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.
Cylinder (locomotive)
On engines with outside cylinders there are three possible variations:There are three common variations:There are three common variations:There are many other variations, e.g. geared steam locomotives which may have only one cylinder.
The only conventional steam locomotive with one cylinder that is known is the Nielson One-Cylinder Locomotive.