South African Class 6E

The South African Railways Class 6E of 1970 is an electric locomotive.

In 1970 and 1971, the South African Railways placed eighty Class 6E mainline electric locomotives with a Bo-Bo wheel arrangement in service. Two more were built for Iscor, for use at the Sishen iron ore mine.^[1]

Manufacturer

The 3 kV DC Class 6E electric locomotive was designed and built for the South African Railways (SAR) in 1970 by Union Carriage and Wagon (UCW) in Nigel, Transvaal, with the electrical equipment supplied by Associated Electrical Industries (AEI) and English Electric (EE).^[2][3]

Operators

South African Railways

Eighty locomotives were delivered to the SAR in 1970 and 1971, numbered in the range from E1146 to E1225. UCW did not allocate builder’s or works numbers to the locomotives it built for the SAR, but used the SAR unit numbers for their record keeping.^[1]

Sishen iron ore mine

In 1970, two Class 6E locomotives were also built new by UCW for Iscor (now Kumba), for use at the Sishen Iron Ore Mine in the Northern Cape. Numbered Iscor F221.01 and F221.02, these two were allocated UCW works numbers 6E.58 and 6E.59 respectively.^[2]

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. A corridor along the centre of the locomotive connects the cabs, which are identical, apart from the fact that the handbrake is located in cab 2. A pantograph hook stick is stowed in a tube mounted below the lower edge of the locomotive body, on the roof access ladder side. The locomotive has three small panels along the lower half of the body on the roof access ladder side, and only one panel on the opposite side.^[1]

Identifying features

In respect of body dimensions and shape, the Class 6E locomotive is identical to the last batch of Class 5E1, Series 5 locomotives, with their squared body corners. The most obvious visual external difference from the Class 5E1, is the replacement of the three small vertically arranged grilles, to the right of centre on each side of the Class 5E and Class 5E1, with a larger double grille on the Class 6E. In respect of the coachwork, the Class 6E is identical to its immediate predecessor, the Class 6E1, Series 1, while its bogies are identical to those of the Class 5E1.^[1]

Characteristics

Compared to the Class 5E1, the Class 6E had improved traction motors, particularly with regard to the insulation of the windings. This resulted in a continuous power output of 563 kilowatts (755 horsepower) per traction motor and a total continuous power output of 2,252 kilowatts (3,020 horsepower) per locomotive, compared to the 364 kilowatts (488 horsepower) per traction motor and 1,456 kilowatts (1,953 horsepower) total of the Class 5E1.^[4]

To ensure the maximum transfer of power to the rails without causing wheel-slip with these more powerful traction motors, the Class 6E was built with carefully designed weight transfer air bellows between the bogies and the frames, which reduced the adhesion of the leading bogie and increased that of the trailing bogie by as much as 15% upon starting off. This feature was controlled by electronic wheel-slip detection devices and an electric weight transfer relay, which reduced the anchor current to the leading bogie by as much as 50A in notches 2 to 16.^[4][5]

Operation

Startup

When there is no compressed air in the locomotive's system to raise a pantograph to start up, a pantograph hook stick is used to manually raise the pantograph. This starts the high voltage motor which drives the auxiliary alternator, to supply 110V power to start the compressor and power other control circuits. Once there is enough main air pressure to keep the pantograph in the raised position, the pantograph hook stick can be dropped.^[6]

The locomotive is controlled via resistors, over which the voltage is dropped in a configuration of series and parallel electrical circuits. The circuit breakers which switch these circuits, work under very high power and voltage and are therefore all pneumatically operated, for insulation purposes. Compressed air is required to open or close the switch actions and air is also used for the weakfield cam switch, which also switches under very high currents.^[6]

Running

Upon starting off and in the low notches, the major part of the voltage is dropped over the banks of resistors and all four traction motors are in series.^[6] The blowers which accelerate the dissipation of heat in the resistor banks, give the Class 6E its very distinctive sound, a deep and loud whine when power is applied.^[5]

As the driver notches up, some of the resistor banks are cut out via the pneumatically operated switches and the voltage increases across the traction motors. The more resistors which are cut out as the driver notches higher, the more power is developed by the traction motors. At around 22 to 28 kilometres per hour (14 to 17 miles per hour), the locomotive switches to a parallel combination, where the two traction motors per bogie are in series electrical circuit, while the two bogies are in parallel electrical circuit. Eventually, when all resistors are cut out, the locomotive is operating in full-field.^[6]

When the traction motors are operated in full-field, be it in series or parallel mode, they are performing at maximum power for normal operation. To increase the speed at this point, if necessary, higher power output is required from the traction motors. The only way to increase power is to force a higher current flow. To accomplish this, the weakfield cam switch switches resistance in parallel with the field coils, which reduces the overall resistance of the field coils. This increases the magnetic flux, and more power is generated by the traction motors over short periods.^[6]

Brakes

The locomotive itself used air brakes, but it was equipped to operate trains with air or vacuum brakes. The brake system would be set up for either air or vacuum train working by means of a turning switch on the driver's brake valve and by pre-setting the appropriate brake valves in the passage.

While hauling a vacuum braked train, the locomotive's air brake system would be disabled and the train would be controlled by using the train brakes alone to slow down and stop. While hauling an air braked train, on the other hand, the locomotive brakes would engage along with the train brakes. While working either type of train downgrade, the locomotive's regenerative braking system would also work in conjunction with the train brakes.

Unlike the Classes 5E and 5E1, whose air brakes could be applied independently on each bogie when the locomotive was stopped, the air brakes on both bogies would be applied together on the Classes 6E and 6E1. The handbrake or parking brake, located in Cab no. 2, only operated on the unit's last axle, or no. 7 and 8 wheels.

Unofficial renumbering

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 "SPOORNET" in Spoornet’s orange era, and blue with the Spoornet logo, but without "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 electric locomotives were eventually repainted in blue during 2012, for use with the Blue Train.^[2][7][8]

The Cape Western region usually had eight electric locomotives in a blue livery on its roster, to be used with the Blue Train when required. When the Cape Western’s Class 5E1s in Blue Train service were withdrawn from mainline passenger service during the 1990s, eight Class 6E1, Series 8 locomotives, numbers E1950 to E1957, were painted blue with whiskers for use with the Blue Train. After four of these blue Class 6E1 locomotives were damaged in a collision between two Trans Karoo passenger trains at Gouda in April 1997, the Bellville Depot was authorised to repaint eight Class 6E locomotives in Spoornet’s orange era Blue Train livery. The authorisation was given for numbers E1171 to E1178.^[2][4]

In the process three locomotives, which were considered to be "better" candidates, numbers E1146, E1157 and E1223, unofficially exchanged unit numbers with numbers E1172, E1177 and E1174 respectively. The evidence of the unofficial number change was still visible, years later, in the slightly different shade of orange around the numbers on the sides of the orange numbers E1146, E1157 and E1223, as illustrated.^[2]

• 
  No. E1172 as no. E1146, Bellville Depot, 28 March 2009
• 
  No. E1174 as no. E1223, Stikland, Cape Town, 29 March 2006
• 
  No. E1177 as no. E1157, Beaufort West, 1 May 2006

Illustration

The Class 6Es for the SAR were delivered in the Gulf Red livery with yellow whiskers, but all of them have since been repainted in various Spoornet liveries. The main picture shows no. E1221 in the Spoornet orange livery, while other liveries which were applied to Class 6E locomotives are illustrated below. No Class 6E locomotive ever served in the older SAR blue and whiskers livery for the Blue Train and no. E1220, as shown here, was painted in that livery only after it was scrapped and its shell was converted to a braai facility at the Bellville locomotive depot.^[2]

• 
  No. E1220’s shell, repainted in SAR blue and whiskers livery and used as a clubhouse at Bellville Depot, 28 March 2009
• 
  No. E1169 in Spoornet’s lined orange livery at Centurion, Pretoria, Gauteng, 30 September 2009
• 
  No. E1175 in Spoornet’s orange era Blue Train livery, approaching Bellville, Cape Town, 19 March 2007
• 
  No. E1213 in Spoornet’s maroon livery at Koedoespoort, Gauteng, 9 October 2009

References

Wikimedia Commons has media related to South African Class 6E.

Locomotives of South Africa
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List of South African locomotive classes South African locomotive numbering and classification