[Tom Bottiglieri]

We did some calculations to find what our desired shaft size was, built a few shafts with diameters a bit over and under that number and tried them all. It turns out in our particular case the base shaft diameter isn't as important as making sure there isn't too much wear on the tread. After it's put it about 10-20 times our tread material becomes noticeably worn and we see drastic changes in the speed.