South African Class GM 4-8-2+2-8-4

Class GM no. 2298 at Krugersdorp, 23 April 1970

Type and origin
Power type	Steam
Designer	South African Railways
Builder	Beyer, Peacock and Company
Serial number	6883-6898
Model	Class GM
Build date	1938
Total produced	16

Specifications
Configuration	4-8-2+2-8-4 "Double Mountain" Garratt
Gauge	3 ft 6 in (1,067 mm) Cape gauge
Leading dia	28.5 in (724 mm)
Driver diameter	54 in (1,372 mm)
Trailing dia	34 in (864 mm)
Wheelbase	Total: 86 ft 4 in (26,314 mm) Engines: 6 ft 4 in (1,930 mm) bogie14 ft 5 in (4,394 mm) coupled 29 ft 10 in (9,093 mm) total
Length	93 ft 4.5 in (28,461 mm)
Height	13 ft (3,962 mm)
Frame	Bar frame, 43 ft (13,106 mm) between pivot centres
Axle load	15 long tons (15.2 t) on 6th driver
Adhesive weight	115.1 long tons (116.9 t)
Loco weight	324,800 lb (147.3 t) empty 174.3 long tons (177.1 t) w/o
Fuel type	Coal
Fuel capacity	10 long tons (10.2 t)
Water cap	1,600 imp gal (7,300 l) front 6,810 imp gal (31,000 l) in Type X-17 auxiliary tank wagon
Firebox: • Firegrate area	64 sq ft (5.946 m²)
Boiler	7 ft (2,134 mm) inside diameter 13 ft 6.5 in (4,128 mm) inside length 8 ft 6 in (2,591 mm) pitch
Boiler pressure	200 psi (1,380 kPa)
Heating surface	3,066 sq ft (284.841 m²)
• Tubes	255 tubes 2 in (51 mm) diameter 50 tubes 5.5 in (140 mm) diameter 2,785 sq ft (258.735 m²)
• Firebox	281 sq ft (26.106 m²) including siphons & arch tubes
Superheater: • Heating area	778 sq ft (72.279 m²)
Cylinders	Four
Cylinder size	20.5 in (521 mm) bore 26 in (660 mm) stroke
Valve gear	Walschaerts

Performance figures
Tractive effort	60,700 lbf (270 kN) at 75% pressure

Career
Operators	South African Railways
Class	Class GM
Number in class	16
Numbers	2291-2306
Delivered	1938-1939
First run	1938
Withdrawn	1974

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The South African Railways Class GM 4-8-2+2-8-4 of 1938 is an articulated steam locomotive.

During 1938 and 1939 the South African Railways placed sixteen Class GM Garratt articulated steam locomotives with a 4-8-2+2-8-4 Double Mountain type wheel arrangement in goods train service.^[1]^[2]^[3]

Manufacturer

By 1938 the rapidly increasing traffic on the line from Johannesburg via Krugersdorp and Zeerust to Mafeking led to the preparation of designs for a Garratt locomotive that would be equal to two Class 19D locomotives by W.A.J. Day, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1936 to 1939. The initial designs of the Class GM were rejected by the Chief Civil Engineer, however, since the weight on the leading and trailing bogies exceeded the acceptable limit for 60 pounds per yard (30 kilograms per metre) rail.^[1]^[3]^[4]^[5]

Class GM's type X-17 water tender

To overcome this, the water capacity of the front water tank was reduced to 1,600 imperial gallons (7,300 litres) while the rear bunker was redesigned to carry no water and with a coal capacity of 10 long tons (10 tonnes). The meagre water supply, which was really only sufficient for shunting purposes, was augmented by semi-permanently coupling a specially built type X-17 auxiliary tank wagon with a 6,810 imperial gallons (31,000 litres) capacity to the locomotive.^[1]^[3]^[4]^[5]

In all other respects the design followed that of the heavy Class GL Garratt. An order for sixteen locomotives was placed with Beyer, Peacock and Company in 1938, while their auxiliary water tank wagons were built in the Pietermaritzburg shops. The locomotives were delivered in 1938 and 1939, erected in the Durban shops and numbered in the range from 2291 to 2306.^[1]^[6]

The boilers were of outstanding proportions to enable the locomotives to cope with one particular bank on the Zeerust line that required continuous steaming for 75 minutes. They were superheated, with bar frames, mechanical stokers and Walschaerts valve gear, and since the proportions of the engine units and the wheel diameters were the same as that of the Class 19D, many of their parts were made interchangeable.^[1]^[2]^[3]

Service

South African Railways

They were placed in service on the Mafeking line out of Johannesburg that they were designed for. This was a difficult section with numerous 1 in 40 gradients, since from the Reef the elevation drops from 5,700 to 4,600 feet (1,700 to 1,400 metres) within 20 miles (32 kilometres), followed by a rise to over 5,000 feet (1,500 metres) in the next 11 miles (18 kilometres) and then another drop to 3,585 feet (1,093 metres).^[5]

The unusual arrangement of auxiliary water tanks, which had first been used in South Africa with the sole Class KM Kitson-Meyer locomotive in 1904, proved to be very effective and was later repeated with the introduction of the Class GMA and Class GO Garratts.^[1]^[3]^[5]

The Class GM remained working on the Mafeking section, initially out of Johannesburg and, after electrification of the West Rand lines, out of Krugersdorp, until they were replaced by diesel traction in 1972. Most of the locomotives were then transferred to work from Pretoria to Pietersburg, where they were employed until they were officially withdrawn from service on 1 August 1973.^[3]^[4]^[5]

Three of them were soon placed back in service when a series of accidents in the Eastern Transvaal led to a shortage of Class GMAM Garratts. Numbers 2301, 2303 and 2304 were recalled from retirement, overhauled and despatched to Breyten to fill the power vacuum. They remained in extended service for nearly two years, initially taking part in the mainline workings to Piet Retief and later employed on short pick-up trips to Ermelo and on the Spitskop colliery shunt. They were finally retired at the end of 1974 when the Class GMAM serviceability returned to normal.^[4]^[5]

Industrial

While the rest were scrapped, the three locomotives that filled the power gap at Breyten were sold to Dunn’s Locomotive Works and were hired out to various coal mines.^[4]^[5]

No. 2301 went to Douglas Colliery in November 1975 and was used for two years with the old tender of Class MC1 number 1643.
No. 2303 was hired to Durnacol, where it worked until circa 1978, coupled to an old Class 1 tender.
No. 2304 was at first hired to Transvaal Navigation Collieries and was transferred to Tweefontein United Colliery in July 1977, but fell into disuse soon afterwards.

Illustration

The main picture shows Class GM number 2298 at Krugersdorp on 23 April 1970. That and the following pictures serve to illustrate both sides of the locomotive.

Class GM at Braamfontein depot, circa 1940
Class GM, circa 1950

References

1 2 3 4 5 6 Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 96–97. ISBN 978-0-7153-5427-8.
1 2 South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended
1 2 3 4 5 6 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 94–95. ISBN 0869772112.
1 2 3 4 5 Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 114. ISBN 0715386387.
1 2 3 4 5 6 7 Durrant, A.E. (1981). Garratt Locomotives of the World. David & Charles. pp. 129-130. ISBN 0-7153-7641-1.
↑ Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives produced by Beyer, Peacock, retrieved 10 November 2012

Wikimedia Commons has media related to South African Class GM (4-8-2+2-8-4).

Locomotives of South Africa

Steam

7' ¼" gauge	East London Harbour 0-4-0 Table Bay Harbour 0-4-0ST Table Bay Harbour 0-4-0T Table Bay Harbour 0-4-0WT

4' 8½" gauge	Cape 0-4-0T Blackie Cape 0-4-2 Cape 2-4-0T CGR 0-4-0ST Aid Natal 0-4-0ST Durban Natal 0-4-0WT Natal Natal 4-4-0T Perseverance

3' 6" gauge Tank engines	CGR 0-4-0ST 1873 CGR 0-4-0ST 1874 CGR 0-4-0ST 1881 Coffee Pot CGR 0-6-0ST 1902 CGR 0-6-0T 1876 Back-to-Back CGR 2-6-0ST 1900 CGR 2-6-0ST 1902 CGR 1st Class 0-4-0ST 1875 CGR 1st Class 0-4-0ST 1876 CGR 1st Class 2-6-0ST 1876 CGR 1st Class 4-4-0T 1875 CGR 2nd Class 4-4-0T 1882 CGR 3rd Class 2-6-0T CGR Railmotor CSAR Class C CSAR Class E CSAR Rack CSAR Railmotor DSWA Eight-Coupled Tank 2-8-0T Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert Port Elizabeth Harbour 0-4-0ST Kowie Railway 0-6-0T Kowie Railway 4-4-0T Metropolitan & Suburban 4-6-2T NGR 2-6-0T Durban & Pietermaritzburg NGR Class I 2-6-2T NGR Class K 0-4-0ST NGR Class K 0-6-0ST NGR Class K 2-6-0T NZASM 10 Tonner NZASM 14 Tonner NZASM 18 Tonner NZASM 19 Tonner NZASM 32 Tonner NZASM 40 Tonner PPR 26 Tonner PPR 35 Tonner Portuguese SAR 0-4-0ST 1903 SAR 0-4-0T no. 69 SAR Class A SAR Class B SAR Class C SAR Class C1 SAR Class C2 SAR Class D SAR Class E SAR Class F SAR Class G SAR Class H SAR Class H1 SAR Class H2 SAR Class J SAR Class K SAR Clayton Railmotor

3' 6" gauge Tender engines	CGR 1st Class 2-6-0 1876 Beyer, Peacock CGR 1st Class 2-6-0 1876 Kitson CGR 1st Class 2-6-0 1879 CGR 1st Class 2-6-0 1891 CGR 1st Class 4-4-0 1879 CGR 1st Class 4-4-0TT 1881 CGR 2nd Class 2-6-2TT 1875 CGR 3rd Class 4-4-0 1883 CGR 3rd Class 4-4-0 1884 CGR 3rd Class 4-4-0 1889 CGR 3rd Class 4-4-0 1898 CGR 3rd Class 4-4-0 1901 CGR 3rd Class 4-4-0 1903 CGR 4th Class 4-4-2 CGR 4th Class 4-6-0TT 1880 CGR 4th Class 4-6-0TT 1882 CGR 4th Class 4-6-0TT 1884 CGR 5th Class 4-6-0 1890 CGR 5th Class 4-6-0 1891 DSWA Eight-Coupled Tender 2-8-0 NGR Havelock NGR Class I SAR Class Exp 1 SAR Class Exp 2 SAR Class Exp 3 SAR Class Exp 4 SAR Class Exp 5 SAR Class Exp 6 SAR Class S SAR Class S1 SAR Class S2 SAR Class 1 SAR Class 1A SAR Class 1B SAR Class 2 SAR Class 2C SAR Class 3 SAR Class 3A SAR Class 3B SAR Class 4 SAR Class 4A SAR Class 5 SAR Class 5A SAR Class 5B SAR Class 6 SAR Class 6A SAR Class 6B SAR Class 6C SAR Class 6D SAR Class 6E SAR Class 6F SAR Class 6G SAR Class 6H SAR Class 6J SAR Class 6K SAR Class 6L SAR Class 6Y SAR Class 6Z SAR Class 7 SAR Class 7A SAR Class 7B SAR Class 7C SAR Class 7D SAR Class 7E SAR Class 7F SAR Class 8 SAR Class 8A SAR Class 8B SAR Class 8C SAR Class 8D SAR Class 8E SAR Class 8F SAR Class 8R SAR Class 8X SAR Class 8Y SAR Class 8Z SAR Class 9 SAR Class 10 SAR Class 10A SAR Class 10B SAR Class 10C SAR Class 10D SAR Class 11 SAR Class 12 SAR Class 12A SAR Class 12B SAR Class 13 SAR Class 14 SAR Class 14A SAR Class 14B SAR Class 14C SAR Class 15 SAR Class 15A SAR Class 15B SAR Class 15C SAR Class 15CA SAR Class 15E SAR Class 15F SAR Class 16 SAR Class 16A SAR Class 16B SAR Class 16C SAR Class 16D SAR Class 16DA SAR Class 16E SAR Class 17 SAR Class 18 SAR Class 19 SAR Class 19A SAR Class 19B SAR Class 19C SAR Class 19D SAR Class 20 SAR Class 21 SAR Class 23 SAR Class 24 SAR Class 25 SAR Class 25NC SAR Class 26 Red Devil

3' 6" gauge Articulated engines	CGR Fairlie CGR Kitson-Meyer SAR Class FC SAR Class FD SAR Class GA SAR Class GB SAR Class GC SAR Class GCA SAR Class GD SAR Class GDA SAR Class GE SAR Class GEA SAR Class GF SAR Class GG SAR Class GH SAR Class GK SAR Class GL SAR Class GM SAR Class GMA SAR Class GO SAR Class HF SAR Class KM SAR Class MA SAR Class MB SAR Class MC SAR Class MC1 SAR Class MD SAR Class ME SAR Class MF SAR Class MG SAR Class MH SAR Class MJ SAR Class MJ1 SAR Class U

2' 6" gauge	Cape Copper 0-6-0T 1871 Cape Copper Britannia Cape Copper Caledonia Cape Copper Clara Class Cape Copper Condenser Cape Copper Scotia Class Namaqua Copper Pioneer

2' & 600mm gauges	ACR Class NG-G16A CGR NG 0-6-0T CGR NG 4-6-2T CGR Type A 2-6-4T CGR Type C 0-4-0T DSWA Class Ha DSWA Class Hb DSWA Class Hc DSWA Class Hd DSWA Jung DSWA Zwillinge NGR Class N 4-6-2T SAR NG 0-4-0T 1899 SAR Class NG1 SAR Class NG2 SAR Class NG3 SAR Class NG4 SAR Class NG5 SAR Class NG6 SAR Class NG7 SAR Class NG8 SAR Class NG9 SAR Class NG10 SAR Class NG-G11 SAR Class NG-G12 SAR Class NG-G13 SAR Class NG-G14 SAR Class NG15 SAR Class NG-G16

Electric

Amcoal Class E38

Diesel

3' 6" gauge Diesel-electric	PRASA Class Afro 4000 SAR Class DS SAR Class DS1 SAR Class 31-000 SAR Class 32-000 SAR Class 32-200 SAR Class 33-000 SAR Class 33-200 SAR Class 33-400 SAR Class 34-000 SAR Class 34-200 SAR Class 34-400 SAR Class 34-500 SAR Class 34-600 SAR Class 34-800 SAR Class 34-900 SAR Class 35-000 SAR Class 35-200 SAR Class 35-400 SAR Class 35-600 SAR Class 36-000 SAR Class 36-200 SAR Class 37-000 Spoornet Class 39-000 TFR Class 35-800 TFR Class 39-200 TFR Class 43-000 TFR Class 44-000

2' gauge Diesel-electric	SAR Class 91-000

3' 6" gauge Diesel-hydraulic	SAR Class 61-000

3' 6" gauge Electro-diesel	Spoornet Class 38-000

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