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GWR 4-4-0 3700 Class edit

 
GWR 3700 Class No. 3433 City of Bath showing tapered boiler and Belpaire firebox
Main article: GWR 3700 Class

In September 1902, whilst still assisting Dean, Churchward had a member of the Atbara Class, no. 3405 Mauritius, reboilered with Belpaire firebox and the first use of a tapered boiler on the GWR. Once he became CME, the boiler became the prototype for Churchward's GWR Standard No. 4 boiler.[1] This experiment led to the design of the City' class, with the first outshopped from Swindon in March 1903, No. 3433 City of Bath.[2] It was fitted with the final form of the Standard No.4 boiler, with slightly curved sides and a tapered top to the firebox.[3] The class soon became one of the most famous classes of locomotives in the world, when City of Truro became the first engine in the world to haul a train at 100 miles per hour in 1904 (although unauthenticated).

Experiments with compunding edit

See also: Compound locomotive
 
Experimental 4-6-0 No. 100 William Dean

In 1901, whilst still assistant to Dean, the GWR board approved Churchward's plan to build a series of two cylinder 4-6-0 locomotives.

4-6-0 No. 100 was out-shopped in February 1902,[4] named Dean (renamed William Dean in June 1902 to mark the latter's retirement). It incorporated a domeless parallel boiler, raised Belpaire firebox, 19 in (48.3 cm) diameter outside cylinders with 30 in (76.2 cm) piston stroke, and boiler pressure of 200 psi (1.38 MPa).[5] The piston valves were driven by rocking levers actuated by the expansion link of Stephenson valve gear – this particular design was only used on no. 100.[6]

No. 98 was out-shopped in March 1903, to a similar design but with a taper boiler, re-designed valve gear layout and cylinders, and a shorter wheelbase.[7] Valve diameters were increased from 6+1⁄2 inches (170 mm) to 10 inches (250 mm).[8]

No. 171 was out-shopped in December 1903, incorporating the improvements to No. 98 but with a 225 psi (1.55 MPa) boiler and minor amendments to the heating surface and grate area. Built as a 4-6-0, in October 1904 it was converted to a 4-4-2 to enable better comparison with the performance of the French de Glehn compound; it was reconverted to 4-6-0 in July 1907.[7] Named Albion in 1904, it received a superheated boiler in 1910.

On succeeding Dean, the GWR board had authorised Churchward to purchase three French de Glehn-du Bousquet four-cylinder compound locomotives, in order to evaluate the benefits of compounding. Similar to the Paris-Orleans Railway's 3001 class and built by Société Alsacienne de Constructions Mécaniques,[9] the first locomotive no.102 La France was delivered in 1903, with Nos. 103 and 104 purchased in 1905. The locomotives had two high pressure cylinders fitted between the frames, and two low pressure cylinders outside.[10]

Each was initially fitted with a standard-pattern GWR chimney, a GWR tender and had their numbers positioned in GWR fashion on the sides of the cab. They were then each placed into service to evaluate performance, and then following engine crew feedback were modified to test other aspects of Churchward's design experimentation and philosophy.[11][12] In 1926, the three locomotives were based at Oxford shed.[13] In operational practice, compounding did not provide any significant improvement in either performance or economy compared to No 171 Albion, Churchward's prototype 4-6-0, which was converted to a 4-4-2 specifically for direct comparison with them.[14]

GWR 4-6-0 2900 Saint class edit

Main article: GWR 2900 Class

Experimental 4-6-0 No. 171 formed the basis of the GWR 2900 Saint Class. It appeared in four production series built between 1905 and 1913, each of which differed in dimensions. There were also differences between members of each series in terms of the boilers used, wheel arrangement (Churchward was unsure of the choice between 4-4-2 and 4-6-0), and arrangements for superheating.

The locomotives performed well as passenger locomotives over all the long-distance routes of the GWR and on all but the fastest express trains until they gradually became displaced to secondary services by the Castle Class in the late 1920s and 1930s. However, the 6 ft 8+1⁄2 in (2.045 m) driving wheels limited their usefulness on freight trains. Churchward had recognized this limitation by the introduction of his GWR 4700 Class 2-8-0 design with 5 ft 8 in (1.727 m) driving wheels in 1919, intended for express goods trains. However, Churchward's successor Charles Collett felt that a smaller-wheeled version of the ‘Saint’ class could form the basis of a successful mixed-traffic class of locomotives. He therefore rebuilt No. 2925 Saint Martin with 6 ft (1.829 m) driving wheels to become the prototype of his successful Hall Class locomotives. Thus the 2900 class became a template for later GWR 2-cylinder 4-6-0 classes including the Modified Hall, Grange, Manor and County classes, all of which were of the same basic design.[15]

The class incorporated many revolutionary advances which were influential in British locomotive design for the next fifty years. According to The Great Western Society, 'Saint' class locomotives "represented one of the most important steps forward in railway traction of the 20th century", and they "are now acknowledged to have had a profound influence on almost every aspect of subsequent steam locomotive development".[16]

Standard locomotive classes edit

Further information: List of GWR standard classes with two outside cylinders

The Saints and their derived classes were only part of Churchward's scheme. Based on a limited number of standard parts—including boilers, cylinders, wheels and valve gear—he planned a range of locomotives for duties such as express passenger, mixed traffic, heavy freight and suburban trains, with both tender and tank versions. He began to construct some of his designs immediately; he also extended the range of designs as the demands of the business required, producing the 4300 Moguls and 4700 express freight engines. His mixed-traffic design did not appear until Collett built the Granges in 1936.

GWR 4-6-0 4000 Class edit

Main article: GWR 4000 Class

The Great Western Railway 4000 or Star class were 4-cylinder 4-6-0 passenger locomotives introduced from early 1907. The prototype was built in May 1906 as a 4-4-2 Atlantic (but later converted to 4-6-0). The design benefited from experience gained from the 'Saint' class and the De Glehn engines. The locomotives proved to be very successful, handling the heaviest long-distance express trains, reaching top speeds of 90 mph (145 km/h), and they established the design principles for GWR 4-cylinder classes over the next twenty-five years.[17]

The Great Bear Pacific edit

 
The Great Bear

GWR 111 The Great Bear was the first 4-6-2 (Pacific) locomotive used on a railway in Great Britain,[18] the only one of that type ever built by the GWR, which is today seen as Churchward's notable failure in locomotive design. No clear GWR commercial reason existed for the design, so it is concluded by many as a further Churchward experiment, considered to explore what came beyond the Star Class when train loads increased beyond their capability.[19] Basically a developed Star class locomotive, the larger boiler over trailing wheels allowed a firebox surface of 182 sq ft (16.9 m2), a 17.5% increase in size compared to the Star Class.[20] It was also built with a Swindon No. 1 superheater.

Due to its weight and 20 long tons 9 cwt (20.8 t) axle load, the locomotive was restricted to the Paddington to Bristol main line, mainly under Paddington driver Thomas Blackall, originally from Aston Tirrold, Oxfordshire. Despite later experimental developments, in service the performance of The Great Bear proved to be disappointing, and not a significant improvement on existing classes.[21] The excellent performance of the Star Class and advent of the First World War brought a stop to further experimentation without significant improvement.

Although not a technical success, The Great Bear was considered the company's flagship locomotive from its introduction until Churchward's retirement in 1922.[22] With the introduction of 4073 Caerphilly Castle in 1923 with a higher tractive effort, the locomotive ceased to have any publicity value and became an embarrassment. Due for heavy repairs in January 1924, it was withdrawn from service by Churchward's successor Charles Collett.[23] It emerged from Swindon later that year as a 4-6-0 Castle Class, given the name Viscount Churchill.

  1. ^ Nock 1977, p. 58
  2. ^ Nock 1977, p. 59
  3. ^ Nock 1978, p. 89
  4. ^ le Fleming 1953, p. H22
  5. ^ Nock 1983, p. 12
  6. ^ Nock 1983, p. 21
  7. ^ a b le Fleming 1953, p. H23
  8. ^ Great Western Society – GW 2900 Class overview (Accessed 26 April 2009)
  9. ^ Haresnape 1993, p. 22
  10. ^ Freezer, Cyril (October 1971). "La France". Railway Modeller. Vol. 22, no. 252. Seaton, Devon: Peco Publications and Publicity Ltd. p. 334.
  11. ^ Rogers 1975, p. 133
  12. ^ Nock 1975, p. 75
  13. ^ "Trains in the vale". Pendon Museum. Archived from the original on 26 June 2008. Retrieved 2008-11-12.
  14. ^ Foster, Richard (Nov 2007). "Churchward: The man and his machines". Steam Railway (342). Peterborough: EMAP Ltd: 66–72.
  15. ^ le Fleming 1953, p. H4
  16. ^ Didcot Railway Centre (21 Apr 2019). "The impossible dream". Retrieved 24 October 2021.
  17. ^ Train: The Definitive Visual History. DK Publishing. 2014. p. 97. ISBN 1465436588. Retrieved 2 October 2020.
  18. ^ Foster, Richard (November 2007). "The man and his machines: The Great Bear". Steam Railway. No. 342. Peterborough: EMAP Ltd. p. 69.
  19. ^ Nock 1983, p. 163
  20. ^ Nock 1983, p. 164
  21. ^ le Fleming 1953, p. H13
  22. ^ Nock 1980, p. 85
  23. ^ Nock 1980, p. 89
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