Elimination of failures in railway gearboxes by regenerative coasting

Railway gearboxes are subjected to vibrations arising from gear meshing, roller bearings forces and wheel-rail contact. This paper shows how peculiar service conditions made the application of a well known and perfectly working gearbox installed on a metro vehicle rather critical. After a long investigation, the root cause of the problem was found in running conditions at top speed, which happened for long distances in coasting, being a rather long section of the line made of quite distant stations on a mild slope line, a situation that that kind of vehicle never encountered in other lines. Remedies are discussed with reference to mechanical and electric features of the vehicle. The adoption of a new procedure, called “regenerative coasting” allowed to potentially solve the problem of premature failures in service.