lve to
change their position.

135. Q. Explain what takes place when an automatic emergency application
is made.

A. Any sudden reduction of brake pipe pressure is felt on the brake pipe
side of the equalizing piston 26 and will cause it and the slide valve
31 to move to the extreme right, compressing the graduating spring 60.
(See Fig. 11.) In this position pressure chamber air can flow to the
application cylinder only as the application chamber is now cut off.
This will cause a quick rise of pressure in the application cylinder,
forcing the application piston and its valves to full application
position, admitting main reservoir air to the brake cylinders and
applying the brake. In emergency position of the automatic brake valve
there is a small port in the rotary valve, called the blow-down timing
port, through which main reservoir air is free to flow to the
application cylinder "g" through the application cylinder pipe "II",
causing a rise of pressure equal to the adjustment of the safety valve.

136. Q. At what pressure is the safety valve adjusted?

A. At sixty-eight pounds.

137. Q. What is the purpose of the quick action cap, and where is it
located?

A. Its purpose is to assist the brake valve in venting brake pipe air
when an emergency application of the brake is made, and is located on
the brake pipe side of the distributing valve in place of the plain cap.
(See Figs. 8 and 11.)

138. Q. Explain the operation of the quick action cap.

[Illustration: Fig. 11. Emergency Position of No. 6 Distributing
Valve with Quick-Action Cap.]

A. In an emergency application, the equalizing piston 26 moves to the
extreme right, the knob on the piston strikes the graduating stem 59,
causing it to compress the graduating spring 46, and move the slide
valve 48 to the right, opening port "j".

[Illustration: Fig. 12. Independent Application.]

Brake pipe pressure in chamber "p" flows to chamber "X", pushes down
check valve 53, and passes to the brake cylinders through port "m" in
the cap and distributing valve body. When the brake cylinders and brake
pipe pressures equalize, check valve 53 is forced to its seat by spring
54, thus preventing air in the brake cylinders from flowing back into
the brake pipe. When a release of the brake occurs and piston 26 is
moved back to its normal position, spring 46 forces graduating stem 59
and slide valve 48 back to release position.

139. Q. Explain the operation of the distri