The assessment of railway track conicity and the question of limit radius

This paper discusses the calculation of the equivalent conicity for railway wheel and rail profile, particularly the assumption that the radius of a curve can be neglected during the calculation. A simple Matlab program shows that the curve radius term can have an influence on the calculated equivalent conicity, and highlights the importance of defining a limit radius at which equivalent conicity cannot be used as a reliable measure of stability. The work is also supported by vehicle dynamics simulation and a methodology is proposed to show the relationship between dynamics oscillation forces and quasi-static curving forces as a function of curve radius, cant deficiency and vehicle speed. The current limit of 2500m based on EN14363 definition of very large radius curve is proved to be a sensible limit, however results from low speed freight traffic show that dynamic oscillation can also be an issue in tighter radius curve.