Brake Tests

131 292. Tests of this character were made both when the cars were running and standing but on account of the disturbing influences en- Fig. 75. BRAKE SHOE PRESSURE MEASURING DEVICE. As applied to the No. 3 clasp brake. countered during the running tests, it was decided to consider only the standing tests, for which the data obtained were more consistent. 293. The data plotted in Fig. 76 should not be understood to signify anything with respect to the rigging efficiencies in running tests, in fact, from observation of the behavior of different types of rigging when making stops it was evident that the efficiency of the transmission of the forces through the brake rigging were considerably different when making a stop than when a standing brake application was made, due to the different positions assumed by the brake shoes and levers, caused by pulling down truck springs and increase of piston travel. Furthermore, with the standard brake rigging considerable binding took place in the measuring device. This affected the accuracy of the readings and is the probable cause of the low efficiency shown in Fig. 76 for the standard brake rigging. Nevertheless, this curve is here given as a matter of information and to make the record of what was done complete. 294. With the other types of brake rigging, however, the results were remarkably consistent. In fact, by the aid of these records, it became possible for the first time to fix upon a logical basis for har- monizing the results obtained in road tests with those obtained in laboratory tests of brake shoes, as is described in Chapter VII.