South African Class GB 2-6-2+2-6-2

South African Class GB 2-6-2+2-6-2

Class GB no. 1650, renumbered no. 2166, Voorbaai, 4 September 1997

Type and origin ♠ Locomotive no. 2166 ♥ Locomotive numbers 2160-2165 Power type Steam Designer Beyer, Peacock and Company Builder Beyer, Peacock and Company Serial number 5942, 6181-6186 Model Class GB Build date 1921, 1924 Total produced 7

Specifications Configuration 2-6-2+2-6-2 (Double Prairie) Driver axle 3rd & 4th coupled axles Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia Coupled dia Trailing dia Wheelbase 53 ft (16,154 mm)  • Engine ♠ 17 ft 5 in (5,309 mm) each ♥ each  • Coupled 8 ft (2,438 mm) each Length:  • Over couplers  • Pivot centres 26 ft 6 in (8,077 mm) Height 12 ft 3 in (3,734 mm) Frame type Plate Axle load ♠ ♥  • Leading ♠ front rear ♥ front rear  • 1st coupled ♠ ♥  • 2nd coupled ♠ ♥  • 3rd coupled ♠ ♥  • 4th coupled ♠ ♥  • 5th coupled ♠ ♥  • 6th coupled ♠ ♥  • Trailing ♠ front rear ♥ front rear Adhesive weight ♠ ♥ Loco weight ♠ ♥ Fuel type Coal Fuel capacity 5 LT (5.1 t) Water cap ♠ front rear ♥ front rear Boiler:  • Pitch 7 ft (2,134 mm)  • Diameter  • Tube plates ♠ 10 ft 4 in (3,150 mm) ♥  • Small tubes ♠ 128: ♥ 119:  • large tubes ♠ 21: ♥ 21:  • Firebox type Belpaire Boiler pressure 180 psi (1,241 kPa) Safety valve Ramsbottom Firegrate area ♠♥ 23 sq ft (2.1 m2) Heating surface ♠ 1,049 sq ft (97.5 m2) ♥ 1,018 sq ft (94.6 m2)  • Tubes ♠ 944 sq ft (87.7 m2) ♥ 914 sq ft (84.9 m2)  • Firebox ♠ 105 sq ft (9.8 m2) ♥ 104 sq ft (9.7 m2) Superheater:  • Heating area ♠ 174 sq ft (16.2 m2) ♥ 203 sq ft (18.9 m2) Cylinders Four Cylinder size 12 in (305 mm) bore 20 in (508 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Bell link-and-pin AAR knuckle (1950s)

Performance figures Tractive effort 18,190 lbf (80.9 kN) @ 75%

Career Operators South African Railways Class Class GB Number in class 7 Numbers 1650 renumbered 2166, 2160-2165 Delivered 1921, 1924 First run 1921 Withdrawn 1967

The South African Railways Class GB 2-6-2+2-6-2 of 1921 was an articulated steam locomotive.

In June 1921, the South African Railways placed a single experimental Class GB Garratt articulated steam locomotive with a 2-6-2+2-6-2 Double Prairie type wheel arrangement in service. Six more of these locomotives entered service in 1924.

Manufacturer

The first experimental model of the eventually seven Class GB branchline Garratt articulated locomotives was one of altogether five Garratt locomotives which were ordered by the South African Railways (SAR) from Beyer, Peacock and Company (BP) in 1914. The rest of the order consisted of three narrow gauge Class NG G11 2-6-0+0-6-2 locomotives and a single experimental Class GA 2-6-0+0-6-2 mainline locomotive. Production was disrupted by the First World War, however, and BP was only able to deliver the narrow gauge locomotives in 1919 and the Cape gauge locomotives in 1921, after cessation of hostilities.

Characteristics

The Class GB was numbered 1650, but the engine number was later changed to 2166. The locomotive was erected in the Durban shops and placed in service in June 1921. It was superheated, with a Belpaire firebox, plate frames and Walschaerts valve gear. The boiler was provided with the Gresley type air valve and mechanical lubrication was provided for the coupled wheel axle boxes.

In 1924, six more locomotives of this Class were placed in service, also built by BP and numbered in the range from 2160 to 2165. They embodied all improvements which experience with the first engine had shown desirable. The main differences between these locomotives and the original were revised boiler proportions and a larger water bunker capacity. The most obvious difference was a more completely enclosed cab with side windows, instead of the curved cut-outs in the cab sides of the first locomotive. They were heavier, compared to the of the engine of 1921.

Service

The first locomotive was placed in service working passenger trains on the Natal South Coast line. It proved to be a successful locomotive, having good riding qualities and flexibility on light track with poor ballasting and many curves of 300-foot (91-metre) radius.

A couple of the second batch of locomotives joined the first one on the South Coast line for a brief period, but most went directly to the Eastern Cape, where they were used on the Port Alfred branch and the Aliwal North to Barkly East line, famous for its reverses and its 1 in 30 (3⅓%) compensated ruling gradients. The Natal locomotives were soon also relocated to work there, when the Class GC Garratts replaced them on the South Coast line later in 1924. They remained working on the Barkly East branchline for many years, until they were withdrawn from service in 1967.

Illustration

The main picture shows the retired first Class GB, no. 2166, originally no. 1650, at Voorbaai near Mosselbaai on 4 September 1997. Since the top of the front bunker is only about 7 feet 6 inches (2,286 millimetres) above the railhead, these locomotives were later equipped with a pedestal between the headlight and the water inlet, to enable crew members to reach the overhead equipment when taking water.

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  No. 2160, c. 1930, with bell couplers and cab side windows

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  No. 2166 with curved cut-out cab sides, Voorbaai, 4 September 1997