Heavy haul train impulse and reduction in train force method

The paper presents an integral simulation system that is able to analyse the train air brake system based on gas flow theory together with the train longitudinal dynamics performance based on multi-body dynamics. The purpose of this analysis is to find the mechanism for occurrence of the maximum coupler force in heavy haul trains. The results show that the maximum coupler force was resulted from either impacting force or squeezing force. The former normally happens to shorter train with larger slack, while the latter happens to longer train of smaller slack. In the former case, the maximum coupler force can be reduced by minimising slack. And in the latter case, it can be reduced by adopting different structure of distributing valve, reducing charging speed to brake cylinders of cars at the front of train and, at the same time, increasing charging speed to brake cylinders of cars at the rear of train, while keeping brake capacity of train unchanged, as presented in this paper.