Power type Electric Model 50 /s Group 7E2 Total produced 40 | Designer 50 /s Group Build date 1983 | |
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Builder Union Carriage and Wagon | ||
The South African Railways Class 7E2, Series 2 of 1983 is an electric locomotive.
Contents
In 1983, the South African Railways placed forty Class 7E2, Series 2 electric locomotives with a Co-Co wheel arrangement in mainline service.
Manufacturer
The 25 kV AC Class 7E2, Series 2 electric locomotive was designed for the South African Railways (SAR) by the 50 c/s Group, a consortium consisting of ACEC of Belgium, AEG-Telefunken and Siemens of Germany, Alsthom-Atlantique and Société MTE of France, and Brown Boveri of Switzerland.
It was built by Union Carriage and Wagon (UCW) in Nigel, Transvaal, who delivered forty locomotives in 1983, numbered in the range from E7176 to E7215. UCW did not allocate builder’s numbers to the locomotives which 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 designated the no. 2 end.
In visual appearance, the Series 2 locomotives can be distinguished from the Series 1 by the vertical grilles just to the rear of the driver’s window, on both sides on the Series 2 locomotives, absent on Series 1. Both series have a large grille to the right of centre on the side opposite the roof access ladder side, near roof level on Series 1 locomotives and low down near sill level on Series 2. The three grilles in line, just to the rear of the side doors on Series 1 locomotives, were replaced with a single long grille on Series 2 locomotives. Like the Class 7E, some of the Class 7E2, Series 2 locomotives have distinctive "eyebrow" rainwater beadings above their cab windscreens, but these were added post-delivery and were not installed on all the units.
Brakes
Control of traction and rheostatic braking on the Class 7E2, Series 2 is by stepless solid-state electronics. The electrical equipment was designed for high power factor operation, obtained by a sector control method. Like the earlier Classes 7E and 7E2, Series 1, these locomotives were equipped with thyristor technology from the 50 c/s Group.
Bogies
To reduce flange and rail wear, the bogies of both series of the Class 7E2 have a shorter wheelbase than the Class 7E, 4,060 millimetres (13 feet 3.8 inches) instead of 4,400 millimetres (14 ft 5.2 in).
The Class 7E2 was built with sophisticated traction linkages on the bogies. 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 adhesion of the leading bogie and increasing that of the trailing bogie by as much as 15% upon starting.
Pantographs
As on the Class 7E, the locomotive's pantograph contact shoe centres are directly above the bogie pivot centres. The reason is to reduce 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 7E2, Series 2 was placed in service on the northern 25 kV AC routes, which stretch from Pyramid South, just north of Pretoria, via Warmbad to Pietersburg and via Brits and Rustenburg to Thabazimbi, where they still serve.
Illustration
The main picture shows no. E7215 in its original SAR Gulf Red and yellow whiskers livery. Other liveries which were applied to Class 7E2, Series 2 locomotives, are illustrated below.