page_title: 4-8-2+2-8-4
section_title: South Africa
hierarchical_section_title: 4-8-2+2-8-4 / Usage / South Africa
caption_attribution_description: English: SAR Class GM 2298 (4-8-2+2-8-4) Location: Krugersdorp Shed
context_page_description: Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 4-8-2+2-8-4 is a Garratt articulated locomotive consisting of a pair of 4-8-2 engine units back to back, with the boiler and cab suspended between them. The 4-8-2 wheel arrangement has four leading wheels on two axles, usually in a leading bogie, eight powered and coupled driving wheels on four axles and two trailing wheels on one axle, usually in a trailing truck. Since the 4-8-2 type is generally known as a Mountain, the corresponding Garratt type is usually known as a Double Mountain.
context_section_description: Five classes of Double Mountain locomotives, three of which were tank-and-tender Garratts, were acquired by the South African Railways (SAR) between 1929 and 1954.
  During 1929 and 1930, the SAR placed eight Class GL Garratt locomotives in service, built by Beyer, Peacock and Company to specifications prepared by Chief Mechanical Engineer (CME) Colonel F.R. Collins DSO. Their tractive effort of 78,650 pounds-force (350 kilonewtons) at 75% boiler pressure made them the most powerful steam locomotives in service anywhere in the Southern Hemisphere at the time. They were originally employed on the Durban to Cato Ridge section of the Natal mainline, until electrification between Durban and Pietermaritzburg in 1938 saw them transferred to the gruelling coal train run between Glencoe and Vryheid. This work entailed the regular haulage of 1200 tons up gradients of 1 in 50 (2%), taxing the Class GL even more heavily than the work for which it was designed. Despite this, they maintained an effective service along this line until its electrification in 1968, after which they spent their final working years operating on the line from Stanger to Empangeni.
  During 1938 and 1939, the SAR placed sixteen Class GM Garratts, built by Beyer, Peacock, in goods train service on the line from Johannesburg via Krugersdorp and Zeerust to Mafeking. After the initial designs by CME W.A.J. Day were rejected by the Chief Civil Engineer because the weight on the leading and trailing bogies exceeded the acceptable limit for 60 pounds per yard (30 kilograms per metre) rail, the water capacity of the front water tank was reduced to 1,600 imperial gallons (7,300 litres) while the rear bunker was redesigned to carry no water and with a coal capacity of 10 tons. The meagre water supply was augmented by semi-permanently coupling a specially built 6,750 imperial gallons (30,700 litres) capacity Type X-17 water tender to the locomotive. In effect, since Garratt locomotives had hitherto been considered as tank engines because they carry all their water and fuel on board, this arrangement introduced the tank-and-tender Garratt. In all other respects, the design followed that of the heavy Class GL Garratt.
  During 1946 and 1947, the SAR placed fifty Class GEA Garratts in service. The order for fifty locomotives was the largest single Garratt order ever placed with Beyer, Peacock. Designed by CME Dr. M.M. Loubser as a development of the Class GE 2-8-2+2-8-2 locomotive, it was the first SAR Garratt to have streamlined water tanks and coal bunkers. Meant for goods traffic on light 60 pounds per yard (30 kilograms per metre) rail on branch lines, the GEA was superheated and had Walschaerts valve gear. It was the only post-war SAR Garratt to be without a mechanical stoker and also one of the largest designs of Garratt to be hand-fired.
  Between 1954 and 1958, 120 Class GMA branch line and Class GMAM mainline Garratts entered service. This was the most numerous Garratt class in the world. A development of the Class GM, the Classes GMA and GMAM were identical and their water and coal capacities could be adjusted to suit by installing or removing plates in the coal and water spaces. They could easily be converted back and forth between the two versions, and often were. Like the Class GM, it was a tank-and-tender Garratt and the water supply was augmented by semi-permanently coupling a 6,815 imperial gallons (30,980 litres) capacity Type X-17 or 6,790 imperial gallons (30,900 litres) capacity Type X-20 water tender to the locomotive. Designed under the supervision of CME L.C. Grubb, they were built by three manufacturers, 55 by Henschel and Son, 33 by Beyer, Peacock and 32 by North British Locomotive Company, subcontracted by Beyer, Peacock.
  Also in 1954, 25 Class GO light branch line Garratts entered service. Designed under Grubb's supervision to operate on lighter rails, they were built by Henschel. In design and general appearance, the Class GO was very similar to the Class GMA, with the chief differences aimed at reducing weight, such as a smaller boiler with a reduced
caption: SAR Class GM Garratt
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