As I convert my small fleet of rolling stock to metal wheels, a few conversations with my friend HK got me wondering. I know modern freight cars have 36" wheels. No debate there. The issue I have is that the left and right hemispheres of my brain can't agree on the visual versus the actual. I'll explain:
I am using FVM wheels. Up till now I have been using 33" wheels because they look right to my eyes (right brain). HK measured the FVM wheels for me and at the wheel face both sets are accurate to the given dimension (33"=33" and 36"=36"), this works for my left brain. Where the odd debate comes in at is that wheel flanges in real life measure about 1" give or take. On a FVM 33" wheel, the flange diameter is 38", or roughly that on a prototypical 36" wheel. The diameter of the FVM 36" flange is over 41", or roughly appropriate for an N Scale 40" wheel. Now my left brain hurts.
I decided I needed to figure out a way to check to see which half of the brain was the crazy one, so I too some prototype photos and lined them up with some model photos. Here are the results:
Photo 1 (FVM 33" Wheel): The overall diameter of the wheel (including the flange) closely matches the overall diameter of a real 36" wheel. Because the flange isn't weathered (and never will be) this stands out as the visual key in the picture to me.