This is an accessory bus! It doesn not need to carry the same power as the third rail! That is to say, most accessories will be operating at 12 volts, and the loss of a few volts at that distance is hardly an issue.
The Beese of the LION are 14 ga. , Him used 4 conductor stranded speaker wire for the beese of him:
1) Green..............Common HARD Ground. (cannot float)
2) Black...............Third Rail (Train Power)
3) White..............Signal and Detection (+16v dc)
4) Red.................Hotel Power (all aux stuff)
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
I would say that 12 and 10 is the upper limit of bigness.
And that the lower level of bigness would be 16.
If you want a REAL OFFICIAL answer, you have to specify the distance to every tap. And the load at every tap.
When you are forced to consider how intermitant and overlapping the loads are, it gets kinda irritating.
So, to simplify, I'd go with 12 copper. It doesn't matter if it's solid or stranded, electrically.
Ed
For that long of a run, I would use 12 or 10 gauge, stranded, of course.
Marlon
See pictures of the Clinton-Golden Valley RR
Whats the best gauge for an accessory bus of 41 feet