If you already have the engines, I would do a 'real world' test by getting Kato Unitrack sections in different curve radii and a power track and try running the engines thru them. The manufacturer's minimum radius info is usually correct, but I like to try it out to be sure.
TRM1,
I would look at it another way: What's the largest radii curve you can fit on your mainline for a 4-8-8-4? I would then strive to maximize your curves rather than minimize them - even if it means less trackage. It will look and operate better.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
Hey All, I"m curious I will be running a modren era loco's on my layout, they all will be six axel locos and one steam loco the UP Big Boy, the question I have is, what's the smallest radius I can go before I start have problems with derailments?? Thanks for the help