Research of hidraulic pump shaft broke problems in the commuter train RA-2

Abstract

New generation diesel commuter trains are equipped with compact diesel engine, which transmits power to train transmission and also to passenger comfort power devices, such as generators and heating and air condition pumps. Compact placement of power system on the train raises new requirements to component mounting accuracy, decrease tolerances of mounting dimensions. In case of train RA-2, modular structure of train equipment is mounted on two basements – engine crankcase, mounted on frame wit flexible support and equipment, mounted on train frame directly. These two bases have different dynamic response to engine vibrations and road caused vibrations that is why it must be connected through flexible drive with equal angular speed. Equipment on frame is fixed tightly, so it demands high axial accuracy of their position; flexible shaft allows axial in-coincidence as big as 1 mm. Intensive exploitation of train reveals that after 7000 of motor-hours of performance, shafts of hydrostatic oil pump was broken in 4 cases. Systematic broke of these shafts brings a task to define causes of such broke and reveal physical nature of broke. This is necessary to avoid such damage in future exploitation and prevent financial loses as well as danger of traffic safety. Research of shaft broke was made in few steps. Initially, shaft rupture metallographic analysis was performed in order to define shaft metal properties and possible defects of shaft metal. Second step was analysis of shaft load and possible influence of static and dynamic loads to shaft working regime, in this case dynamical influence of eccentricity of pulley and inertial forces was neglected, while pulley was balanced in advance. Finally, equipment mounting design was analyzed, in order to find kinematic errors in the system and possible reason of radial load in shaft. At the end of paper results of research are presented and conclusions wit recommendations are given.