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The WAGR P and Pr classes are two classes of 4-6-2 "Pacific" type steam locomotives designed for express passenger service on the Western Australian Government Railways narrow gauge mainline network. The initial designs were prepared by E.S. Race〔Gunzburg, A., ''A History of WAGR Steam Locomotives'' (1982), p.102〕 and together the two classes had a total build number of thirty-five locomotives, the P and Pr classes entering service in 1924 and 1938 respectively. Both classes were used on express passenger services, greatly improving the economy and speed of long-distance passenger travel in Western Australia, the results of which were most visible on the West Australian stage of the Trans-Australian Railway, the 'Westland Express'.〔Higham, G., ''Marble Bar to Mandurah'' (2007), chapter: 'The Great Western Express', specifically pp.137-139〕 The need for more powerful locomotives in the 1920s resulted in the introduction of twenty-five P class locomotives which provided a significant improvement in power, speed and economy over previous WAGR locomotives, quickly proving to be a highly successful design.〔McNicol, S., ''WAGR Steam Locomotives in Preservation'' (1994), P and Pr class entries, p.18〕 The Great Depression of the 1930s, coupled with the effects of The Great War, thwarted the WAGRs later expansion and acquisition plans resulting in many obsolete locomotives remaining in operation into this period. As a result, ten new P class locomotives featuring detail improvements to boilers, valves and bogies were introduced in 1938, a year before the outbreak of the Second World War. The new locomotives became the first WAGR engines to be given names, each bearing that of a prominent West Australian river. These 'River class' locomotives were very successful and proved so invaluable to the operation of the wartime WAGR that eight P class locomotives were modified to their standard.〔Rogers, P., ''Troops, Trains and Trades'' (1999), pp7-8〕 All eighteen locomotives were officially classified as the 'Pr Class' in 1946.〔Gunzburg, A., ''A History of WAGR Steam Locomotives'' (1982), Pr class details, pp.103-104〕 The initial ten P class locomotives were built for the WAGR by the North British Locomotive Company in Glasgow while the remainder, including the new ten Pr class locomotives, were built locally by the WAGRs Midland Government Railway Workshops in Midland near Perth.〔 One example of the P class (''P 508'') and one example of the Pr class (class leader ''Pr 521 Ashburton'') are preserved in non-working order at the Australian Railway Historical Society's Rail Transport Museum in Bassendean, Perth.〔See ARHS website on P and Pr class, accessed via (), January 2, 2009〕 ==Background== By the early 1920s the WAGR had obtained only a handful of new locomotive designs since the beginning of the twentieth century and there was a particular lack of large passenger locomotives.〔Higham, G., ''Marble Bar to Mandurah'' (2007), chapter: 'Making up a train', pp.195-196〕 The Annual Report of 1920 pointed out the large numbers of obsolete locomotives in service and steadily growing rail traffic, stressing the need for more powerful engines.〔 The most substantial design then in service was the E class 4-6-2s of 1902, of which 65 locomotives had been built for operation in Western Australia and served on a variety of services. Likewise the 20 D class 4-6-4T tank locomotives had helped alleviate pressure on suburban services while the 57 F class 4-8-0s did the same for goods. However, all had been introduced (and subsequently superheated) prior to the First World War, meaning that by the 1920s they were becoming inadequate. At this time the most significant operation requiring new locomotives were the long distance passenger services, particularly on the Perth - Kalgoorlie and Perth - Albany expresses, both of which covered distances in excess of 350 kilometres.〔 In 1923 approval was given for the construction of ten new superheated pacific type locomotives for operation on heavier mainline rails, suitable for the hauling of the expresses. The locomotives were based on plans drawn up in 1920 under Chief Mechanical Engineer of the WAGR Ernest A. Evans which called for a new design with large diameter driving wheels, a large firebox and a two-wheel trailing wheel for stable operation at speed.〔 The final outline drawings were prepared by E.S. Race in the Midland Railway Workshops and completed in December 1923. Influence for the new P class designs were drawn from both the New Zealand Railways Ab and the Tasmanian R class pacifics.〔 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「WAGR P and Pr classes」の詳細全文を読む スポンサード リンク
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