How does one wire a layout for catenary or third-rail power? Are both rails still A and B so diesels and steam can also run? Is the overhead wire A or B (red or black)?
This all depends on whether you intend to use the overhead for power. If you are going to run steam, diesel, etc, then staying with the rail for power all around is simplest.
You could try to use both rails and overhead, but this would require insulated wheelsets on one side and that equipment that pulls from the wire never be turned. That way there’s independent power of ops. This was done in DC days to allow separate control between electric and other power. However, DCC sort of eliminates that as an issue for the most part.
There are a few specialized reasons I can imagine using the overhead for power, but for most it’s probably easier to stick with rail power, even if you erect a wire or caternary, for mixed traffic.
Model traction layouts would have both rail = ground and the wire be live.
LION has third rails, but it is all faked, and without actual metal rails present.
HIM would like to have had placed real metal rails there, at least they could activate the signals.
ROAR
Pick one. Seriously. Just stay consistent.
Correct! If you do not like the way the train is moving, just switch them.
Some pan equipped equipment has the pan connected to what would have been either the right or the left rail. You have to test this out to see how the unit is wired, and then wire your wire accordingly.
But to do it RIGHT (on a traction layout with no regular DC equipment) make the tracks (both of them) GROUND. Then put the power on the overhead wire.
LION has never had success building overhead wires, big furry paws mitigate against such subtle work, so him just put the pans up an imagines that there is a wire there.
ROAR
Agreed, but is there a manufacturer’s standard as to which (left or right) is connected to the pantograph?
No it does not make a difference and as far as I know there is no standard unless you are building to some modular standard. NTRAK does have a standard but even reversed modules can be easily fixed at the plugs between modules. DCC is AC. With AC there is no polarity. Instead the difference between the two wire is call phase. Phase needs to be the same so once a color is chosen for the overhead, stick to it.
Even with DC the choice would be yours. The positive wire is positive only when the train is moving in one direction. It’s negative if the train is reversed.
Martin Myers