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The South African Railways Class GL 4-8-2+2-8-4 of 1929 is an articulated steam locomotive. During 1929 and 1930 the South African Railways placed eight Garratt articulated steam locomotives with a 4-8-2+2-8-4 Double Mountain type wheel arrangement in service. Constructed at Beyer, Peacock and Company's Gorton Foundry, they were originally designed to work on the Durban to Cato Ridge section of the Natal mainline. The Class GL was eventually displaced to the route between Glencoe and Vryheid, before spending their final working years operating on the line from Stanger to Empangeni.〔 ==Genesis== The Class GL had its origin in the steady increase in loads experienced by the Natal mainline in the years prior to World War I. The old Natal mainline had gradients of 1 in 30, whilst the newer line, relocated to provide an easier route, still had of near-uninterrupted 1 in 66 gradients. Moreover, the tight curvature of the line, with curves of as little as radius, precluded the use of large, long wheelbased rigid locomotives and restricted their length to a coupled wheelbase of . These factors, combined with ever-increasing train weights, ensured that the line quickly became a bottleneck.〔〔 The decision to electrify the line from Glencoe Junction to Durban had been taken in 1914, coincidentally the year in which the South African Railways (SAR) ordered its first Cape gauge Garratt, the . Electrification was placed in abeyance, along with the delivery of the Class GA, until the war’s end.〔 Despite this delay, the process of electrification began in earnest in 1922, and by 1926 full electrified haulage had been instituted between Glencoe and Pietermaritzburg, with lashups of three electric locomotives being used on the heaviest freights. These trains were then hauled onward to Durban by a pair of Class 14 4-8-2 locomotives.〔 Meanwhile, the success of the Class GA Garratt, which was approximately equivalent in power output to two Class 14 locomotives, in proving the basic suitability of the Garratt design for South African conditions, coupled with the economies in crew, fuel and water consumption it offered, provided a healthy incentive for the SAR to consider a new Garratt class for use on the Natal mainline. The aim was to eliminate double-heading as a regular practice, with such a locomotive to be equivalent to three of the Class 1E electric locomotives that were then in use, or two Class 14 steam locomotives.〔〔 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「South African Class GL 4-8-2+2-8-4」の詳細全文を読む スポンサード リンク
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