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The BR Standard Class 7, otherwise known as the ''Britannia'' Class, is a class of 4-6-2 ''Pacific'' steam locomotive designed by Robert Riddles for use by British Railways for mixed traffic duties. Fifty-five were constructed between 1951 and 1954. The design was a result of the 1948 locomotive exchanges undertaken in advance of further locomotive classes being constructed. Three batches were constructed at Crewe Works, before the publication of the 1955 Modernisation Plan. The ''Britannia'' Class was based on several previous LMS locomotive designs,and also significantly influenced by the Bulleid SR Pacifics, notably in the boiler and rear truck design, incorporating the best practices in locomotive technology as regards labour-saving and lowering maintenance costs; various weight-saving measures also increased the route availability of a ''Pacific''-type locomotive on the British Railways network.〔 The ''Britannias'' received a positive reception from their crews, with those regularly operating the locomotives giving them favourable reports as regards performance.〔 However, trials in some areas of the British Railway network returned negative feedback, primarily due to indifferent operation of the locomotive, with its effects on adhering to timetables. The ''Britannias'' took their names from great Britons, former Star Class locomotives, and Scottish firths.〔 The class remained in service until the last was withdrawn in 1968. Two survived into preservation, the first-of-class, number 70000 ''Britannia'', and 70013 ''Oliver Cromwell''. Number 70000 has hauled mainline excursions and 70013, after a period of display following limited steaming, returned to mainline steam in 2008 for the first time since leaving British Railways ownership. 70000 was returned to the main line in 2011. ==Background== Locomotive exchanges were commissioned by the fledgling British Railways (BR) during 1948, to test the best and worst aspects of locomotive design within the Big Four railway companies that had existed before nationalisation. The research gained from operating the best designs of the GWR, LMS, LNER and Southern railways on different areas of the British Railways network paved the way for several new classes of standardised locomotives to be constructed.〔 These new locomotive designs were intended to replace some of the ageing designs inherited by British Railways. The new classes were designed by Robert Riddles, who had previously designed the WD Austerity 2-8-0 and WD Austerity 2-10-0 locomotives for wartime use. The first design requested by the Railway Executive was for a new express passenger "Pacific" locomotive, designed specifically to reduce maintenance and using the latest available innovations in steam technology from home and abroad. Various labour-saving devices were utilised to produce a simple, standard and effective design, able to produce equivalent power to some of the "Pacifics" that were still available as legacies of the Big Four.〔 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「BR Standard Class 7」の詳細全文を読む スポンサード リンク
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