Originally Posted by
tomato coupe
The following diagram shows the relationship between the three radii, where Ru = unloaded radius, Rl = loaded radius, and Re = effective radius. Your illustration shows the effective radius and the "patch" radius as being the same. They are not, in general.
Can just about read that. A higher quality image would have helped.
What’s the definition of the “effective radius” there? Cos based on the image alone it’s “distance from hub to an arbritrary dotted line”. Does PC=CA? And if so, why?