Modelling of a passive hydraulic steering for locomotives

Abstract

During the past few decades, substantial improvements were made to rail infrastructure worldwide. This was necessary to accommodate the ever increasing transportation demand and requirements. Nowadays, trains are required to transport heavier loads and to travel at higher speeds. One of the major improvements was achieved by the development of the off-flange curving bogie designs to reduce wheel and rail wear. Off-flange designs include passive steering and actively controlled steering. The development and implementation of self-steering bogies on locomotives was promoted in the early 1980’s by two major locomotive manufacturers. Up to date, thousands of these locomotives, with built-in self-steering bogies, have been manufactured and taken into service (Swenson, 1999). Most self-steering bogies have mechanical linkage systems to steer the wheel sets. As an alternative to the mechanical linkage system, the DCD Group (a South African manufacturer of rail and mining equipment) initiated the development of a Passive Hydraulic Steering (PHS) system. First PHS prototype systems, developed by DCD, have proven that huge wear reduction possibilities exist on both, rails and wheels. In addition the prototype systems also significantly decreased noise and vibration levels when negotiating tight corners (Swenson & Scott, 1996 and DCD Rolling Stock, 2012). However, existing prototype solutions require further improvements and development for optimisation. To be able to identify and implement improvements, the need exists to perform modelling and testing of the systems to obtain a better understanding of the operation and suitability of a complete unit. The aim of this research project is thus, to mathematically model an existing prototype PHS system and validate the model with data from experiments and tests. This model can then be used in order to improve and optimise performance, cost and reliability of the system, before mass production is considered. A literature survey was conducted, focusing on general wheel and rail wear mechanisms, techniques to improve wheel and rail life and on existing techniques for modelling the hydraulics and multi-body dynamics of locomotive systems. The literature survey was followed by extensive laboratory tests on component basis, a quarter PHS system and on the full PHS system. From these tests all parameters needed for the characterisation of the PHS and the mathematical model were determined. These tests also provided data for the validation of the PHS model. Finally, a mathematical model of the PHS system was successfully generated and validated. This model can now be used in a multi-body dynamic locomotive simulation to evaluate its effectiveness. The results and findings of the literature survey, experiments and modelling are reported on and discussed in this report.