In 1906 Churchward fitted a more powerful Standard No. 4 boiler to his successful 3100 Class 2-6-2T to create the GWR 3150 Class. These showed themselves to be successful locomotives but their 65 long tons 0 cwt (145,600 lb or 66 t) weight and 2,000 imp gal (9,100 l; 2,400 US gal) water capacity meant that they tended to be restricted to suburban passenger traffic. Churchward was looking forward to the replacement of various of his predecessor’s 4-4-0 classes on secondary duties. In 1911 he therefore designed a tender version of the 3150 class which would be suitable for a wide range of intermediate duties.
The class was ‘a total synthesis of standard parts, using the outside cylinders of the Saint, the wheels of ’31XX’ 2-6-2 tank and the No.4 boiler, in its superheated form.’[2] No prototype was required as the fundamental design had proved itself.
The locomotives quickly proved themselves to be so useful that they were produced more or less continuously in a series of batches (or lots) over a twelve year period (1911-1923), sometimes incorporating detailed differences. Two further lots were built in 1925 and 1932 by Churchward's successor, Charles Collett.
The first twenty examples, numbered 4301-20, were delivered by Swindon Works between June and October 1911. These had inside steam pipes, and were among the first GWR locomotives to be fitted with top feed apparatus.[4] Nos. 4311–20 had boilers designed to operate at 225 psi (1.55 MPa) pressure but only 4315 and possibly 4316 ever worked at that pressure.
Three further batches, totalling a further forty locomotives (4321-4360) were built at Swindon and delivered June 1913 and May 1914, before the onset of the First World War impeded further production. These locomotives (and all subsequent examples had frames lengthened by 9 in (229 mm) at the rear to give better access for maintenance as well as providing more room in the cab.
The class proved to be ‘just the type that was needed during the 1914-18 war and were accordingly built in considerable numbers during that period.’[6] Six batches, totalling one hundred locomotives (numbered 4361-4399, 4300, 5300-5359) were built between May 1915 and September 1918, and a further ten (5360-5369) between January and June 1919. From 1917 detailed changes were made to the design giving better weight distribution between the wheels which were later applied to other members of the class[7] Eleven examples of the class were transported to France during World War I in the service of the Railway Operating Division of the British Army and these were 5319 - 5326 and 5328 - 5330. One survives in preservation.
The first three of these lots were for seventy locomotives built between June 1919 and July 1921 (Nos. 5370-99 and 6300-6341). Lot 216 was for a further 28 locomotives (6342-6369) but Swindon works was then unable to keep pace with the demand for them and only the first twenty were completed after delay, between March and December 1923. The remainder (6362-9 and 7320/1) were later built under lot 230 in 1925.[8] 6320 was converted to oil firing between 1947 and the equipment was removed in 1949.
As Swindon works could not keep pace and order was placed with Robert Stephenson and Company in 1921 for fifty locomotives (Nos. 6370-99 and 7300-7319). The first 35 of these (Lot 218) were built by the company between April 1921 and January 1922. The remaining fifteen were built at Swindon from parts manufactured by RSH between November 1921 and January 1922. In 1925 Nos. 7300–7304 were modified for better balance and had detail alterations.
In 1932, Collett built a further twenty examples (9300 – 9319) to a modified design with side window cabs, outside steam pipes and a screw reverse. He also extended the frames, increasing the weight to 65 long tons 0 cwt (145,600 lb or 66 t) (72.8 short tons), which placed them in the Red band of route availability. After passing into British Railways ownership, these locomotives were modified back to light buffer beam design and were renumbered 7322–7341 between 1956 and 1959.
The class were widely used in Devon and Cornwall where the track had many sharp curves. It was found that flange wear on the leading driving wheels became excessive as a result of these bends. In November and December 1927 additional weight was added to the front end of four examples so that the pony truck would be forced to impart more side thrust to the main frames on bends. These locomotives reverted to their original state, but between January and March 1928, 65 engines of 5300 series received additional weight on the pony truck, and 3000 was added to their running numbers, temporarily creating an ‘8300 Class’.
In the West by Kevin MacLeod is licensed under a Creative Commons Attribution 4.0 license. [ Ссылка ]
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