The Effects of Train Brake Delay Time on In-Train Forces

In long trains, the braking signal from locomotive control valve takes a few seconds to reach the end cars. As a result, there is a time delay in the braking of the neighbouring cars (locomotives and wagons). This causes the running of rear cars into front cars, thus producing large forces in the buffers and couplers. The induced compression and tensile forces are mainly of longitudinal nature and considered to be responsible for large amount of expenses regarding rolling stock and track repairs as well as deterioration of safety operation of the trains. The effects of the train brake delay time on longitudinal dynamic behaviour of the freight trains are investigated in this article using simulation method. The freight trains considered are those currently operating in Iranian railways. The simulations are carried out for three different cases of long, medium, and short brake application delay times. For each case, three different train forward velocities are considered. The computed results presented here include in-train compression and tensile forces. Different modes of longitudinal dynamic interactions along the train length are also observed by simulations. The results are compared in order to give some new insight into the effect of train braking delay time on train longitudinal dynamics during braking.