South African Class NG G12 2-6-2+2-6-2

The South African Railways Class NG G12 2-6-2+2-6-2 of 1927 was an articulated narrow-gauge steam locomotive.

South African Class NG G12 2-6-2+2-6-2
Class NG G12 no. 57, c. 1930
Type and origin Power type Steam Designer Beyer, Peacock and Company Builder Société Franco-Belge Serial number BP 6365-6366, FB 2506-2507 Model Class NG G12 Build date 1927 Total produced 2
Specifications Configuration: ​  • Whyte 2-6-2+2-6-2 (Double Prairie)  • UIC 1'C1'+1'C1'h4t Driver 3rd & 4th coupled axles Gauge 2 ft (610 mm) narrow Leading dia. 21 in (533 mm) Coupled dia. 30 in (762 mm) Trailing dia. 21 in (533 mm) Wheelbase 40 ft (12,192 mm)  • Engine 12 ft 7 ^1⁄2 in (3,848 mm) each  • Coupled 5 ft 9 in (1,753 mm) each Pivot centres 21 ft (6,401 mm) Length: ​  • Over couplers 45 ft 10 in (13,970 mm) Height 10 ft (3,048 mm) Frame type Plate Axle load 3 LT 15 cwt (3,810 kg)  • Leading 3 LT 10 cwt (3,556 kg) front 3 LT 10 cwt (3,556 kg) rear  • Coupled 3 LT 15 cwt (3,810 kg)  • Trailing 3 LT 5 cwt (3,302 kg) front 3 LT 5 cwt (3,302 kg) rear Adhesive weight 22 LT 10 cwt (22,860 kg) Loco weight 36 LT (36,580 kg) Fuel type Coal Fuel capacity 2 LT (2.0 t) Water cap 800 imp gal (3,640 l) front 200 imp gal (909 l) rear Firebox type Round-top  • Firegrate area 10.5 sq ft (0.98 m^2) Boiler: ​  • Pitch 5 ft 3 in (1,600 mm)  • Diameter 3 ft 6 ^3⁄8 in (1,076 mm)  • Tube plates 8 ft 6 in (2,591 mm)  • Small tubes 73: 1 ^3⁄4 in (44 mm)  • Large tubes 10: 5 ^1⁄4 in (133 mm) Boiler pressure 180 psi (1,241 kPa) Safety valve Pop Heating surface 423.5 sq ft (39.34 m^2)  • Tubes 378.5 sq ft (35.16 m^2)  • Firebox 45 sq ft (4.2 m^2) Superheater: ​  • Heating area 97.5 sq ft (9.06 m^2) Cylinder size 8 ^1⁄2 in (216 mm) bore 16 in (406 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Johnston link-and-pin Bell-and-hook (Langkloof)
Performance figures Tractive effort 10,400 lbf (46 kN) @ 75%
Career Operators South African Railways Class Class NG G12 Number in class 2 Numbers 56-57 Delivered 1927 First run 1927 Withdrawn 1952 Scrapped 1959

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.[1][2][3]

Manufacturer

The success of the five Class NG G11 Garratt narrow-gauge locomotives which had been placed in service on the Avontuur line in the Langkloof and the Stuartstown line in Natal between 1919 and 1925 led to the decision by Col F.R. Collins DSO, Chief Mechanical Engineer of the South African Railways (SAR), to acquire a smaller Garratt type for two new light-rail narrow-gauge branch lines which were completed in 1926. In 1927, orders were placed with Beyer, Peacock and Company for the design and construction of two lightweight narrow-gauge Garratt locomotives with a 2-6-2+2-6-2 Double Prairie type wheel arrangement.[1][3]

Beyer, Peacock sub-contracted their construction and the two locomotives were delivered by the Belgian locomotive builders Société Franco-Belge in November 1927. They were allocated separate works numbers by Beyer, Peacock as well as Franco-Belge and were numbered NG56 and NG57 upon delivery.[1][2][4][5]

Characteristics

The locomotives were superheated, with outside plate frames, Walschaerts valve gear, inclined cylinders, piston valves and round-topped 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.[1][3]

Classification

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.[2][3]

Service

The Class NG G12 was obtained for use on the new narrow-gauge lines from Fort Beaufort to Seymour and from Upington to Kakamas which had been completed in 1926, since it had become obvious that the Class NG6 Lawleys which had been used during the construction of these lines would not be able to cope with the expected daily traffic once the lines were in full operation.[3]

Upon arrival, the two locomotives were first put to work in South West Africa for a trial period, after which no. NG56 was assigned to Upington and no. NG57 to Fort Beaufort.[3]

While they both mostly remained with their assigned depots, they were at times temporarily assigned to narrow-gauge branch lines 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 South West Africa 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.[3]

Both locomotives were subsequently sold to the Rustenburg Platinum Mines, no. NG56 in 1952 and no. NG57 in 1953, where they were renumbered 5 and 6 respectively. They were both scrapped in 1959.[6]

References

1. Espitalier, T.J.; Day, W.A.J. (1946). The Locomotive in South Africa - A Brief History of Railway Development. Chapter VII - South African Railways (Continued). South African Railways and Harbours Magazine, February 1946. pp. 134-135.
2. South African Railways and Harbours Narrow Gauge Locomotive Diagram Book, 2'0" Gauge, S.A.R. Mechanical Dept. Drawing Office, Pretoria, 28 November 1932
3. Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 106–107, 110. ISBN 0869772112.
4. Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives produced by Beyer, Peacock, retrieved 10 November 2012
5. Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives from Other Builders, retrieved 10 November 2012
6. 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