Optimisation of turnout frog profile geometry using revenue service wheel profiles

Lee, J., A. de O. Lima, M.S. Dersch and J.R. Edwards. 2023. Optimisation of turnout frog profile geometry using revenue service wheel profiles. Vehicle System Dynamics. doi:10.1080/00423114.2023.2218948.


Railroad turnouts are an essential element of the track infrastructure that facilitates the movement of trains between adjacent or diverging tracks. Turnout frogs are subjected to high wheel impact forces due to the inherent need for a discontinuity in their geometry. To develop an optimised frog geometry to minimise wheel impacts, a parametric study was designed and executed that considered three critical design parameters: point (i.e. nose) slope, relative height difference between wing and point, and longitudinal wing slope. Four hundred wheel profiles were extracted from a dataset of one million revenue service wheel profiles based on a wheel classification methodology previously developed. Wheel impact was quantified for each frog geometry case based on wheel transfer distribution and vertical wheel trajectory which were analysed using a developed Python algorithm. A total of 30 unique geometries were evaluated, including the existing standard design geometry for a N.A. heavy point conformal frog. Results demonstrated that each parameter affects different locations along the frog and total impact is most affected by point slope. Lastly, an optimised frog geometry was selected that ensures well-distributed wheel transfer locations preventing the concentration of damage, and results in low total impact at the transfer point.