The astute among you will have recognised that this is not strictly a steam locomotive, even if it looks like one around the cylinders.
This diesel-pneumatic loco was designed to solve the problem of power transmission between the diesel engine and wheels. Time has shown that diesel-electric is the way to go, but in earlier years it was by no means obvious that dragging around a heavy generator and lots of electric motors was a good idea.
Built in 1929, V3201 was the first high-performance Diesel loco on the Deutsch ReichsBahn. It used the MAN Lo6 Vu 45/42 engine, originally developed for use in U-boats. (surprise, surprise) It was a 6-cylinder 1000/1200hp engine direct-coupled to a MAN 2-cylinder double-acting single-stage air compressor.
It is a fundamental problem with pneumatic power transmission that a lot of energy is released as heat during compression. Usually this has to be dissipated to stop the compressor overheating, making the process very inefficient.
This locomotive tackled the problem by heating the air further after it left the compressor, using the diesel exhaust in heat exchangers, and then drove pistons with the hot air exactly as if it was steam.
Axle loading was 18 tons
http://www.dself.dsl.pipex.com/museum/LOCOLOCO%5Cdiesair%5Cdiesair.htm
