Using the Dirac approach to model the motion of a railway vehicle when its wheel flange climbs the rail

An approach to formulate a mathematical model is proposed to describe the railway vehicle motion when its wheel flange is rolling on the railhead. This model makes it possible to construct an analytical estimate of the vehicle derailment with respect to the vehicle construction and the motion conditions. This model is based on the primary Dirac constraints and its solution is not similar to the solution of the classical no-slip nonholonomic model. The primary Dirac constraints are caused by the degeneration of the system's Lagrange function when the contact creep force stiffness tends to infinity and the ratio of the wheelpair mass to the vehicle mass tends to zero.