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|boilerpressure = |cylindercount = Two, outside |cylindersize = |tractiveeffort = |operator = |operatorclass = SECR / SR: U |powerclass = |withdrawndate = 1962–1966 |disposition = Four preserved, remainder scrapped }} The SR U class were 2-6-0 (mogul) steam locomotives designed by Richard Maunsell for passenger duties on the Southern Railway (SR). The class represented the penultimate stage in the development of the Southern Railway’s mogul "family", which improved upon the basic principles established by GWR Chief Mechanical Engineer (CME) George Jackson Churchward for Great Western Railway (GWR) locomotives.〔 The U class design drew from experience with the GWR 4300 and N classes, improved by applying Midland Railway ideas to the design, enabling the SECR to influence development of the 2-6-0 in Britain.〔Scott-Morgan, p. 46〕 The U class was designed in the mid-1920s for production at a time when more obsolete 4-4-0 locomotives were withdrawn, and derived from Maunsell’s earlier SECR K (“River”) class 2-6-4 tank locomotives. The first 20 members of the U class were rebuilds of the K class locomotives, one of which was involved in the Sevenoaks railway accident. A further 20 U class locomotives were built in 1928 to fill the gap in cross-country and semi-fast express passenger services after the withdrawal of the K class. The design also continued the standardisation of the Southern Railway locomotive fleet by using parts designed to be interchangeable with other Maunsell-designed classes. A total of 50 locomotives were built over three batches between 1928 and 1931, and the design formed the basis for the 3-cylinder U1 class of 1928. They were able to operate over most of the Southern Railway network, gaining the nickname "U-Boats" after the submarine warfare of the First World War, and continued to operate with British Railways (BR). The class saw continuous use until 1966, when all members of the U class were withdrawn from service.〔Casserley, p. 440〕 Four U class locomotives have been preserved on two heritage railways in the south of England.〔Langston, p. 112〕 == Background == The history of the U class is complex as it is linked to the fate of the 2-cylinder K ("River") class 2-6-4 tank locomotives. The design work had for a new passenger 2-6-0 with 6 ft (1.83 m) driving wheels was complete by 1927, when the involvement of a K class locomotive in the Sevenoaks rail crash presented an opportunity to bring forward construction of the class.〔Southgate, (''Steam World'', 2008 (251)), p. 21〕 The K class tank engines were the passenger counterpart to the N class 2-6-0 mixed-traffic design, and were noted for rough-riding over the cheaply laid track of the former SECR.〔Clarke, (''Steam World'', 2008 (249)), p. 54〕 The class was withdrawn from service, and the inquiry that followed determined that the rough-riding contributed to the crash.〔 Its recommendation was that the K class should be rebuilt to 2-6-0 tender locomotives, using tried and tested features used by Maunsell and his assistant, the former GWR engineer Harold Holcroft on the N class.〔Clarke, (''Steam World'', 2008 (249)), p. 55〕 The N class principles applied to the U class design aided mass production, and incorporated several features found on the GWR 4300 Class locomotives designed by Churchward.〔 An order made in 1926 for a second batch of 20 K class locomotives was delayed until 1928, when the specification was revised to construct U class locomotives.〔 It was intended to replace several elderly 4-4-0 classes within the former SECR's running fleet, and attempted to standardise and ease maintenance of locomotives by sharing parts with other Maunsell designs.〔 The style of the new locomotive reflected the Midland Railway influence of another of Maunsell’s assistants, the ex-Midland Railway engineer James Clayton.〔 The addition of a tender increased the operating range of the U class over its K class predecessors, and the wheel arrangement applied to the former K class locomotives improved the locomotive’s stability when operational.〔Casserley, H.C.: 'End of the Maunsell moguls—the Southern maids-of-all-work' (''Railway World'': 1966, 27), pps. 436–440)〕 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 U class」の詳細全文を読む スポンサード リンク
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