feeder wires - Model Railroader Magazine

HoosierLine

For wire I suggest 18 gauge for the feeders and 14 gauge for the main bus.

You mention 128 linear feet of main line.  Does that mean 60 feet out and another 60 back?  Or is it a double main line, 30 out and 30 back?

The killer is the overall length of the run, either from your cab power distribution panel (in DC) or from your base station (in DCC.)  There's no reason that you have to have a single, linear bus.  You can add branches, and the bus wiring does not have to match the track path.

If you have very long runs, over 25 feet or so, you might actually want to go with #12 wire for your track bus.  This will result in less loss at the end of the line.  On the other hand, I think the suggestion of using #18 wire for feeders is overkill.  I have a much smaller layout than the one you're planning, but I use #18 for my bus and #22 for my feeders.  I have no problems with power distribution, but, as I said, my layout is much smaller.