South African Class GMA 4 8 2 2 8 4

Manufacturers

The light rail branchline Class GMA and mainline Class GMAM Garratt locomotive, a single Class which could be configured for either branchline or mainline working, was a development of the large Class GM branchline locomotive which was introduced on the South African Railways (SAR) in 1938. Like the Class GM, the Class GMA was a tank-and-tender Garratt which ran with a semi-permanently coupled auxiliary water tender to augment its meagre water capacity.

The locomotive was designed in 1952 under the supervision of L.C. Grubb, Chief Mechanical Engineer (CME) of the SAR from 1949 to 1954. An order for the first 25 of these locomotives was placed with Henschel and Son in Germany. They were built in 1953 and were delivered and placed in service in 1954, numbered in the range from 4051 to 4075. These first 25 locomotives were equipped with Type X-17 water tenders, built by the SAR in its Pietermaritzburg shops in 1953.

A second batch of 35 locomotives was delivered by Beyer, Peacock and Company (BP) in 1956. Of these, 23 were built by BP and numbered in the range from 4076 to 4098, while the other twelve, numbered in the range from 4099 to 4110, had been subcontracted by BP to the North British Locomotive Company (NBL). These twelve engines therefore bore works plates showing BP as well as NBL as builders.

This was followed by a third and final batch of sixty locomotives in 1958. Of these, thirty were delivered by BP, of which only ten, numbered in the range from 4121 to 4130, had actually been built by BP. The other twenty, numbered in the ranges from 4111 to 4120 and 4131 to 4140, had once again been subcontracted by BP to NBL. These twenty therefore also bore works plates showing BP as well as NBL as builders. The other thirty locomotives of the third batch, numbered in the range from 4141 to 4170, were again built by Henschel in Germany.

The locomotives of the second and third batches were equipped with Type X-20 water tenders, built by in the Pietermaritzburg shops between 1956 and 1958.

Characteristics

The light rail branchline Class GMA and the mainline Class GMAM were the same locomotive, of which the water and coal capacities could be adjusted to suit by installing or removing plates in the coal and water spaces. As a result, it is virtually impossible to list the GMA and GMAM versions separately since they could easily be converted back and forth between the two versions, and often were. Up until about 1962, for example, the division was 20 Class GMA and 100 Class GMAM, but by 1969 there were 69 Class GMA and 39 Class GMAM, two locomotives having by then been scrapped after accident damage. By 1975, on the other hand, there were only 25 Class GMA against 93 Class GMAM.

As was done with the predecessor Class GM, the new locomotive carried water only in its front tank, but with the capacity increased from the Class GM's 1,600 imperial gallons (7,270 litres) to either 1,650 imperial gallons (7,500 litres) for the Class GMA or 2,100 imperial gallons (9,550 litres) for the Class GMAM. Likewise, the rear bunker carried only coal, but with the capacity increased from the Class GM's 10 long tons (10,160 kilograms) to either 11 long tons 12 hundredweight (11,790 kilograms) for the Class GMA or 14 long tons (14,220 kilograms) for the Class GMAM.

As with the Class GM, the Class GMA's water supply was augmented by semi-permanently coupling a purpose-built auxiliary water tender. The first batch of 25 locomotives were tended by the same Type X-17 water tender which was used with the Class GM, with a capacity of between 6,750 and 6,815 imperial gallons (30,700 and 31,000 litres). The rest of the locomotives were tended by Type X-20 water tenders with a capacity of 6,790 imperial gallons (30,900 litres).

The locomotive was designed to operate on 60 pounds per yard (30 kilograms per metre) rails despite the maximum axle loading of 15 long tons 14 hundredweight (15,950 kilograms) of the Class GMAM. This had been accomplished by restricting the weight on the leading and trailing bogies to 22 long tons (22,350 kilograms) and balancing the coupled wheels so that the hammer blow was equal for all wheels and did not exceed one ton on any wheel at 45 miles per hour (72 kilometres per hour).

The locomotive was thoroughly modern in design, with a one-piece Commonwealth cast steel frame with Franklin spring-loaded wedge horns, manufactured in the United States of America. Like the Class 25 locomotive, it had roller bearing axle boxes on all wheels, but not on the crank-pins, with cannon boxes on all axles except those of the inner Bissel trucks, which had outside bearings. It had a U-shaped foundation ring, welded to the inner and outer firebox bottom edges, and an all welded firebox. The engine units also had Commonwealth cast steel type frames.

The boiler's inside diameter was 6 feet 11 ¹⁄₂ inches (2,121 millimetres) at the first ring and 7 feet 1 ¹⁄₄ inches (2,165 millimetres) at the firebox end. The boiler had an inspection manhole, fitted to the top of the boiler aft of the dome. The locomotive was superheated, with a mechanical stoker and Walschaerts valve gear. It could negotiate curves of 275 feet (84 metres) radius with a gauge widening of not more than ³⁄₄ inch (19 millimetres) and a superelevation of 4 ¹⁄₂ inches (114 millimetres).

Some of these locomotives, intended for working in areas where there were tunnels such as on the East London mainline, were initially equipped with steam-operated smoke deflecting cowls over their chimneys. When the smoke cowls were later removed, these specific locomotives could still be identified by their almost non-existent chimneys, which had to be shorter in order to enable the cowls to fit within the loading gauge.

South African Railways

The 120 locomotives of this class made it the most numerous Garratt class in the world. The Class GMA and Class GMAM saw service on main and secondary lines in many parts of South Africa. Prior to electrification, a number were employed in Transvaal on the Komatipoort line across the pass between Waterval Onder and Waterval Boven, and also on the coal line from Witbank to Germiston and the line from Krugersdorp via Zeerust to Mafeking.

In Natal, the bulk of the Class was based at Pietermaritzburg, from where they worked most trains on the two heavily graded branchlines to Greytown and Franklin. Others worked on the Natal North Coast line between Stanger and Empangeni, while some assisted the Class GL on the coal line between Vryheid and Glencoe.

The Cape Western system's locomotives were stationed at Worcester, from where they worked the old New Cape Central Railway (NCCR) line via Riversdale to Mosselbaai until it was dieselised. Between 1981 and 1984, a number were allocated to the Cape Northern system to work the line from Vryburg to Mafeking, where they largely replaced the Class 19D locomotives which had earlier dominated on this line. This turned out to be their last term in mainline service, since they were replaced by Class 25NC locomotives in 1984, when the line was relaid with heavier rail.

Most of the Class was then allocated to the Cape Midland system, with most of them initially stationed at Voorbaai where, in 1984, they replaced the Class GEA on trains from Mosselbaai to Riversdale and across the Montagu Pass to Oudtshoorn. Their allocation was later extended to the sheds at Sydenham in Port Elizabeth, Rosmead, Klipplaat and Graaff-Reinet, with the result that they worked most of the trains over the route from Port Elizabeth to Rosmead via Klipplaat and across the Lootsberg Pass from Graaff-Reinet.

Towards the end of their service lives, the Eastern Transvaal system still had an allocation of them, where locomotives from the Waterval Boven and Breyten sheds worked the line down to Vryheid in Natal.

They were the last class of Garratt to remain in service with the SAR. All but three were withdrawn from service by April 1988 and those three were also retired shortly afterwards.

Zimbabwe and Mozambique

During the period from August 1979 to September 1981, altogether 26 locomotives of the Class were hired to Zimbabwe-Rhodesia, but not all at the same time since they were rotated, with Capital Park in Pretoria as their nominal home for the occasions when they had to return to South Africa for major repairs. On the Rhodesia Railways (RR), later the National Railways of Zimbabwe, they worked from Bulawayo to Gwelo and to Wankie and beyond to Victoria Falls.

Six of these locomotives were loaned by RR to the Caminhos de Ferro de Moçambique (CFM) for a short while, to work the CFM Centro line from Beira to Umtali in Zimbabwe.

In Zimbabwe-Rhodesia, these locomotives normally worked chimney first, with the water tank at the rear. Since the Rhodesian bush war was still ongoing in 1979, the locomotives were equipped with armour plating around the cab. Since this obscured the number plates, the engine numbers were then usually stencilled on the cabsides. The Class GMAM was similar in size with a similar coal capacity to the Rhodesia Railways 20th class 4-8-2+2-8-4 Garratt, but it had a voracious appetite for coal and frequently ran low on fuel, with the result that trains often had to be dumped. In an attempt to solve this problem, RR extended the height of the Class GMAM's coal bunker by a foot to increase the capacity.

Industrial and private

Several locomotives of the class were sold into industrial service and some later ended in preservation in private ownership. The majority went to the Randfontein Estates Gold Mining Company (REGM), while two were sold to the Hotham Valley Railway in Western Australia where they were to haul tourists in ex SAR passenger coaches. These two locomotives, however, never left South Africa.

Works numbers

The builders, works numbers and years built of these locomotives are listed in the table.

Illustration

The main picture shows Class GMAM no. 4079 Lindie Lou turning around on the triangle at Capital Park in Pretoria in September 2006. The following pictures illustrate the locomotive in service and in preservation.