Abstract

There has been renewed interest in rail transportation driven by the need for alternatives to congested highways and environmental concerns. The conventional railway truck designed for operation at high speed of approximately 200 km/hr makes use of stiff primary suspension elements to provide good dynamic stability. The curving performance of such a vehicle is poor because of wheelset misalignment in curves resulting in increased wheel and rail wear. This increases the maintenance cost. The wheelset misalignment also leads to increased lateral forces which raises the potential for derailment due to wheel climb. One of the aspects of the railway truck design that needs improvement is better compatibility between dynamic stability at high speeds and the ability of the vehicle to steer around curves. In this thesis, modified truck designs are considered with an objective to improve both the high speed stability and curving behaviour. The performance of the following designs are compared: (i) Conventional truck ( C truck ); (ii) Radial truck ( R Truck ); (iii) Conventional truck with yaw damper ( CD truck ) and (iv) Unsymmetric Suspension truck with yaw damper ( USD truck ). The USD truck has longitudinal asymmetry in the suspension according to direction of motion i.e. the primary stiffness in the leading axle is different from the trailing axle. Another truck considered for evaluation is the Unsymmetric Wheelset truck ( UW truck ) in which the trailing axle is an Independently Rotating Wheelset (IRW). By choosing suitable values of primary yaw dampers, it is possible for CD truck and USD truck to achieve higher critical speed in comparison to C truck and US truck for a given bending stiffness The non-linear curving analysis has shown that USD truck achieves better curving performance in comparison to other truck designs on curvatures up to 12 degrees. Thus it is possible for a properly designed USD truck to achieve near perfect steering as well as maintain good dynamic stability. Validation of the results from this study has been carried out using the software New and Untried Car Analytic Regime Simulation (NUCARS). NUCARS is a multi-body dynamic program for railway vehicle design and performance evaluation and is an industry-wide standard in North America. The analysis of performance using NUCARS also shows that USD truck has better curving behaviour compared to other truck designs for curvatures up to 12 degrees