What are the two components of dowty retarder?

Dowty retarder is a small independent hydraulic device installed on the waist of the rail and has the function of automatically reducing the speed of the vehicle. The word Dottie is derived from the name of Dowty Mining Equipment Ltd., UK. Firstly, it was developed by P.E. Checkley, chief engineer of the Railway Department of the British Doughty Company. Initially installed at the British Railways Tinsley and Bescot marshalling stations. The sliding cylinder and housing are its two components.

The sliding cylinder is equipped with a speed valve, which can automatically determine whether the vehicle speed exceeds the critical speed value; the sliding cylinder is equipped with a pressure valve, which can absorb the kinetic energy of the vehicle. Each dowty retarder has a critical speed value. When the vehicle speed is higher than this value, the dowty retarder will play a brake role, otherwise it will not play a brake role. The t-dj 302 retarder with a critical speed of 1.25m/s made in China consumes 932j per brake.