STEAM LOCOMOTIVE ENGINEMAN’S. Manual - part 31

Chapter 13: - General Westinghouse Brake – Questions and Answers

If a brake fails to apply, what may be the cause?

This may be due to any one of the following causes.

Auxiliary reservoir not charged, due to the brake being
cutout or the feed grooves blocked up. Defective triple
piston rings, which will allow air to pass from the auxiliary
reservoir without moving the triple – this is more likely to
occur at the rear of a long train; triple nipple exhaust made
up.

What test can be made to determine if the triple piston
rings are satisfactory?

Apply the brake and then open the release valve for a
second, if the rings are in good order, the brakes should then
release.

What would be the effect of a leaky graduating valve?

When a service reduction is made and the triple valve is at
lap position, the flow of air from the auxiliary to the brake
cylinder would continue until the auxiliary pressure was
below that in the train pipe, when the triple valve would be
moved to release position and the brake would release.

If the pin of the graduating valve should break, how
would this affect the triple?

There would be no effect in the release position but, when a
train pipe reduction was made to apply the brake, the triple
piston would move while the graduating valve would remain
closed on its seat, due to the broken pin, thus cutting off
auxiliary pressure to the brake cylinder; consequently, there
would be no application of that brake.

What is the standard brake piston travel on engines and
tenders?

Minimum

Max. (when leaving a depot)

Engines

2 ½ in.

3 ½ in.

Tenders

4 ½ in.

7 in.

What will be the effect if the brake piston travel is too
long?

If the piston travel is too long, it will take greater reductions
to cause the auxiliary reservoir and brake cylinder pressures
to equalize, and when equalized the pressure is low, brought
about by auxiliary pressure expanding into a larger space,
resulting in a loss of brake power.

Chapter 13: - General Westinghouse Brake – Questions and Answers

When the volume of the brake cylinder is increased due to a
long piston travel, it means that less pressure is obtained on
the brake piston for a given reduction than would be the
case if the travel were shorter.

Why is it a dangerous practice to apply and release
brakes repeatedly, without fully charging auxiliary
reservoirs?

Each time the brake is applied, air from the auxiliary
reservoir passes to the brake cylinder, thus reducing the
pressure. At the release of the brakes the triple valve is
moved to release position, in which the auxiliary reservoir is
charged.

Should a further application be made before the auxiliary is
fully recharged there will be a lower pressure in the auxiliary
at the second application, and a heavier train pipe reduction
will be required to apply the brakes.

If these applications are continued, succeeding reductions
will have to be made heavier to apply the brake. Auxiliary
reservoir pressure will become too low and control of the
brakes will be lost.

How long does it take to charge an auxiliary reservoir?

It would take 70 seconds to build up to 70 lb per square inch
in the auxiliary reservoirs, equal to 1 lb per second, providing
the standard train pipe pressure was available at the triple
piston.

Why are the feed grooves not made larger, so as to
permit the auxiliary reservoir to be charged faster?

If the feed grooves were made too large, a heavy reduction
of train pipe pressure would have to be made to apply the
brakes. If a light reduction were made, air from the auxiliary
reservoir would flow through the feed grooves into the train
pipe without moving the triple piston.

Furthermore, on release of the brakes on a long train, the
train pipe pressure, after forcing the leading triples to release
position, would feed the front auxiliary reservoirs so quickly
that the increased pressure would not reach the rear of the
train, and would fail to release the brakes on that portion of
the train.

Chapter 13: - General Westinghouse Brake – Questions and Answers

How would it be known if the Westinghouse Tap was
closed between the engine and the first vehicle?

By observing the strength and duration of the train pipe
exhaust, when applying the brake. The exhaust of the air is
proportional to length of train. Should the cock be closed,
the equalising piston will promptly lift, but instead of the air
discharge being of a normal duration, it will quickly weaken
or cease.

When necessary to raise the train pipe pressure to 90 lb
with the M3 feed valve, how will this be carried out?

Place the Automatic Brake Valve in running position, chalk
mark the adjusting screw and its casing, and then turn the
adjusting screw upwards three quarters of a turn, when 20 lb
extra pressure will be indicated on the black hand of the
small gauge.

Annex A: - Figures

ANNEX A

FIGURES AND DIAGRAMS

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