CUT THE WIRES Some ideas on unconventional layout wiring John Rodway The points can be of live or dead frog types. They each have to energise just one of the diverging routes at a time. There is no need for a break at A because the two lengths of rail are permanently connected by the common return wire. A gap in the rail has no electrical significance. However, a break is required at B since the polarity of the two lengths of return rail that make the inner rail of the loop line will change, depending upon the lie of the two points. If it wasn’t there, there could be short circuits and/or an inability to isolate locos when the points are changed. This diagram assumes that the slip is fully wired internally and isolates routes for which the blades are not set. Both rails of the slip must be isolated from the more important line at C and D. However, rail gaps are not required on those lines that finish in dead-ends, such as sidings. This diagram also shows that the feed and return do not have to be attached to the slip itself. They can be some distance away. The feed can be soldered anywhere along the rail between E and F without affecting the electrical circuit. Likewise, the return can be anywhere between G and H. It makes no difference to electricity reaching the locomotive. As far as selecting the polarity of the frog and the rails that are supplied through it, the power is effectively coming from the notional position. Connections at E and G would only be used if they resulted in shorter runs of wire from the control panel. There is no need for the long Wire J as the same electrical function is obtained by the short Link K within the control panel. Both section and isolating switches must be ‘on’ for power to reach the isolatable sub-section, just as with the conventional system. In the conventional method all rail breaks are in the feed rail. Wire M takes power from the track adjacent to the rail gap and returns it through Wire L. Wires N and P deal with power on the feed side rail, no matter what polarity is supplied through the point. In the unconventional system,Wire M is replaced by Link S within the control panel, as previously described.The switched return involves Link Q within the panel and Wire R ‘out in the country’.Together they allow any return current to get back to the panel. Stand 1 is isolated by the point. Stands 2 and 3 are energised by switched common returns.This allows a loco to be moved between the two whilst a loco remains at Stand 1 with the point set against it.This move might be required when ash has been dropped into the pit at Stand 2 and the loco then moves into the shed over Stand 3 for further attention.     Don’t get me wrong, this article neither supports DCC nor advocates attacking wiring looms with a chain saw. (Though I’ve had to sort out some layouts where this would have been a good starting point.) No. I’m just reporting a few unusual ways of reducing the amount of wiring on multi-section, tworail layouts that use common return and isolating points. I work on the basis that reducing the amount of wiring has several benefits. It:      • saves on work, material and expense,      • speeds initial proving of the system during construction and commissioning,      • reduces the number of places where things can go wrong in service,      • cuts the time when finding these faults. The track plan should reflect the intended traffic and the likely moves that the locomotives and rolling-stock will make. Plan the track, signalling and wiring at the same time, preferably before construction actually starts. Check that all prototypical moves can be made, especially if more than one locomotive is involved. If they can’t because the proposed wiring won’t allow it, then something needs to change, (and it won’t be the prototype!). Planning allows rail breaks to be installed at exactly the right places, and their connections to be tested as track-laying proceeds. This is far better than retro-fitting them to the permanent way, when there is the chance of disturbing the existing carefully-formed alignments. Common returns The basic theory of common return requires that sections are electrically- separated from each other. Insulated fish-plates are one way of providing the traditional double rail breaks that puts this principle into effect. However, breaks may not be required between all the rails that are connected to the ‘return’ side. Once the track plan is settled, check if any contiguous lengths of the return rail are always connected directly to the common return. If they are, then there is no need for an isolated joiner between them. Figure 1 shows where this idea works and, more importantly, where it does not. Benefits:      • Fewer problems of gauge alignment at the remaining single rail break, .      • Extended rail continuity means better pick-up., and      • Less wiring. Total isolation is mandatory for single and double slips. However, the isolation need not be immediately next to the crossing. It could be a little way down the track. For any lines that are deadends (usually sidings) there is no need for the traditional isolation gaps on those roads. This is shown in Figure 2. Benefits:      • Less chance of misalignment of tracks during laying.      • The connections to the rails do not have to be made within the confines of the slip itself, but can be where the rails are less vulnerable to damage by the heat of a soldering iron. Figure 2 also illustrates another point. On conventional wiring diagrams, notional feed and return wires are shown at the heel end of a series of points or at the centre of slips. However, there is no need for the actual connections to be made at such locations. Since the rails are conductors throughout their length, it doesn’t matter to the locomotive where the actual soldered connections are made along the length of rail. This means that they can be away from parts of the track already crowded with point motors and other bits, etc. It might be more convenient, and even provide shorter wire runs, to make the connections at the buffer stops, as suggested in Figure 3. Isolated sections The conventional way of wiring an isolatable sub-section is to run a pair of wires, one from each side of the rail break in a single rail, back to a switch on the control panel. (Wire J and its companion in Figure 4A.) The flow of current is easy to understand, especially if the feed is some way along the track. However, the wire that supplies the isolating switch can be fed directly off the section switch within the control panel (Link K in Figure 4B) rather than having to bring current back to the panel from the rail itself. Figure 4 shows a single controller, but there is no essential difference if cab-control is being employed. Benefits:      • Saving one run of wire. This can be significant for distant isolating sub-sections and umbilical cords on portable layouts.      • Fault-finding is easier too, since the origins of the electrical feed to both main and sub-section can be tested at the panel end. Switched common return A more difficult concept is that of switching the return rather than the feed to control a dead-end. This is useful where there are two adjacent sidings, each with an isolatable sub-section next to the buffers. If both isolating breaks were in the feed rails, then there would have to be a wire back from the inner feed-side rail to the switch in order to supply it with whatever power/polarity was being provided through the frog of the point. This is shown in Figure 5A as the long Wire P. With the switched return alternative in Fig 5B, the short Link Q within the control panel fulfils a similar function, though with the opposite polarity. Benefits:      • Saving another run of wire. And also makes for      • Easier fault finding. Since switched return is unusual, it is important that accurate records are kept and that all feeds and returns are clearly labelled within the control panel and underneath the baseboards. Engine sheds Engine sheds may have a chain of isolating sub-sections within a single road. It would be normal to treat each length as a separate section, equivalent to much longer sections out on the running lines. Each would have a switch fed by the controller. If cabcontrol were being used, each might have to be a 2-way centre-off type. The cost might be justified for large sheds, where more than one locomotive is being moved at a time. For smaller sheds, this may not be the case. Figure 6 shows how the ‘in-panel links’ have been applied on Gillan & Brown - the O gauge industrial layout of Romiley Methodist Railway Modellers. And finally, with unconventional wiring, it is essential that everything is recorded and explained in a series of clear diagrams. It may be possible to remember the reasoning behind certain wiring strategies for weeks or even months. But will the memories be as fresh when a fault appears after several years? And what happens when somebody else has to deal with the wiring? I appreciate that not everybody will be comfortable using unconventional wiring. For some the benefits will be outweighed by the challenge of the unorthodox. Indeed, for layouts that are the targets of my imaginary chain-saw, those where the wiring has been installed by try-anything-and-see-if-it-works, I’d rather it had been done strictly by the book. But unconventional wiring has its advantages in certain circumstances.