Turns out I was trying EastCoastIron's suggestion (but not having see that reply yet). And I'd agree with Boilermaker1, based on my limited observations. I have a coupler on only one end of the car (waiting for Atlas trucks for the older ones, and Lionel conversion kits for the newest two).
Using finger power - with one car coupled to PC 86-footer - they made it through Atlas 40.5" radius, going both directions. On 36", though, at least one outside wheel was lifting off the rail. ADD: Oh, I tried a couple cars to couple to the PC car - one relatively light - an Atlas 5161 hopper - and one heavy, a Berwick 60-foot box car.
This is with the NWSL 36-inch wheelsets in the Lionel truck frames.
Ok, this pic is with 36" radius on the inside, and 40.5" on the outside. Roughly 4.5-inch center-to-center. This is as close as they got. The one on the inside is stock, 3-rail.
David
