A. Probably no more difficult question to answer could be asked, as the
service braking of a train must be governed by the condition surrounding
it; meaning, relation of brake power to weight of train; rail condition;
speed and grade. To prevent breaking in two and other damage, freight
trains should be stopped with one brake application, which may consist
of one or more reductions, up to full service. Generally speaking, the
slack should be bunched before the brakes are applied, and this may best
be done by gradually closing the throttle and allow the train to drift
some little distance. The first reduction should not be less than five
or more than eight pounds. The brakes should be applied as soon as
possible after the slack has had time to run in, the object of this
being to have the train slack adjusted while the brakes are least
effective, due to the high speed and light brake cylinder pressure. It
is at this time that damage may be done to the train; therefore, if the
slack be kept bunched or stretched, as the case may be, the possibility
of train damage will be greatly reduced. To obtain this condition,
complete the stop with as light a brake application as permissible. When
the brake is first applied, the engineer should note if the tendency be
for the train slack to bunch or stretch, and having learned that the
train is inclined to stretch badly, he can keep the slack stretched by
making the initial brake pipe reduction before shutting off steam, then
shut off steam gradually as soon as the brake valve exhaust port closes,
the object in working steam being to prevent the slack running in as the
application is made, which in turn will prevent severe jerks due to the
slack running out as the rear brakes become effective. Where the
locomotive is equipped with an independent release feature, its brakes
should be kept released while the train brakes are being applied.
198. Q. Is it considered good practice to attempt making an accurate
stop with a freight train?
A. It may be said to be very poor judgment to attempt making an accurate
stop with a freight train, such as a spot stop for coal or water or a
close-up stop for a switch. Some engineers seem to think that it is a
reflection on their judgment if an accurate stop is not made, but this
is not so, due to the fact that no two trains brake alike, and the same
train may not brake twice alike. Therefore, aim for a smooth stop, which
means a safe stop, leaving accuracy out of the question until the time
comes when you are handling a passenger train.
199. Q. What precaution should be taken after a stop is made on a heavy
grade?
A. The air brakes should be released and a sufficient number of hand
brakes applied to hold the train. Never rely on the air brake to hold
the train for any length of time.
200. Q. Why is it dangerous to repeatedly apply and release the brakes
without giving time for the auxiliaries to fully recharge?
A. As time is required to charge the auxiliaries, the feed groove in the
triple valve being small, if the brakes are repeatedly applied and
released without giving time to recharge, the braking power will be
lost.