Resistance to motion is an important input for train performance simulations, and the Davis equation is a well-known resistance formula, widely used for freight trains. It is known to give conservative values, and has numerous variants such as Modified Davis and Adjusted Davis with factors of e.g. 0.7 being applied to the formula. There is confusion about the right constants to use, and frequently specifications for equipment contain values which are inappropriate. This paper begins with a review of some of the published formulae, and then presents a methodology for calculating the overall resistance of trains of known weight and composition operating on known track geometry, using tractive effort, GPS location and speed records downloaded from locomotive data loggers. A simulation program was modified to take the time history of tractive effort as an input, and to calculate velocity, which is then compared with the recorded speed. The “Davis” formula parameters are adjusted iteratively until the calculated speed approximately matches the actual speed. This approach is used to benchmark values of published constants and to suggest appropriate values for trains operating in Australia.
Content Notes:
Please cite as Szanto, F., Rolling Resistance Revisited, CORE 2016 Conference on Vehicle/Track Dynamics and the Wheel-Rail Interface, May 16-18, 2016, Melbourne, Australia
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