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| driverdiameter = | wheelbase = (224 Class) | length = | axleload = | weightondrivers = (224 Class) | locoweight = | tenderweight = | locotenderweight = | tendertype = | fueltype = Coal | fuelcap = | watercap = | boiler = | boilerpressure = | firearea = (224 Class) | tubearea = (224 Class) | fireboxarea = (224 Class) | totalsurface = (224 Class) | cylindercount = Two, inside | cylindersize = | valvegear = | valvetype = | tractiveeffort = | trainheating = | locobrakes = | trainbrakes = | operator = North British Railway | fleetnumbers = 224, 264, 420–3 | withdrawndate = 1914–19 | disposition = All scrapped | notes = }} The NBR 224 and 420 Classes consisted of six steam locomotives of the 4-4-0 wheel arrangement built by the North British Railway (NBR) in 1871 and 1873. No. 224 had three claims to fame: it was the first inside-cylinder 4-4-0 to run in Great Britain; the locomotive involved in the Tay Bridge disaster; and after rebuilding in 1885, was the only compound-expansion locomotive on the NBR and one of just three tandem compounds in Britain. Intended for express passenger trains on the Edinburgh–Glasgow, Edinburgh–Carlisle, and Burntisland–Dundee routes, they handled these well. When trains from London to Edinburgh began to be forwarded via Carlisle over the NBR in mid-1876, these heavier trains were beyond the locomotives' capabilities, and they had to be removed from front-line service on the Carlisle line. Rebuilt between 1885 and 1897, they remained in service until 1914–19. ==History== Thomas Wheatley became locomotive superintendent of the North British Railway (NBR) at the start of February 1867. During his tenure of seven years, he provided the NBR with 185 new locomotives; but only eight of these were suitable for hauling express passenger trains, the first two of which were 2-4-0s built in 1869 (the 141 Class), which were considered to be very good engines. In 1871, Wheatley followed these with two 4-4-0s, nos. 224 and 264, which were built at the NBR's Cowlairs locomotive works. These two locomotives formed the 224 Class. A leading bogie was chosen because of the preponderance of sharp curves on the NBR; the bogie wheels were quite small, at diameter, and had solid centres, without spokes. The bogie centre was fixed, as opposed to the Adams type used later by the NBR, and the bogie wheelbase was . The coupled wheels were diameter, and the other principal dimensions were: cylinders diameter by stroke; coupled wheelbase . No. 224 was the first inside-frame inside-cylinder 4-4-0 to run in Great Britain, and predated the G&SWR 6 Class by some two years, the latter being introduced in July 1873. This layout, the 4-4-0 with inside frames and inside cylinders, became widespread across most of Great Britain, with the Great Western Railway being the only main-line company which did not eventually possess the type. There had been earlier 4-4-0 designs on other railways, but these either had outside cylinders (such as nos. 160 & 161 (built 1860) of the Stockton and Darlington Railway) or outside frames (such as the "Whitby Bogies" (1864–65) of the North Eastern Railway). The 224 Class were used on express passenger trains, no. 264 being used both on the Waverley route between Edinburgh and and on the line between Edinburgh and Glasgow. No. 224 was used in Fife, which in the days before the construction of the Forth Bridge, was an isolated part of the NBR system. The 224 Class were followed in 1873 by the four locomotives of Wheatley's 420 Class, nos. 420–3. These differed from the 224 Class in several respects: the bogie wheels were diameter instead of ; the coupled wheelbase was instead of ; the dome was mounted on the boiler barrel instead of the firebox; and the rear wheel splashers were shaped to the wheel instead of being square-topped. They were intended for use on the Waverley route, over which an increase of traffic was anticipated: the Midland Railway (MR) were at the time building their Settle and Carlisle line. This route not yet being open, and the English traffic being entirely in the hands of the London and North Western Railway who worked closely in tandem with the Caledonian Railway, the NBR's main rival, the trains over the Waverley route were comparatively light and well within the capabilities of the 420 Class. The MR opened the Settle and Carlisle line on 1 May 1876, and a through service using that route between London St Pancras and Edinburgh Waverley was introduced at the same time. North of , the trains were operated by the NBR over their Waverley route. Each company used its own locomotives over their respective lines, and initially the locomotives used by the NBR were the 420 Class, no. 421 being equipped with the Westinghouse brake (as were three other locomotives at a cost of £90, or £}} as of , per engine), the brake with which MR carriages were then fitted. But these locomotives proved insufficiently powerful, a second engine often being needed to assist in climbing the gradients, particularly those at Falahill (between and ) and at Whitrope (between and ). Wheatley's successor, Dugald Drummond, offered the opinion that NBR express locomotives of the period were "like skinny chickens, all legs and wings". As a result, Drummond designed a new class of 4-4-0 (the 476 Class) which began to displace the Wheatley 4-4-0s from the through trains in 1877, and which were capable of maintaining the schedule of 2 hr 35 min for (with three intermediate stops). The 420 Class remained on the Waverley route, but were used on the local trains, which were lighter than the through trains from England. 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「NBR 224 and 420 Classes」の詳細全文を読む スポンサード リンク
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