Brake Tests

110 brakes being applied on the head end of the train beyond the closed angle cock just as fully as were those behind the closed angle cock in which portion of the train the emergency application originated. 239. It will be understood from what has been said of the operation of the electro-pneumatic equipment in service or emergency applica- tions that if an angle cock is closed after a train is charged the brake can be applied electrically by the engineman, either in service or emer- gency, but when so applied it will be impossible to release the cars back of the closed angle cock. This would serve notice to the engineman 4 _21. C that something was wrong. 240. It should not be understood that this feature protects in any way against the failure to open an angle cock when an empty car or train is being charged up as it is self-evident that until the brake system on such cars is charged the brake mechanism is useless. SUBSEQUENT DEVELOPMENT AND FURTHER TESTS. 241. The universal valve as originally applied was used throughout the tests without any modification whatever. But special attention was called in paragraphs 169, 194 and 199 to certain features of its operation, the results of which suggested the possibility of improve- ment without material modification. 242. These indications received the attention of the manufacturers and as a result slight modifications in the construction of the universal valve were made. However, rather than introduce factors which would affect the comparative value of the test results it was decided to com- plete the official program of the tests with the valves as first supplied, it being considered that the improvement accomplished by the modi- fications referred to could be amply illustrated by the records of the performance of the improved valve in laboratory tests. In fact, it is pertinent to point out here that laboratory test records, when properly analyzed, furnish all the information that can be desired with regard to the efficiency and effectiveness of the air brake apparatus so far as its immediate function (controlling of the air pressure in the reservoirs and brake cylinders) is concerned. 243. Accordingly, the records of the laboratory tests of the im- proved universal valve as now going into service on P. R. R. P-70 cars are shown in Figs. 42-A, 43-A, 44-A, 55-A, 56-A and 57-A, that the per- formance of the improved valve may be directly compared with that of the valves used during the tests. Full Service Brake APPLICATION. Pneumatic Equipment. 244. A comparison of Fig. 42-A, with Fig. 42 indicates clearly the improvement in uniformity of pneumatic service application which has been accomplished.