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The Great Western Railway 6000 Class or King is a class of 4-6-0 steam locomotive designed for express passenger work. With the exception of one Pacific (''The Great Bear''), they were the largest locomotives the GWR built. They were named after kings of the United Kingdom and of England, beginning with the reigning monarch, King George V, and going back through history. Following the death of King George V, the highest-numbered engine was renamed after his successor; and following the abdication of the latter, the next-highest engine was also renamed after the new King. ==Background== This class was designed under the direction of C. B. Collett, as an enlarged version of Collett's Castle Class, which in turn was an enlargement of George Jackson Churchward's Star Class. Churchward had proposed fitting the diameter boiler used on his 4700 Class 2-8-0 on to a 4-6-0 chassis in 1919 to create a more powerful express locomotive, but had been prevented from doing so due to weight restrictions on several bridges on the GWR main line. Collett's Castle class of 1923 was therefore a compromise with a boiler. However, bridge strengthening and a better understanding of the effect of hammer blow on structures brought about by the work of the 'Bridge Stress Committee' set up by the Department of Scientific and Industrial Research led to the relaxation of these restrictions. The new design was partly to meet future traffic requirements, but was also a response to the Great Western Railway publicity department's desire to regain the title of having the 'most powerful express passenger steam locomotive in Britain', which had been taken from the Castle Class in 1926 by the Southern Railway Lord Nelson Class. The engines, as originally designed, delivered tractive effort, with bore by stroke cylinders and boiler. At a request from Sir Felix Pole, the Great Western's General Manager, to get the tractive effort up to above (a major goalpost), the cylinders were enlarged to bore, bringing the figure up to . This increase was removed on all members of the class at their first major overhaul. The distinctive design of the leading bogie (with outside bearings on the fore wheel and inside bearings on the rear wheel) was to allow for these larger cylinders. The first, No. 6000 ''King George V'', appeared in 1927 and was sent on a tour of North America, for the Centenary celebrations of the Baltimore and Ohio Railroad (B&O), where its sleek appearance and smooth performance impressed all who witnessed it. The application of pressurised oil lubrication showed its advantages over the largely grease-lubricated American Locomotives, and was even incorporated into a later design for the B&O in 1928. ''King George V'' was presented with a brass bell to mark the occasion. The original scheme for the 'Kings' had been to name them after cathedrals, but when the US trip was planned it was felt that a more unmistakably British icon was needed. During planning and construction the engine was dubbed the 'Super-Castle'. They were engines to be reckoned with, powering the Western Region's crack expresses like the Cornish Riviera Limited up until the end of regular steam hauled express services on the WR. The 'Kings', however, were unable to serve Cornwall, due to the Royal Albert Bridge being too weak for their weight, and so when they were hauling the Cornish Riviera Limited, they had to be swapped for a 'Castle' or 'Hall' at Devonport. An interesting fact is that although the railway claimed that the class was built in response to longer and heavier trains, it was several years after its introduction before the platforms at the company's major stations were lengthened to accommodate these trains. The class was restricted to the London-Taunton-Plymouth (via both Bristol and ) and London-Birmingham-Wolverhampton (via Bicester) main lines, and even then, only after bridge strengthening had taken place, due to the engines' large boilers giving them a high axle weight of . William Stanier based his LMS Princess Royal Class design on the King Class, but with an enlarged boiler and firebox necessitating a 4-6-2 wheel arrangement. In 1947 experiments had been made with a four-row high-degree superheater in No. 6022 ''King Edward III'', owing to a decline in the availability of high-calorific South Wales steam coal, on which the GWR had always relied for its good locomotive performance. During the 1948 locomotive exchanges, ''King Henry VI'' had performed disappointingly using Yorkshire coal, despite demonstrating the 4-6-0 type's unique sure-footedness when climbing out of Kings Cross, where pacific types were apt to slip alarmingly. After this, four-row superheaters were fitted to the class, and modifications were also made to the draughting arrangement, using No. 6001 ''King Edward VII'' as a test-bed. From September 1955 double blast-pipes and chimneys were fitted, initially to No. 6015 ''King Richard III''. Following successful testing the whole of the class was subsequently modified and, as a result, their final years in British Railways ownership saw the very best of their performance, particularly on the steep South Devon banks at Dainton, Rattery, and Hemerdon. They were all withdrawn in 1962, replaced by the western region's short lived diesel Hydraulic ''Western'' Class locomotives. 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「GWR 6000 Class」の詳細全文を読む スポンサード リンク
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