South African Class 18E, Series 2

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South African Class 18E, Series 2
Class 18E 18-670.JPG
No. 18-670 at Beaufort West, 27 March 2013
Type and origin
Power type Electric
Designer Union Carriage and Wagon
Builder Transnet Rail Engineering
Model Spoornet 18E
Build date 2009-2015
Total produced 279
 • AAR B-B
 • UIC Bo'Bo'
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Wheel diameter 1,220 mm (48.0 in)
Wheelbase 11,279 mm (37 ft 0.1 in)
 • Bogie 3,430 mm (11 ft 3.0 in)
Pivot centres 7,849 mm (25 ft 9.0 in)
Panto shoes 6,972 mm (22 ft 10.5 in)
 • Over couplers 15,494 mm (50 ft 10.0 in)
 • Body 14,631 mm (48 ft 0 in)
Width 2,896 mm (9 ft 6.0 in)
 • Pantograph 4,089 mm (13 ft 5.0 in)
 • Body height 3,937 mm (12 ft 11.0 in)
Loco weight 88,904 kg (196,000 lb) max
Power supply Catenary
Current source Pantographs
Traction motors Four AEI-283AY
Gear ratio 18:67
Loco brake Air & Rheostatic
Train brakes Air & Vacuum
Couplers AAR knuckle
Operators Transnet Freight Rail
Class Class 18E
Power class 3 kV DC
Number in class 279
Numbers 18-421 to 18-435, 18-600 to 18-863
Delivered 2009-2015
First run 2009

The Transnet Freight Rail Class 18E, Series 2 of 2009 is a South African electric locomotive.

In 2000, Spoornet embarked on a program to rebuild Class 6E1, Series 6 to 11 locomotives to Class 18E, Series 1 locomotives. Most of the Class 6E1s which had previously been reclassified or modified to Class 16E or Class 17E respectively, were rebuilt to Class 18E as well. Rebuilding to Series 1 locomotives ceased in 2009, with 446 units rebuilt.[1]

Commencing in late 2009, all further rebuilt Class 6E1 locomotives for Transnet Freight Rail and the Passenger Rail Agency of South Africa were designated Class 18E, Series 2. These were rebuilt from Class 6E1, Series 2 to 8 locomotives and from one Class 18E, Series 1.[1]


The 3 kV DC Class 6E1 electric locomotive was built for the South African Railways (SAR) by Union Carriage and Wagon (UCW) in Nigel, Transvaal, with the electrical equipment supplied by the General Electric Company (GEC). Eleven series of Class 6E1 were delivered between 1969 and 1984, with altogether 960 units built. 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.[2]


Rebuilding to Class 18E, Series 1 locomotives ceased in 2009, with 446 units rebuilt, the last Series 1 locomotive being no. 18-525. The rebuilding to Class 18E, Series 2 locomotives commenced in late 2009 and was done by Transnet Rail Engineering (TRE), now Transnet Engineering (TE), at its Koedoespoort shops in Pretoria. For Transnet Freight Rail (TFR) locomotives, the Series 2 number range begins with no. 18-600.[1][3]

In 2012 and 2013, fifteen Series 2 locomotives were also rebuilt for the Passenger Rail Agency of South Africa (PRASA). These were numbered in the range from 18-421 to 18-435 and were delivered in a new light blue and charcoal livery, designed by Peter Stow.[1][3]

By the time the rebuilding to Class 18E, Series 1 ceased, all available Class 6E1, Series 9 to 11, nearly all Series 8 and several Series 6 and 7 locomotives had been rebuilt. Most of the Class 18E, Series 2 locomotives were therefore rebuilt from Class 6E1, Series 2 to 7 locomotives and two Series 8 locomotives.[1]


The Class 6E1 is a dual cab locomotive and has 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.[4]

The rebuilt Class 18E locomotive, on the other hand, is a single cab unit, since cab 1 was stripped of all controls during the rebuilding, to have additional equipment and a chemical toilet installed. Since the driving cab's noise level had to be below 85 decibels, cab 2 was selected as the Class 18E driving cab, primarily based on its lower noise level compared to cab 1, which is closer and more exposed to the compressor's noise and vibration. Another factor was the closer proximity of cab 2 to the low voltage switch panel. The fact that the handbrake was located in cab 2, was not a deciding factor, but was considered an additional benefit.[1][3][4][5]

Brake systems[edit]

Air brakes[edit]

Brake rack in Class 18E no. 18-089

Since it was probably not intended at the beginning of the project to rebuild virtually the whole fleet of Class 6E1s to Class 18Es, most of the early rebuildings were done on the newest of the Class 6E1 fleet, Series 8 to 11. One of the reasons was that these series, numbers E1896 and up, already had an air equipment frame brake system, commonly referred to as a brake rack, similar to that intended for the Class 18E, which would reduce the overall per-unit cost of rebuilding.[6]

Another consideration was possibly that their bodywork usually required less heavy repairs than the older models in terms of rust and other damage, such as bent panels and frames.[1]

Similar considerations possibly also applied when older Class 6E1s of Series 6 and 7 began to be rebuilt in 2003, since these units, in the number range from E1646 to E1895, used the same brake valve as that of the Class 18E. The result by 2013, however, was a fleet of already ageing Class 18Es and ancient Class 6E1s, the latter mostly of Series 6 and older models.[1]

The Class 6E1 locomotives were built with an air brake system consisting of various valves, connected to each other with pipes, commonly referred to as a “bicycle frame” brake system. The compressed air pipe is run through bolster and other members and then in a zig-zag pattern under the locomotive's belly to extend its length, to allow the maximum amount of moisture to condense on the way to the reservoirs. As a result, it has multiple pipe connections. A weakness of the system was that, after an accident or even a hard coupling, these pipes tended to develop leaks at the joints which were extremely difficult to repair.[6]

Underbelly compressed air pipes

When Class 6E1, Series 7 and earlier locomotives began to be rebuilt, it was necessary to retrofit them with a brake equipment frame or brake rack. Since this already increased the per-unit rebuilding cost, it was decided to simultaneously re-route the compressor pipe away from bolster and other members, to the outside of the bodywork on the locomotive's right side, from below and to the right of the no. 1 end cab door to just before the second sandbox lid from the no. 1 (now rear) end. An added advantage was that the pipe would run cooler and more moisture would condense on the way to the reservoirs. The same modification was not done on locomotives which were rebuilt from Class 6E1, Series 8 to 11.[6]

Dynamic brakes[edit]

The Class 6E1 locomotives were equipped with regenerative brakes. With regenerative braking, the energy generated by the traction motors is dissipated by the resistor grid banks at the substations, when it is not absorbed by other locomotives in the same electrical section. A stumbling block was that the regeneration equipment at many of the sub-stations along the route was unreliable and, since there was no guarantee that another train would be in the same section to absorb the regenerated energy, there was always the risk that line voltage could exceed 4.1 kV, which would make either the sub-station or the locomotive trip out.[7]

As a result. the rebuilt Class 18E locomotives were equipped with rheostatic braking instead of regenerative braking. With rheostatic braking, the energy generated by the traction motors is dissipated by the resistor grids on the locomotive itself. The rheostatic braking of the Class 18E was superior and very reliable for higher speed trains, compared with the regenerative braking of the older Classes 6E1 and 17E locomotives.[7]


Class 6E1 Series 2 to 11 bogies

The Class 6E1 was built with sophisticated traction linkages on their 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.[8]

During rebuilding to Class 18E, Series 1, all traction motors underwent a complete refurbishment and were tested back-to-back to ensure quality. On the Series 2 locomotives, light or medium overhauled traction motors were also used due to cost considerations, provided they passed the back-to-back testing process. This and some other cost-saving measures, such as installing porta-pottys instead of the extremely expensive chemical toilets, constitute the main differences between the Series 1 and 2 Class 18E. Their performance and operating characteristics are identical.[1]

New equipment[edit]

The rebuilding included the installation of Alsthom micro-processor control technology. New equipment in the totally refurbished Class 18E locomotive include the following:[3]

  • A transducer, to relay vacuum and compressed air pressure to an electric signal.
  • Dual-purpose main resistance modules, which replaced the accelerating resistance system and which are used for motoring and rheostatic braking. The resistance blowers use AC motors which are powered through inverters.[1]
  • A DC current transformer (DCCT), which measures the current flowing to and from certain equipment, such as the traction motors, or total overhead line current.
  • A potential divider, to measure the voltage in the overhead equipment and traction motors.
  • A main processor unit (MPU), located in high tension compartment 1, used for primary (master) control of the locomotive.
  • Remote input-output modules (RIOM), located in high tension compartment 2, in the low tension panel and the driving compartment, used for secondary (slave) control of the locomotive.
  • Two digital display units (DDU), mounted on the driving console, to display, for example, information like speed, current draw and available overhead voltage, current draw of the traction motors in each bogie, rheostatic braking current generated per bogie, as well as performance information about all the locomotives in the consisted set.[3]
  • Overspeed protection, which will automatically open the line switches if any pair of wheels slips and a speed of 95 kilometres per hour (59 miles per hour) is exceeded.[5]
  • The driver's cab and console received a lot of attention to ensure crew comfort and safety. It included the installation of an air conditioner and windows which offer better protection against rocks thrown by trackside vagrants.[1]


Beginning in 2009, before rebuilding to Series 2 commenced and in an attempt to reduce theft, the 110V battery bank was relocated from the locomotive sides, below the frame and between the bogies, to cab 1, where the toilet occupies less than half of the available space. On the Series 1 locomotives, this appears to have been done only with numbers 18-510 and later. Identifying features are a small grille to the left of the cab 1 side door and, in most cases, the remaining battery box frames without side covers.[1]


Identifying features[edit]

The most obvious visual feature to distinguish the Class 18E from the Class 6E1, is the filled in driver’s windows at the rear end where the toilet is installed. The remaining rear windscreen still has the slanted upper edge of the Class 6E1 windscreens, but the new front windscreens on the Class 18E are rectangular.[5]

On the sides, obvious visual distinctions from the Class 6E1 are the left one of the two large grilles, which was removed and the opening filled in, two new large grilles which are installed in the centre lower sides to serve as air intakes for the rheostatic braking resistance blowers, and a large access door to one of the high-tension compartments, which was installed in place of the rightmost small window which was in the upper sides of the Class 6E1, to the rear of the driver's window. On the left side, the air intakes for the air conditioner in the cab are installed between the top three steps of the roof access ladder.[5]

Locomotives rebuilt from Class 6E1, Series 2 to 7, have part of the compressed air piping sunk into a recess which runs along the left half of the lower edge of the body on the locomotive’s right side, the side opposite the roof access ladder side. This pipe was not rerouted on locomotives rebuilt from Class 6E1, Series 8.

Lineage identification[edit]

All features which distinguished Class 6E1, Series 8 or older locomotives from each other are still present on the Class 18E rebuilds, in many instances making it possible to visually determine the Class 6E1 origin of a Class 18E locomotive. Examples are shown in the pictures below. Some of these spotting features are:[4]

  • The side doors with:
    • mid-door mounted door handles on ex Series 2 to early Series 7 locomotives; and
    • low mounted handles with a mid-door drawer pull type handle at mid-door level on ex late Series 7 and Series 8 locomotives.
  • On ex Series 8 locomotives, the large hatch door on each side, below the second small window to the right of the side door on the roof access ladder side, and below the first window immediately to the right of the side door on the opposite side.
No. 18-677, ex Series 3 no. E1322, with narrow stirrup step
  • On ex Series 6 and 7 locomotives, the smooth sides without hatch doors and the rainwater beading above the small grilles on the sides, just to the right of the side doors. On some ex Series 6 or later locomotives which have been observed, however, this beading is absent, possibly because it had been removed for some reason.
  • On locomotives rebuilt from series 2 to 7, the recessed pipe on the right side.
  • On ex Series 2 to 5 locomotives, the absence of the rainwater beading above the small grilles on the sides just to the right of the side doors.
  • On locomotives rebuilt from Series 2, and series 3 in the number range from E1296 to E1345, the narrower stirrup middle step below the side doors.

Project termination[edit]

The rebuilding project was abruptly terminated in January 2015, with 31 locomotives still on the Class 18E rebuilding line at Koedoespoort, possibly to vacate the assembly line for the construction of the new Classes 21E and 22E locomotives. Of these uncompleted locomotives, three were dispatched to Transwerk's Durban shops for their rebuilding to be completed, while those Class 6E1s which were still on the stripping, shell rewiring and equipment installation production lines, were to be removed and scrapped. The last Class 18E to be completed at Koedoespoort, was no. 18-863.[1]

Table of rebuilds[edit]

With one exception, all the Class 18E, Series 2 locomotives were rebuilt from Class 6E1, Series 2 to 8 locomotives. No. 18-862 was rebuilt from the scrapped Class 18E, Series 1 no. 18-040, which had originally been rebuilt from Class 6E1, Series 10 no. E2131 in 2002.[9]

Class 18E, Series 1 no. 18-040

Since TFR, PRASA and TE are separate corporate entities, serviceable Class 6E1 locomotives for rebuilding are sold to TE and rebuilt Class 18E locomotives are then sold back to TFR or PRASA. Profit-wise, it is to TE's benefit to also use the shells of wrecked or burnt locomotives to rebuild, depending on the condition of the shell. Since 2003, when Series 1 numbers 18-066 and 18-075 were built from burnt Class 6E1 shells, several locomotives had therefore been rebuilt from wrecked or burnt and scrapped shells.[1]

No. 18-040 had been left parked on a siding in the veld. When a crew went back to start it, they found virtually an empty shell, completely stripped by metal thieves. Since TFR considered the locomotive not economically repairable, it was scrapped. The shell, with the bogies, was bought by TE since it was already modified to the Class 18E specifications, and was used to build no. 18-862. Since it had been scrapped, the 18-040 number could not be used again.[9]

The table shows the original Class 6E1 number, series and year built for each Class 18E, Series 2 locomotive, as well as the year it was rebuilt to Class 18E. All the table columns are sortable.[1][3]


The Class 6E1 series lineage identification features are illustrated in the following pictures. Note the external compressed air pipe on the right side of locomotives rebuilt from Class 6E1, Series 2 to 7.

Rebuilt from Class 6E1, Series 2
Rebuilt from Class 6E1, Series 3
Rebuilt from Class 6E1, Series 4
Rebuilt from Class 6E1, Series 5
Rebuilt from Class 6E1, Series 6
Rebuilt from Class 6E1, Series 7
Rebuilt from Class 6E1, Series 8


  1. ^ a b c d e f g h i j k l m n o Information gathered from the rebuild files of individual locomotives at Transnet Rail Engineering’s Koedoespoort shops, or obtained from John Middleton as well as several Transnet employees
  2. ^ "UCW - Electric locomotives" (PDF). The UCW Partnership. Archived from the original (PDF) on 12 October 2007. Retrieved 30 September 2010. 
  3. ^ a b c d e f 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. 49, 51, 57–58. 
  4. ^ a b c 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
  5. ^ a b c d 18E Locomotive (TFR leaflet used in driver training, c. 2010)
  6. ^ a b c Information obtained from Transnet engineers and drivers
  7. ^ a b Operation - South African Classes 6E, 6E1, 16E, 17E and 18E
  8. ^ Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 128–129. ISBN 0869772112. 
  9. ^ a b Suid-Afrikaaanse Spoorweë / SA Railways / Ulolwe, comment by Philmar du Plessis on 29 May 2015 at 19:01