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 typeSteam
DesignerBeyer, Peacock and Company
BuilderBeyer, Peacock and Company
Serial number6232
ModelClass GG
Build date1925
Total produced1
Specifications
Configuration:
​
 • Whyte2-6-2+2-6-2 (Double Prairie)
 • UIC1'C1'+1'C1'h4
Driver3rd & 4th coupled axles
Gauge3 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)
Wheelbase67 ft 4 in (20,523 mm)
 • Engine21 ft 4 1⁄2 in (6,515 mm) each
 • Coupled10 ft (3,048 mm) each
Pivot centres35 ft 4 in (10,770 mm)
Length:
​
 • Over couplers74 ft 2 3⁄4 in (22,625 mm)
Height12 ft 11 7⁄16 in (3,948 mm)
Frame typePlate
Axle load16 LT 4 cwt (16,460 kg)
 • Leading13 LT 13 cwt (13,870 kg) front
14 LT 5 cwt (14,480 kg) rear
 • 1st coupled15 LT 3 cwt (15,390 kg)
 • 2nd coupled15 LT 14 cwt (15,950 kg)
 • 3rd coupled15 LT 15 cwt (16,000 kg)
 • 4th coupled16 LT 4 cwt (16,460 kg)
 • 5th coupled15 LT 19 cwt (16,210 kg)
 • 6th coupled15 LT 15 cwt (16,000 kg)
 • Trailing12 LT 12 cwt (12,800 kg) front
12 LT 5 cwt (12,450 kg) rear
Adhesive weight94 LT 10 cwt (96,020 kg)
Loco weight147 LT 15 cwt (150,100 kg)
Fuel typeCoal
Fuel capacity10 LT (10.2 t)
Water cap3,500 imp gal (15,900 l) front
1,100 imp gal (5,000 l) rear
Firebox typeBelpaire
 • Firegrate area52 sq ft (4.8 m2)
Boiler:
​
 • Pitch7 ft 9 in (2,362 mm)
 • Diameter6 ft 9 in (2,057 mm)
 • Tube plates11 ft 8 5⁄8 in (3,572 mm)
 • Small tubes288: 2 in (51 mm)
 • Large tubes36: 5 1⁄2 in (140 mm)
Boiler pressure180 psi (1,241 kPa)
Safety valveRamsbottom
Heating surface2,589 sq ft (240.5 m2)
 • Tubes2,374 sq ft (220.6 m2)
 • Firebox215 sq ft (20.0 m2)
Superheater:
​
 • Heating area362 sq ft (33.6 m2)
CylindersFour
Cylinder size18 in (457 mm) bore
26 in (660 mm) stroke
Valve gearWalschaerts
Valve typePiston
CouplersJohnston link-and-pin
Performance figures
Maximum speed57 mph (92 km/h)
Tractive effort39,900 lbf (177 kN) @ 75%
Career
OperatorsSouth African Railways
ClassClass GG
Number in class1
Numbers2290
Delivered1925
First run1925
Withdrawn1938
Scrapped1947

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.[1][2][3][4][5]

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.[1][3][4][5][6]

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.[1]

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.[1]

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.[1][2]

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.[1][2][3]

Illustration
  • No. 2290 as delivered, c. 1925

References
  1. Holland, D. F. (1972). Steam Locomotives of the South African Railways. 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 47–49. ISBN 978-0-7153-5427-8.
  2. 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, January 1946. p. 12.
  3. Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 92–93. ISBN 0869772112.
  4. South African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 Aug 1941). Locomotive Diagram Book/Lokomotiefdiagramboek, 3'6" Gauge/Spoorwydte. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. p. 32.
  5. South African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 Aug 1941). Locomotive Diagram Book/Lokomotiefdiagramboek, 2'0" & 3'6" Gauge/Spoorwydte, Steam Locomotives/Stoomlokomotiewe. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. p. 32.
  6. Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives produced by Beyer, Peacock, retrieved 10 November 2012
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