TM 55-203
retarded only on the first 30 cars, those beyond
releasing at the normal rate; but as those at the head
b. Quick-Action Feature. This functions when a
end commence to release first and those at the rear end
emergency rate of brake pipe reduction takes place
last, the result is a practically uniform release on the
from any cause. This feature insures a quick drop of
train as a whole.
brake pipe pressure (by opening direct communication
between the brake pipe and the brake cylinder) at the
e. Uniform Recharge Feature. This feature insures
triple valve which in turn causes the next triple valve to
that the recharge will be nearly uniform throughout a
function in the same manner, thereby propagating the
long train, so that the tendency of the head brakes to
emergency rate of brake pipe reduction and securing
reapply is reduced when the brake valve is returned to
maximum brake cylinder pressure through the entire
running position, and a more nearly uniform
train at a fast rate.
reapplication short after a release is possible. This
uniform recharge is brought about by decreasing the
c. Quick-Service Feature. This feature produces
size of the charging port or grooves when the triple
uniform and quick application of the brakes in service
valve is in retarded release position (the piston sealing
applications on long trains and reduces shocks. There
against the slide valve bush, except at one point where
are two service positions of the triple valve ports, quick
there is a feed groove smaller than that in the piston
service and full service. When the valve is in quick-
bush), and as this can only be when the pressure in the
service position, the usual service port is only partially
brake pipe is higher than that in the auxiliary reservoir, it
open and in addition the quick-service ports are in
is seen that where the pressure is the highest the
registration so that air is vented from the brake pipe into
charging ports ,are the smallest, while where the
the brake cylinder, which hastens the transmission of
pressure is the lowest, as at the rear end, the charging
the reduction through a train. When the parts are in full-
ports are the largest; thus, the recharge is more uniform
service position, the service port is fully open and the
because the high pressure will charge as quickly through
quick-service ports do not register. The proper position
a small port as the low pressure will through a large port.
is automatically assumed by the triple valve. On short
trains the brake pipe pressure will fall more rapidly for a
certain reduction at the brake valve than on long trains.
8-21.
Equipment Parts
Consequently, when the train is long the triple valve
ports will be stopped in quick-service position, as the
partial opening of the service port will permit the
a. General Following is a list of the parts which
auxiliary reservoir pressure to fall as rapidly as the
make up the single capacity K freight car brake
brake pipe pressure is reducing. But when the train is
equipment, with a short description of each. These parts
short, the triple valve ports will move directly to full
service position as the rate of reduction is such that the
paragraphs.
full opening of the service port is necessary in order that
the auxiliary reservoir pressure may keep pace with that
b Triple Valve Type K. This has connections
in the brake pipe.
through its seat on the auxiliary reservoir to the brake
cylinder and the auxiliary reservoir, and a pipe
d. Uniform Release Feature. This brings about
connection to the brake pipe branch pipe. It operates in
uniform release of the brakes on long trains and
response to a suitable increase or decrease in brake
,lessens the possibility of shocks during the release
pipe pressure, so as to charge the auxiliary reservoir by
operation. A spring is placed on the auxiliary reservoir
opening communication to it from the brake pipe; apply
end of the triple valve with a projecting stem which
the brakes in service, by allowing the compressed air
stops the triple valve slide valve in what is called full
stored in the auxiliary reservoir to flow into the brake
release position, unless the pressure in, the brake pipe
cylinder; and release the brakes, by allowing the lair in
is raised materially higher than that of the auxiliary
the brake cylinder to escape to the atmosphere.
reservoir. When the pressure in the brake pipe is in-
creased about 3 pounds above that of the auxiliary
c. Brake Cylinder. This has a piston and rod is
reservoir, the spring is compressed and the slide valve
connected through the brake levers and rods to the
consequently makes a further inward travel to retarded
brakeshoes that when the piston is forced
thereby making the release of brake cylinder pressure
slower than before. In a 50-car train or longer, it is
impossible to raise the brake pipe pressure 3 pounds
higher than the auxiliary reservoir for more than 30 cars
back in the train; therefore, the brake cylinder exhaust is
8-36
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