airbreak

An air brake is a braking system that uses compressed air to actuate wheel brakes. It is common on railway rolling stock and many heavy road vehicles, such as trucks and buses, and is used in some aircraft braking systems. The system relies on a compressor to fill tanks and on valves to apply or release braking pressure.

Operation relies on distributing air pressure from reservoirs to brake cylinders. When the brake is applied, the service valve increases pressure in the cylinders, pushing brake shoes or pads against the wheels. Releasing the brake vents the pressure, allowing springs or other means to return the brakes to the released state. In trains, a brake pipe distributes pressure along the train, and a loss of pipe pressure can trigger an emergency brake.

Main components include a compressor, reservoirs, air dryers, control valves, and brake cylinders with associated piping. Rail systems often employ a triple valve or Westinghouse-type mechanism to translate reservoir pressure into brake application and emergency response. Vehicle systems may use a similar arrangement with simpler control valves.

Maintenance is essential to prevent leaks and moisture damage. Regular checks, draining moisture from reservoirs, testing the brake pipe, and inspecting hoses and connections are standard practices. Benefits of air brakes include rapid response and reliable performance under heavy loads; drawbacks include susceptibility to leaks and freezing in cold weather.

The modern air brake was developed in the late 19th century, notably by George Westinghouse, and became a standard for railways and heavy vehicles worldwide. Variants include electrically controlled pneumatic systems and combinations with other braking technologies.