Figuring out pulley sizes for certain RPMs
I am making a buffing machine for polishing up musical instruments. I'd like to make it so I can use three speeds, for 6, 8, and 10 inch buffing wheels. How do I calculate the diameter of the pulleys needed to get certain RPMs, and more importantly, certain surface feet per minute on each of those size buffs. There's nothing that sucks more than having the tuba you just fixed get chucked across the room by a wheel that's too fast.
I plan on using a 1720 RPM motor and I know the proper RPM for a 6 inch wheel is 3600. I guess if I can figure out the SFPM for that, I should aim for the same amount for the other sized buffs, right?
PS Is there anyone in Central Illinois (Champaign/Urbana)?
Stuart de Haro