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GCR Classes 8D and 8E were two pairs of three-cylinder compound steam locomotives of the 4-4-2 wheel arrangement built in 1905 and 1906 for the Great Central Railway. ==History== In 1903, the Great Central Railway (GCR) had given comparative trials to two pairs of two-cylinder express passenger steam locomotives designed by their Chief Mechanical Engineer, John G. Robinson. These were similar in most respects, the main difference being that one pair (class 8B) were of the 4-4-2 wheel arrangement, whereas the other pair (class 8C) were 4-6-0. These trials demonstrated that the 4-4-2 was best for the GCR conditions, and so five more of class 8B were ordered, soon followed by a batch of 12. Whilst these were under construction, it was decided to compare the merits of these locomotives against a three-cylinder compound of similar size. Accordingly, two compounds of the 4-4-2 wheel arrangement were built: no. 258 in December 1905 followed by no. 259 in February 1906, and these formed ''Class 8D''. The class 8D locomotives were designed by Robinson according to the principles of Walter M. Smith, in which there were three cylinders: the boiler fed a single high-pressure cylinder placed between the frames, where the steam was partially used; it was then passed to two low-pressure cylinders mounted outside the frames, which extracted the remaining useful work from the steam. The same system had already been tried by Smith's employers, the North Eastern Railway in their class 3CC of 1898, and with great success by the Midland Railway (MR) in their 1000 class of 1902. The GCR engines used the same size cylinders as the MR engines, but were arranged differently. On the MR engines, all three cylinders drove the same axle, but the GCR engines were designed so that the high-pressure cylinder drove the front coupled axle as on the MR engines, whereas the low-pressure cylinders drove the rear coupled axle; the first use of this arrangement in Britain. Walter M. Smith's son, John W. Smith, joined the GCR at Gorton on 20 August 1906 as Works Manager & Chief Draughtsman. The GCR ordered ten more 4-4-2s for delivery in 1906: of these, eight were to the class 8B design, and two were compounds. These two, nos. 364/5, shared a number of components with the eight class 8B engines, and were sufficiently different from the two compounds of class 8D to warrant a separate classification, so became ''Class 8E''. No more 4-4-2s were built for the GCR, of any of these classes, although in 1908, Robinson did consider ordering more compounds: but the introduction of superheating soon provided a simpler method of reducing coal consumption. The four locomotives therefore remained the only compounds on the GCR. They were later given superheaters: the first was no. 365 in 1911, but it was not until 1927 before the last, no. 258, was superheated. Initially based at Gorton, they were used on the express passenger trains between and . In 1920/21, the Manchester-London trains having become too heavy for them, they were transferred to Leicester, for use on the expresses between and London Marylebone. In 1932/33 they moved to Immingham, where they were mainly used on services between and , or . Withdrawal occurred between December 1946 and December 1947. 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「GCR Classes 8D and 8E」の詳細全文を読む スポンサード リンク
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