_GETTING UP THE HILL._
SPECIAL SKILL AND ATTENTION REQUIRED TO GET A TRAIN UP A STEEP GRADE.
In the last chapter, some details were given of the methods pursued in
starting out with a heavy fast freight train. Where a train of that
kind has to climb heavy grades, special skill and attention are needed
in making the ascent successfully.
GETTING READY FOR THE GRADE.
The track for the first two miles from the starting-point is nearly
level, permitting the engineer and fireman to get ready for a long pull
not far distant. At the second mile-post a light descending grade is
reached, which lasts one mile, and is succeeded by an ascending grade
two and a half miles long, rising fifty-five feet to the mile.
WORKING UP THE HILL.
At the top of the descending grade, the engineer shuts off the steam
while the fireman oils the valves: then he puts on a little steam,
using a light throttle while the train is increasing in speed, until
the base of the ascent is nearly reached, when he gets the throttle
full open, letting the engine do its best work in the first notch
off the center. By this time the train is swinging along thirty miles
an hour, and is well on to the hill before the engine begins to feel
its load. Decrease of speed is just becoming perceptible when the
valve-travel gets the benefit of another notch, and the engine pulls
at its load with renewed vigor. But soon the steepness of the ascent
asserts itself in the laboring exhausts; and the reverse-lever is
advanced another notch, to prevent the speed from getting below the
velocity at which the engine is capable of holding the train on this
grade. While the engineer is careful to maintain the speed within
the power of his locomotive, he is also watchful not to increase the
valve-travel faster than his fire can stand it; for, were he to jerk
the lever two or three notches ahead at the beginning of the pull,
the chances would be that he would “turn” its fire, or tear it up so
badly that the steam would go back on him before he got half a mile
farther on. Before the train is safe over the summit, it will probably
be necessary to have the engine working down to 18 inches: but the
advance to this long valve-travel is made by degrees; each increase
being dependent upon, and regulated by, the speed. The quadrant is
notched to give the cut-off at 6, 9, 12, 15, 18, and 21 inches.
Repeated experiments, carefully watched, have convinced the engineer
of this locomotive, that its maximum power is exerted in the 18-inch
notch; so he never puts the lever down in the “corner” on a hill. A
great many engines act differently, however, showing increased power
for every notch advanced. If the cars in the train should prove easy
running,--and there are great differences in cars in this respect,--it
may not be necessary to hook the engine below 15 inches, or even 12
will suffice for some trains; but this can only be determined by seeing
how it holds the speed in the various notches.
WHEEL-SLIPPING.
As the engine gets well on to the grade, and is exerting heavy
tractive power, the wheels are liable to commence slipping; and it
is very important that they should be prevented from doing so. An
ounce of prevention is known to be worth a pound of cure; and it pays
an engineer to assure himself that no drips from pump-glands, or
feed-pipes, or cylinder-cocks, or from any other fountain, are dropping
upon the rails ahead of the driving-wheels. There is no use telling an
engineer of the decreased adhesion which the drivers exert on half-wet
rails, from what they do on those that are clean and dry. Knowing the
difference in this respect, every engineer should endeavor to prevent
the wetting of the rails by leaks from his engine; for hundreds of
engines get “laid down” on hills from slipping induced by this very
cause.
HOW TO USE SAND.
The first consideration in this regard is to have clean, dry sand, and
easy-working box-valves. Then the engineer should know how far the
valves open by the distance he draws the lever. In starting from a
station, or working at a point where slipping is likely to commence,
the valves should be opened a little, and a slight sprinkling of sand
dropped on the rails. This often serves the purpose of preventing
slipping just as well as a heavy coating of sand. And it has none of
the objectionable features of thick sanding. Trains often get stalled
on grades by the sand-valves being allowed to run too freely. It is not
an uncommon occurrence for engineers to open the valves wide, and let
all the sand run upon the rails that the pipe will carry, so that a
solid crust covers each rail, and every wheel on the train gets clogged
with the powdered silica; and, after the train has passed over, a
coating is left for the next one that comes along.
The wheels scatter their burden of powdered sand into the axle-boxes,
and it grinds its way inside the rod-brasses, and part of it gets
wafted upon the guides; and in all these positions it is matter
decidedly in the wrong place. And this body of sand under the wheels
increases the resistance in the same way, as a wagon is harder to pull
among gravel than it is on a clean, hard road: the indiscreet engineer
complains about the train being stiff to haul; and the chances are,
that he goes twice up the hill before the whole train is got over.
Uncle Toby’s plan is, when pulling on a heavy grade, to open the valve
enough to let the drivers leave a slight white impression on the rails.
If they slip, he gives a few particles more sand, but decreases the
supply again so soon as the drivers will hold with the diminished
quantity. Uncle Toby seldom needs to double a hill.
SLIPPERY ENGINES.
These remarks apply to ordinary engines with ordinary rail-conditions.
Occasionally we find an engine inveterately given to slipping, and no
conditions seem able to keep it down. Such an engine is as ready to
whirl its wheels as an ugly mule is to kick up its heels, and upon as
little provocation. With a dirty, half-wet rail, an engine of this kind
loses half its power. The causes that make an engine bad for slipping
are various. Very hard steel tires, or excess of cylinder power, are
the most frequent causes of slipping; but badly worn tires sometimes
produce a similar effect; or the blame may rest in a short-wheel
base, deficient in weight, or in too flexible driving-springs. To get
a slippery engine over the road when the rails are moist and dirty,
requires the exercise of unmeasured patience by the engineer. Job was a
cantankerous old Arab beside the engineer who passes cheerfully through
this ordeal. The tendency of an engine to slip may be checked to some
extent by working with the lever well ahead towards full stroke, and
throttling the steam. This gives a more uniform piston-pressure than
is possible while working expansively. Of two evils, it is best to
choose the least. The smallest in this case is losing the benefits of
expansion, and getting over the road.
FEEDING THE BOILER.
Some engineers claim that the most economical results can be obtained
from an engine by running with the water as low as possible, consistent
with safety. They hold, that, so long as the water is sufficiently high
to cover the heating-surfaces, there is enough to make steam from;
and the ample steam-room remaining above the water, assures a more
perfect supply of dry steam for the cylinders than can be had from the
more contracted space left above a high-water line. Old engineers,
running locomotives furnished with entirely reliable feeding-apparatus,
may be able to carry a low-water level advantageously, especially
with light trains and level roads; but with ordinary men, average
pumps or injectors, and the common run of roads, a high-water level
is safest. With a high-water level the temperature of the boiler can
be kept nearly uniform; for the increased volume of water holds an
accumulated store of heat, which is not readily affected by the feed.
And the surplus store is convenient to draw upon in making the best of
a time-order, or in getting over a heavy grade. Then, if the pumps or
injectors fail, a full boiler of water often enables a man to examine
the delinquent feeding-apparatus, and set it going; whereas, with low
water, the only resource would be to dump the fire.
CHOICE OF PUMP AND INJECTOR.
The engine on this train has one pump and one injector. The pump is
preferred for ordinary feeding-purposes, and is kept graduated to
supply the needs of the boiler while the engine is working, without
the foot-cock being moved. On a heavy pull, the pump in this condition
would not keep up the water-level; so the injector is called upon to
make up the deficiency. When the engine gets upon the heavy part of the
grade, it makes steam very freely; and, when the indications of getting
hot appear, the injector is started. During the remainder of the
ascent, the water is supplied as liberally as it can be carried; and
the top of the grade finds the engine with a full boiler. This enables
the engineer to preserve a tolerably even boiler temperature; for in
running down the long descent which follows, where the engine runs
two miles without working steam, the pump can be shut off, and sudden
cooling of the boiler avoided. The preservation of flues and fire-box
sheets depends very much upon the manner of feeding the water. Some
men are intensely careless in this matter. In climbing a grade, they
let the water run down till there is scarcely enough left to cover the
crown-sheet when they reach the summit. Then they dash on the feed, and
plunge cold water into the hot boiler, which is then peculiarly liable
to be easily cooled down, owing to the limited quantity of hot water
it contains. The fact of having the steam shut off, greatly aggravates
the evil; for there is then no intensity of heat passing through the
flues to counteract the chilling effect of the feed-water. If it is
necessary to pump while running with the steam shut off, the blower
should be kept going; which will, in some measure, prevent the change
of temperature from being dangerously sudden. There will probably be
some loss from steam blowing off, but that is the smaller of two evils.
Engineers are not likely to feed the boiler too lavishly when working
hard, for the injection of cold water instantly shows its effect by
reducing the steam-pressure. But this is not the case when running with
the throttle closed. The circulation in the boiler is then so sluggish,
that the temperature of the water may be reduced many degrees, while
the steam continues to show its highest pressure.
Writers on physical science tell us that the temperature of water and
steam in a boiler is always the same, and varies according to pressure;
that, at the atmosphere’s pressure, water boils at 212 degrees,
and produces steam of the same temperature. At 10 pounds above the
atmospheric pressure, the water will not evaporate into steam until it
has reached a temperature of 240 degrees, and so on: as the pressure
increases, the temperature of water and steam rises. But under all
circumstances, while the water and steam remain in the same vessel,
their temperature is the same. This is an acknowledged law of physical
science; yet every locomotive engineer of reflection, who has run on a
hilly road, knows that circumstances daily happen where the law does
not hold good.
FALL OF BOILER-TEMPERATURE NOT INDICATED BY THE STEAM-GAUGE.
If an engine, of the class represented as pulling our train, passes
over the top of the grade with half an inch of water in the glass,
there will be about 700 gallons in the boiler. Now, suppose it runs
down the hill without using steam, and keeps pumping till the water
rises six inches in the glass, there will be about 200 gallons more
water in the boiler. It is no unusual thing to do this with a mild
fire, and yet have no diminished tension of steam shown by the
gauge, although 200 gallons of water of about 60 degrees have been
injected amongst 700 gallons at 361 degrees, the temperature due to a
steam-pressure of 140 pounds. This ought to reduce the mean temperature
below 300 degrees, yet the pointer of the steam-gauge keeps indicating
140. That the pressure of steam and the temperature of the water do not
accord, is shown directly the throttle is opened to perform work. The
brisk circulation due to the rush of steam through the dry pipe now
brings the temperature of water and steam to equilibrium, and backward
the index of the steam-gauge travels. The steam-pressure goes back
faster than is due to the supply drawn for the cylinders; because the
latent heat of the steam passes into the water, helping to bring the
whole contents of the boiler to an even temperature.
SOME EFFECTS OF INJUDICIOUS BOILER-FEEDING.
Meanwhile, with an engine operated in this fashion, the train will
probably stand for fifteen minutes, till sufficient steam is raised to
proceed with.
The fact that newly injected water does not immediately rise in
temperature to the heat indicated by the pressure-gauge, can also be
tested by filling up a boiler with an injector while the engine is at
rest on a side-track. Working an injector causes greater circulation
than feeding with a pump, and the water goes into the boiler at a
higher temperature. For this reason the injector is superior to the
pump as a feeding-medium. But, if the engineer pulls out directly after
filling up the boiler with an injector, the steam will go down a few
pounds, no matter how good a fire may be on the grates.
On level roads, the pump or injector should be set to supply the needs
of the boiler; and a skillful engineer can regulate this so well, that
the foot-cock has seldom to be moved. The best results in getting
trains over the road, and in preserving boilers, are obtained in this
way. The runner who adopts the intermittent system of feeding is always
in trouble, or, as the boys say, “he is always nowhere.”
CAREFUL FEEDING AND FIRING PRESERVE BOILERS.
A case where the conservative effect of careful firing and feeding was
strikingly illustrated, came under the author’s notice a year or two
ago. During the busiest part of the season, the fire-box of a freight
engine belonging to a Western road became so leaky that the engine was
really unfit for service. Engines, like individuals, soon lose their
reputation if they fail to perform their required duties for any length
of time. This engine, “29,” soon became the aversion of train-men. The
loquacious brakeman, who can instruct every railroad-man how to conduct
his business, but is lame respecting his own work, got presently to
making big stories out of the amazing quantity of water and coal that
“29” could get away with, and how many trains she would hold in the
course of a trip. The road was suffering from a plethora of freight,
and extreme scarcity of engines; and on this account the management was
reluctant to take this weakling into the shop. So the master mechanic
turned “29” over to Engineer Macleay, who was running on a branch
where delays were not likely to hold many trains. Mac deliberated
about taking his “time” in preference to the engine, which others had
rejected, but finally concluded to give the bad one a fair trial. The
first trip convinced the somewhat observant engineer that the tender
fire-box was peculiarly susceptible to the free use of the pump, and
to sudden changes of the fire’s intensity of heat. So he directed the
fireman to fire as evenly as possible, never to let the grates get bare
enough to let cold air pass through, to keep the door closed except
when firing, to avoid violent shaking of the grates, and never to
throw more than three or four shovelfuls of coal into the fire-box at
one time. His own method was, to feed with persistent regularity, to
go twice over heavy parts of the division in preference to distressing
the engine by letting the water get low, and then filling up rapidly.
This system soon began to tell on the improved condition of the
fire-box. The result was, that, within a month after taking the engine,
Mac was pulling full trains on time; and this he continued to do for
five months, till it was found convenient to take the engine in for
rebuilding.
OPERATING THE DAMPERS.
According to the mechanical dictionary, a damper is a device for
regulating the admission of air to a furnace, with which the fire can
be stimulated, or the draught cut off, when necessary. Some runners
regard locomotive dampers in a very different light. They seem to think
the openings to the ash-pan are merely holes made to let air in, and
ashes out; that doors are placed upon them, which troublesome rules
require to be closed at certain points of the road to prevent causing
fires. Those who have made their business a study, however, understand
that locomotive dampers are as useful, when properly managed, as are
the dampers of the base-burner which cheers their homes in winter
weather. To effect perfect combustion in the fire-box, a certain
quantity of oxygen, one of the constituents of common air, is required
to mix with the carbon and carbureted hydrogen of the coal. The
combination takes place in certain fixed quantities. If the quantity
of air admitted be deficient, a gas of inferior calorific power will
be generated. On the other hand, when the air-supply is in excess of
that needed for combustion, the surplus affects the steam-producing
capabilities of the fire injuriously; since it increases the speed
of the gases, lessening the time they are in contact with the
water-surface, and a violent rush of air reduces the temperature of
portions of the fire-box below the heat at which carbureted hydrogen
burns.
LOSS OF HEAT THROUGH EXCESS OF AIR.
In the fire-boxes of American engines, where double dampers are the
rule, far more loss of heat is occasioned by excess of air than there
is waste of fuel through the gases not receiving their natural supply
of oxygen. The blast from the nozzles creates an impetuous draught
through the grates; and when to this is added the rapid currents of air
impelled into the open ash-pan by the violent motion of the train, the
fire-box is found to be the center of a furious wind-storm. The excess
of this storm can be regulated by keeping the front damper closed, and
letting the engine draw its supply of air through the back damper. When
the fire begins to get dirty, and the air-passages between the grates
become partly choked, the forward damper can be opened with advantage.
So long as an engine steams freely with the front damper closed, it
is an indication that there is no necessity for keeping it open. With
vicious, heavy firing, all the air that can be injected into the
fire-box is needed to effect indifferently complete combustion; and the
man who follows this wasteful practice can not get too much air through
the fire. Consequently, it is only with moderately light firing that
regulation of draught can be practiced. Running with the front damper
open all the time is hard on the bottom part of the fire-box, and the
ever-varying attrition of cold wind is responsible for many a leaky
mud-ring.
LOSS OF HEAT FROM BAD DAMPERS.
In Britain, where far more attention has been devoted to economy of
fuel than has been bestowed upon the matter this side of the Atlantic,
locomotives are provided with ash-pans that are practically air-tight,
and the damper-doors are made to close the openings. In many instances,
the levers that operate the dampers have notched sectors, so that the
quantity of air admitted may equal the necessities of the fire. British
locomotives, as a rule, show a better record in the use of their fuel
than is found in American practice; and a high percentage of the saving
is due to the superior damper arrangements.
Imagine the trouble and expense there would be with a kitchen-stove
that had no appliance for closing the draught! Yet some of our
locomotive builders turn out their engines with practically no means of
regulating the flow of air beneath the fire.