Vacuum brakes

Vacuum brakes are a type of brake system used on trains. vacuum brakes were invented in 1877 in the USA.

Vacuum brakes, allow brakes to be applied throughout an entire train at the same time, and are also failsafe, because if anything goes wrong with the braking system, or the train breaks up, the brakes are automatically applied.

Vacuum brakes were a big step forward in train safety. Prior to their invention, a train had to rely on the brakes of the locomotive at the front of a train, and the brakes on the Guard's van or Caboose at the back to stop an entire train. If the brakes werent applied at the same time front and back, the train could break up, accidents of this type were common.

Vacuum brakes have now been largely superceeded by Air brakes[?] which work on a similar principle but use compressed air[?] instead of a vacuum.

How they work

The brakes themselves are in the form of metal shoes which press against the train's wheels creating friction which slows the train down.

On a train equiped with vacuum brakes, every wagon or coach is equiped with at least one set of brakes, the default position of each brake shoe is on. Behind each brake shoes is a vacuum cylinder which contains a piston, which draws the brake shoe forwards or backwards, or into the on or off positions.

An airtight pipe runs along the entire length of the train, the air is pumped out of this pipe, by a pump in the locomotive to form a vacuum. As a vacuum forms in the vacuum cylinder behind the piston, the piston is pushed backwards by atmospheric pressure, thereby drawing the brake shoe backwards into the off position.

The brakes will automatically move forward to the default on position if the vacuum is broken. The train driver can apply the brakes by opening a valve which lets air into the pipe thus braking the vacuum. Or if the train breaks up or the pipe develops a leak, the vacuum will be broken and the brakes will come on.