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::''Disambiguation: LNER Class A1, LNER Thompson Class A1/1, LNER Peppercorn Class A1'' The London and North Eastern Railway LNER Gresley Classes A1 and A3 locomotives represented two distinct stages in the history of the British "Pacific" steam locomotives designed by Nigel Gresley. They were designed for main line passenger services, initially on the Great Northern Railway (GNR), a constituent company of the London and North Eastern Railway after the amalgamation of 1923, for which they became a standard design. The change in class designation to A3 reflected the fitting to the same chassis of a higher pressure boiler with a greater superheating surface and a small reduction in cylinder diameter, leading to an increase in locomotive weight. Eventually all of the A1 locomotives were rebuilt, most to A3 specifications, but no. 4470 was completely rebuilt as Class A1/1. The names for the locomotives came from a variety of sources. The first, ''Great Northern'', was named after its parent company. Others were given the names of high-ranking railway officials, but most were given the names of famous racehorses. One was named after the company's most famous long-distance passenger train, the ''Flying Scotsman''. ''Flying Scotsman'' is the sole survivor of the class to be preserved. It is currently under mechanical overhaul at the National Railway Museum. ==Class A1: Great Northern genesis== The new Pacific locomotives were built at the Doncaster "Plant" in 1922 to the design of Nigel Gresley, who had become Chief Mechanical Engineer of the GNR in 1911. The intention was to produce an engine able to handle, without assistance, mainline express services that were reaching the limits of the capacity of the Ivatt large-boilered Atlantics. Gresley's initial Pacific project of 1915 was for an elongated version of the Ivatt Atlantic design with four cylinders.〔Brown, F.A.S: ''Nigel Gresley Locomotive Engineer'', pp. 40–42〕 Finally realising that he was in a design impasse, he took as a model the new American Pennsylvania Railroad class K4 Pacific of 1914. This in turn had been updated from a series of prototypes scientifically developed in 1910 under Francis J. Cole, Alco's Chief Consulting Engineer at Schenectady〔Westing, F. & Stauffer, A. : ''Erie Power", pp. 272, 274–5〕 and the Pennsylvania's K29 Alco prototype of 1911, also designed by Cole.〔Stauffer, Alvin F. : ''Pennsy Power'', p.146〕 Descriptions of those locomotives appeared in the British technical press at the time and gave Gresley the elements necessary to design a thoroughly up-to-date locomotive. 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「LNER Gresley Classes A1 and A3」の詳細全文を読む スポンサード リンク
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