OK, I didn't actually pull the 27 wire cable through a conduit. The units involved were cab units, and had a 2 1/2 by 2 1/2 inch wiring duct (Hoffman or =) running from the electrical cabinet to the rear terminal box over the back door. I laid the cable in that duct, along with some additional wires for back up-light, etc. I can see where actually pulling that large a cable could damage it, though, especially at any tight bends.

That brings up another thought for the list of suggestions. If you have to set any cable in a tray that has open slots in the bottom or sides, be sure to anchor it about every six inches with a very tight tie wrap. This is actually a major issue right now with a particular class of locomotives on one of the largest commuter rail operations. They were wired with cable trays having slotted sides (with the wire not adequately secured), and after seven or eight years of operation they are finding that most of the control wiring in the trays has been sliced and abraded through continual small movements of the wires inside the tray when the locomotive stops and starts.

PC