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}} |length = over buffers |width = |height = |framesize = |axleload = full |locoweight = full |fueltype = Coal |fuelcap = |watercap = |firearea = |fireboxarea = |tubearea = |totalsurface = |boilerpressure= |boiler = |cylindercount=Two, inside |cylindersize= |valvegear=Stephenson |valvetype=Slide valves |tractiveeffort= |operator = GWR » BR |fleetnumbers=See Numbering below |trainheating = steam |locobrakes = steam |trainbrakes = vacuum |safety = ATC |powerclass = |axleloadclass = GWR: Blue until 1950, then Yellow |withdrawndate = 1956–1966 |preservedunits = 16 | notes = }} The Great Western Railway (GWR) 5700 Class, or 57xx class, is a class of 0-6-0 pannier tank steam locomotive, built between 1929 and 1950. 863 were built, making them the most prolific class of the GWR, and one of the most numerous classes of British steam locomotive. Although officially designated by GWR as "light goods and shunting engines", they were also used for passenger working on branch, suburban, and shorter mainline journeys. They were distributed across most of the GWR network and, after nationalisation of the railways in 1948, across the British Railways Western Region, and also other regions. The 5700s were not as glamorous as the GWR Castles and Kings, but became just as much of an icon of the GWR. As a result of the 1955 Modernisation Plan, the 5700 Class was withdrawn from BR service between 1956 and 1966. Nineteen withdrawn locomotives were sold to London Transport and industry, of which ten were later preserved, along with six that were retrieved from scrapyards. == Background== The GWR started designing and building 0-6-0 tank locomotives in 1860, and this continued into the BR era until 1956, with a total of 2,393 being built. The GWR also used 0-6-0 tank locomotives from other manufacturers' designs (from its subsidiary and absorbed railways' stock), and since 1898 it always had at least 1,000 tank locomotives in stock. The early 0-6-0 tank engines were fitted with either saddle tanks (wrapped over the boiler) or side tanks (mounted at the side of the boiler and reaching down to the running platform). GWR first fitted pannier tanks (mounted on the side of the boiler but not reaching down to the running platform) in 1898 to nine 4-4-0 tank locomotives and, in 1901, to five 0-6-0T locomotives which were also fitted with Belpaire fireboxes. The shape of the Belpaire firebox gives a larger surface area which improves heat transfer and steam production, but their rectangular shape made them difficult to combine with saddle tanks. Locomotives fitted with pannier tanks have a lower centre of gravity than those with saddle tanks (enabling higher speeds on curves), and access for maintenance is easier than for those fitted with side tanks. Churchward's period as Chief Mechanical Engineer (1901–21) is well known for significant improvements in locomotive design and manufacture, and the development of standard designs. However, the scope of the standard designs did not include the 0-6-0 tank locomotive, and the GWR did not introduce any new 0-6-0 tank designs from 1897 to 1928 (with exception of the GWR 1361 class of five 0-6-0 saddle tanks in 1910). However, pannier tanks and Belpaire fireboxes became the standard for the rebuilding of various 0-6-0 tank locomotives (projected in 1902 and getting fully underway by 1910). The rebuilding program also included a number of other changes including: * improved cab designs, eventually becoming fully enclosed * superheating, which by 1929, had been found to have little benefit on shunting engines * adaptation for working with autocoaches for push–pull trains (auto-working) * increasing boiler pressures, for example, the various rebuilds of the GWR 2721 class started at , increasing to , and then to With the completion of grouping in 1923, GWR's collection of 0-6-0 tank locomotives was expanded with the stock from 28 acquired companies. The acquired tank locomotives came from different manufacturers, were a mixture of side, saddle and pannier, and varied widely by size and state of repair. In addition, GWR's stock was wearing out, and the variety of classes was problematic for maintenance and rostering. Collett had to produce a new standard design for 0-6-0 pannier tanks. The result was the 5700 class. 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 5700 Class」の詳細全文を読む スポンサード リンク
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