The South African Railways Class S1 0-8-0 of 1947 was a steam locomotive.

In 1947, the South African Railways placed twelve Class S1 shunting steam locomotives with an eight-coupled wheel arrangement in service, built in the Salt River workshops in Cape Town. A further 25, built in Scotland, were placed in service in 1954.Espitalier, T.J.; Day, W.A.J. (1947). The Locomotive in South Africa – A Brief History of Railway Development. Chapter VII – South African Railways (Continued). South African Railways and Harbours Magazine, May 1947. pp. 402-404.Espitalier, T.J. (1947). Locomotives Designed and Built in South Africa – The S1, in service this month, is not the first locally-built engine. South African Railways and Harbours Magazine, October 1947. pp. 841-843.

The Class S1 was the fifth locomotive type to be designed and built in South Africa, after the Natal Government Railways 4-6-2TT Havelock of 1888, the Class 2C of 1910, the Class 20 of 1935 and the Class ES of 1936.

Manufacturers A huge increase in traffic before and during the Second World War years led to the available dedicated shunting locomotives of the South African Railways (SAR) being very much over-taxed, to the extent that they had to be supplemented by mainline locomotives. By 1943, the options were to either relegate Class 14 and other mainline engines to shunting duties or to augment the number of existing Class S shunting locomotives. The requirement for a shunting locomotive type more powerful than the Class S was identified, but since the war was still in progress, it was not viable to obtain locomotives from the usual overseas suppliers.

Dr. M.M. Loubser, Chief Mechanical Engineer (CME) of the SAR from 1939 to 1949, therefore prepared designs for a larger version of the Class S locomotive which could be built in the SAR's own workshops. The result was the Class S1 0-8-0 shunting locomotive, of which the first of twelve was delivered from the Salt River shops in Cape Town in October 1947.

Twelve locomotives were built, numbered in the range from 374 to 385. The first locomotive to be released from the Salt River shops in 1947 was no. 375, which was formally handed over to the Operating Department by the senior member of the Railway Board, Mr F.T. Bates. In honour of the occasion and in view of the approaching inauguration of the Voortrekker Monument in 1949, it was named Voortrekker.Soul of A Railway, System 5, Part 1: Bloemfontein. Captions 22, 23. (Accessed on 1 March 2017)

A further 25 Class S1 locomotives were subsequently ordered from the North British Locomotive Company (NBL) in Glasgow. They were built in 1953 and delivered in 1953 and 1954, numbered in the range from 3801 to 3825.North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser

Local production Even though it was not wholly a South African product with its imported main bar frames, tyres, superheater elements and some proprietary fittings, the Class S1 was the fifth recorded instance of locomotives designed and constructed in South African workshops after the Natal Government Railways' engine Havelock of 1888, the Class 2C of 1910, the Class 20 of 1935 and the Class ES of 1936. The Class S1 was, however, the first steam locomotive to be home-built in quantity.Espitalier, T.J.; Day, W.A.J. (1944). The Locomotive in South Africa – A Brief History of Railway Development. Chapter III – Natal Government Railways. (Continued). South African Railways and Harbours Magazine, June 1944. pp. 421-422.Espitalier, T.J.; Day, W.A.J. (1944). The Locomotive in South Africa – A Brief History of Railway Development. Chapter III – Natal Government Railways (Continued). South African Railways and Harbours Magazine, August 1944. p. 599.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, April 1946. p. 296.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, August 1946. pp. 630-631.

Characteristics At the time, the Class S1 was the world's most powerful shunting locomotive on Cape gauge and equivalent track, and all the latest developments were incorporated in its design. Since shunting locomotives are designed to operate at slow speeds in tightly curved shunting yards, there was no need for the leading or trailing wheels which are necessary to improve high speed stability on mainline locomotives. Their absence also simplified design and reduced repair costs. In addition, it is desirable to have as large a proportion of the engine weight as possible carried on the coupled wheels to obtain the maximum adhesion.

The locomotives had bar frames, Walschaerts valve gear to actuate their diameter piston valves, and were superheated. While their cylinders, driving wheel diameter, frame and many other features were similar to that of the earlier Class S shunting locomotives, their boilers were much larger, being a shortened version of Loubser's specially designed boiler which was used on the Class 12AR. The main difference from the Class 12AR boiler was in their barrel lengths. Each barrel consisted of three courses for the Class 12AR and two courses for the Class S1, the hind courses being identical. In addition, the Class 12AR had a deeper firebox. These Class S1 boilers could also be fitted to the original Class S engines, but no such reboilerings are known to have taken place.

The Class S1 boiler was provided with SAR standard boiler fittings, such as a multi-valve steam regulator fitted in the smokebox, a duplex top-feed valve for the delivery of feedwater from the injectors, a soot blower and external exhaust pipe to the smokebox, and a steam turret for the distribution of steam to the various steam-operated mechanisms. The valves for the latter were mounted on the steam turret and were fitted with spindles which extended into the cab from where they were operated by means of handwheels.

The locomotive was built with a Watson cab with a slanted front to allow easy access to the firebox cladding which covered the flexible firebox stays and stay caps. The cab was wide and was fitted with hinged adjustable glass windscreens for the lookout and a rigid extended footplate instead of the older fall plate. The cab footsteps were attached to the rigid platform.

The engine was tended by a new Type JT1 tender, built with an underframe and bogies identical to those of the Type JT tender. As on the Type GT tender of the Class S, the top sides of the Type JT1 tender's coal bunker were set inwards to afford the crew the maximum rearward field of vision. The front of the engine and the back of the tender were fitted with modified and strengthened draft gear. The intermediate drawgear between engine and tender was similar in design to that of the Class 15F. The engine and tender were both fitted with vacuum brakes.

Service The Class S1 was noted for its efficient and economical working. They were the SAR's largest and finest shunting locomotives with an enormous shifting and accelerating ability and could cope with block loads of up to .

They were initially placed in service in the yards in Cape Town, but they ended up being used mainly in marshalling yards on the Western Transvaal System and also on the Cape Northern System, employed at Braamfontein, Millsite in Krugersdorp, Bloemfontein and Kimberley. Bloemfontein had one of the SAR's more important marshalling yards where goods trains from the north were sorted into consists bound for East London, Port Elizabeth, Mossel Bay, Cape Town and a host of Cape country towns. In its heyday, Bloemfontein's retarder yard had 40 tracks, 24 for southbound traffic and 16 for northbound. There were two humps with two primary and five secondary retarders, the latter split into three for southbound and two for northbound traffic. The hump leads were served around the clock by Class S1 engines no. 374 and 375.

By the 1970s they were distributed between Beaconsfield, Bloemfontein, Germiston, Kaserne, Springs and Witbank. By 1982 they were all stationed at Germiston and its sub-depot at Kaserne, after which they began to be withdrawn from service. The withdrawal was probably expedited by the closure of the Koedoespoort works in Pretoria to steam repairs, since it was impractical to let them do long-distance running to the next nearest steam locomotive works at Bloemfontein. None of them were sold into industrial service.

Works numbers The builders, works numbers, years built and SAR locomotive numbers of the Class S1 are listed in the table. +SAR Class S1 0-8-0BuilderWorksno.YearSARno.SAR1947 374 SAR1947 375 SAR1947 376 SAR1947 377 SAR1947 378 SAR1947 379 SAR1947 380 SAR1947 381 SAR1947 382 SAR1947 383 SAR1947 384 SAR1947 385 NBL27261 1953 3801 NBL27262 1953 3802 NBL27263 1953 3803 NBL27264 1953 3804 NBL27265 1953 3805 NBL27266 1953 3806 NBL27267 1953 3807 NBL27268 1953 3808 NBL27269 1953 3809 NBL27270 1953 3810 NBL27271 1953 3811 NBL27272 1953 3812 NBL27273 1953 3813 NBL27274 1953 3814 NBL27275 1953 3815 NBL27276 1953 3816 NBL27277 1953 3817 NBL27278 1953 3818 NBL27279 1953 3819 NBL27280 1953 3820 NBL27281 1953 3821 NBL27282 1953 3822 NBL27283 1953 3823 NBL27284 1953 3824 NBL27285 1953 3825

Preservation Only one example is preserved.

Number Works nmr THF / Private Leaselend / Owner Current Location Outside SOUTH AFRICA ? 375 THF Transnet Heritage Foundation Bloemfontein Locomotive Depot

Sandstone Heritage Trust – 2017016 Locomotive status – January 2017. (Accessed on 13 December 2019)

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