PRACTICAL IDEAS FOR BETTER RAILWAY MODELLING

In order to get the best electrical pick up from a model locomotive, the wheels must be clean. With a conventional model, a common way of cleaning is to turn the loco upside down and apply an electrified wire brush to the wheels, or some other abrasive material such as a fibreglass brush to the spinning wheels. Anyone who has tried to clean loco wheels using this method, where the wheels are sprung or compensated, will know that it is almost impossible. Furthermore, even with rigid wheelbase locos, there is a potential for damaging the fine detail on the loco during this process.

Cleaning is not so critical on a compensated loco because, with all wheels hard on the track, pick-up, even with tarnished wheels, is still likely to be good. Often it needs no more than to spin the loco wheels on the track while physically holding it back to knock some of the gunk off. If wheels are very dirty however, or even rusted, something more needs to be done. Also, if a device could be constructed that avoided heavy handling of a model, advantages for all model locos would be considerable.

In developing a new, reliable and easy-to-use system, I considered making up a special piece of track where the rails were mildly abrasive. The problem was that most abrasive materials that I could think of, were not electrically conducting, and were either too abrasive and/or would wear too quickly.

Remembering the fibreglass brush technique, I considered that the best abrasive material, if electrical conductivity was not an issue, would indeed be fibreglass. Moreover, I knew that this material could easily be obtained in sheets in the form of printed circuit board (PCB), and thus I decided to proceed along these lines.

Should anyone not have a supply of PCB, it can be obtained from some electrical shops such as Dick Smiths and some model shops. However, it must be of the fibreglass variety as the Bakelite type would be useless. By far the easiest and cheapest way of obtaining the material however, is to visit a printed circuit board manufacturer, and ask if you can raid their rubbish bin for off cuts.

Finding some 1.6imm single-sided PCB in the scrap bin, I cut two rectangular pieces about 50imm in width and of a length just more than that of the longest loco needing wheel cleaning. Setting these pieces of PCB on edge with the copper sides facing each other, I made up a piece of ‘track’ by screwing the pieces together using spacers of a length equal to the track gauge (see Fig.1). I could have soldered the sides together using scrap pieces of PCB, but knew that the whole thing would need to be dismantled again before the whole device was finished.

Using some coarse-grade emery paper and a dead-flat surface, I sanded the tops of the ‘rails’ until a perfect running surface was obtained.

The only method that I could think of to attain electrical pick up was to construct some device that would make contact with the bottoms of the flanges of the loco. Any system of bringing wires out directly from the loco would have caused too much complication.

In order that electrical contact should be reliable, two metal bars were made up, one for each rail, and these were arranged to be sprung upwards (see Fig.2). I made these bars out of 3.2imm thick brass, which again I got from the scrap bin, but in the absence of such material, a piece of PCB could be used (ideally double sided) with sheet metal soldered to the contact face.

Having made the contact bars, they were screwed to the inside faces of the running rails. Elongated slots were made for the screw holes in such a way that the bar could slide up and down, and when uppermost, the bar would be just below the height of the running rails.

A simple springing device was then needed. Fig.2 shows how this was done with two levers sharing a common pivot point, and an extension spring pulling the two together. Again these were made from the same brass sheet as the contact bars, although any rigid material would do. A variety of springs can be obtained from almost any hardware shop.

The sprung levers and contact bars would, of course, need to be assembled separately with the PCB plates that make up the running rails. After that, all that would remain would be to assemble the whole thing, solder a wire to each of the inside faces of the PCB plates, and the device should be ready for use.

If metal spacers between the running plates had been used, these would cause a short circuit, and would need to be isolated by cutting gaps in the PCB. Also, something needs to be done at the ends of each running rail to stop the loco running off the end of the device. The easiest thing here is solder on some scraps of PCB to act as buffer stops.

When loco wheels have been cleaned using this device, the fibreglass contact faces will be filthy. A rag and solvent such as methylated spirits need to be on hand to keep everything clean. You will be amazed how much dirt comes off. Also in time, the contact faces of the fibreglass will become smooth and lose efficiency. Depending on how much the device is used, one should expect a year or two before this happens. When it does however, the contact faces should be roughed up again on a flat surface using coarse emery paper.