Working ability of phosphoric iron brake shoes installed on EMU trains
The paper tackles the correlation problem of iron brake shoes' rig tests results to results obtained in their field tests employing the so called «abandonment» method implemented through compulsory uncoupling of experimental cut of cars at its prescribed speed. The research by the authors has found that in trial trips of an EMU train, equipped with type F iron brake shoes from two different manufactures with phosphorus content from 1.0 to 1.5 % (GOST 28186), the recorded brake equipment efficiency used to be 20 to 40 % lower than the calculated one while the force values were in practically full conformity with corresponding calculations' data (the difference didn't exceed 10 %). And this despite the fact that both manufactures' brake shoes under consideration have conformity certificates, meaning that they passed at least the prescribed rig tests (at 146 kN axle-load and 30 kN pressure force) and laboratory qualification (hardness tests and check of chemical composition). In accord with the planned test cycle there was carried out additional investigation involving brake shoes from two more manufactures. Irrespective of the fact that all the selected brake shoes met the GOST 28186 as related to hardness and chemical composition, their efficiency indices were essentially different in terms of braking distance and wear resistance. Notably the spread of braking distances could be observed during the rig as well as field tests. That is why the authors bring up the issue of improving current testing procedure.