South African Class 7E

This article is about the South African electric locomotive. For the steam locomotive, see South African Class 7E 4-8-0.

South African Class 7E
No. E7058 at Swartkops, Port Elizabeth, 22 April 2013
Type and origin Power type Electric Designer 50 c/s Group Builder Union Carriage and Wagon Model 50 c/s Group 7E Build date 1978-1979 Total produced 100
Specifications Configuration: ​  • AAR C-C  • UIC Co'Co' Gauge 3 ft 6 in (1,067 mm) Cape gauge Wheel diameter 1,220 mm (48.0 in) Wheelbase 13,800 mm (45 ft 3.3 in) ​  • Bogie 4,400 mm (14 ft 5.2 in) Pivot centres 10,200 mm (33 ft 5.6 in) Panto shoes 10,200 mm (33 ft 5.6 in) Length: ​  • Over couplers 18,465 mm (60 ft 7.0 in)  • Over body 17,536 mm (57 ft 6.4 in) Width 2,896 mm (9 ft 6.0 in) Height: ​  • Pantograph 4,200 mm (13 ft 9.4 in)  • Body height 3,942 mm (12 ft 11.2 in) Axle load 21,000 kg (46,000 lb) Adhesive weight 123,500 kg (272,300 lb) Loco weight 123,500 kg (272,300 lb) Power supply Catenary Current pickup(s) Pantographs Traction motors Six MG 680 ​  • Rating 1 hour 540 kW (720 hp)  • Continuous 500 kW (670 hp) Gear ratio 20:117 Loco brake Air & Rheostatic Train brakes Air & Vacuum Couplers AAR knuckle
Performance figures Maximum speed 100 km/h (62 mph) Power output: ​  • 1 hour 3,240 kW (4,340 hp)  • Continuous 3,000 kW (4,000 hp) Tractive effort: ​  • Starting 450 kN (100,000 lbf)  • 1 hour 319 kN (72,000 lbf)  • Continuous 300 kN (67,000 lbf) Brakeforce 210 kN (47,000 lbf)
Career Operators South African Railways Spoornet Transnet Freight Rail PRASA Class Class 7E Power class 25 kV 50 Hz AC Number in class 100 Numbers E7001-E7100 Delivered 1978-1979 First run 1978

The South African Railways Class 7E of 1978 is an electric locomotive.

In 1978 and 1979, the South African Railways placed one hundred Class 7E electric locomotives with a Co-Co wheel arrangement in mainline service. They were the first 25 kV AC locomotives to enter service in South Africa.

Manufacturer

The 25 kV AC Class 7E electric locomotive was designed for the South African Railways (SAR) by the 50 ^c/s Group, consisting of ACEC of Belgium, AEG-Telefunken and Siemens of Germany, Alsthom-Atlantique and Société MTE of France, and Brown Boveri of Switzerland. The locomotives were built by Union Carriage and Wagon (UCW) in Nigel, Transvaal, which was the sub-contractor for mechanical components and assembly.

Builder’s plate on E7058

One hundred Class 7E locomotives were delivered in 1978 and 1979, numbered in the range from E7001 to E7100. Beginning with the Class 7E, the SAR numbering practice for electric locomotives was changed to make the class number a part of the locomotive’s number. From the Class 1E through to the last of the Class 6E1 series of locomotives, all electric locomotives were numbered sequentially in the number range from E1 to E2185, with twelve numbers in the range skipped.

UCW did not allocate builder’s numbers to the locomotives it built for the SAR, but used the SAR unit numbers for their record keeping.

Orientation

These dual cab locomotives have a roof access ladder on one side only, just to the right of the cab access door. The roof access ladder end is marked as the no. 2 end.

Judging from early photographs of Class 7E locomotives, the distinctive "eyebrow" rainwater beadings above the cab windscreens were added post-delivery.

Features

Electric equipment

Control of traction and rheostatic braking on the Class 7E is by stepless solid-state electronics. The electrical equipment was designed for high power factor operation, obtained by a sector control method. These were the first South African AC electric locomotives with thyristor technology from the 50 ^c/s Group.

Bogies

The Class 7E was built with sophisticated traction linkages on the bogies, similar to the bogie design which was introduced on the Class 6E1 in 1969. Together with the locomotive's electronic wheelslip detection system, these traction struts, mounted between the linkages on the bogies and the locomotive body and colloquially referred to as grasshopper legs, ensure the maximum transfer of power to the rails without causing wheelslip by reducing the traction force of the leading bogie and increasing that of the trailing bogie by as much as 15% upon starting off.

Pantographs

The Class 7E was the first SAR electric locomotive on which the pantograph contact shoe centres were located directly above the bogie pivot centres. This reduces the possibility of pantograph hookups on catenary in sharp curves, such as in turnouts, as a result of sideways movement of the pantograph in relation to the overhead wire.

Service

The Class 7E was designed primarily for goods train service on South Africa’s 25 kV 50 Hz AC electrified lines. Until 1978, all electrified mainline routes in South Africa used 3 kV DC, but from that year all new mainline electrification projects bar one used 25 kV AC. The one exception is the 50 kV AC Sishen-Saldanha line. There are four isolated 25 kV AC routes.

• From Pyramid South to Pietersburg and via Brits to Thabazimbi.
• From Ermelo to the Richards Bay Coal Terminal at Richards Bay.
• From Port Elizabeth to De Aar and from there northward to Kimberley and southward to Beaufort West.
• From East London to Springfontein in the Free State.

When it was electrified, the well known double line "racetrack" between Kimberley and De Aar was single-lined and the section was signalled for single-track centralised traffic control (CTC) with long crossing loops. Here the Class 7E finally replaced South Africa’s last big Class 25NC steam locomotives. The second set of tracks were left in place, but unelectrified and isolated from the electrified track. However, in anticipation of increased ore traffic to the Eastern Cape from Hotazel, north-west of Kimberley, work on electrifying the second track commenced in July 2008.

The Class 7E was initially placed in service on the coal line from Ermelo to Richards Bay. When later model 25 kV AC locomotives were acquired, a few Class 7E locomotives went to the Pyramid South and East London lines, but the majority were transferred to the Cape Midland system to work goods and passenger traffic from Kimberley via De Aar to either Port Elizabeth or Beaufort West.

Regional co-operation

A 30c postage stamp, depicting a pair of Class 7E locomotives hauling an ore train, was one of a set of four commemorative postage stamps which were issued by the South African Post Office on 15 February 1990. The theme illustrated interdependence and regional co-operation in Southern Africa and, on this stamp, the integrated railway systems which stretched from Cape Town in the south to as far north as Dar es Salaam in Tanzania. The artwork and stamp design was by the noted stamp designer and artist A.H. Barrett.

The Blue Train

In the SAR and Spoornet eras, when the official liveries were Gulf Red and yellow whiskers for the SAR, and initially orange and later maroon for Spoornet, many selected electric locomotives and some diesel-electrics were painted blue for use with the Blue Train, but without altering the layout of the various paint schemes. Blue Train locomotives were therefore blue with yellow whiskers in the SAR era, blue with the Spoornet logo and the name "SPOORNET" in Spoornet’s orange era, and blue with the Spoornet logo but without the name "SPOORNET" in Spoornet’s maroon era. Later, in Spoornet’s blue era, there was no need for a separate Blue Train livery, while in the Transnet Freight Rail (TFR) era one Class 14E and the surviving Class 14E1 DC/AC dual voltage electric locomotives were eventually repainted in blue during 2012 for use with the Blue Train. When the Class 14E1 was retired in 2015, two Chinese-built Class 20E dual voltage electric locomotives were repainted in blue for Blue Train service.

When the section from Kimberley to Beaufort West was electrified, six Class 7E locomotives, numbers E7004 to E7009, were painted blue with yellow whiskers for use with the Blue Train on that section.

Illustration

All the Class 7E locomotives were delivered new in the SAR Gulf Red and yellow whiskers livery. The main picture shows no. E7058 in its original livery at Swartkops on 22 April 2013. Illustrated below are some of the other liveries which Class 7E locomotives served in.

• 
  No. E7008 in SAR Blue Train livery on a goods train near Die Put, about 16 kilometres (10 miles) south of De Aar, 2 May 1985
• 
  No. E7067 in Spoornet orange livery at Beaufort West, Western Cape, 2 August 2007
• 
  No. E7061 in Spoornet maroon livery at Beaufort West, Western Cape, 16 September 2009
• 
  No. E7047 in Spoornet blue livery with solid numbers at Beaufort West, Western Cape, 1 May 2006
• 
  No. E7100 in Spoornet blue livery with outline numbers at De Aar, Northern Cape, 26 August 2007
• 
  No. E7010 in PRASA’s Shosholoza Meyl livery at the Edwin Swales shops, Durban, 4 June 2010