Field Investigations on Rolling Stock Components Designed to Overcome Low Adhesion Related Problems

The tangential force that a braking or tractive wheel can exert on a rail is limited by the friction coefficient available at the surfaces in contact for a given normal load. In clean steel-on-steel contacts the friction coefficient is known to be higher than the adhesion requirements of the majority of the existent rolling stock. However, in the presence of contamination (e.g. leaves, water, grease, and rust) the friction level can decrease to values far below those required in normal traction and braking operations. In particular, fallen leaves have been identified by many railways to cause considerable low adhesion problems in autumn. Despite the available countermeasures the adhesion problems still seem to persist in the majority of the affected networks. This could to a large extent be due to the lack of fundamental understanding on the effectiveness of the countermeasures used under different operating conditions. In this paper, the effectiveness of two rolling stock components, namely locomotive sanders and permanent magnetic track brakes, in leaf contaminated contacts is investigated by means of full-scale tests in a stabling yard. An electrical locomotive has been used to asses the performance of the sanders, whereas the tests with permanent magnetic track brakes have been carried out with an electrical multiple unit.