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

The South African Railways Class GM 4-8-2+2-8-4 of 1938 was 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 on the Mafeking line out of Johannesburg.^[1][2][3]

Manufacturer

By 1938, the rapidly increasing traffic on the line from Johannesburg via Krugersdorp and Zeerust to Mafeking necessitated some means to increase its capacity quickly. Electrification to at least as far as Koster was proposed, but would take a considerable time to complete. This led W.A.J. Day, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1936 to 1939, to prepare designs for a Garratt locomotive which would be equal to two Class 19D locomotives.^{[1][2][3][4][5]}

W.A.J. Day

The initial designs of the Class GM Garratt were rejected by the Chief Civil Engineer, however, since the weight on the leading and trailing bogies of each engine unit would exceed the acceptable limit for the 60 pounds per yard (30 kilograms per metre) rail of the Mafeking line. To overcome the axle load objections, the water capacity of the front water tank was reduced to 1,600 imperial gallons (7,270 litres) while the rear bunker was redesigned to carry no water and with a coal capacity of 10 long tons (10.2 tonnes). The meagre water supply, which would really only be sufficient for shunting purposes, would be augmented by semi-permanently coupling a purpose-built auxiliary water tender to the locomotive.^{[1][2][3][4][5]}

In effect, since Garratt locomotives had hitherto been considered as tank engines because they carry all their water on board, this arrangement introduced the tank-and-tender Garratt. In all other respects, Day's design followed that of the heavy Class GL Garratt. An order for sixteen locomotives was placed with Beyer, Peacock and Company in 1938, while the sixteen water tenders 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][2][6]

Characteristics

The locomotives were superheated, with bar frames, Walschaerts valve gear, steam-operated reversing gear and 11 inches (279 millimetres) diameter piston valves. 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][7]

The boilers were of outstanding proportions to enable the locomotives to cope with one particular bank on the Zeerust line which required continuous steaming for 75 minutes. The boiler barrel and outer firebox shell was made of nickel steel plates, while the steel inner firebox was stayed with flexible and rigid stays, the flexible stays arranged at suitable positions along the side and back plates and also along the two front rows of the firebox crown. The firebox tube plate and inner back plate were similar to those of the Class GL. The firebox was fitted with two Nicholson thermic syphons to increase water circulation and also to provide additional heating surface. In addition, two arch tubes leading from the tube plate to the back plate provided more heating surface while supporting the brick arch.^[1][2][3]

Their type H.T-1 mechanical stokers were capable of delivering 15,000 pounds (6,804 kilograms) of coal per hour, which ensured a high firing rate when required. The stoker was driven by a totally enclosed double-acting two-cylinder variable-speed reversing steam engine, located on the hind pivot casting and operated from the cab. The coal bunker on the rear engine unit's frame was designed with sloping sides to allow the coal to gravitate to the mechanical stoker's conveyor screw trough, which extended the full length of the bunker.^[2]

An M.L.S. multiple-valve regulator superheater header was fitted, arranged with the regulator valves located on its saturated steam side. The regulator spindle passed through the smokebox side and the operating rods were led along the left side of the boiler to the cab. Steam was fed to the superheater header through a 7 inches (178 millimetres) diameter internal steam pipe from a standpipe in the shallow dome. As an experiment, two of the engines were equipped with patent steam driers, fitted in the dome.^[2]

Two of the engines were equipped with live-steam injectors on the right-hand side and exhaust steam injectors on the left-hand side. On the other fourteen, the boiler was fed by two no. 13 live-steam injectors, one on each side and situated immediately in front of the firebox, mounted low enough to ensure that water could still be drained effectively from the water tender when the engine was on a 1 in 40 (2½%) gradient. The injector feed pipes led to a combined top-feed check valve, situated on the first barrel plate on the top centre-line of the boiler. Feedwater entered the boiler through a spray nozzle, beneath which was a baffle tray. The boiler was completely lagged with asbestos mattresses and covered with planished steel, carried on a steel crinoline structure and secured in position by stainless steel bands.^[2]

The axle boxes of the leading and trailing wheels on each engine unit were equipped with roller bearings, while the solid bronze coupled wheel axle boxes were fitted with Ajax grease lubrication systems. Soft grease lubrication was used throughout for the motion gear, except the piston rods, valve spindles and main crossheads, which were oil-lubricated. Two four-feed sight lubricators, arranged in the cab, supplied oil to the steam chests, cylinders and the ball joint of the main steam pipes on each engine unit.^[2]

The main cradle frame was carried on adjustable pivots. The front pivot was a spherical type, located on the front engine unit's frame between the driving and trailing coupled wheels, while the rear pivot was a flat oil-bath type, located on the rear engine unit's frame over the driving wheels. Both engine unit frames were formed of two continuous bars, 33 feet 7 inches (10,236 millimetres) long and extending from the buffer beams at the outer ends to the cross-beams over the Bissel wheels at the inner ends. The front engine unit was equipped with steam as well as vacuum brake gear, while the hind unit was equipped with steam brake gear and handbrake gear.^[2]

Class GM's Type X-17 water tender

Their Type X-17 water tenders had a 6,750 imperial gallons (30,700 litres) capacity. In spite of initial criticisms and doubts, the unusual arrangement of water tenders, which had earlier only been seen on the Kitson-Meyer locomotives of the Cape Government Railways and Central South African Railways in 1903 and 1904, proved to be very effective and was later repeated upon the introduction of the Classes GMA and GO Garratts. The on-board 1,600 imperial gallons (7,270 litres) water tanks on the front engine units were only used when the water tenders were temporarily disconnected from the engines at running sheds.^[1][2][3][5]

Service

South African Railways

The Class GM was placed in service on the Mafeking line out of Johannesburg, which it was designed for. The Johannesburg-Zeerust section, over a distance of 140 miles (225 kilometres), was the most difficult on the line. A considerable part of it consisted of numerous 1 in 40 (2½%) grades and curves of 500-foot radius (152-metre) since, from the Reef, the elevation dropped 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).^[2][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 which 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 Type MP1 tender of Class MC1 no. 1643.^[4][5]
• No. 2303 was hired to Durnacol, where it worked until c. 1978, coupled to an old Type SH tender off a Class 1 locomotive.^[4][5]
• 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.^[4][5]

Preservation

Three locomotives were set aside for preservation, but no. 2301 was scrapped in January 2011. By 2016, only two of them still survived in preservation by Transnet Heritage Foundation, no. 2292 at Millsite and no. 2304 at the Witbank shed.

Illustration

References

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 0-4-0VB Table Bay 0-4-0ST Table Bay 0-4-0T Table Bay 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 CGR 0-4-0ST 1881 Coffee Pot CGR 0-6-0ST CGR 0-6-0T 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 CGR 1st Class 4-4-0T CGR 2nd Class 4-4-0T CGR 3rd Class 2-6-0T CGR Railmotor CSAR Class C CSAR Class E CSAR Rack 4-6-4RT CSAR Railmotor Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert Port Elizabeth 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 13 Tonner NZASM 14 Tonner NZASM 18 Tonner NZASM 19 Tonner NZASM 32 Tonner NZASM 40 Tonner PPR 26 Tonner PPR 35 Tonner Portuguese 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 Railmotor SAR Dock 0-4-0ST SAR Dock 0-4-0T SWA 2-8-0T 3' 6" gauge Tender engines CGR 1st Class 2-6-0 1876 BP 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 CGR 1st Class 4-4-0TT CGR 2nd Class 2-6-2TT 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 1882 Joy CGR 4th Class 4-6-0TT 1884 CGR 5th Class 4-6-0 1890 CGR 5th Class 4-6-0 1891 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 1st SAR Class 14C 2nd SAR Class 14C 3rd SAR Class 14C 4th 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 1928 SAR Class 16DA 1930 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 SAR Katanga SWA 2-8-0 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 John King & Miner Cape Copper Britannia Cape Copper Caledonia Cape Copper Clara Cape Copper Condenser Cape Copper Scotia Namaqua Copper Pioneer Walvis Bay 2-4-2T Hope 2' & 600mm gauges ACR Class NG-G16A CGR NG 0-4-0T CGR NG 0-6-0T CGR NG 4-6-2T CGR Type A 2-6-4T CGR Type C 0-4-0T NGR Class N 4-6-2T SAR Dutton SAR NG 0-4-0T 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 SWA Class Ha SWA Class Hb SWA Class Hc SWA Class Hd SWA Jung SWA Zwillinge
Electric	Amcoal Class E38 SAR Class ES SAR Class ES1 SAR Class Exp-AC SAR Class 1E SAR Class 2E SAR Class 3E SAR Class 4E SAR Class 5E s1 SAR Class 5E s2 SAR Class 5E s3 SAR Class 5E1 s1 SAR Class 5E1 s2 SAR Class 5E1 s3 SAR Class 5E1 s4 SAR Class 5E1 s5 SAR Class 6E SAR Class 6E1 s1 SAR Class 6E1 s2 SAR Class 6E1 s3 SAR Class 6E1 s4 SAR Class 6E1 s5 SAR Class 6E1 s6 SAR Class 6E1 s7 SAR Class 6E1 s8 SAR Class 6E1 s9 SAR Class 6E1 s10 SAR Class 6E1 s11 SAR Class 7E SAR Class 7E1 SAR Class 7E2 s1 SAR Class 7E2 s2 SAR Class 7E3 s1 SAR Class 7E3 s2 Spoornet Class 7E4 SAR Class 8E SAR Class 9E s1 SAR Class 9E s2 SAR Class 10E SAR Class 10E1 s1 Spoornet Class 10E1 s2 SAR Class 10E2 SAR Class 11E SAR Class 12E Spoornet Class 14E Spoornet Class 14E1 TFR Class 15E Spoornet Class 16E Spoornet Class 17E Spoornet Class 18E s1 TFR Class 18E s2 TFR Class 19E TFR Class 20E TFR Class 21E TFR Class 22E
Gas-electric	SAR Gas-electric
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 TFR Class 35-800 SAR Class 36-000 SAR Class 36-200 SAR Class 37-000 Spoornet Class 39-000 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
List of South African locomotive classes South African locomotive numbering and classification

South African steam locomotive tenders
Cape gauge	Type CL Type CZ Type ET Type ET1 Type EW Type EW1 Type EW2 Type FT Type GT Type HT Type JT Type JT1 Type JV Type KT Type LP Type MP Type MP1 Type MR Type MS Type MT Type MT1 Type MT2 Type MX Type MY Type MY1 Type SH Type SK Type TJ Type TL Type TM Type WE Type WG Type X-17 Type X-20 Type XC Type XC1 Type XD Type XE Type XE1 Type XF Type XF1 Type XF2 Type XJ Type XM Type XM1 Type XM2 Type XM3 Type XM4 Type XP1 Type XS Type YB Type YC Type YE Type YE1 Type ZA Type ZB Type ZC Type ZE
List of South African locomotive classes South African locomotive history