TRIPLE VALVES 179 



manner similar to a quick-action application. With a train 

 of all K triple valves, this feature very materially reduces the 

 time of application below that required by H triples; applies 

 the brakes more uniformly throughout the train; insures the 

 application of all the brakes with light brake-pipe reductions; 

 gives a higher brake-cylinder pressure, increasing the brake- 

 cylinder pressure about 1 Ib. on equalization with standard 

 piston travel; and effects a considerable saving in air. By 

 venting brake-pipe air into the brake cylinders, the K triple 

 reduces the time of discharge of brake-pipe air from the brake- 

 valve exhaust for a given reduction considerably below the 

 time necessary with H triples. 



The quick-service feature operates only on trains of such 

 lengths that the volume of the brake pipe is too large for 

 brake-pipe pressure to be reduced at the proper rate through 

 the brake-valve exhaust. If the reduction can be made at 

 the proper rate, as with short trains, the quick-service feature 

 automatically becomes inoperative. 



Retarded- or Uniform-Release Feature. To release the 

 brakes, main-reservoir pressure is thrown into the brake 

 pipe, so as to cause a wave of pressure to flow from the head 

 end toward the rear. The head triples feel the impulse first 

 and move to release position quite 'an interval before the 

 rear triples. They cannot be prevented from going to release 

 position first; therefore, to get a uniform release of the brakes 

 throughout the train the exhaust port of the head triples is 

 restricted, which retards the exhaust of brake-cylinder air 

 sufficiently to permit the head and rear brakes to let go at 

 about the same instant. 



The object of the retarded- or uniform-release feature is 

 to retard the exhaust from the brake cylinders of the head 

 brakes so as to make the release of the brakes more uniform 

 throughout the train. With H triples, the head brakes begin 

 to release first. After a 15-lb. reduction on an eighty-car 

 train, they fully release 30 sec. before the rear brakes. With 

 K triples, the head triples move to release position first, 

 but about the first thirty triples are forced past normal 

 release to retarded-release position and their brake cylinders 

 release through a restricted port; only the rear triples move 



