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SAR Class 1E Electric Locomotives

   
 
Class 1E external view

South African Railways Class 1E electric freight locomotives shortly after entering service in the mid-1920s. Photograph by Metropolitan-Vickers.


Summary
The locos were built by Metropolitan-Vickers, Swiss Locomotive and Machine Works and Vickers in Britain and Switzerland for the South African Railways and Harbours Board. They were landed in South Africa from 1924 and entered service from early 1925, after the first electrified section was completed. They had operational lives of up to 55 years before retirement in the late 1970s and early 1980s. Two appear to have been preserved for static display.

Significance to New South Wales Railways Electrification
The S.A.R. "Class 1E" electric locomotives used traction motors constructed for operation at 1500 volts. These locomotives enabled Metropolitan-Vickers to demonstate it could meet the N.S.W. Railway's design specification for Sydney suburban motor-car equipment in 1924, using two motors per car, each rated for 1500 volt operation (fed from 1500 volt DC overhead). The combination of multiple-unit control and regenerative braking made these locomotives the prototypes for most subsequent DC locomotive designs by Metropolitan-Vickers. When the N.S.W. 46 class were ordered in 1950, Metrovick had been successfully building similar electric locomotives for more than 25 years.

About the locos
The "Class 1E" electric locomotives were ordered and designed for the electrification of the Glencoe to Pietermaritzburg route in Natal (a province of South Africa). In the early 1920s this single track mountain line had heavy mineral traffic towards the port of Durban, but the alignment had severe gradients and tight curves. The existing working by steam engines was considered too slow and inefficient, and electrification of this 171 mile section was determined to be the best method of increasing the capacity of the line.
Class 1E side corridor

An internal view along the side corridor between the two cabs. The end of the supply generator and the central (interlocked) high tension compartment can be seen. Photograph by Metropolitan-Vickers.

The electrification scheme was designed by consulting engineers Messrs. Merz and McLellen. The scheme was technologically advanced for the time in two aspects:-

  • The adoption of 3000 volt DC supply overhead wiring with traction motors operated at 1500 volts.
  • The reported first time combination for locomotives in regular traffic of being fitted for multiple unit control with regenerative braking.

3000 volts was the highest direct current overhead voltage then in use. The higher voltage required more insulation and careful design to control arcing in the substation and locomotive electrical equipment, which increased the cost of the equipment. However the higher voltage allows fewer substations and smaller and lighter catenary for the same voltage drop, with a consequent saving in materials.

Regenerative braking involves using the traction motors as generators. This enables a train running downhill to feed power back into the overhead for use by other trains. However regeneration also allows faster downhill running in the case of sustained gradients, as the excess energy can be off-loaded from the train via the overhead wiring, rather than dissipated inefficiently as heat by the train air-brake system. Regeneration thus reduces both brake shoe wear and thermal damage to wheels, and leaves the air brakes always available at full capacity for normal use.

The contract for the first 78 locomotives was awarded to Metropolitan-Vickers in late 1922. This was Metrovick's second significant locomotive order; construction of the S.A.R. locos followed the completion of 20 Bo-Bo 600v DC (third rail) electric locomotives for the London Metropolitan Railway. The success of the S.A.R. locomotive design was confirmed by the order of 17 additional locomotives from Metrovick in 1925.

Brief details of the S.A.R. "Class 1E" electric locomotives are as follows:-

  • Voltage: 3000 D.C.
  • Gauge 3' 6"
  • Wheel arrangement: Bo+Bo
  • Weight: 66 tons
  • Axle load: 8.25 tons
  • Length over buffers: 43' 8" (13.31 m)
  • Width: 9' 2¼" (2.80 m)
  • Height to lowered collector: 13' (3.96 m)
  • One hour rated Horsepower: 1200 (899 kW)
  • Tractive Effort at one hour rating: 22,000 lbs (97.9 kN)
  • Tractive Effort at 25% adhesion: 37,000 lbs (164.6 kN)
  • Maximum Speed: 45 mph (72.5 km/h)
  • Wheel Diameter: 48 inches (1219 mm)
  • Gear Ratio: 4.41
  • Minimum curve radius: 300 feet (91.4 m)
  • Control Voltage: 100 D.C.
  • Multiple Unit operation: Up to 4 units
Class 1E side corridor

A view of the drivers cab from the door visible at the far end of the corridor in the photo above. Note the drivers position is on the right hand side in South Africa. Photograph by Metropolitan-Vickers.

The Metrovick electrical equipment includes; four 225 kW traction motors, supply motor generator (16kW), exciter motor generator (28kW), pantographs, compressor motor and exhauster motor (for vacuum train brakes). Traction control is by means of the Metrovick "unit switch" system for line switches and resistance (electrically interlocked individual electro-pneumatic contactors), and cam-operated contactor groups for motor combination, field tapping, reversing and motoring/braking. Control equipment is of the 1920 type, with manual notching and regenerative braking, directly operated by the driver's master controller (or jumpered train lines when operating in multiple unit). Two motor combinations are provided; series and parallel. With six or three sets of two motors, respectively, across the line voltage.

No locomotives of this type remain in service. It is reported three units are currently preserved. These are: E1 at Millsite, Krugersdorp; E23 at the Union Carriage and Wagon Works at Nigel; and E25 at the loco E25 at Danskraal loco depot, Ladysmith. The remaining withdrawn locomotives of this class have been scrapped. (Thanks to Carlos das Neves Vieira for this information.)

Please contact us if you can provide more information or any original technical documents relating to these locomotives.

References: Various issues of the Metropolitan-Vickers Gazette (particularly December 1922 and March 1925) and Electric Traction by A.T. Dover (1929).

Locomotive notes by Hugh Burns.

August 2006

 Further Information
Related reading:
South African Electrification - Progress of Big Power Schemes (external link) (1930s periodical article).
South African Electric Trains Class 1E and 3E (external link) (more pictures).

See Also:
SETS Preserved Electric Locomotive 4615



 
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