Wheel climb derailment criteria for evaluation of rail vehicle safety

Abstract

Criteria for evaluating safety of rail vehicles with respect to wheel climb derailment are reviewed. The relationship between flanging wheel lateral to veritical force ratio at impending derailment and angle of attack, lateral velocity and longitudinal creep is discussed. This ration has no explicit relationship with time duration. Empirical relations in current use result from specific vehicle and track operating conditions tested. It is observed that the lateral to vertical force ratios on the non-flanging wheel at impending derailment are controlled by the same kinematic parameters of axle motion as on the flanging wheel. The information available from measurements on the non-flanging wheel are sufficient to permit definition of new wheel climb safety criterial that are consisstent with current wheel-rail interaction force theory which include situations where lateral to verical forces in excess of Nadal's limit may be achieved.\n