TM 55-203
Figure 8-48. Quick-service lap position .
sure, as already explained. It is well known that in
pressure to build up more rapidly in chamber H of the
freight trains when the engineman releases the brakes,
triple valves toward the front end of the train than in
the rapidity with which the brake pipe pressure increases
those at the rear. As soon as the pressure is enough
on any car depends on the posi(tion of the car in the
greater than the auxiliary reservoir pressure remaining
train. Those cars toward the front, receiving the air first,
in chamber R after the application as above described,
will have their brake pipe pressure raised more rapidly
to overcome the friction of piston, graduating valve, and
than those in the rear. With the old standard apparatus,
slide valve, all three are moved toward the right until the
this is due to two things: the friction in the brake pipe;
piston stem strikes the retarding stem 31. The latter is
and the fact that the auxiliary reservoirs in the front
held in position by the retarding spring 33. If the rate of
begin to recharge, thus tending to reduce the pressure
increase of the brake pipe pressure is small as, for
head by absorbing a quantity of air and holding back the
example, when the car is near the rear of the train, it will
flow from front to rear of the train. The retarded-release
be impossible to raise the pressure in chamber H 3
feature of the type K triple valve overcomes the second
pounds higher than that in the auxiliary reser-
point mentioned, taking advantage of the first while
doing so. The friction of the brake pipe causes the
8-51
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