NO. 6 ET LOCOMOTIVE BRAKE 265 



When the application -cylinder pressure is reduced to 75 lb., a 

 main-reservoir pressure of 130 lb. will force air into the applica- 

 tion cylinder through the small port n in the rotary valve of the 

 automatic brake valve as fast as it can escape from the applica- 

 tion cylinder through the small port x in the equalizing valve, 

 so that a pressure of 75 lb. will be maintained in the application 

 cylinder and consequently in the locomotive-brake cylinders. 

 When the equalizing piston 26 and valves 28 and 31 are 

 in emergency position, and the application piston and valves 

 5 and 16 have moved to service position and then lapped 

 the ports in the application-valve and exhaust-valve seats, 

 the distributing valve is said to be in automatic emergency 

 lap position. 



If the emergency application is caused by a burst hose, by the 

 opening of a conductor's valve, or by the train parting, the 

 automatic brake valve must be lapped to save main-reservoir 

 air. Under these conditions the distributing valve will operate 

 in the same manner as previously explained, but, since the auto- 

 matic brake valve is not in emergency position, no main-reser- 

 voir air will pass to the distributing valve through the applica- 

 tion-cylinder pipe, therefore, the brake-cylinder pressure will 

 not be as high as if the application were made by the automatic 

 brake valve. In high-speed service carrying 110 lb. of brake- 

 pipe pressure, the brake-cylinder pressure will be reduced to 

 68 lb., this being governed by the safety valve. If only 70 lb. 

 of brake-pipe pressure is carried, the resulting brake-cylinder 

 pressure will be but 50 lb. After a full-service application, if 

 a greater brake-cylinder pressure is necessary, main-reservoir 

 pressure may be conveyed to the application cylinder of the 

 distributing valve by placing the automatic brake valve in 

 emergency position. 



Automatic Release After an Emergency Application. The 

 automatic brake valve is operated in the same manner to 

 release the brakes after an emergency application as after a 

 service application, but the effect on the distributing valve is 

 somewhat different. When the H-6 brake valve is placed in 

 release position, the brake-pipe pressure in chamber p of the 

 distributing valve is increased above that in the equalizing- 

 valve chamber and the equalizing piston and the valves 28 and 



