Convert air pressure into a strong mechanical force to apply the foundation brakes.

The air brake chamber is the foundational component of the air brake system.The air brake chamber works that same as a shiny hydraulic piston on a digger. On the digger, the hydraulic cylinder converts hydraulic oil pressure to mechanical force.

Another analogy is a hydroelectric turbine. Water pressure is forced through a small chute and past a turbine. The water pressure turns the turbine which powers an electric generator. The turbine converts water pressure into rotary mechanical force to turn a generator and create electricity.

In a similar manner to the hydraulic piston and hydroelectric turbine, the air brake chamber converts air pressure into strong mechanical force. Inside the brake chamber a rubber diaphragm expands like a balloon when air pressure is exerted. When the rubber diaphragm expands, it pushes on a steel plate which forms part of the push rod.

The most common brake chamber in an air brake equipped vehicle is a Type 30. The Type 30 denotes the surface area of the diaphragm; a type 30 has 30 square inches of surface area. If 100 pounds per square inch (psi) of air pressure is exerted against the diaphragm, the brake chamber creates 3000 pounds of mechanical force.