South African Class ES1

      South African Class ES1
      SAR Class ES1 E 502.jpg
      Class ES1 shunting locomotive, circa 1930
      Power type Electric
      Designer English Electric
      Builder English Electric
      Model SAR ES1
      Build date 1924
      AAR wheel arr. B
      UIC classification Bo
      Gauge 3 ft 6 in (1,067 mm) Cape gauge
      Wheel diameter 38 in (965 mm)
      Wheelbase 10 ft 5 in (3.175 m)
      Length 22 ft (6.706 m) over headstocks
      24 ft 5 in (7.442 m) over couplers
      Height 10 ft (3.048 m)
      Axle load 12+320 long tons (12.3 t)
      Locomotive weight 24+520 long tons (24.6 t)
      Electric system(s) 208 cell battery
      Traction motors Two
      Transmission 5.4:1 Gear ratio
      Power output 50 hp (37 kW)
      Tractive effort 8,500 lbf (38 kN) 1 hour
      Career South African Railways
      ESKOM
      Class Class ES1
      Power class 235V, 196A[1]
      Number in class 1
      Number E123, renumbered E502
      Nicknames Queen Mary
      Delivered 1924
      First run 1924
      Last run 1978
      Disposition Retired

      In 1924 the South African Railways placed a single Class ES1 battery-powered shunting locomotive in service at the construction site of the Colenso power station. In 1927 the power station and the locomotive was sold to the Electricity Supply Commission (ESKOM), and in 1937 the locomotive was purchased back from ESKOM for use at the Danskraal locomotive depot.[2]

      Manufacturer

      During the electrification of the Glencoe to Pietermaritzburg section of the Natal mainline, a mountainous single track line that carried heavy mineral traffic towards the port of Durban on an alignment with severe gradients and tight curves, the Colenso power station was built by the South African Railways (SAR) to supply the power for this line.[3] A single battery-powered electric shunting locomotive, the only battery-powered locomotive to ever see service on the SAR, was purchased from English Electric in 1924 for use at the power station construction site.[2]

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      Characteristics

      The centre-cab locomotive had a Bo wheel arrangement, with the two axles being driven by two 37 kilowatts (50 horsepower) traction motors, operating at 235 volts and powered by a 208 cell nickel-iron alkali type battery with a 435 amp-hour capacity.[2]

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      Service

      The locomotive remained in service at the Colenso power station after 1927, when the power station and all its equipment, including the battery locomotive, was sold to the Electricity Supply Commission (ESKOM), the state-owned South African national power corporation.[2]

      In 1937 the locomotive was purchased back from ESKOM by the SAR, designated Class ES1 with running number E123, and stationed at the Danskraal locomotive depot at Ladysmith where it was used as a shunter to move unpowered steam locomotives. Nicknamed "Queen Mary", it was later renumbered to E502. It remained in service at Danskraal until it was withdrawn from service in 1978.[2]

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      References

       
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      1. ^ South African Railways Index and Diagrams Electric and Diesel Locomotives, 2’0” & 3’6” Gauge, circa 1940, as amended
      2. ^ a b c d e Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 135. ISBN 0869772112. 
      3. ^ "South African Railways Power Plant". Electric Railway Journal 60 (24): 914. 9 December 1922. Retrieved 15 September 2010. 
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      Last modified on 28 November 2012, at 20:57