How locomotives are made
Most diesel locomotives do not drive the wheels with the engine. The diesel makes electricity, and motors turn the axles.
- stations
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- things upstream
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- raw sources
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- steps from the ground
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The short version
A diesel-electric locomotive is a steel frame carrying a big diesel engine, a generator or alternator and electric traction motors. The frame is welded, the wheelsets and bogies are built separately, and the engine and electrics are mounted and wired. The body is lowered on the bogies, painted, and tested on track.
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Weld the underframe
Heavy steel plate and beams are welded into the underframe, the backbone that carries the engine and takes the pull of a train.
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Forge the wheels and axles
Wheels and axles are forged and machined to shape, then pressed together as wheelsets. They have to cope with huge weights on small contact patches.
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Build the bogies
Wheelsets, bearings and springs are mounted in a steel truck, called a bogie. Each axle has a traction motor hung on it, with gears linking motor to axle.
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Assemble the diesel engine
The prime mover is a large diesel with many cylinders. It is built up from a cast block, crankshaft, pistons and heads in the same way as a car engine, only far bigger.
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Couple the generator
The engine drives a main generator, or on bigger units an alternator with rectifier, whose electricity is carried by thick cables to the traction motors.
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Wire the control system
Governor and electronic controls manage engine speed and the electrical load. A single throttle lever coordinates engine and generator, a scheme worked out by Hermann Lemp.
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Lower the body on the bogies
A crane lifts the finished body and sets it down on its bogies. Brake lines and cabling are then connected.
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Paint and test on track
After painting, the locomotive is fueled and run on a test track, pulling load units to confirm power and braking.
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Worth repeating
- Werner von Siemens showed an electric locomotive in Berlin in 1879. Its 2.2 kW motor pulled three cars at 13 km/h, and it carried 90,000 passengers in four months.
- By 1925 a small number of diesel locomotives of 600 horsepower were in service in the United States.
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Sources
Cite this page: "How locomotives are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/locomotive