to his engine; and he stopped by compulsion,
and found it would not move either way. He felt certain that both
eccentrics on one side had slipped; and, considering himself equal to
setting any number of eccentrics, he got down, and fixed them in what
he supposed was the proper position. But, on trying to move the engine,
he found it still refused to go. He kept working at those eccentrics
without result till his water got low, and he was compelled to dump
the fire; the consequence being, that the engine went cold, and was
towed home. When an examination was made, it was found that a broken
valve-yoke was the cause of trouble.
LOCATING DEFECTS OF THE VALVE-MOTION.
When any thing goes wrong with the valve-motion, the first point of
investigation is, to find out which side is at fault. This can be
ascertained by opening the cylinder-cocks, and giving the engine steam.
With the reverse-lever in forward motion, the forward cylinder-cocks
should show steam when the crank-pins are traveling below the axle, and
the back cocks should blow when the pins make their similar revolution
above the axle. Any departure from this method of steam distribution
will make one side work against the other. When the engineer has
satisfied himself on which side the defect lies, he will do well to
thoroughly examine the eccentrics with their straps and rods, the links
with their hangers and saddles, the rocker box and arms with all the
bolts and pins connecting these articles. What might be regarded as a
trifling defect, sometimes makes an engine lame. I have known a loose
valve-stem key put an engine badly out of square. Eccentric-rods,
slipping, often produce this effect. When the eccentrics are found in
the proper position, the rocker-box secure in the shaft, and all the
bolts, pins, and keys in good order, and in their proper positions, the
fault may be looked for in the steam-chest.
POSITION OF ECCENTRICS.
With engines where keys are not used to secure the eccentrics to
the shaft, their slipping on the road is a common occurrence.
Eccentric-strap oil-passages getting stopped up, or neglect in not
oiling these straps or the valves, puts an unnecessary tension on
the eccentrics, which often results in their slipping on the shaft.
Engineers ought to mark the proper position for eccentrics on the
shaft; so that, when slipping happens, it can be adjusted without the
delay that often occurs in calculating the right position. When the
crank-pin is on the forward center, the body of the go-ahead eccentric
is above the axle, and the body of the back-up eccentric is below
the axle, each of the eccentrics being advanced about 1/16 of the
revolution from the right angle position towards the crank-pin; or,
to state it more accurately, the center of the eccentric is advanced
a horizontal distance to equal the lap and lead of the valve. If the
valve had neither lap nor lead, the eccentrics would stand exactly at
right angles to the crank. As it is, both of them have a tendency to
hug the crank; the eccentric which regulates the distribution of steam
following the crank. Every engineer should familiarize himself with the
correct position of eccentrics, so that, when trouble happens with the
valve-gear on the road, he will experience no difficulty in grappling
with the mishap.
METHOD OF SETTING SLIPPED ECCENTRICS.
The slipping of one eccentric is a trifling matter, which can be
quickly remedied if the set screws are in a position where they can be
reached conveniently. If it is a go-ahead eccentric, set the engine
on the center of the disabled side,--no matter which center,--put the
reverse-lever in the back notch of the quadrant, and scratch a line
with a knife on the valve-stem close to the gland. Then put the lever
in the forward notch, and move the slipped eccentric till the line
appears in the point where it was made. Fasten the set screws, and
the engine will be found true enough to proceed with the train. Care
must be taken in moving the eccentric to see that the full part is not
placed in the same position as the other one, or they will both be set
for back motion. A back-up eccentric slipped, while the go-ahead one
remains intact, can be adjusted in a similar way; the scratch on the
valve-stem being made with the engine in full forward motion, and the
adjustment of the eccentric done in full back motion. The philosophy
of this method is, that the valve is in nearly the same position at
the beginning of the stroke for the forward or back motion; and the
position of the eccentric, which has not moved, is used to find the
proper place for the one which slipped. Should the unusual circumstance
of both eccentrics on one side slipping overtake an engineer, he will
have to pursue a different method of adjustment. The most systematic
plan is to place the engine on the forward center, and set the go-ahead
eccentric above the axle, and the back-up eccentric below the axle.
With the reverse-lever in the forward notch, advance the top eccentric
till the front cylinder-cock shows steam, which can be ascertained by
blocking the wheels, and slightly opening the throttle. That will put
the go-ahead eccentric near enough to the proper position for running.
For the back-up eccentric, pull the reverse-lever into back motion,
and turn the eccentric towards the crank-pin till steam appears at the
front cylinder-cock; and that part of the motion will be right. Or the
back-up eccentric can be set by the forward eccentric in the manner
described where one eccentric has slipped.
SLIPPED ECCENTRIC-RODS.
Where slotted rods are used, they frequently slip, making the engine
lame. The cause of trouble in such a case can be identified by moving
the engine slowly, with the cylinder-cocks open. The disturbance to
the regularity of the valve’s motion, caused by a slipped rod, will
admit steam prematurely on one end of the cylinder, while it delays the
admission on the other end. The valve is made to travel more on one
side of the exhaust center than on the other. Lengthening or shortening
the valve-stem has a similar effect, but this makes the engine lame
in both gears; while the slipping of an eccentric-rod only makes the
engine lame in the motion that the rod belongs to. This is subject to a
slight modification, however; for the back-motion eccentric being badly
out of square, will affect the correctness of the forward motion, when
the engine is working close hooked up. But in full motion it will not
be perceptible.
DETECTING THE CAUSE OF A LAME EXHAUST.
If in moving the engine ahead slowly, with the cylinder-cocks open, it
is found that steam is admitted to the cylinder before the piston has
nearly reached the center or dead point, or that the back cylinder-cock
does not show steam till after the piston has passed the back center,
the eccentric-rod is too long. The rod being too short produces
precisely an opposite effect. The steam arrives late on the back
stroke, and ahead of time on the forward stroke. This is different
from the action of the steam where an eccentric has slipped. In that
case, there will be pre-admission of steam before the beginning of both
strokes, or post-admission, that is, late arrival of steam, for both
strokes. Take a go-ahead eccentric for example. If it slips backward
on the shaft, its effect will be to delay the admission of steam
till after the beginning of each stroke; and, if it slips forward,
the result will be to accelerate the lead of the valve opening the
steam-port before the piston has reached the commencement of each
stroke.
WHAT TO DO WHEN ECCENTRICS, STRAPS, OR RODS BREAK.
When either of these accidents happens, the safest plan is to take
down both straps and rods on the defective side. Some engineers leave
the back-up eccentric strap and rod on, when the forward strap or rod
has broken; but it is a little risky under certain conditions. After
getting the eccentric straps and rods down, drop the link-hanger
away from the tumbling-shaft, disconnect the valve-stem, and tie the
valve-rod to the hand-rail. Then set the valve in the middle of the
seat, so that it will cover both the steam-ports, and hold it in
that position by pinching the stem with the gland, which is done by
screwing up the gland obliquely. Take down the main rod, and block
the cross-head securely at the back end of the guides. Good hardwood
blocking prepared beforehand should be used for this purpose, and it
ought to be fastened with a rope or marline. A neater plan for holding
the cross-head in place is described by Frank C. Smith, in the _Torch_.
He says, “Have the blacksmith make a hook out of a piece of inch and a
half round iron; also a piece about fifteen inches long by one and a
half thick, and four inches wide, with a hole through the center for
the shank of the hook to pass through. This shank is threaded for a
nut. Now, when it is necessary to block a piston, get it to the back
end, pass the hook around the wrist of the cross-head, and the other
end through the straight piece which bears against the yoke supporting
the back end of the guides; run up a nut on the shank of the hook,
hard against the cross-piece, and the piston is secured.” The piston
being properly fastened, it is a wise supplement to the work to tie the
cylinder-cocks open, or to take them out altogether. The engine is now
ready to proceed on one side.
Young engineers can not be too strongly impressed with the necessity
for having the cross-head properly secured before trying to move
the engine. I have repeatedly known of serious damage being caused
by placing too much confidence in weak blocking. Taking out the
cylinder-cocks is a wise security against accidents of this kind; for,
should a little steam be passing through the valve, it has a port of
escape without putting heavy pressure on the piston.
DIFFERENT WAYS OF SECURING THE CROSS-HEAD.
In regard to the method of securing the piston when one side of an
engine is taken down, there is considerable diversity of opinion among
engineers. Some men maintain that the proper and quick plan is, merely
to move the piston to one end of the cylinder, pushing the valve in
the same direction, so that the steam-port will be open at the end
away from the piston. This will keep the cylinder full of steam, and
hold the piston from moving. But, if by any accident the valve should
be moved to the opposite end of the seat, steam would get to the wrong
end of the cylinder, and the piston would certainly smash out the head.
Another risky plan, practiced by men economical of work, is to place
the valve on the center of the seat, and let the piston go without
fastening. These slipshod methods do not pay.
BROKEN TUMBLING-SHAFT.
This accident is very serious; but it need not disable the engine,
although it will lessen the engineer’s power to manage it freely. To
get the engine going, calculate the position the links must stand in
to pull the train, and cut pieces of wood to fit between the block and
the top and bottom of the links, so that the latter may be kept in the
required position. For forward motion, there will be short pieces in
the top, and long pieces in the bottom. When back motion is needed,
reverse the pieces of wood. A common plan is to use one piece of wood,
working the engine in full gear.
The same treatment will keep an engine going when the tumbling-shaft
arms, the reach-rod, the link-hanger, or the saddle-pin breaks. The
failure of a link-hanger or saddle-pin will only necessitate the
blocking of one side.
BROKEN VALVE-STEM, OR VALVE-YOKE.
For a valve-stem broken, the eccentric-strap or link need not be
interfered with. If the break is outside the steam-chest, take down
the valve-stem rod, and set the valve on the middle of the seat; take
down the main rod, and secure the piston as previously directed. With
a valve-stem broken inside the chest, or a valve-yoke broken, a little
additional work is necessary. The steam-chest cover must now come up,
and the valve be secured in its proper place by pieces of wood, or any
other material that will keep it from moving; and the stuffing-box must
be closed, to prevent escape of steam through the space vacated by the
valve-stem.
WHEN A ROCKER-SHAFT OR LOWER ROCKER-ARM BREAKS.
A broken rocker-shaft, or the fracture of the lower arm, entails the
taking down of both eccentrics and the link, besides the main rod,
and the securing of the valves and piston. The breaking of an upper
rocker-arm is equivalent to a broken valve-stem, and requires the same
treatment.
MISCELLANEOUS ACCIDENTS TO VALVE-MOTION.
Accidents to the valve-seat, such as the breaking of a bridge, can be
fixed for running the engine home on one side, by covering the ports,
and stripping that side of the engine, just as had to be done for
a broken valve-yoke. If a serious break in a bridge occurs, it is
indicated by a tremendous blow through the exhaust port, out by the
stack. A mishap of much less consequence than a broken bridge is a
“cocked” valve, and the small mishap is very liable to be mistaken for
the greater one. Where the yoke is tight fitted, or out of true with
the line of the stem, some engines have a trick of raising the valve
away from the seat, and holding it there. This generally happens going
into a station; and, when steam is applied in starting out, an empty
roar sounds through the stack. Moving the valve with the reverse-lever
by quick jerks will generally reseat a cocked valve, but sometimes it
gets stuck so fast that it has to be hammered out of the yoke.
When a locomotive shows the symptoms which indicate a broken valve, a
broken bridge, or a cocked valve, the engineer should exhaust every
means of testing the matter from the outside before he begins an
interior inspection by raising the steam-chest cover. If jerking the
valve with the reverse-lever, or moving the engine a little, will not
stop the blow, he should disconnect the valve-stem, and shake the valve
by that means.
When a valve breaks, disabling its side of the engine so badly that it
can not be used, the valve should be taken out, and a piece of strong
pine-plank secured over the ports.
BROKEN STEAM-CHEST COVER.
A very serious and troublesome accident, which may come under the head
of steam-distribution gear, is the breaking of a steam-chest, or of
a steam-chest cover. It takes skillful management to get an engine
along when this has happened. The most effectual way to restrain
loss of steam when a chest or cover has broken, is to slack up the
steam-pipe, and slip a piece of iron plate, lined with sheet-rubber,
leather, canvas, or any other substance that will help to make a
steam-tight joint, into the lower joint of the steam-pipe. If this
is properly done, it ends the trouble, when the joints are tightened
up. But the difficulties in the way of loosening steam-pipe joints in
a hot smoke-box are often insurmountable, especially when the nuts
and bolts are solid from corrosion, which is generally the case where
they have not been touched for months. In such a case it is better to
resort to the more clumsy contrivance of fitting pieces of wood into
the openings to the steam-passage, and bracing them in place by means
of the steam-chest bolts. A man of any ingenuity can generally, by this
means, save himself the humiliation of being towed home, and yet avoid
spending much time over the operation. When the engineer has succeeded
in securing means for preventing the escape of steam, the main rod must
be taken down, and the valve-stem rod disconnected from the rocker-arm.
In this instance the piston needs no further attention, after the main
rod has been disconnected; for there will be no ingress of steam to the
cylinder to endanger its safety.
STEAM-PIPE BURSTED.
The breaking of a steam-pipe in the smoke-box is even a more harassing
mishap than a bursted steam-chest or cover. The only remedy for this
is the fastening of an iron plate to the top joint of the steam-pipe,
thereby closing up the opening. A heavy plug of hard wood may be driven
into the opening, and braced there for a short run; but such a stopper
is hard to keep in place, owing to the shrinkage caused by the intense
heat of the smoke-box.
TESTING THE VALVES.
An experienced engineer will most easily determine the existence of
leaks between the valves and their seats when the engine is working,
and the indications of that weakness have already been noticed. But it
sometimes happens that a man wishes to test the condition of the valves
when the engine is at rest. This can be most readily accomplished
by placing the engine so that the rocker-arm stands in the vertical
position. Open the smoke-box door so that the exhaust nozzles can be
seen. Now block the wheels, and give the engine steam. If the valve
blows, the steam will be seen issuing from the nozzle on the side under
examination. As the tendency of a slide-valve is to wear the seat
concave, it sometimes happens that a valve is tight on the center,
yet leaky in other positions. Moving the valve with the reverse-lever
as far as can be done without opening the steam-port, will sometimes
demonstrate this. The cranks should be placed on the eighths positions
when the valves are being tested.