How do steam locomotives work?
A. Steam engines came in three basic varieties: reciprocating pistons, geared drives, and experimental turbines. All work by boiling water to make pressurized steam, and the energy in this steam is used to move the engine. The earliest engines burned wood for fuel. Most steam engines used coal, and towards the end of the steam era oil was used, primarily to get around air pollution regulations. In a reciprocating piston design the pressurized steam is sent into expansion cylinders, which were usually mounted on the outside front end of the frame. The steam expands to push a piston back, and the piston is connected via a crosshead to the main driving rods. These rods convert the linear motion of the piston to the circular motion of the driving wheels. There are many variations on this design, such as using multiple cylinders to increase the amount of energy extracted from the steam but they all fall into the category of improvements to the basic design. Note that once the steam has been
