Steam Locomotives of a Leisurely Era – 1933 – ‘Princess’ Pacifics London Midland & Scottish Railway

Princess Louise at first temporarily numbered M6206 and later 46206, in 1948

One of Mr. (later Sir) William Stanier’s first designs after his appointment as Chief Mechanical Engineer of the LMS. Stanier came from the Great Western, and introduced a number of features of that Company’s practice to the LMS for the first time, including the use of a taper boiler. His first two Pacifics, Nos. 6200 ‘The Princess Royal’ and 6201 ‘Princess Elizabeth, which appeared in 1933, were given thorough trials before any more were built, after which ten similar engines, Nos.6203-12 came out in 1935 with slight modifications following the experience gained with the first two engines, chief amongst these was an increase in the superheater heating surface. The four cylinders on this class has each its own independent set of Walschaert valve gear, but No.6205 later had its inside sets replaced by rocking levers actuated from the outside pair. As might have been expected, these locomotives soon proved themselves to be greatly superior to anything previously seen on the North Western main line. In 1936, in anticipation of the introduction of a high speed service between London and Glasgow, No.6201 was tested with a light load of 230 tons, seven coaches, and succeeded in covering the distance of 401½ miles, non-stop, in the remarkable time of 353½ minutes.

Concurrently with Nos. 6203-12, there appeared No.6202, which differed radically from its sisters. The boiler, wheels, etc., were identical, but in place of the normal cylinders and reciprocating motion it was propelled by turbines, a large one on the left hand side of the engine, for forward motion, and a smaller one on the right hand for reverse running. It was not the first turbine driven locomotive in this country, other experiments in this direction having been made in the 1920s, but it was undoubtedly the only successful turbine design to appear. Many snags were encountered and the engine spent a good proportion of its life in the works undergoing modifications, but nevertheless when it was in service it was a very good engine, and performed work equal to that of its orthodox sisters. It was a beautiful machine to see in action, with its soft purr and even torque, which resulted in almost complete absence of slipping, even with the heaviest load, a fault to which most ‘Pacifics’ designs are particularly prone.

It ran as a turbine until 1952, when it was rebuilt with a normal 4-cylinder propulsion. Previously nameless, it now became ‘Princess Anne’, but its life under its new metamorphosis was exceedingly short, as it was involved in the disastrous Harrow accident in that year, and damaged beyond repair. All the other ‘Princesses, now BR Nos. 46200, 46201 and 46203-12, were in active service in 1959.

‘Princess’ class – Driving wheels – 6’ 6”, Cylinders – 16¼”x 28”, Pressure – 250 lb., Tractive effort – 40285 lb., Weight – 104½ tons, BR classification – 8P
No.6202 – Driving wheels – 6’ 6”, Cylinders – N/A, Pressure – 250 lb., Tractive effort –N/A., Weight – 110½ tons, BR classification – N/A