| South African Class GG 2-6-2+2-6-2 | |
|---|---|
| GG 2290 at Cape Town, circa 1930 | |
| Power type | Steam |
| Designer | Beyer, Peacock and Company |
| Builder | Beyer, Peacock and Company |
| Serial number | 6232[1] |
| Model | Class GG |
| Build date | 1925 |
| Total produced | 1 |
| Configuration | 2-6-2+2-6-2 "Double Prairie" Garratt |
| Gauge | 3 ft 6 in (1,067 mm) Cape gauge |
| Leading wheel diameter |
30 in (762 mm) |
| Driver diameter | 57 in (1,450 mm) |
| Trailing wheel diameter |
30 in (762 mm) |
| Wheelbase | Total: 67 ft 4 in (20.523 m) Engines: 10 ft (3.048 m) coupled 21 ft 4.5 in (6.515 m) total |
| Length | 74 ft 2.75 in (22.625 m) |
| Height | 12 ft 11.4375 in (3.948 m) |
| Frame | Plate frame, 35 ft 4 in (10.770 m) between pivot centres |
| Axle load | 16.2 long tons (16.5 t) on 4th driver |
| Weight on drivers | 94.5 long tons (96.0 t) |
| Locomotive weight | 235,000 lb (106.6 t) empty 147.75 long tons (150.1 t) w/o |
| Fuel type | Coal |
| Fuel capacity | 10 long tons (10.2 t) |
| Water capacity | 3,500 imp gal (16,000 l) front 1,100 imp gal (5,000 l) rear |
| Boiler | 6 ft 9 in (2.057 m) int dia 11 ft 8.625 in (3.572 m) int length 7 ft 9 in (2.362 m) pitch |
| Boiler pressure | 180 psi (1,240 kPa) |
| Firegrate area | 52 sq ft (4.831 m2) |
| Heating surface: Tubes |
288 tubes 2 in (50.8 mm) ext dia 36 tubes 5.5 in (140 mm) ext dia 2,374 sq ft (220.552 m2) |
| Heating surface: Firebox |
215 sq ft (19.974 m2) |
| Heating surface: Total |
2,589 sq ft (240.526 m2) |
| Superheater area | 362 sq ft (33.631 m2) |
| Cylinders | Four |
| Cylinder size | 18 in (457 mm) bore 26 in (660 mm) stroke[2][3] |
| Valve gear | Walschaerts[4] |
| Top speed | 57 mph (92 km/h) |
| Tractive effort | 39,900 lbf (177.5 kN) at 75% boiler pressure |
| Career | South African Railways |
| Class | Class GG |
| Number in class | 1 |
| Number | 2290 |
| Delivered | 1925 |
| First run | 1925 |
| Withdrawn | 1947 |
| Disposition | Retired |
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" wheel arrangement in fast main line passenger service.[2][3][4]
Contents |
The Class GG 2-6-2+2-6-2 Garratt locomotive was a development of the Class GB that was designed for the South African Railways (SAR) with large driving wheels for fast passenger service on main line duties. A single locomotive, number 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.[2][4]
The Class GG had the largest driving 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, as required. It was, however, the only instance of this appliance being used on any SAR locomotive.[2]
In order to keep costs down, the cylinders were not enlarged to compensate for the increased wheel diameter, with the result that its tractive effort was inferior to that of the Class 15CA that was introduced on the same line a year later.
It 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 gradients and hauled 340 long tons (345 tonnes) in sixty-two minutes up the 15 miles (24 kilometres) of 1 in 40 gradient of the Hex River Pass without the help of a banking locomotive.[2]
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.[2][4]
The main picture shows Class GG 2290 at the Old Cape Town Loco Depot near Tennant Road, circa 1930.
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