What is the mininmum radius curve for a UP big boy in N scale but should not look too tight or
too much over hang? I am thinking no less than 16 inches.
I can’t speak to minimum as that depends upon the loco. However, the NMRA Recommended Practice RP-11, Curvature and Rolling Stock shows that a loco of that type would probably need 17.375" or greater curves to operate well and look good.
You can check the recommendations at the NMRA Standards site at http://www.nmra.org/standards/ You would probably fall into the O or P classification.
Roger
I think Roger is giving good advice about checking NMRA RP11, but I’m also a great believer in in the empirical or experimental method for answering questions like this. Put down some flextrack in a 16" radius curve and see how your Big Boy looks on it. You can also lay a parallel track on whatever centers you’d like to use and check for clearance of the Big Boy’s overhang. Experiments like these aren’t hard to do and will answer questions to your own satisfaction.
Good luck,
Andy
Andy Sperandeo
MODEL RAILROADER Magazine