Steam locomotive

A steam locomotive, also known as an iron horse, is a type of locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, coke, oil or, rarely, wood) to heat water in the locomotive's boiler to the point where it becomes gaseous and its volume increases 1,600 to 1,700 times. Functionally, it is a self-propelled steam engine on wheels.

In most locomotives the steam is admitted alternately to each end of its cylinders in which pistons are mechanically connected to the locomotive's main wheels. Fuel and water supplies are usually carried with the locomotive, either on the locomotive itself or in a tender coupled to it. Variations in this general design include electrically powered boilers, turbines in place of pistons, and using steam generated externally.

Steam locomotives were first developed in the United Kingdom during the early 19th century and used for railway transport until the end of the 20th century. Richard Trevithick built the first steam locomotive known to have hauled a load over a distance at Pen-y-darren in 1804, although he produced an earlier locomotive for trial at Coalbrookdale in 1802. Salamanca, built in 1812 by Matthew Murray for the Middleton Railway, was the first commercially successful steam locomotive. Locomotion No.