Lionel response to min curve question.

It was my opinion as a kid decades ago that min curve requirements were a way to sell more expensive track systems like tubular O or Super O. That opinion faded away as the mfg's produced bigger and longer engines that could not negotiate tight curves.

Lately I have been thinking my former kid way more and more as some shorter - smaller engines are being marked for wider curves.

Your best bet is to look at the length of the loco, the truck arrangement and decide for yourself. A 17" loco is not designed for 031 in all respect to those with tigHt curves. Seriously 031 should be set up for 027 locos or it won't likely work. 

I have other Lionel diesels such as a SD40-2, U33C, and SD40T that are over 17" long and they go around O31 just fine - granted with alot of overhang. 

I have asked LIONEL this in the past cuz one catalog said O31 and one said O36.  They wrote back that the SD70ACe runs on O31.  I'm gonna wait for someone to try these out before I spend 500 bucks for one of those Norfolk Southern Heritage diesels.

Remember when the Genset diesel was first listed? The catalog said "operates on 042 but 054 is suggested. Well guess what a latter catalog said minimum curve 031.