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 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.