locomotive

Engine for hauling railway trains. In 1804 Cornish engineer Richard Trevithick built the first steam engine to run on rails. Locomotive design did not radically improve until English engineer George Stephenson built the Rocket in 1829, which featured a multitube boiler and blastpipe, standard in all following steam locomotives. Today most locomotives are diesel or electric: diesel locomotives have a powerful diesel engine, and electric locomotives draw their power from either an overhead cable or a third rail alongside the ordinary track.

In a steam locomotive, fuel (usually coal, sometimes wood) is burned in a furnace. The hot gases and flames produced are drawn through tubes running through a huge water-filled boiler and heat up the water until it turns to steam. The steam is then fed to the cylinders, where it forces the pistons back and forth. Movement of the pistons is conveyed to the wheels by cranks and connecting rods. Diesel locomotives have a powerful diesel engine, burning oil.

The engine may drive a generator to produce electricity to power electric motors that turn the wheels, or the engine drives the wheels mechanically or through a hydraulic link. A number of gas-turbine locomotives are in use, in which a turbine spun by hot gases provides the power to drive the wheels.