Brake Tests

23 Train Slack Action Recorder. 55. The relative movement or slack action between cars was recorded by an instrument shown in Fig. 16. The drum was driven by a spring motor at constant speed. The instrument was securely fastened to the floor of one car and the pencil of the device was connected by a wire to the adjacent car. This wire was always kept under tension by a spring. As long as there was no relative motion between these adjacent cars the pencil remained stationary and traced a line parallel to the normal datum line on the diagram. Any change in slack between these cars caused a corresponding movement of the pencil, tracing a record similar to that shown in Fig. 86. 56. These instruments were located between the first and second, sixtli and seventh, and eleventh and twelfth cars. 57. A time record was provided for these instruments so that it was possible to analyze the slack action with respect to time at differ- ent points in the train. (Chapter VI.) Brake Shoe Pressure. 58. Special apparatus was developed to measure the actual pres- sure delivered to the brake shoes. This apparatus, and the results obtained are described in detail in Chapter IV. Track. 59. The tests were made on the south bound track of the Atlantic City Division of the W. J. & S. R. R. The portion of the track over which the braking was done was level, and part of a tangent about 25 miles long terminating at Absecon Station, a slight descending (0.3 per cent.) grade approaching the measured test track was in favor of the train attaining speed. The point at which the brakes were applie was 2,880 feet north of mile post 9. 60. The track for a distance of 5,000 feet south of the zero point was wired for circuit breakers, which were placed at intervals of 25 feet up to 1,200 feet from the zero point, and at intervals ol 50 feet from there on to the 5,000 foot point. Preceding the zero point, eight circuit breakers were located, 66 feet apart from which the initial speed of train (speed at the trip) was determined. 61. A cabin, located near the zero circuit breaker, contained the clock and chronograph (Fig. 17) from which in connection with t e track circuit breakers, the speed of the train before and during the stop was obtained. A diagram of the complete track apparatus and chron ograph connections is shown in Fig. 18.