Brake Fade - Railroads

Railroads

Railroads have been using disk brakes on passenger cars for more than 60 years, but coupled with a Rolokron anti-lock system to avoid the creation of flat spots (or “square wheels”) when wheels lock and skid on the rail surface (audible as steady bang-bang-bang noise as a train goes by—not to be confused with the bang-bang...bang-bang....bang-bang sound made by wheels rolling over a rail joint). Usually, brake disks are installed in the center of the axle, but in some applications (such as Bombardier Bi Level commuter cars), only one disk is used, mounted on the axle end outside the truck frame. High speed trains (such as the TGV) may use four disks per axle.

Freight cars (and some passenger cars like multiple-unit cars whose traction motors do not yield room on axles to allow the placement of disk brakes) are equipped with clasp brakes which directly grab the rolling surface of the wheels (much like the old horse buggy brakes of yesteryear). Such brakes are an external-shoe drum brake; but unlike band brakes and many internal-shoe drum brakes, there is no self-assist/self-servo effect, and so they are far less susceptible to locking than self-assist brakes. Due to high stiffness and relatively low power, these clasp brakes are even less prone to lockup than many disc brakes, and so freight cars using them are not equipped with anti-lock systems.