Brake Tests

81 and therefore the emergency application is made earlier in the stop than with the pneumatic equipment. 179. The result of these several advantages is to produce a much shorter stop (about 500 * feet, Fig. 95) than with a full service electro- pneumatic application. This shows clearly the increased safety factor of the improved brake equipment over that now in service for conditions requiring the greatest possible stopping power after a service application of the brakes has been started. 180. As a matter of interest a composite brake cylinder indicator card and deceleration curve for both the PM and electro-pneumatic equipment have been plotted on Fig. 48 to show the effect of emergency application following a partial service application. 181. A comparison of the curves for the PM and electro-pneumatic equipment shows clearly the quicker rate of rise of service brake cylinder pressure and the quicker and much more effective brake cylinder pres- sure obtained with the new equipment when the emergency application is made. The results of this action are shown in the more prompt rise of and the higher value reached by the deceleration curve for the electro- pneumatic equipment and the correspondingly shorter stop obtained. Full Service Followed by Emergency Application. PM Equipment. 182. Fig. 49 shows a full service application of the brakes fol- lowed by an emergency application using the PM equipment. This is practically the same as Fig. 41, which illustrates the action of the PM equipment when a full service application is made without any emergency application following. The curves of Fig. 49 show that the making of an emergency application followmg a full service appli- cation with the PM equipment produced no appreciable effect. This is borne out by a comparison of the length of the stop in the two cases. (Fig. 95.) 8 UC PNEUMATIC EQUIPMENT. 183. Fig. 50 shows that serial quick action, an emergency rate of application and maximum emergency brake cylinder pressure are obtained when an emergency application is made, following a full service application with the UC pneumatic equipment. 184. However, the longer the time required to make the full service application compared with that required to make a partial service application results in a greater distance being traveled by the train before the emergency application occurs. Therefore, the stop is longer (by about 80 feet) than when an emergency application follows a partial instead of a full service application. The length of stop with an emergency application following a full service application with the UC pneumatic equipment is over 200 feet shorter than the full service only. • Nore.—Speed 60m.p.h. understood for this and all similar references unless otherwise stated.