ENGINEER'S BRAKE VALVES 119 



in the rotary valve connects with port in the seat. There- 

 fore, when the double cut-out cock is turned to the position 

 that cuts out the brake pipe, it makes a direct opening from 

 port i in the distributing valve through the double-heading 

 pipe to the atmosphere, and is the passage through which the 

 air escapes from the application chamber when the automatic 

 brakes are being released. 



Release Position. The purpose of release position is to 

 provide a large and direct passage from the main reservoir 

 to the brake pipe, to permit a rapid flow of air into the latter 

 to insure a quick release and recharging of the train brakes, 

 but without releasing the engine and tender brakes. 



Air at main-reservoir pressure flows through port a in the 

 rotary valve to port b in the valve seat and to the brake pipe. 

 At the same time, port j in the rotary valve registers with the 

 equalizing port g in the valve seat, permitting main-reservoir 

 pressure to enter chamber D above the equalizing piston. 



In this position, port 5 in the rotary valve registers with 

 warning port r in the seat and allows a small quantity of air 

 to escape into the exhaust cavity ex, which makes sufficient 

 noise to attract the engineer's attention to the position in 

 which the valve handle is standing. If the handle is allowed 

 to remain in this position, the brake system will be charged 

 to main-reservoir pressure. To avoid this, the handle must 

 be moved to running or holding positions. The small groove 

 in the face of the rotary valve that connects with port s, extends 

 to port p, in the valve seat, allowing main-reservoir pressure to 

 flow to the excess-pressure head of the pump governor. 



Holding Position. The holding position is so named because 

 the locomotive brakes are held applied, as they are in release 

 position, while the train brakes feed up to the feed- valve 

 pressure. All ports register as in running position, except port I, 

 which is closed. Therefore, the only difference between run- 

 ning and holding positions is that in the former the application 

 chamber is open to the atmosphere, while in the latter it is 

 not. 



Emergency Position. The emergency position is used when 

 the most prompt and heavy application of the brakes is 

 desired. Port x in the rotary valve registers with port c in 



