I'm helping a friend get into the hobby. He needs to choose his scale. I need a chart comparing minimum track radii for HO, S, O27 and O. I know I have seen it but can't find it.
Minimum radius is determined by the engines and cars you will be running. See the NMRA for their standards http://www.nmra.org/standards/sandrp/rp-11.html
Another take on the same can be found here. I'd just add a reminder that the minimums are based on operation, and that appearance can often require/request much more.
