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(last edited July 18, 2005) Front Page | Recent Changes | Title Index | User Preferences | Random Page | HelpThis is the most common type of train brake. It uses compressed air to apply the brake block (or pad) to the wheel and to control the operation of the brake along the train. The compressed air is supplied by a motor driven compressor on the locomotive or train.
The brake control is actuated from a "driver's brake valve". This valve is used to feed air to the brake pipe or to allow air to escape from the brake pipe. A fall in brake pipe air pressure causes a brake application on each vehicle whilst a restoration of pressure causes the brake to release.
A distributor (or "triple valve" as it was always called and sometimes still is) on each vehicle monitors the pressure in the brake pipe. When brake pipe pressure falls, the distributor allows air from an auxiliary reservoir on the vehicle to pass to the brake cylinders to apply the brake. When brake pipe pressure rises, the distributor releases the air from the brake cylinder and recharges the auxiliary reservoir for the next application. The release of air from the brake cylinder allows the block to be released from the wheel by a spring.
