Geared steam locomotive
A geared steam locomotive is a type of steam locomotive which uses gearing, usually reduction gearing, in the drivetrain, as opposed to the common directly driven design.
Steam locomotive
Early steam locomotives had two cylinders, one either side, and this practice persisted as the simplest arrangement. The cylinders could be mounted between the main frames (known as "inside" cylinders), or mounted outside the frames and driving wheels ("outside" cylinders). Inside cylinders are driven by cranks built into the driving axle; outside cylinders are driven by cranks on extensions to the driving axles.