Brake Tests

95 was the same throughout the series of tests covered by this report. The pneumatic emergency function of the valve has subsequently been improved, however, by a slight modification of the emergency portion of the device and the improved results thereby obtained are described in Par. 241. Mixed Equipment Stops. 200 In order to determine how well the operation of the UC pneumatic equipment harmonizes with that of the PM equipment, when mixed in various ways in the same train, a number of tests were made, both service and emergency stops, and the action of the brakes and of tlie train as a whole during a stop carefully noted. 201. All service stops, no matter what the arrangement of the UC and PM equipments, were free from objectionable shock. They in- dicated that the gradual introduction into service of cars with UC equipment will result in an improvement in the handling of trams generally, without introducing any undesirable features of operation or manipulation. 202. The improvement in the release of the brakes was particu- larly noticeable, showing that not only was the release improved in proportion to the number of UC equipment cars in the train, but also that the more UC equipment cars, the greater was the certainty in „.leasing the PM equipment cars used in the same train. That is to say, the UC equipment actually assisted to insure a certain and prompt release of the PM brakes. (See Par. 118.) EMERGENCY TEST WITH Mixed EQUIPMENT Trains. 203 The UC equipment was used with its standard nominal brak- ing power of 150 per cent. Under these conditions shocks and somewhat rough stops were experienced with certain train make-ups and at some speeds which, although more severe than would be desirable in ordinary train service, were not severe enough to be prohibitive, considering the necessity for and the infrequency of emergency applications and the material share which the relatively low braked locomotive contributed during these shocks.. 204. In this connection it should be noted that if the UC equip- ment is arranged to give a nominal braking power of only 125 per cent, instead of 150 per cent, (as used during the mixed train tests) its braking power will be much closer to the emergency braking power developed by the PM equipment on cars now in service. The use of 125 per cent, emergency braking power should, therefore, practically eliminate the possibility of the retardation on different cars in the same train being sufficiently great to cause shocks of any consequence. TRAIN Stops. Emergency STOP AT 30 M.P.H. 205. High braking power on locomotive and mixed UC and PM equipments on cars as follows:—