|
The SR Merchant Navy class (originally known as the ''21C1 class'', and later informally known as ''Bulleid Pacifics'', ''Spam Cans'' or ''Packets''), is a class of air-smoothed 4-6-2 Pacific steam locomotives designed for the Southern Railway of the United Kingdom by Oliver Bulleid. The Pacific design was chosen in preference to several others proposed by Bulleid. The first members of the class were constructed during the Second World War, and the last of the 30 locomotives in 1949. Incorporating a number of new developments in British steam locomotive technology, the design of the Merchant Navy class was among the first to use welding in the construction process; this enabled easier fabrication of components during the austerity of the war and post-war economies.〔Arlett (1989), pp. 29–30〕 The locomotives featured thermic syphons and Bulleid's innovative, but controversial, chain-driven valve gear.〔 The class members were named after the Merchant Navy shipping lines involved in the Battle of the Atlantic, and latterly those which used Southampton Docks, a publicity masterstroke by the Southern Railway, which operated Southampton Docks during the period.〔Burridge (1975), p. 60〕 Due to problems with some of the more novel features of Bulleid's design, all members of the class were modified by British Railways during the late 1950s, losing their air-smoothed casing in the process. The Merchant Navy class operated until the end of Southern steam in July 1967. A third of the class has survived and can be seen on heritage railways throughout Great Britain. ==Background== The Southern Railway was the most financially successful of the "Big Four", but this was largely based on investment in suburban and main line electrification .〔Whitehouse & Thomas, p. 49〕 After the successful introduction of the SR Schools class in 1930 the railway had lagged behind the others in terms of modernising its aging fleet of steam locomotives. Following the retirement of the General Manager of the Southern Railway Sir Herbert Walker and Richard Maunsell the Chief Mechanical Engineer (CME) in 1937, their successors considered that the time had come to change this situation.〔Whitehouse & Thomas, p. 59〕 In March 1938 the new General Manager Gilbert Szlumper authorised Oliver Bulleid, Maunsell's replacement, to prepare designs for twenty express passenger locomotives.〔Bradley (1976), p. 3-52.〕 The deteriorating international situation prior to the Second World War was an additional factor in this decision.〔 Bulleid's first suggestion was for an eight-coupled locomotive with a 4-8-2 wheel arrangement for the heavily loaded Golden Arrow and Night Ferry Continental express trains,〔 although this was quickly modified to a 2-8-2 equipped with a Helmholtz "Bissel bogie" – a system already successfully applied on the Continent.〔Bulleid (1977), pp. 52–53〕 However, both proposals for eight-coupled locomotives were resisted by the Southern Railway's Chief Civil Engineer, so a new 4-6-2 Pacific design was settled upon instead.〔Harvey (2004), pp. 6–9〕 The new design was intended for express passenger and semi-fast work in Southern England, though it had to be equally adept at freight workings due to the nominal "mixed traffic" classification Bulleid applied to the class for them to be built during wartime.〔 Administrative measures had been put in place by the wartime government preventing the construction of express passenger locomotives due to shortages of materials and a need for locomotives with freight-hauling capabilities.〔Creer & Morrison (2001), p. 7〕 Classifying a design as "mixed traffic" neatly circumvented this restriction. 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 Merchant Navy class」の詳細全文を読む スポンサード リンク
|