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The R class was an express passenger steam locomotive that ran on Australia's Victorian Railways from 1951 to 1974. A long overdue replacement for the 1907-era A2 class 4-6-0, their development and construction was repeatedly delayed due to financial constraints caused by the Great Depression and later the manpower and materials shortages of World War II and the immediate postwar period. Orders eventually totalling 70 locomotives were placed with the North British Locomotive Company of Glasgow. Once initial teething problems were overcome, R class locomotives proved to be a success and their power and speed enabled faster timetabled services. However, they were almost immediately superseded by mainline diesel-electric and electric locomotives on the VR from 1952 onwards. With successive orders of diesel-electric locomotives through the 1950s and 1960s gradually displacing them, all but seven of the class were withdrawn and cut up for scrap. Four of the remaining locomotives were later restored to operating condition between 1984 and 1998. These have seen use ranging from hauling special heritage train services through to substituting for modern diesel-electric locomotives on regular intercity rail services run by V/Line and West Coast Railway. Another surviving example, number R 704, was originally displayed at the Festival of Britain in 1951 and is now on permanent display at the Australian Railway Historical Society museum in North Williamstown, Victoria. == History == Within a few years of the introduction of the A2 class 4-6-0 in 1907, it was clear that increasingly heavy train loads would require a more powerful locomotive on principal main lines. From as early as 1918, a series of drawings for potential 4-6-2 'Pacific' type locomotives began to emerge from the VR's Locomotive Design Section, some of which were ultimately developed into the 3 cylinder S class heavy Pacific of 1928. However, plans for a smaller 2 cylinder Pacific, with an axle load below 20 tons to allow operation across the VR mainline network, were put on hold during the 1930s. This was partly due to the decline in traffic and revenue due to the Great Depression, and partly due to the improved power outputs and efficiency from the A2 locomotives after the application of a series of smokebox design and draughting changes referred to as 'Modified Front End' in the mid-1930s. By 1943 however, the situation had changed. There was a massive increase in traffic brought by the advent of World War II, and the A2s were by this point well past their prime. The VR Locomotive Design Section once again turned their attention to the proposed Pacific replacement. The addition of a mechanical stoker, the enlarging of the grate from for increased performance and the use of heavy bar-frame construction for increased durability significantly increased the projected weight of the locomotive. To keep the axle load to 19.5 tons, the design by 1944 had changed from a 4-6-2 'Pacific' to a 4-6-4 'Hudson' wheel arrangement. 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「Victorian Railways R class」の詳細全文を読む スポンサード リンク
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