PLW Great Western Railway 4900 Class

Description

The Great Western Railway 4900 Class or Hall Class is a class of 4-6-0 mixed-traffic steam locomotives designed by Charles Collett for the Great Western Railway. A total of 259 were built at Swindon Works, numbered 4900–4999, 5900–5999 and 6900–6958.

By the end of 1923 the Great Western Railway (GWR) was well served with express passenger locomotives of the Saint and Star classes and had recently introduced the Castle Class. However, the mixed-traffic 2-6-0 locomotives of the 4300 Class were beginning to struggle with the increasing loads. George Jackson Churchward had recognised this with the introduction of the 4700 class 2-8-0 with 5 ft 8 in (1. 727 m) driving wheels, intended for express goods and relief passenger trains. However, Charles Collett preferred the idea of a Saint Class with smaller wheels to undertake these duties as this would provide a leading bogie. He therefore rebuilt number 2925 Saint Martin with 6 ft (1. 829 m) driving wheels. The prototype of the new class was rebuilt in 1924 and the cylinders were realigned in relation to the driving axle and a more modern 'Castle'-type cab was fitted. Saint Martin emerged from Swindon Works in 1924 and embarked on three years of trials. During this period Collett introduced other modifications such as changing the pitch of the taper boiler and adding outside steam pipes.

After extensive trials during 1925–1927, Collett was satisfied with the performance of his prototype, subject to minor amendments and placed an order for eighty more with Swindon works (Lot 254) in 1928. The prototype was renumbered 4900 in December 1928 and the new locomotives were numbered 4901-80 and appeared at regular intervals until February 1930. They were named after English and Welsh country houses with 'Hall' in their titles and so became known as the 'Hall Class'. They differed little from the prototype; the bogie wheel diameter had been reduced by two inches from 3 ft 2 in (0. 965 m) to 3 ft 0 in (0. 914 m) and the valve setting amended to give an increased travel of 7. 5 in (191 mm). The overall weight of the locomotive had increased by 2 long tons 10 cwt (5,600 lb or 2. 5 t) to 75 long tons 0 cwt (168,000 lb or 76. 2 t) but a tractive effort of 27,275 lbf (121. 33 kN) compared favourably with the 24,935 lbf (110. 92 kN) of the 'Saint'. The original locomotives were built with Churchward 3,500 imp gal (16,000 L; 4,200 US gal) tenders but after 4958 Collett's larger 4,000 imp gal (18,000 L; 4,800 US gal) types became standard although a few later locomotives were fitted with smaller tenders if these were available as they entered service. The fir