Retarder (railroad)
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In
rail transport Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in railway track, tracks, which usually consist of two parallel steel railway track, rails. Rail transport is one of the two primary means of ...
, a retarder is a device installed in a
classification yard A classification yard (American English, as well as the Canadian National Railway), marshalling yard (British, Hong Kong, Indian, and Australian English, and the former Canadian Pacific Railway) or shunting yard (Central Europe) is a railway y ...
used to reduce the speed of
freight car Goods wagons or freight wagons (North America: freight cars), also known as goods carriages, goods trucks, freight carriages or freight trucks, are unpowered railway vehicles that are used for the transportation of cargo. A variety of wagon types ...
s as they are sorted into
train A train (from Old French , from Latin">-4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ... , from Latin , "to pull, to draw") is a series of connected vehicles th ...
s.


Construction

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 Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...
as they roll through them.


Computer control

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.


Inert retarder

An inert retarder holds a cut of classified railcars to keep them from rolling out of a yard.U.S. Federal Railroad Administration, Washington, D.C. (1983)
"Definitions: Inert retarder."
''Railroad Noise Emission Compliance Regulations.'' ''Code of Federal Regulations,'' .


See also

*
Dowty retarders Dowty may refer to: * Dowty Group, a British aircraft equipment manufacturing business People with the surname * Alan Dowty, international relations scholar *David Dowty David Roach Dowty (born 1945) is a linguist known primarily for his work in s ...
*
Retarder (mechanical engineering) A retarder is a device used to augment or replace some of the functions of primary friction-based braking systems, usually on heavy vehicles. Retarders serve to slow vehicles, or maintain a steady speed while traveling down a hill, and help pre ...
* Wheel stop


References

Rail yards Railway buildings and structures Rail freight transport {{Rail-transport-stub