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The SR West Country and Battle of Britain classes, collectively known as ''Light Pacifics'' or informally as ''Spam Cans'', are air-smoothed 4-6-2 ''Pacific'' steam locomotives designed for the Southern Railway by its Chief Mechanical Engineer Oliver Bulleid. Incorporating a number of new developments in British steam locomotive technology, they were amongst the first British designs to use welding in the construction process, and to use steel fireboxes, which meant that components could be more easily constructed under wartime austerity and post-war economy.〔Arlett (1989), p. 29–30〕 They were designed to be lighter in weight than their sister locomotives, the Merchant Navy class, to permit use on a wider variety of routes, including in the south-west of England and the Kent coast. They were a mixed-traffic design, being equally adept at hauling passenger and freight trains, and were used on all types of services, frequently far below their capabilities. A total of 110 locomotives were constructed between 1945 and 1950, named after West Country resorts or Royal Air Force (RAF) and other subjects associated with the Battle of Britain. Due to problems with some of the new features, such as the Bulleid chain-driven valve gear, sixty locomotives were rebuilt by British Railways during the late 1950s.〔Fairclough & Wills (1970), p. 11〕 This produced a design highly similar to the rebuilt Merchant Navy class.〔Fairclough & Wills (1970), p. 34〕 The classes operated until July 1967, when the last steam locomotives on the Southern Region were withdrawn. Although most were scrapped, twenty locomotives found new homes on heritage railways in Britain. ==Background== The financial success enjoyed by the Southern Railway during the 1930s was based on the completion of its London suburban electrification scheme in 1929 and the subsequent electrification of the main lines to Brighton and the Sussex Coast and to Guildford and Portsmouth.〔Whitehouse & Thomas (2002), p. 34〕 Despite electrification plans, the Southern Railway's less heavily used lines in the West Country beyond Salisbury did not merit the cost. Lines in Devon and Cornwall were meandering, heavily graded, and although with heavy summer holiday traffic were lightly used during the winter months.〔 The seasonality of railway traffic meant that the West Country branches were worked by the ageing T9 class 4-4-0 and the versatile N class 2-6-0, which could be better utilised on mixed-traffic services elsewhere.〔 As a result, an order was placed with Brighton railway works in April 1941 for twenty passenger locomotives of a type to be determined.〔Bradley (1976), p. 55〕 During 1943, Bulleid began planning for the post-war locomotive requirements of the railway and identified the need for a stop-gap steam locomotive design for those main lines in South East England scheduled for electrification, had the Second World War not taken place. Although the new Merchant Navy class was available for the heaviest Continental expresses, the resumption of frequent passenger services over poorly maintained infrastructure, following the war, would require a lighter locomotive with wider route availability.〔Bradley (1976), p. 55〕 At the same time, there would be a continuing need for fast freight locomotives, capable of operating on both electrified and non-electrified routes, without impeding the intensive use of the system by passenger trains.〔Whitehouse & Thomas (2002), p. 60〕 Suburban electrification used electric multiple units, which had no equivalent freight design. Although Bulleid built two prototype electric locomotives in 1941, these were, as yet, unproven, and freight haulage would be undertaken by steam traction for the foreseeable future.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「SR West Country and Battle of Britain classes」の詳細全文を読む スポンサード リンク
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