Brake Tests

114 GENERAL Comparison of SERVICE APPLICATIONS. UC Pneumatic and Electro-Pneumatic Equipments. 249. Fig. 44-A for the improved valves corresponds to Fig. 44 for the valves used during the test and brings out still more clearly the gain in uniformity of response in service brake applications. Emergency APPLICATION. UC Pneumatic Equipment. 250. The relatively slow rate of propagation of serial quick action with the UC pneumatic equipment as used during the tests (Pars. 193 and 194, Fig. 55), tended to produce undesirable slack action and rough emergency stops as already explained. 251. Improvement in this particular is especially desirable and has been accomplished as shown by indicator cards (Fig. 55-A). It will be seen that the pneumatic serial action with the improved valves, Fig. 55-A is slightly better than for the PM equipment as shown in Fig. 53 and that this has been accomplished without any sacrifice in the time to build up the maximum cylinder pressure which was charac- teristic of the valves used during the test (Fig. 55). 252. This material reduction in the time required for the transmis- sion of quick action throughout the train will correspondingly minimize the effects of such slack action as may be unavoidable due to the effect of the locomotive and whatever slack may exist between the cars? Electro-Pneumatic Equipment. 253. In Fig. 56-A are shown indicator cards for an electro-pneumatic emergency application with the improved valves. These are practic- ally identical to those shown in Fig. 56, showing that the action of the improved valves in electro-pneumatic applications remain unchanged from the satisfactory performance observed during the tests. General Comparison of Emergency Application. UC Pneumatic and ELECTRO-PNEUMATIC Equipment. 254. Fig. 57-A shows curves for the improved valves for comparison with those of Fig. 57 for the valves used during the test. The perform- ance of the electro-pneumatic equipment in the two cases is substantially identical while in the case of the pneumatic equipment a marked im- provement is shown by the material reduction in time element for the curves of Fig. 57-A compared with those of Fig. 57.