Have just started benchwork (4X8) for my HO layout. Somewhere on the 'net I came across reference and a picture having to do with "bus" lines, two wires under the length of the table which, as I understood it at the time, serve for connecting various electrics, such as street and buildling lights. Now I can't find the link. Can anyone tell me more about "bus" lines? Good idea? How to do it? Thanks, eagle37
A bus is a heavy length of wire designed to minimize resistance down its length...it is meant to get the most power from the power source down to the far reaches of the layout without causing a severe reduction in the voltage that is needed to "carry" the working amperage for the use of various devices...motors chief among them. Once the bus has run below the general length of the layout, thinner gauge feeder wires, say 22 gauge, are soldered or crimped onto that bus, fed up through tiny holes in the surface of the layout..near the tracks, and soldered or otherwise fastened positivley (electrically) to the rails. The thinness of these feeders is not a problem because they don't have to reach far, generally, only a matter of 4-20" at most...so little loss of voltage over their lengths. Think of arteries and then capillaries...same-same. You will probably not need a bus on your layout. Once trackage gets over 20' or so, a bus becomes a good idea. You can actually run a second set of 22 gauge feeders from your power source to the opposite side rails if you have something like a large oval or a folded loop. The idea is to try to keep the "pressure", the voltage, high along all the track length. A bus would serve no useful return for you for the 4X8 you are building. Just use two sets of feeders, one for the close side of the layout's tracks, and one other to reach the far side. You'll be fine. If you do experience power drop-out, it will probably be from weakly bonding metal joiners between the rail sections. Use new ones, prop up the tracks better so that they don't wobble and eventually weaken the joiners, or solder a set of feeders directly to a rail for a best practise.
Regarding accessories, turnouts lights and animated bits, I would recommend having them on a separate power supply with it's own "bus" (or not). This means the different things don't interfere with each other, and a train shorting out doesn't turn off all the house / street lights, and so forth. More importantly, a turnout that shorts the track halfway through being thrown would never unshort if it was powered from the tracks. Plus you if they are separate, you can turn off one or another when you're not using them. Handy for wiring and/or show and tell. Thus, three separate buses: track, with thick wires turnouts and other trackside accessories lighting and animation, probably doesn't need very thick wires For only 4x8, your "bus" may be as simple as two wires across the diagonal of the layout with the controller at one end and the track at the other. Rail + joiners are such poor conductors that you will get a voltage drop on even a 4x8 oval!
Hmm. Different opinions on need for bus on 4X8 layout. Given the choices, I suppose that though bus lines may not be necessary, couldn't hurt. I might as well lay them in there at this early stage of construction.So thanks for both opinions. eagle37
I was jumping at the chance to answer this thread when I saw it. HOWEVER, COverton has covered it pretty nicely.
