Here is 2200's solution, First off, the axle that the arm rotates on is live, (meaning it spins with the arm) The axle is a 3/8 bolt just like the ones provided in the KOP. We modify them by turning down the last 1/2 inch of the bolt to .250" diameter.
Thinking ahead, we ordered some free belts and sprockets from Gates. The rest is a piece of aluminum, 2 #10 machine screws, a .250 ID .375 OD bearing, and a long shaft potetiometer.
PIC:
- Bochek