On the Replacement of Shoe-Wheel Brakes by Pad-Disk for Railroad Freight Cars

Abstract

Most of railroad freight cars use brake shoes directly applied onto the wheels. This system causes wheel heating, which in turn gives rise to thermal stresses and loss of mechanical strength. An alternate solution is a system of brake disks and pads, which would not heat the wheels, like disk brakes. Because temperature is one major factor affecting braking performance, a study of the viability of replacing shoe brakes by disk brakes must evaluate and compare the heating of wheels and disks. The present work evaluates the heating of disk-pad systems when used for braking freight cars in the same conditions regularly applied to shoe-wheel brakes. In addition, stop distance for both systems are evaluated for regular speeds of freight railroads. Preliminary numerical simulations were done to choose the critical brake condition and to check whether the expected temperatures would exceed the temperature limits, damaging the friction materials and systems. Following that, real scale tests were conducted in critical braking conditions for both types of brake systems. Dynamometer tests were performed in real scale at the Railroad Laboratory of the State University of Campinas, Brazil. Results showed that, as far as system heating is concerned, there is nothing to prevent the replacement of the current system by a disk-pad system. Besides, the stop distance for both systems is also in the recommended range.