The loco arrived from Ebay yesterday, and today I ran it on an 18" radius test loop. I ran it clockwise, counterclockwise, forward and reverse without derailment. Apparently Broadway Ltd fixed the tight radius problem MR found when they reviewed it.
Thanks for the link. I also found the April 2004 MR product review. It found that at 18" it was subject to derail. They recommended 20", and 24" was better.
One source, apparently from the original run, says recommended minimum radius is 18":
https://www.hobbylinc.com/htm/bro/bro5220.htm
(Page way down)
I have been looking at this D&RGW On30 loco on Ebay, but there is no info on minimum radius. I also can not find that info on the Broadway Ltd site. Can anyone tell me what the minimum radius would be for that loco?