South African Class GL 4-8-2+2-8-4
The South African Railways Class GL 4-8-2+2-8-4 of 1929 was an articulated steam locomotive. In 1929 and 1930, the South African Railways placed eight Class GL Garratt articulated steam locomotives with a 4-8-2+2-8-4 Double Mountain type wheel arrangement in service. Built by Beyer, Peacock & Company in Manchester, England, 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. Origin The Class GL had its origin in the steady increase in loads experienced by the Natal mainline in the years prior to the First World War. The old Natal mainline had gradients of 1 in 30 (3⅓%) whilst the newer line, relocated to provide an easier route, still had of near-uninterrupted 1 in 66 (1½%) gradients. Moreover, the tight curvature of the line with curves of as little as radius precluded the use of large, long wheelbased, non-articulated locomotives and restricted them to a coupled wheelbase of . These factors combined with ever-increasing train weights ensured that the line rapidly 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 Class GA . Electrification was placed in abeyance along with the delivery of the Class GA until the end of World War I. 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 steam locomotives. The success of the Class GA Garratt in proving the suitability of the Garratt design for South African conditions coupled with the economies in crew, fuel and water consumption it offered, provided an 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 which were then in use, or two Class 14 steam locomotives. Manufacturer Colonel F.R. Collins DSO, the Chief Mechanical Engineer (CME) of the SAR from 1922 to 1929, prepared the specifications and the contract for the design and construction of these locomotives, the Class GL, was awarded to Beyer, Peacock & Company. The locomotive was to be approximately equal to two Class 14 locomotives in power output with a maximum permitted axle loading of owing to the use of rail on both sections of the mainline, and a maximum all-up weight of . Since these locomotives would be some 48% larger and more powerful than any locomotive previously employed on the SAR and up to twice the track gauge