180 TRIPLE VALVES 



to normal release position and exhaust through the full size 

 of the exhaust port. The relative sizes of the restricted and 

 normal exhaust ports are such that the head and rear triples 

 exhaust their brake cylinders in approximately the same time; 

 consequently, the brakes release uniformly throughout the 

 train and in less than half the time required by H triples. 

 This results in much smoother operation, and greatly reduces 

 the shocks and consequent break-in-twos, slid flat wheels, and 

 damage to equipment and lading. 



To move a triple valve to retarded-release position, the 

 brake-pipe pressure must be raised about 3 Ib. above auxiliary- 

 reservoir pressure. On a long train it has been found impossible 

 to obtain this difference of pressure beyond about thirty cars 

 back of the engine; consequently, the triple valves beyond that 

 point do not go to retarded-release position. 



Uniform-Recharge Feature. The object of the uniform-re- 

 charge feature is to increase the rate of rise of brake-pipe 

 pressure in the rear end and to make the auxiliary reservoirs 

 throughout the train recharge at approximately the same rate, 

 thus insuring a more prompt action of the rear-end brakes and 

 preventing the head brakes from reapplying when the brake 

 valve is moved to running position. When H triple valves are 

 used, all the feed -grooves are of the same size; consequently, 

 the head auxiliaries overcharge on account of the higher 

 brake-pipe pressure they are subjected to with the brake valve 

 in release position. Thus, when the brake valve is moved 

 to running position, the pressure in the head end of the brake 

 pipe drops until it equalizes with the lower pressure in the rear 

 end of the brake pipe and the head-end brakes reapply. 



With K triple valves, the feed-groove (located in the ridge 

 on the back of the triple position) through which the auxiliary 

 charges when the triple is in retarded-release position, is about 

 half as large as the feed-groove used when the triple is in 

 normal release position; consequently, the head-end auxiliaries 

 charge through a restricted opening that compensates for the 

 higher brake-pipe pressure in the head end and permits more 

 of the air passing into the brake pipe to flow to the rear end 

 of the train, charging the brake pipe to a higher pressure, and 

 releasing and recharging the brakes more promptly. 



