TRIPLE VALVES 217 



auxiliary-reservoir pressure was confined in the supplementary 

 reservoir during the time that the brakes were applied, this 

 pressure now assists in recharging the auxiliary reservoir. 

 The auxiliary reservoir, therefore, begins to recharge from two 

 sources from the brake pipe through the feed-groove and 

 through ports y and j, and from the supplementary reservoir, 

 equalizing with it through ports x and k. As the supplement- 

 ary reservoir is charged only to standard auxiliary-reservoir 

 pressure, it only assists in quickly recharging up to the point 

 of equalization of the two reservoirs, after which both reser- 

 voirs must be recharged together. As the supplementary 

 reservoir is about two and one-half times the size of the aux- 

 iliary reservoir, every pound of pressure it is reduced in charg- 

 ing raises auxiliary pressure 2? Ib. Thus, after a 21-lb. 

 reduction from 90 Ib., equalization will occur when supple- 

 mentary-reservoir pressure is reduced 6 Ib., or to 84 Ib.; aux- 

 iliary pressure will be raised 15 Ib., or from 69 to 84 Ib. The 

 reservoirs, therefore, will equalize for about two-thirds of the 

 recharge, and will have to be recharged from the brake pipe 

 for the other third ; but as this occurs through the feed -groove t 

 and the quick-recharge port y, the time of full recharge is 

 much less than the time for the old triples. During recharge 

 and while graduating the release of the brakes, the pressures 

 on the brake-pipe and auxiliary-reservoir sides of the main 

 piston 4 are nearly balanced. This insures a prompt response 

 of the brakes to any reduction or increase of brake-pipe pressure, 

 irrespective of what operation may have just preceded. If, 

 after releasing the brakes, the brake valve is placed in run- 

 ning position, the triple piston will remain in release position, 

 and the auxiliary and supplementary reservoirs will be fully 

 recharged. 



Quick-Service Position. When a service reduction is made 

 in brake-pipe pressure, the pressure in chamber H is reduced 

 faster than air can pass through the feed-groove *. As the 

 auxiliary-reservoir pressure in chamber R is then greater than 

 that in chamber H, the main piston 4 will be moved to the 

 left, closing the feed -groove i, and shutting off comnranica- 

 tion between the brake pipe and the auxiliary reservoir. The 

 graduating valve moves with the main piston 4 and closes 



