Hudson5432, my layout has 2 areas where the radii is 36”. While I mainly run steam, largest being a large SP 2-8-0 I do have a number of Diesel engines. A GP 10, a CF 7, a BL2, a couple of SW 1s and a Whitcomb switcher. All are 4 axle and will easily handle the 36" radii. I’d guess a 6 axle unit might have trouble. My layout is posted in the 2 rail layout video thread.
Peter