South African Class NG G12 2-6-2+2-6-2
Class NG G12 no. 57, circa 1930
|Type and origin|
|Designer||Beyer, Peacock and Company|
|Serial number||BP 6365-6366, FB 2506-2507 |
|Model||Class NG G12|
|Configuration||2-6-2+2-6-2 "Double Prairie" Garratt|
|Gauge||2 ft (610 mm) narrow gauge|
|21 in (533 mm)|
|Driver diameter||30 in (762 mm)|
|21 in (533 mm)|
|Wheelbase||Total: 40 ft (12.192 m)
5 ft 9 in (1.753 m) coupled
12 ft 7.5 in (3.848 m) total
|Length||45 ft 10 in (13.970 m)|
|Height||10 ft (3.048 m)|
|Frame||Plate frame, 21 ft (6.401 m) between pivot centres|
|Axle load||3.75 long tons (3.8 t) per driver|
|Weight on drivers||22.5 long tons (22.9 t)|
|Locomotive weight||36 long tons (36.6 t)|
|Fuel capacity||2 long tons (2.0 t)|
|Water capacity||800 imp gal (3,600 l) front
200 imp gal (910 l) rear
|Boiler||3 ft 6.375 in (1.076 m) inside diameter
8 ft 6 in (2.591 m) inside length
5 ft 3 in (1.600 m) pitch
|Boiler pressure||180 psi (1,240 kPa)|
|Firegrate area||10.5 sq ft (0.975 m2)|
|73 tubes 1.75 in (44.4 mm) diameter
10 tubes 5.25 in (133 mm) diameter
378.5 sq ft (35.164 m2)
|– Firebox||45 sq ft (4.181 m2)|
|– Total||423.5 sq ft (39.344 m2)|
|Superheater area||97.5 sq ft (9.058 m2)|
|Cylinder size||8.5 in (216 mm) bore
16 in (406 mm) stroke
|Tractive effort||10,400 lbf (46 kN) at 75% pressure|
|Operator(s)||South African Railways |
|Class||Class NG G12|
|Number in class||2|
In 1927 the South African Railways placed two Class NG G12 Garratt articulated steam locomotives with a 2-6-2+2-6-2 Double Prairie type wheel arrangement in service. They were the smallest Garratt locomotives to see service in South Africa.
The South African Railways (SAR) placed orders for two light weight narrow gauge Garratt locomotives with a 2-6-2+2-6-2 Double Prairie type wheel arrangement with Beyer, Peacock and Company in 1927. Beyer, Peacock sub-contracted their construction and the two locomotives were delivered by the Belgian locomotive builders Société Franco-Belge later in 1927. They were allocated separate works numbers by Beyer, Peacock as well as Franco-Belge, and were numbered NG56 and NG57 upon delivery.
The locomotives were superheated, with outside plate frames, Walschaerts valve gear and round top fireboxes. Designed for light 20 pounds per yard (9.9 kilograms per metre) rail, their lightness of construction made them popular with the fitters who had to maintain them.
The system of grouping narrow gauge locomotives into classes was only adopted by the SAR somewhere between 1928 and 1930 and at that point these two locomotives were designated Class NG G12, with the letters "NG" indicating narrow gauge and the "G" prefix to the classification number identifying it as a Garratt locomotive.
The Class NG G12 was obtained for utilisation on the new narrow gauge lines from Fort Beaufort to Seymour and from Upington to Kakamas, since it had become obvious that the Class NG6 Lawleys that had been used during the construction of these lines would not be able to cope with the expected daily traffic once the lines were opened.
Upon arrival, the two locomotives were first put to work in South West Africa (SWA) for a trial period, after which no. NG56 was assigned to Upington and no. NG57 to Fort Beaufort.
While they both mostly remained with their assigned depots, they were at times temporarily assigned to branches in other areas of the country to assist with seasonal demands on those branches. In 1940, when the Seymour branch was regauged to Cape gauge, no. NG57 was also assigned to the Kakamas branch. Both remained there until 1949, when the Kakamas line was also widened to Cape Gauge and they were returned to SWA for a brief period. From there, no. NG56 was allocated to Port Shepstone in Natal and no. NG57 to Humewood Road in Port Elizabeth, where they remained until both were withdrawn from service in 1952.
- List of South African locomotive classes
- Narrow gauge locomotive numbering and classification
- South African locomotive history
- The 2-6-2+2-6-2 "Double Prairie"
- Two foot gauge railways in South Africa
- Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives produced by Beyer, Peacock, retrieved 10 November 2012
- Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives from Other Builders, retrieved 10 November 2012
- South African Railways and Harbours Narrow Gauge Locomotive Diagram Book, 2’0” Gauge, S.A.R. Mechanical Dept. Drawing Office, Pretoria, 28 November 1932
- Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 106–107, 110. ISBN 0869772112.
- Middleton, John N. (1989). South African Railways Locomotive Allocations - 1989 (4th, 1989 ed.). Auckland Park, South Africa: Railway Preservation Group. p. 20. ISBN 0-620-13670-7