South African Class 7E2, Series 2

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South African Class 7E2, Series 2
SAR Class 7E2 Series 2 E7215.JPG
No. E7215 at Pyramid South, Pretoria, 6 October 2009
Type and origin
Power type Electric
Designer 50 c/s Group
Builder Union Carriage and Wagon
Model 50 c/s Group 7E2
Build date 1983
Total produced 40
Specifications
AAR wheel arr. C-C
UIC class Co'Co'
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Wheel diameter 1,220 mm (48.0 in)
Wheelbase 13,460 mm (44 ft 1.9 in)
 • Bogie 4,060 mm (13 ft 3.8 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 17,500 mm (57 ft 5.0 in)
Width 2,896 mm (9 ft 6.0 in)
Height:
 • Pantograph 4,190 mm (13 ft 9.0 in)
 • Body height 3,942 mm (12 ft 11.2 in)
Axle load 21,000 kg (46,000 lb)
Adhesive weight 124,000 kg (273,000 lb)
Loco weight 124,000 kg (273,000 lb)
Power supply Catenary
Current collection Pantographs
Traction motors Six MG-680
 • Rating 1 hour 515 kW (691 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 88 km/h (55 mph)
Power output:
 • 1 hour 3,090 kW (4,140 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)
Career
Operators South African Railways
Spoornet
Transnet Freight Rail
PRASA
Class Class 7E2
Power class 25 kV 50 Hz AC
Number in class 40
Numbers E7176-E7215
Delivered 1983
First run 1983

The South African Railways Class 7E2, Series 2 of 1983 is an electric locomotive.

In 1983, the South African Railways placed forty Class 7E2, Series 2 electric locomotives with a Co-Co wheel arrangement in mainline service.[1]

Manufacturer[edit]

Builders’ plate, no. E7204

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.[2][3]

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.[1]

Orientation[edit]

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.[1]

SAR Class 7E2 Series 2 E7204 ID.JPG

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.[1]

Features[edit]

Brakes[edit]

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.[2] Like the earlier Classes 7E and 7E2, Series 1, these locomotives were equipped with thyristor technology from the 50 c/s Group.

Bogies[edit]

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).[1][2]

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.[2]

Pantographs[edit]

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.[1]

Service[edit]

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.[4]

Illustration[edit]

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.

References[edit]

  1. ^ a b c d e f South African Railways Index and Diagrams Electric and Diesel Locomotives, 610mm and 1065mm Gauges, Ref LXD 14/1/100/20, 28 January 1975, as amended
  2. ^ a b c d Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 129–131. ISBN 0869772112. 
  3. ^ "UCW - Electric locomotives" (PDF). The UCW Partnership. Archived from the original (PDF) on 12 October 2007. Retrieved 30 September 2010. 
  4. ^ Middleton, John N. (2002). Railways of Southern Africa Locomotive Guide - 2002 (as amended by Combined Amendment List 4, January 2009) (2nd, Dec 2002 ed.). Herts, England: Beyer-Garratt Publications. pp. 50–51, 61xx–yy.