Those who have been following my ramblings on this build have heard several variations.
Originally I was making a large (30-40") contact wheel, and the grinder would be similar in operation to most three wheel grinders.
Then I was leaning on a two wheel system with the drive wheel being the small wheel.
Then a direct drive main wheel on a two wheel system.
All these required building expensive and close tolerance parts that needed to be very heavy duty. While not completely abandoned, these were not the best options.
Then I hit upon using something already made to turn, handle lots of force, was adjustable, cheap, and readily available to anyone, anywhere.
I came up with using a front wheel drive auto or truck wheel and the mounting hardware. Think about it, it has the steering arm, which can become the tracking, the upper and lower mounting arms to bolt to the frame, the arms also move up and down to allow tension adjustment and belt change, a CV joint to drive it, and a hard rubberized serrated or smooth contact wheel called a tire. A plus is that it is fairly water-resistant. There are common tire sizes available from 4" to 6" tread width in diameters from 20-30". Larger diameter tires may be possible.
If you want to drive it from a 6" drive wheel, just remove the CV joints.
My current direction is for a standard junk yard build with the thinnest and largest tire size that I can find reasonably. I would love a 145/90/24 but that isn't a likely find. A 15-16" wheel will give a 24" diameter. A 20" wheel will get around 30"", but finding a thin tire for a 20" rim isn't likely.
If any of you gear-heads have info on the narrowest and highest profile tire that will fit a standard rim size, and the car type it will fit, let me know by PM or email.
...staying tuned in.