How to figured out RADIUS, what is the FORMLUA?
Radius is easy. If you make a full circle of track, no straights, just curves, you go from the center of the circle to the center of the track, between the rails. That's the radius of the track. 10" radius make a circle little bigger than 20" when measured from the outside of the track across to the outside of the track. Also, radius is 1/2 of the diameter.