South African Class 7E

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'  • Commonwealth 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)  • 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 source 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 Nicknames MacGyver 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.

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.

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 only twelve numbers in the range skipped over the years.

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.

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.

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.

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 wheel slip 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 wheel slip by reducing the traction force of the leading bogie and increasing that of the trailing bogie by as much as 15% upon starting off.