South African Class DS
| Company type | Diesel-electric locomotive |
|---|---|
| Industry | Railway |
| Founded | 1939 |
| Headquarters | Durban , South Africa |
| Products | Locomotives |
South African Railways Class DS
The Class DS diesel-electric locomotive, introduced in 1939, marked the South African Railways' initial venture into diesel-electric traction.
This pioneering unit was a solitary shunting locomotive manufactured by Allgemeine Elektricitäts-Gesellschaft (AEG) and commenced operations at the Congella yards near Durban the same year. It represented the first diesel-electric locomotive to be incorporated into the South African Railways' roster.
Diesel versus steam locomotives
By approximately 1935, the South African Railways (SAR) began seriously evaluating the potential acquisition of diesel locomotives. Despite South Africa's abundant coal reserves, which provided some of the world's cheapest pit-head coal at that time, and the absence of domestic oil production, diesel-electric locomotives presented clear operational benefits. These included eliminating the need for water stops during journeys, enabling extended runs without refueling or locomotive changes, and offering significantly greater availability rates.
Initial investment costs strongly favored steam locomotives, whose cost per unit of power declined as their size increased—an economic benefit not observed with diesel-electrics. Diesel-electric locomotives with power ratings exceeding 1,500 horsepower (1,100 kilowatts) typically cost three to four times more upfront than steam engines of comparable power. Moreover, unless equipped with supercharging, diesel engines experienced a 3% loss in rated power output for every 1,000 feet (305 metres) rise in altitude.
Manufacturing background
Due to challenges in securing sufficient high-quality water supplies in the dry regions of South Africa and South West Africa, especially along the route from De Aar through Upington to Keetmanshoop, SAR decided to trial diesel traction. This led to the introduction of its first two diesel-electric shunting locomotives in 1939.
The initial unit was a single twin-engine centre-cab locomotive featuring a Bo-Bo wheel configuration, procured from Berlin-based Allgemeine Elektricitäts-Gesellschaft (AEG) for shunting duties. This locomotive was classified as Class DS and originally numbered D137 before being renumbered to D513. Both designations fell within the electric locomotive numbering series but were prefixed with "D" to denote diesel rather than "E" for electric.
Technical features
Weighing 66 long tons 8 hundredweight (67,470 kilograms), this locomotive was powered by two eight-cylinder diesel prime movers manufactured by Maschinenfabrik Augsburg-Nürnberg (MAN), each delivering 265 horsepower (198 kilowatts), positioned on either side of the cab. Situated inline between each engine and the cab were an AEG main generator rated at 110 kilowatts (150 horsepower) and an auxiliary generator rated at 12 kilowatts (16 horsepower). Each engine utilized water cooling assisted by a fan belt-driven off the engine itself, drawing air through a standard radiator assembly.
The bogies closely resembled those fitted to the Class 1E electric locomotives, incorporating two DC traction motors connected in series on each bogie. Each axle was powered by a force-ventilated, axle-suspended DC motor, with the pair on each bogie electrically linked in series. The cab featured mechanically interlocked dual controls, allowing operation from either end of the locomotive.
Service
The locomotive was assigned to operate at the Congella yards located near Durban. Although its performance did not meet expectations, it continued to be utilized for a span of 28 years.
Ultimately, the SAR's inaugural diesel-electric locomotive was transferred to Cape Town, where it was dismantled at the Salt River Works in November 1966.
Illustration
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Class DS no. D137, circa 1940
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References
External links
Media related to South African Class DS at Wikimedia Commons