CO-CO 20001 COMES TO LIFE

The search for suitable prototype locomotives which may have worked to Peacehaven led me to consider adding a SR Co-Co electric loco to the fleet. This became my first attempt at scratch-building and enabled me to fill a perceived gap in the fleet. I had experience of the Bulleid Co-Co electric locomotives in the 1960s and these locos certainly worked to Newhaven so could well have turned up at Peacehaven from time to time. Reference to an excellent book on these locomotives, Southern Way Special Issue No. 11 The ‘Booster’ Locos CC1/CC2/20003 by Simon Lilley and John Wenyon, published in 2015, gave all the information I needed to build the model including scale general arrangement drawings.

The body profile on these locos is pretty well slab-sided, putting the task of body construction within my skill level. I decided to make the bodyshell structure from 1.5mm aluminium sheet and my initial thoughts were to make the structure in five main parts; two bodysides, two solebars and a baseplate/floor.

My attempt at folding the 1.5mm aluminium sheet for the solebars proved unsuccessful since the material was too thick to look effective. These locomotives have very prominent main frames so I had to find something better.

My saving grace, following a visit to my local model shop, was in discovering shallow channel section plastic strips. I selected a size almost to scale for the locomotive (8 x 2mm) and, although these components would not offer any structural strength, they enabled me to simplify the design and improve the appearance. The bodysides were marked out on aluminium sheet and cut out using tin snips. In the process of cutting, the sheet coils up but being soft is easily smoothed out with soft jaws in the vice and gentle hand-straightening.

Openings for the cab windows and various ventilation grilles were marked out and made by drilling through the sheet and filing to the correct rectangular shape. There are many bodyside ventilation grilles on these locomotives so making the openings was tedious but straightforward enough. Drilling a chain of holes for each and then opening these out to rectangles of the appropriate size using needle files.

The challenge was then to find a means of representing the grille slats themselves. My local model shop again came to the rescue and I selected suitable sections of OO scale plastic station fencing that could be cut to size and glued into the openings.

The structural part of the solebars was also made from 1.5mm aluminium, as was the baseplate/floor of the locomotive. Once these had been cut and the baseplate folded into an inverted U shape, assembly could begin. The various components were fixed together using 2mm countersunk head set screws and nuts. I have found 2mm a useful size for all sorts of applications and have a good stock to hand. I decided to give the structural box extra strength by inserting cab rear bulkheads, by folding the sheet into a shallow channel shape and securing in place with the countersunk set screws and nuts. Holes for the heads of the set screws were, of course, countersunk and once the assembly was finally bolted up and checked for squareness, the heads were filed flush with the panelling. Any remaining imperfections were dealt with by placing a dab of P38 body filler and sanding down until smooth.

The cab fronts were made using the 1.5mm aluminium sheet. In this case, there was little space to fit flanges needed to bolt them in place so they were simply glued in place with two-part epoxy adhesive. Openings were needed for the cab windscreens and holes were also drilled for the six positions of the headcode marker lights. The light fittings were represented by gluing on 3mm diameter washers with the addition of half-washers, also glued on, to represent the drop-down flaps used on these locomotives. LED headlamps were placed behind the fittings in relevant positions, bearing in mind that the headcodes on the Southern represent the route of the train being worked. In one position a 3mm magnet was fitted behind one of the dummy fittings, allowing a removable tail lamp to be carried when running light engine.

The cab was finished by making and fitting the cab roof mouldings. These are simply blocks of plastic, cut and filed to shape. Fixing of these proved a challenge as I found that the gluing technique was simply not strong enough. I ended up bolting a small flat fishplate under the roof dome, and then used the 2mm set screw technique to attach these to the top flange of the relevant cab bulkhead. An advantage here is that the cab roofs can be unbolted, if needed, to gain access to the cab interior. This has been handy to service the LED marker lights and to add driving seats and drivers put in as an afterthought. I’ve not gone to the trouble of fitting solenoid-operated drivers as the cabs are quite dark inside and the driver cannot readily be seen. However, when the loco is moving forwards the LED marker lights come on and there is some back-spill from the light. Thus the driver in the leading cab does become visible.

To aid smooth running I decided to install a flywheel and selected a suitable motor with double shaft which would allow this. As the aluminium construction makes the loco quite light extra weight has been added inside the body. Current pick-up in the bogie design is in American-style where each bogie picks up from either the positive or negative rail. I have adopted the practice of adding extra pick-ups where possible and in this case fitted a couple of plunger pick-ups to the wheels on the ‘insulated’ side. As well as enhancing current collection this also enables the bogie to be test run before fitting to the loco frame.

I needed to add the obvious external bogie end and side frames, which are made from plastic sheet. Initially I tried fixing these in place using adhesive but this proved to be inadequate for good security. Once again I resorted to using the 2mm nut and bolt method for the structural joints. Sandboxes, axleboxes and leaf springs are glued to the side frames and these came from the casting supplier, Laurie Griffin. The individual components, whilst not specifically designed for the SR Co-Co locomotive, were selected from the comprehensive range of castings offered for other locomotive types. The sand boxes are GWR type, axleboxes from an LNER locomotive tender and the side springs of a relevant size from the coaching stock range. Other external features, the shoe beams and shoe fuse boxes are assembled from off-cuts of scrap plastic and glued on.

I have tried various glues and have developed a preference for UHU. Whilst it is a bit stringy it is does allow repositioning of components as it gradually dries and once hardened off results in a firm rigid joint suitable for decorative items. Having assembled the bogies I realised I would need a sub-frame to make the wiring installation easier and to maintain the necessary electrical insulation between the two bogie frames. This was made from plastic using a 1in x ¼in moulding and I was able to select suitable spacers over the bogie pivots to give the correct body height when the whole assembly was put together.

There was a good deal of trial and error in this process, until eventually arriving at the correct spacer thickness.

With the sub-frame in position it is possible to run the entire bogie assembly as a separate item, aiding testing which can be carried out before the body shell is fitted. Another decision was to determine the position of the vertically mounted motor. To make the sub-frame simpler I placed it at the outer end of the powered bogie and, of course, a suitable opening in the body baseplate could then be located immediately behind the No.1 end cab bulkhead.

The roof of these locomotives carries a pantograph which were needed on the SR locomotives, as it was considered unsafe to install live conductor rails in marshalling yards. As a result, locos were equipped with ‘trolley-wire’ overhead power supply for traction current.

For the model Judith Edge Kits supply a pantograph kit of the correct pattern. I much appreciated the fact that the etch for this kit included several spare washers enabling me to complete the construction despite dropping and losing some of these small items. I built the pantograph directly onto a rectangle of brass sheet which in turn was screwed into position in the pantograph well.

The model was completed by adding cab handrails and vacuum pipes on the cab ends. Crests and lettering are from the Historical Model Railway Society series of transfers. Initial thoughts that a second traction motor may be needed were unfounded and Co-Co 20001 has proved to be a good addition to the fleet, managing the 1-in-100 gradient with ease and being equally at home working a variety of passenger, parcels and freight trains.