South African Class GG 2-6-2+2-6-2

The South African Railways Class GG 2-6-2+2-6-2 of 1925 was an articulated steam locomotive.

South African Class GG 2-6-2+2-6-2
GG no. 2290 at Cape Town, c. 1930
Type and origin Power type Steam Designer Beyer, Peacock and Company Builder Beyer, Peacock and Company Serial number 6232 Model Class GG Build date 1925 Total produced 1
Specifications Configuration: ​  • Whyte 2-6-2+2-6-2 (Double Prairie)  • UIC 1'C1'+1'C1'h4 Driver 3rd & 4th coupled axles Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 30 in (762 mm) Coupled dia. 57 in (1,448 mm) Trailing dia. 30 in (762 mm) Wheelbase 67 ft 4 in (20,523 mm) ​  • Engine 21 ft 4+1⁄2 in (6,515 mm) each  • Coupled 10 ft (3,048 mm) each Pivot centres 35 ft 4 in (10,770 mm) Length: ​  • Over couplers 74 ft 2+3⁄4 in (22,625 mm) Height 12 ft 11+7⁄16 in (3,948 mm) Frame type Plate Axle load 16 LT 4 cwt (16,460 kg) ​  • Leading 13 LT 13 cwt (13,870 kg) front 14 LT 5 cwt (14,480 kg) rear  • 1st coupled 15 LT 3 cwt (15,390 kg)  • 2nd coupled 15 LT 14 cwt (15,950 kg)  • 3rd coupled 15 LT 15 cwt (16,000 kg)  • 4th coupled 16 LT 4 cwt (16,460 kg)  • 5th coupled 15 LT 19 cwt (16,210 kg)  • 6th coupled 15 LT 15 cwt (16,000 kg)  • Trailing 12 LT 12 cwt (12,800 kg) front 12 LT 5 cwt (12,450 kg) rear Adhesive weight 94 LT 10 cwt (96,020 kg) Loco weight 147 LT 15 cwt (150,100 kg) Fuel type Coal Fuel capacity 10 LT (10.2 t) Water cap. 3,500 imp gal (15,900 L) front 1,100 imp gal (5,000 L) rear Firebox: ​  • Type Belpaire  • Grate area 52 sq ft (4.8 m2) Boiler: ​  • Pitch 7 ft 9 in (2,362 mm)  • Diameter 6 ft 9 in (2,057 mm)  • Tube plates 11 ft 8+5⁄8 in (3,572 mm)  • Small tubes 288: 2 in (51 mm)  • Large tubes 36: 5+1⁄2 in (140 mm) Boiler pressure 180 psi (1,241 kPa) Safety valve Ramsbottom Heating surface: ​  • Firebox 215 sq ft (20.0 m2)  • Tubes 2,374 sq ft (220.6 m2)  • Total surface 2,589 sq ft (240.5 m2) Superheater: ​  • Heating area 362 sq ft (33.6 m2) Cylinders Four Cylinder size 18 in (457 mm) bore 26 in (660 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Johnston link-and-pin
Performance figures Maximum speed 57 mph (92 km/h) Tractive effort 39,900 lbf (177 kN) @ 75%
Career Operators South African Railways Class Class GG Number in class 1 Numbers 2290 Delivered 1925 First run 1925 Withdrawn 1938 Scrapped 1947

In 1925, the South African Railways placed a single Class GG Garratt articulated steam locomotive with a 2-6-2+2-6-2 Double Prairie type wheel arrangement in fast mainline passenger service.

Manufacturers

The Class GG 2-6-2+2-6-2 Double Prairie type Garratt locomotive was a development of the Class GB. It was designed for the South African Railways (SAR) with large coupled wheels for fast passenger service on mainline duties. A single locomotive, no. 2290, was delivered from Beyer, Peacock and Company in 1925. It was superheated, with a plate frame, a Belpaire firebox and Walschaerts valve gear. The Class GG was the only Garratt locomotive on the SAR that was intended primarily for passenger working.

Characteristics

At 57 inches (1,448 millimetres) diameter, the Class GG had the largest coupled wheels yet seen on a Garratt locomotive in South Africa. An innovation was a coal pusher at the back of the coal bunker, designed to ease the work of the fireman by pushing the coal forward to the front of the bunker when required. It was the only instance of this appliance being used on any SAR locomotive.

To keep costs down, the cylinders were not enlarged to compensate for the increased wheel diameter. As a result, the locomotive's tractive effort was inferior to that of the Class 15CA which was introduced on the same line between Touws River and De Aar a year later.

The locomotive was capable of speeds of 57 miles per hour (92 kilometres per hour), but it was found to be unsteady at high speed due to the absence of a leading bogie on each engine unit. It could handle a load of 1,245 long tons (1,265 tonnes) on 1 in 80 (1¼%) gradients and hauled 340 long tons (345 tonnes) up the 15 miles (24 kilometres) of 1 in 40 (2½%) gradient of the Hex River Railpass in sixty-two minutes without the help of the usual banking locomotive.

Service

It was initially placed in service at Touws River and employed to work the Union Limited and Union Express fast passenger trains south of De Aar, but because of its unsteadiness at speed it was taken off fast passenger traffic and demoted to ordinary passenger and goods train working out of Cape Town. No more Class GG locomotives were ordered and since it was a non-standard locomotive, it was staged by 1938 and scrapped in 1947.

Illustration

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  No. 2290 as delivered, c. 1925