Hi all,
I did a presentation on this issue at one of the ORG Layout Design Roundtables at York. I've attached the Power Point from that presentation to this post. The presentation includes a graphic that demonstrates how the extremes of overhang and encroachment are measured. There's also a list of the measurements for the most extreme locomotives and rolling stock for each radius.
In my experience the most extreme overhangs are on the MTH DM&IR Yellowstone (more than the Big Boy), the MTH W-1 electric, and the MTH UP Coal Turbine (used the W-1's chassis but with body changes). For encroachment the limit setter on O-72 is the Atlas 89 ft. flat car. Not many people have that car, so I also listed encroachment measurements for several more common passenger cars.
