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.
Steam turbine locomotive
Henschel converted a normal DRG Class 38 steam locomotive to use a steam turbine in 1927. The locomotive itself was little modified, the major changes being to the tender which was fitted with coupled driving wheels in a 2-4-4 layout, driven by separate forward and reverse turbines. Both turbines were driven by intermediate pressure exhaust steam from the original cylinders. A condenser in the tender provided a vacuum for the turbine exhaust, increasing thermal efficiency. As the final exhaust was at negligible pressure, the original smokebox blastpipe had to be replaced by an electric draught fan in the smokebox.