Stanier Class 7P "Turbomotive"
No. 6202 "Turbomotive" taken around the time of building
See page for author, Public domain, via Wikimedia Commons
Technical Data
Introduced: 1935
No. Built: 1
Wheel arrangement: 4-6-2 "Pacific"
The steam turbine-driven one-off locomotive no. 6202 (referred to as "Turbomotive", although not officially named as such) is perhaps one of steam's "What if" stories. Originally conceived as the third member of the initial "Princess Royal" locomotives, the decision was taken to fit the locomotive with a non-condensing steam turbine of the Ljungstrom type that was being developed in Sweden in the 1930s. This would replace the conventional steam piston driven systems normally used; the turbine system applying a even torque to the driving axles which would eliminate hammer-blow, a problem with conventional systems that caused damage to the railway lines being used. The locomotive would enter service in 1935.
Initial trials showed some promise, but there were issues that persisted with the design throughout its life. The reverse turbine suffered from a lack of power, and the one-off nature of the locomotive meant that spare parts were often not available "off the shelf" and maintenance crews were not as familiar with the design as they were with standard locomotives; the result was often extended times out of service. The locomotive cost £20,383 to build, as opposed to £12,657 for the first of the standard "Princess Royal" class locomotives, and £8,538 each for the second batch of "Princess Royals" (covering 10 locomotives); at a time of economic downturn, it is perhaps not surprising the LMS was unwilling to spend these sorts of amounts on an unproven design as opposed to proven conventional ones. Perhaps had World War Two not intervened, the concept might have been revisited, but by the time that was concluded, there was even less money available for further development.
February 1939 saw the locomotive fitted with smoke deflectors, as drifting exhaust frequently caused visibility issues for the footplate crew. Post-war, the locomotive still had issues that resulted in frequent stoppages, and the decision was eventually taken to rebuild it along the lines of a standard "Princess Royal" class locomotive (there were some slight differences), and this was completed in August 1952. The rebuilt locomotive was given the name "Princess Anne" (after the daughter of Queen Elizabeth II)
Tragically, on the 8th October 1952, the rebuilt locomotive was involved in the Harrow and Wealdstone crash, the worst-ever peacetime railway disaster in British history. It was subsequently written off and scrapped, but since its loss created a shortfall of locomotives for the Midland Region of British Railways, a one-off Standard Class 8P no. 71000 "Duke of Gloucester" was built to replace it (perhaps another example of a "What if" locomotive).
Preservation
As pointed out, the locomotive was scrapped and thus not preserved. Some proposals to build a new version have been suggested in recent times, but none are currently active, and it looks like this class of locomotive will remain extinct.