South African Class GO 4-8-2+2-8-4
|South African Class GO 4-8-2+2-8-4|
No. 2592 standing out of service at De Aar loco depot, 14 November 1979
|Type and origin|
|Designer||South African Railways|
|Builder||Henschel and Son|
|Serial number||Henschel 28705-28729 |
|Configuration||4-8-2+2-8-4 "Double Mountain" Garratt|
|Gauge||3 ft 6 in (1,067 mm) Cape gauge|
|30 in (762 mm)|
|Driver diameter||54 in (1,370 mm)|
|30 in (762 mm)|
|Minimum curve||275 ft (84 m)|
|Wheelbase||Total: 86 ft 4 in (26.314 m)
6 ft 10 in (2.083 m) bogie
14 ft 5 in (4.394 m) coupled
30 ft 4 in (9.246 m) total
|Length||93 ft 10 in (28.600 m)|
|Height||13 ft (3.962 m)|
|Frame||Cast frame, 45 ft (13.716 m) between pivot centres|
|Axle load||13.4 long tons (13.6 t) on 7th & 8th drivers|
|Weight on drivers||106.8 long tons (108.5 t)|
|Locomotive weight||326,600 lb (148.1 t) empty
172.1 long tons (174.9 t) w/o
|Fuel capacity||11 long tons (11.2 t)|
|Water capacity||1,660 imp gal (7,500 l) front
6,750 imp gal (30,700 l) in Type X-20 auxiliary tank wagon
|Boiler||6 ft 2.75 in (1.899 m) inside diameter at 1st ring
6 ft 4.125 in (1.934 m) inside diameter at firebox
13 ft 6.5 in (4.128 m) inside length
6 ft 9.5 in (2.070 m) pitch
|Boiler pressure||200 psi (1,380 kPa)|
|Firegrate area||56.6 sq ft (5.258 m2)|
|241 tubes 2 in (50.8 mm) diameter
36 tubes 5.5 in (140 mm) diameter
2,399 sq ft (222.874 m2)
|– Flues||26 sq ft (2.415 m2)|
|– Firebox||200 sq ft (18.581 m2)|
|– Total||2,625 sq ft (243.870 m2)|
|Superheater area||546 sq ft (50.725 m2)|
|Cylinder size||18.5 in (470 mm) bore
26 in (660 mm) stroke 
|Valve gear||Walschaerts |
|Tractive effort||49,430 lbf (220 kN) at 75% pressure|
|Operator(s)||South African Railways|
|Number in class||25|
In 1954 the South African Railways placed twenty-five Class GO light branchline Garratt articulated steam locomotives with a 4-8-2+2-8-4 Double Mountain type wheel arrangement in service. It was the last new steam locomotive type to be acquired by the Railways.
The Class GO 4-8-2+2-8-4 Garratt locomotive was designed to operate on lighter rails. The designs were prepared in 1952 under the supervision of L.C. Grubb, the Chief Mechanical Engineer (CME) of the SAR from 1949 to 1954, and an order for twenty-five of these locomotives was placed with Henschel and Son in Germany, immediately following on the order for the first batch of the Class GMA Garratt that was built by the same manufacturer. They were built in 1953 and were delivered and placed in service in 1954, numbered in the range from 2572 to 2596.
The Class GO turned out to be the last new steam locomotive type to be acquired by the Railways before full scale electrification and dieselisation commenced. The Class 5E mainline electric locomotive entered service a year after the Class GO, and the Class 31-000 diesel-electric locomotive in 1958.
In design and general appearance the Class GO was very similar to the Class GMA, with an identical one piece "Commonwealth" cast steel frame and roller bearing axle boxes on all wheels, but not on the crankpins. It had cannon boxes on all axles except those of the inner pony trucks, which had outside bearings. Many parts were, in fact, interchangeable. The chief differences were aimed at reducing weight, such as a smaller boiler with a reduced diameter, a smaller firebox and grate area and a half ton smaller capacity coal bunker.
On the coal bunker this basically involved altering the inverted "L" front end profile of the Class GMA bunker to a "\" profile on the Class GO bunker, as well as lowering the bunker height from more or less in line with the cab roof on the Class GMA to somewhat below the cab roofline on the Class GO. The engine units were identical, except that the cylinders had been lined and sleeved to reduce the bore from 20.5 to 18.5 inches (521 to 470 millimetres) to suit the smaller boiler. This resulted in a correspondingly reduced tractive effort, from 60,700 to 49,430 pounds-force (270 to 220 kilonewtons) at 75% boiler pressure.
In order not to overstress the rails, driving wheel balancing was arranged to limit the hammer blow effect to a maximum of one ton per wheel at 45 miles per hour (72 kilometres per hour). The end result was a locomotive with a maximum axle load of 13.4 long tons (14 tonnes) that could operate on 45 pounds per yard (22 kilograms per metre) rails. It was superheated, with a mechanical stoker and Walschaerts valve gear, and could negotiate curves of 275 feet (84 metres) radius with a gauge widening of not more than 0.75 inches (19.1 millimetres) and a superelevation of 4.5 inches (114 millimetres).
The most obvious visible differences between the Class GMA and Class GO were their coal bunker front ends, with the inverted "L" profile of the Class GMA and the "\" profile of the Class GO. On both locomotives their engines for their mechanical stokers were situated in the cutout on the front or cabside ends of their coal bunkers, but on the right or driver’s side on the Class GMA and on the left or fireman’s side on the Class GO.
The Class GO also had a slightly longer chimney as a result of the smaller diameter boiler. As was done with the Class GM and Class GMA, the Class GO carried water only in its front tank while the rear bunker carried only coal. The meagre water supply was therefore also augmented by semi-permanently coupling a purpose-built Type X-20 auxiliary tank wagon with a capacity of 6,750 imperial gallons (30,700 litres) to the locomotive.
Upon delivery, they were briefly put to work on the line from Krugersdorp to Zeerust, after which they were relocated to the line from Belfast to Steelpoort in the Eastern Transvaal, stationed at Lydenburg. This is one of the toughest lines on the SAR with a ruling gradient of 1 in 33, that climbs in 95 miles (153 kilometres) from a nadir at 2,427 feet (740 metres) to the summit at Nederhorst at 6,875 feet (2,096 metres), the highest point on the SAR.
When the Steelpoort line was dieselised in 1972, they went to work on the branchline from Umtata to Amabele in Transkei and on the Greytown branchline out of Pietermaritzburg in Natal. They were unpopular in Transkei, however, being too small to replace two Class 14CRB locomotives, while their coupled wheelbase per engine unit was longer than that of the Class 14CRB and therefore took less kindly to the sharp curves at the Kei River crossing.
As a result, the Transkei locomotives were soon also relocated to Natal, where most of them ended up on the Natal North Coast line, stationed at Stanger, Empangeni and Gingindlovu. From Empangeni they also worked the line to Golela on the Swaziland border, and they also served briefly on the Eshowe and Nkwalini branchlines. They were soon withdrawn from the Eshowe branch, however, as a result of their tendency to start fires while climbing the 1 in 30 gradients through sugar cane fields.
Like the Class GMA, the Class GO was a successful locomotive that gave good service. However, after they were displaced by diesel-electric locomotives, the whole Class was relocated to De Aar in 1977, where the locomotives spent seven years standing idle before they were abruptly all written off in 1984, after only twenty-two years of actual revenue service. None were sold into industrial service.
The main picture shows number 2592 after being withdrawn from service, staged at the De Aar loco depot, on 14 November 1979. The only preserved Class GO locomotive is no. 2575, which is on display at the Outeniqua Transport Museum in George.
- Articulated locomotive numbering and classification
- List of South African locomotive classes
- South African Class GEA 4-8-2+2-8-4
- South African Class GL 4-8-2+2-8-4
- South African Class GM 4-8-2+2-8-4
- South African Class GMA 4-8-2+2-8-4
- South African locomotive history
- The 4-8-2+2-8-4 "Double Mountain"
- Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives from Other Builders, retrieved 10 November 2012
- Henschel-Lieferliste (Henschel & Son works list), compiled by Dietmar Stresow
- Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 113–114. ISBN 978-0-7153-5427-8.
- South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended
- Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 96. ISBN 0869772112.
- Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 118. ISBN 0715386387.
- Durrant, A.E. (1981). Garratt Locomotives of the World. David & Charles. pp. 132-136. ISBN 0-7153-7641-1.