Thanks John! That's the kind of re-assurance I need as I push my saws through walls and plywood. Dave mentions there will be found somewhere something that truly needs bigger than O-72 (I found some more obscure RR modeling websites where minimum curves were all over 100 and I bet the modeling was exquisite). But I detect vast experience and knowledge in John's summary of the answer, that lots of big trains will run O-72 fine. I figure, whatever exception that undoubtedly can be found, my train won't be it!
And now I'm wondering, is my modeling question about the minimum turn radius related to why real locomotives were sometimes built as articulating units? Was that so they weren't too long as a rigid straight line? Wouldn't our scale version of that problem be the reason some curves could be too tight? Probably it comes down to the length of each truck and maybe also the maximum turn angle of each truck?
