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.
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.