Hornby R2389 Builth Castle Class 4-6-0 4086 in GWR Green
GWR 4073 Class or Castle Class
The 4073 Class or Castle class were 4-6-0 steam locomotives of the Great Western Railway, built between 1923 and 1950. They were designed by the railway's Chief Mechanical Engineer, Charles Collett, for working the company's express passenger trains. They could reach speeds of up to 100 mph (161 km/h).
The origins of this highly successful design date back to the Star Class of 1907 which introduced the basic 4-cylinder 4-6-0 layout with long-travel valves and Belpaire firebox that was to become characteristic of GWR express passenger locomotives. The Star class was designed to take the top express trains on the GWR, with 61 in service by 1914, but after World War 1 there was a need for an improved design. To meet this need, Chief Mechanical Engineer GJ Churchward had in mind an enlarged Star class design with a standard No.7 boiler, as fitted to his GWR 4700 Class express freight 2-8-0. However, this combination would have taken the axle load over the 20-ton limit then set by the civil engineers, and in the end, nothing came of the idea.
C. B. Collett succeeded Churchward as Chief Mechanical Engineer of the GWR in 1922 and immediately set about meeting the need for a new locomotive design that would both supplement the Stars and replace them on the heaviest expresses. Collett's solution was to take the basic layout of the Star with an extended frame and add a newly designed No.8 boiler which was both larger and lighter. The increased amount of steam that this produced allowing an increase in the cylinder diameter from 15 in × 26 in (381 mm × 660 mm) to 16 in × 26 in (406 mm × 660 mm). The extended frame allowed for a side window cab and an increased grate area. The result was an increase in the tractive effort to 31,625 lb and a locomotive that looked attractive and well proportioned while remaining within the 20-ton axle limit.
Unlike the Star class, there was no prototype. Collett was sufficiently confident of the design to place an order with Swindon railway works (Lot 224) for ten locomotives in 1923, although there was a four-month delay between the appearance of the first example in August 1923 and the second in December, to allow for the correction of any teething problems. Thereafter the remaining eight locomotives came out at regular intervals until April 1924. They were 4073–4082, the number series continuing unbroken from the Star class. The last 12 Star class locomotives, which were built in 1922–23, had been given names of abbeys in the western area served by the GWR. The new locomotives were named after castles, also in the west, beginning with 'Caerphilly Castle'.
Over the twenty-seven years from August 1923 to August 1950, 155 Castles were built new at Swindon Works, and a further sixteen were converted from other classes. In February 1952, two engines, 4082 Windsor Castle and 7013 Bristol Castle swapped names and numbers: 7013 was disguised as 4082 to run George VI's funeral train and the numbers were never swapped back. 4082 was withdrawn from service in 1964 as 7013 and 7013 was withdrawn from service as 4082 in 1965.
OO Gauge 1:76 Scale Castle Class 4-6-0 4086 "Builth Castle" in GWR Green DCC compatible but no socket.
Era 3 The Big Four - LMS GWR LNER & SR: 1923-1947