South African Class DS
Class DS shunting locomotive, c. 1940
Type and origin
Power typeDiesel-electric
DesignerAllgemeine Elektricitäts-Gesellschaft
BuilderAllgemeine Elektricitäts-Gesellschaft
ModelSAR DS
Build date1939
Total produced1
Specifications
Configuration:
​
 • AARB-B
 • UICBo'Bo'
 • CommonwealthBo-Bo
Gauge3 ft 6 in (1,067 mm) Cape gauge
Wheel diameter42 in (1,067 mm)
Wheelbase30 ft 4 in (9,246 mm) ​
 • Bogie8 ft 6 in (2,591 mm)
Pivot centres21 ft 10 in (6,655 mm)
Length:
​
 • Over couplers46 ft 6 in (14,173 mm)
 • Over beams43 ft 8 in (13,310 mm)
Height12 ft 11+3⁄4 in (3,956 mm)
Axle load16 LT 12 cwt (16,870 kg)
Adhesive weight66 LT 8 cwt (67,470 kg)
Loco weight66 LT 8 cwt (67,470 kg)
Fuel typeDiesel
Fuel capacity455 imp gal (2,070 L)
Prime moverTwo MAN 265 hp (198 kW)
Engine typeDiesel
GeneratorTwo AEG 110 kW (150 hp) main
Two AEG 12 kW (16 hp) auxiliary
Traction motorsFour AEG
CylindersEight
Gear ratio5.67:1
CouplersAAR knuckle
Performance figures
Power output410 hp (310 kW)
Tractive effort:
​
 • Starting35,200 lbf (157 kN)
Factor of adh.4•2
Career
OperatorsSouth African Railways
ClassClass DS
Number in class1
NumbersD137, renumbered D513
Delivered1939
First run1939
ScrappedNovember 1966

The South African Railways Class DS of 1939 was a diesel-electric locomotive.

The first diesel-electric locomotive on the South African Railways was a single Class DS AEG diesel-electric shunting locomotive which was placed in service at the Congella yards near Durban in 1939.[1][2]

Diesel-steam comparison

Around 1935, the question of purchasing diesel locomotives for the South African Railways (SAR) was seriously considered. Even though South Africa was a coal-rich country with, at the time, the lowest pit-head prices in the world and no oil wells, there were definite advantages in favour of the diesel-electric locomotive. It did not need to take water en route, could undertake very long runs without the need to refuel or change locomotives and had a much higher rate of availability.[2]

The first costs were much in favour of steam locomotives, for which it decreased in cost per unit of power as the size increased, an advantage that the diesel-electric did not seem to have. Large diesel-electric locomotives of more than 1,500 horsepower (1,100 kilowatts) were usually three to four times greater in first cost than steam locomotives of equal power. In addition, unless it was supercharged, a diesel lost 3% of its rated power output with every increase of 1,000 feet (305 metres) in altitude.[2]

Manufacturer

As a result of the problems experienced to obtain adequate water supplies of good quality in the arid regions of South Africa and South West Africa, particularly on the section from De Aar via Upington to Keetmanshoop, the SAR decided to experiment with diesel-powered traction and introduced its first two diesel-electric shunting locomotives in 1939.[1][2][3]

The first of these was a single twin-engined centre-cab locomotive with a Bo-Bo wheel arrangement which was ordered from Allgemeine Elektricitäts-Gesellschaft (AEG) in Berlin for use as a shunting engine. The locomotive was designated Class DS and was initially numbered D137, but it was soon renumbered to D513. Both numbers were in the electric locomotive number range, but with a "D" for diesel instead of an "E" for electric number prefix.[1][2]

Characteristics

The 66 long tons 8 hundredweight (67,470 kilograms) locomotive was powered by two Maschinenfabrik Augsburg-Nürnberg (MAN) 265 horsepower (198 kilowatts) eight-cylinder diesel engine prime movers, one on either side of the cab. An AEG 110 kilowatts (150 horsepower) main generator and an AEG 12 kilowatts (16 horsepower) auxiliary generator were mounted directly in line between each engine and the cab. Each engine was water-cooled with a fan which was belt-driven by its engine and which drew air through a conventional radiator.[1][2]

The bogies were very similar to those of the Class 1E electric locomotive, each with two DC traction motors arranged in series. Each bogie axle was driven by a force-ventitated axle-suspended DC traction motor, with the two motors on each bogie electrically arranged in series. The cab was equipped with mechanically interlocked dual controls to enable operation in either direction.[1][2]

Service

The locomotive was placed in service at the Congella yards near Durban. Even though performance-wise the results were rather disappointing, it nevertheless remained in service for 28 years.[1][2]

The first diesel-electric locomotive on the SAR eventually found its way to Cape Town where it was scrapped at the Salt River Works in November 1966.[1][2]

Illustration

References

  1. 1 2 3 4 5 6 7 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 136-137. ISBN 0869772112.
  2. 1 2 3 4 5 6 7 8 9 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, March 1947. pp. 230-231.
  3. ↑ South African Railways and Harbours Locomotive Diagram Book, 2'0" & 3'6" Gauge Steam Locomotives, 15 August 1941, as amended

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