It was at the same time when the ‘management’ of the Consolidated Shales Mining Company decided to build this heavy-haul railway, that the decision was made that it would also be the first predominantly electrically powered heavy-haul railway in this part of the world - This decision to ‘Go Electric’ was quickly arrived at, as the ‘company’ had recently gained access to an abundant supply of power from a new local offshore gas field that it had quietly helped to develop during recent years!

Given that the ‘company’s’ line is, in an area that is subject to frequent storms and vicious cyclones, the requirements and specifications for the new Overhead Line Equipment needed to be carefully considered before any construction work on the project could commence – Firstly, the structures that were going to support the overhead conductor wiring would need to be sufficiently sturdy so as to be able to withstand the repeated buffeting they would receive from the regular periods of high winds, and secondly the conductor wiring support system would have to be as simple as possible so that any repairs needed after a storm could be speedily undertaken, ready for the continuation of the transport of ore.

A thorough study of other electrically powered heavy-haul railways around the world was undertaken, and in particular, attention was paid to the type of Overhead Line Equipment that is still in use today on the 'Orex' line between the Iron Ore Mines at Sishen and Saldahna Bay in South Africa. Here regular 4km (2.5mile) long trains of 342 wagons, are worked by up to 7 locomotives, with two leading the train, two cut in at the 114th car, two more cut in at the 228th car, and the final one pushing at the rear, all of which are controlled by one driver in the leading loco through a ‘Locotrol’ Radio Distributed Power (R.D.P.) system - These vast ‘Orex’ trains are run on a purpose built 861km (535mile) long ‘Cape Gauge’ (1.067metre/3ft6in) railway at speeds up to 90kmh (56mph) on a daily basis, on a permanent way that can only be described as being in an absolutely ‘A1’ condition. The trains in use here also use a mixture of electric and diesel traction in the same locomotive consists, and, it was by using this format (although with much shorter trains and without R.D.P.) that the Consolidated Shales Mining Company intended to operate its own new railway.

Unlike the Consolidated Shales Heavy-Haul Railway, the ‘Orex’ line is not plagued by long periods of high winds, although a problem does exist with short-circuiting, which is caused by deposits of sea-salt on the high-tension insulators at the Saldahna Bay end of the line where it runs along the arid coast of the Southern Atlantic Ocean.

On the ‘Orex’ system’s main lines only, dropper wires are used to suspend their system’s overhead contact wire at regular intervals from a second upper wire that is known as a ‘Messenger Wire’: This ‘Messenger Wire’ in turn is suspended over the rails by using fixings on insulators that are again in turn fastened to the overhead supporting structures. Where the contact wire passes under an overhead supporting structure, an additional insulated ‘Register Arm’ attaches it to the structure in order to keep the entire network of wiring, or ‘knitting’ as it is known, in an accurate position over the rails. This is the most widely used method of electrifying railways with overhead equipment around the world.

With regards to all of the other ‘Orex’ lines, including the passing loops etc. a single ‘tramway-like’ contact wire suffices to keep things simple and costs down. Where used, this single wire is directly attached to the overhead supporting structures by special fixings on insulators, and although several locomotive pantograph pick-ups can be in contact with this wire at the same time, problems rarely occur as only relatively low speeds are involved.

Overhead Line Equipment as used on the 'Orex' Line in South Africa - Photo: B.W.Ring

 

After much thought, the Consolidated Shales Mining Company’s ‘management’ took the decision to use the ‘Orex’ line’s single contact wire system throughout its own system to deliver power to their new electric locomotives, but it was also decided that in order to combat the power of the cyclones that the system would encounter, additional strength for the overhead supporting structures would be needed through the use of much heavier duty ‘H’ beams in their construction than normal.

A full survey of the new railway was undertaken immediately after the completion of track laying, and it was decided at an early stage that only the lines that were directly involved with the transportation of ore, together with the line that by-passes the ore load-out at Coolamusta Mine and the two chord lines that provide access to the Engine Terminal at Steamer Bay near Harrison Point, would be fitted with Overhead Electric Equipment.

 

After determining exactly what parts would be required for the entire project, a production line was created, and the first items to emerge from it were around seventy-five separate insulators – These are made from 12mm and 18mm diameter nylon washers that were purchased in bulk on the internet from a firm called Nylon & Alloys Ltd (http://www.nylonalloys.co.uk). They were assembled by mounting the different sized washers alternately in a ratio of 6x12mm to 5x18mm onto a length of 6mm diameter styrene rod (Part No. MR-250P), from EMA Models of Norwood in South London (http://www.ema-models.co.uk). After gluing each assembly together, the rodding was then cut so that it was flush with the outer surface of the washer at each end.

Method of producing insulators

 

The next items to be made were the insulator slide assemblies to which the insulators are fixed. These slide assemblies suspend the insulators over the rails, and are made so that they slide onto the cross members of the overhead supporting structures before being finally secured so that they accurately hold the overhead conductor wire in position as required. Especially extended slide assemblies with double insulators are used where pointwork is involved, as at these locations two overhead conductor wires come to within a half of a locomotive pantograph’s width of each other without joining.

Slide assembly for locating insulators onto overhead line structures

 

The material that was to going to be used for the actual overhead conductor wire was decided upon at a very earlier stage, and it was decided to use lengths of Code 100 Flat Bottom ‘00’ scale nickel-silver rail, as it was deemed to be reasonably rigid and relatively easy to suspend from the insulators.

To attach the overhead conductor wire to the insulators, special fixings were manufactured. These are made from 18mm long strips of ‘H’ Beam (the same length as the diameter of the insulators) and are also made from material again supplied by EMA Models (Part No: PSH-6). Each fixing is provided with a hole through the thin part of its centre web, the hole being the same diameter as the width of what would normally be the bottom surface of the rail being used to form the overhead conductor wire. A fine slot is then provided through from the bottom web of the ‘H’ Beam to the centre of the hole, and it is through this slot and hole that the overhead conductor wire is finally threaded - When completed, these fixings are glued to the underside of the insulators, which in turn are glued to the underside of the slide assemblies, ready for mounting onto the cross members of the overhead supporting structures.

Method of threading conductor wire onto insulator assembly

 

A standard design of overhead supporting structure was finalised for both single lines, and plain double lines before the detailed designs were drawn up for the remaining bespoke structures - A standard thickness of 15.9mm was decided upon for all of the ‘H’ beams that were going to be used in each structure, and a sufficient quantity of the material required was again ordered from EMA Models (Part No. PSH-20).

The optimum height above the rail for the overhead conductor wire was determined to be 263mm (10+3/8in), and, after taking into account the combined height of the Peco G45 track the ‘company’ uses, the insulator, the insulator slide, and the thickness of the cross member of the supporting structure, it was found that the required height from the top of the cross member to ground level was 320mm (12+5/8in). This produces about 10mm (3/8in) of depression from full height on the pantograph of each locomotive as it passes beneath each structure - Production of all the structures commenced, and after completion the erection of the entire system began.

 

The first structures to be erected were those that were going to suspend the overhead conductor wires over pointwork. Here, it is essential that the twin insulators are located directly over each of the middle two rails where the four rails of the points-set are equidistant from each other. This because this is where the locomotive’s pantograph will be transferred from one run of overhead conductor wire to another when the locomotive uses one of the two routes available to it.

 

All Overhead Line Structures are fitted with identification plates for maintainance and repair purposes. Each plate carries two letters to denote the line for which the structure carries the conductor wire, and four digits to denote the exact position along the line where it has been erected.... for example:

Overhead Line Structure No. OC
Is situated on the 'Ore Cycle' Lines, at:
 
  12
12 Meters
 
  65
+ 65 Centimeters
from the '0' zero marker of the line

 

Where curves are encountered, the first structure on the curve is situated where the slot of its overhead wire fixing is directly over a point that is 10mm (3/8in) inside the inner edge of the outer running rail. On 918mm (3ft) radius curves, further structures are situated with their overhead wire fixings at 400mm (15+3/4in) intervals, again directly over the same position inside the inner edge of the outer running rail.

 

With regards to plain sections of running line, a maximum span of 640mm (25+3/16in) is allowed between structures. This is enough to keep the locomotive pantographs comfortably in contact with the contact wire in mid-span without the fear of the wire either bowing or deflecting. It is important that the slots of the overhead wire fixings on straight sections of line are set so that they are again directly 10mm (3/8in) over the inside of left and right running rail in an alternate ‘zig-zag’ manner. This will prevent grooves from being worn into the top of the locomotive’s pantographs and evens out any possible wear and tear.

 

After all of the completed overhead supporting structures were erected, the lengths rail forming the overhead conductor wires were threaded through the slots in the insulator fixings, and the insulator slides to which they are fixed by means of the insulators were then secured into position on the cross-members of the overhead supporting structures. The wires were then joined together with fishplates, with a ‘run-off’ being provided for one of the wires at each point-set. Each ‘run-off’ is raised away from the continuing overhead conductor wire and terminated on the next structure by means of a horizontally mounted insulator – Small lengths of multi-strand wire are then used to electrically bond the separate runs of overhead conductor wire together.

 

One feature of the Chord Lines at Harrison Point, is that they are crossed by 'Gricer's Bridge' foot crossing – Here, the height of the overhead conductor wire above rail level is gradually reduced on the crossing’s approaches to 245mm (9+5/8in), and a protective bridge is provided to prevent any possible damage caused by any person crossing the line!

 

As with any Model Railway, both indoors or outdoors, it is always advisable to provide access to the interior of any tunnel-like infrastructure. This is so that one can deal within its confines, any argumentative locomotives, rolling stock, or, as in the case of the Consolidated Shales Heavy-Haul Railway, overhead line equipment problems that may occur. To comply with this, the top decking of 'Gricer's Bridge' is hinged upwards so that access can be gained to the area below.

 

 

Finally, and most importantly, the fish-plated joints in the overhead conductor wires were all bonded together using a good quality solder, not only to obtain a good electrical connection, but also to obtain rigidity within the system. When doing this, it is imperative to ensure that where they meet, the undersides of both wires present a smooth and continuous surface to the locomotive pantograph, as any gaps or irregularities can result in ‘snagging’, which in turn can lead to the ripping down of the immediate network of both the ‘knitting’ and the structures.

 

It is intended that power will supplied to the locos via this system by a 12v battery charger, with the overhead conductor wire being positively charged, and the running rails negatively charged. The running rails will all be bonded to a return wire, which will be carried for the whole length of the system by means of separate cable runs between the overhead supporting structures.

So far the system has withstood the punishment of several cyclones and has proved itself through the sturdiness to which it has been built.