Study on the Coupler Stability of Locomotive SS_(3B) Running on the Long Heavy Down Grade

The coupler stabilizing principle of Coupler No.13 under the longitudinal compressive force was researched so as to solve the problem of derailment of the locomotive in braking.Take Locomotive SS3B for example.The dynamic model of four locomotives coupled in series to draw a 3 000 t freight train was set up,where Coupler No.13 was used to connect the locomotive and vehicles.The stabilizing ability of Coupler No.13 of the locomotive running on the 30‰ long heavy down grade was studied.The position stop mode was used to restrict the rotation angle of the coupler with respect to the rear frame of Coupler No.13.There was not enough buffing during the course of coupler rotation till it reached the stop,this led the wheel set lateral force and derailment coefficient to their peak values instantaneously when the longitudinal compressive force was applied on the coupler.However,the continuous action of the wheel set lateral force and derailment coefficient were found within the safety restriction zone.The phenomenon could be reproduced by dynamic simulation.The results show that the maximum longitudinal compressive force on Coupler No.13 of Locomotive SS3B running on the 30‰ long heavy down grade is about 1 100 kN and the longitudinal compressive force on the coupler may cause partial abrasion to the wheels in braking.