Diesel multiple unit

A diesel multiple unit (DMU) can be:

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• a multiple unit powered by a diesel engine. (A multiple unit car contains both passenger accommodations and propulsion systems.)
• a combination of diesel powered locomotives operating under the control of one engine-driver, coupled together consecutively, usually at the head end of the train, which further consists of wagons or carriages.

DMU classification is subdivided into the form of the transmission: Diesel Mechanical Multiple Unit has a mechanical transmission; Diesel Hydraulic Multiple Unit has a hydraulic transmission; Diesel Electrical Multiple Unit has an electrical transmission.

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The diesel engine may be overboard or underslung. When underslung, it is also referred to as Railcar.

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A regional rail train composed of DMU cars "scales" well (I.e. adding additional cars automatically adds power). Distribution of the propulsion among the cars also results in a system that is less vulnerable to single-point-of-failure outtages. Because they operate on diesel, there is no need to run overhead electric lines or electrified track, which can result in lower system construction costs.

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More rugged than light rail, DMU systems can be safely operated within freight rail corridors, though safety regulations in the U.S., and scheduling concerns, require that they be operated on separate tracks. In the USA, Federal Railway Administration rules effectively prohibit the type of lightweight DMUs used elsewhere in the world.

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When used with diesel locomotives, the connections typically consist of seven air hoses and one electrical cable. The largest hose, located next to the coupler is the main air brake line. Outboard of this are two smaller hoses which link the air compressors on the locomotives. Further out are two hoses which control the brakes on the locomotives independently of the rest of the train. The two outermost hoses control the application of sand to the rails. An electrical cable above the coupler transmits throttle information from one locomotive to the next. Locomotives set up to use slugs have extra connections for transmitting electricity.

Related Topics:
Coupler - Slugs

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DMU manufactuers include:

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• Bombardier Transportation of Montreal, Canada
• Colorado Railcar
• Rotem Company of Seoul, South Korea
• Siemens Desiro DMU
• Integral Coach Factory of Chennai, India
 
Diesel multiple unit: See also ►