LMS Turbomotive

The LMS Turbomotive, officially LMS No. 6202, was a unique non-condensing turbine-driven express passenger locomotive designed by William Stanier in collaboration with Metrovick and built at Crewe Works in 1935, representing one of the most technically ambitious and genuinely unusual locomotive experiments in British railway history. Rather than conventional piston cylinders driving the wheels via connecting rods, the Turbomotive used a Ljungström steam turbine to drive the leading coupled axle through reduction gearing, with a smaller reverse turbine for backward movement.

Stanier was attracted to the turbine concept because steam turbines are inherently more thermally efficient than reciprocating piston engines at sustained high power output: they expand steam continuously rather than in discrete pulses, eliminating the thermodynamic losses associated with the admission and exhaust cycle of a conventional cylinder. The Metropolitan-Vickers turbine specified for No. 6202 produced around 2,400 hp, significantly more than the 1,900 hp of a conventional Princess Royal Class Pacific, and in theory the locomotive should have been more efficient on sustained high-speed running.

In practice the Turbomotive proved operationally complex and maintenance-intensive: the turbine required specialist attention that the LMS's conventional steam depots could not easily provide, and periods of unavailability were frequent. Despite this, when running well it was genuinely impressive, regularly achieving high speeds and low coal consumption on the Euston–Liverpool expresses. It worked in service from 1935 until 1949, when it was withdrawn for major overhaul. The decision was taken not to reline the turbine but to rebuild the locomotive as a conventional Princess Royal Class Pacific, in which form it became No. 46202 Princess Anne — only to be destroyed in the Harrow and Wealdstone rail disaster of October 1952, one of Britain's worst peacetime railway accidents. No. 6202 in its turbine form was not preserved.