Retarder (railroad)

In rail transport, a retarder is a device installed in a classification yard used to reduce the speed of freight cars as they are sorted into trains.

Each retarder consists of a series of stationary brakes surrounding a short section of each on the track that grip and slow the cars' wheels through friction as they roll through them.

[1] Modern retarders are computer controlled to apply a precise amount of pressure on the wheels so that cars rolling down a yard's hump are slowed to a safe speed for coupling with cars already standing on the yard's tracks.

[2] An inert retarder holds a cut of classified railcars to keep them from rolling out of a yard.

This rail-transport related article is a stub.

The retarders grip the sides of the wheels on passing cars to slow them down.
Classification bowl of Kornwestheim classification yard (near Stuttgart , Germany ). Two retarders are clearly visible in this photo.
A type of car retarder. As the cylinder 15 pushes an end of the lever 2A , the rotation motion of the lever 2A pivoted at the rod 4a makes the brake shoe 11A at the opposite end thrust against the wheel 13 , so as to brake the car. Peter M. Noble, United States Patent 3,827,533, 1974.