@dkdkrd posted:However, NMRA's recommended practice for O-gaugers having such equipment is a minimum radius of 72"...or, in O3R parlance O-144...a 12-foot diameter!!
I'm not sure what the standard is, don't care. I run Overland 2 rail brass passenger cars (20"0) through 56" radius mainline easily, 48" or even less in storage yards. True story. I don't blame anyone for quoting the NMRA, but really, I'm not sure that the MMRA rules most practical layouts. I would not be constrained by what the NMRA says in any event. Good luck.