Geared steam locomotive
This gearing is part of the machinery within the locomotive and should not be confused with the pinion that propels a rack locomotive along the rack between the rails. The geared steam locomotives that have been built have been for conventional track, relying on the adhesion between wheels and rail.
Piston rod
Almost all steam locomotives have used a similar design of cylinder, with a crosshead slide mounted adjacent to the cylinder and a short piston rod between them.
In some cases, tail rods were also used. These were rare in the United Kingdom, but relatively common in Europe, at least for large locomotives.