Rotary Base Construction:

Here is the rotary base. I machined a disk 8" in diameter and 1" thick from nylatron. I then cut out the internal shape and atached a Gates notched belt to the internal surface with Gorilla glue.

The second 8"x8" nylatron blank was machined to hold the disk. The pinnion placement was measured and drilled for a perfect alignment to the internal ring gear.

The disk sits on the base and turns very smoothly. The pinion has 12 teeth and the belt 116 teeth. This gives me a ~ 9.66 to 1 reduction.

A window regulator motor is connect to the pinnion by a coupling.

The elbow joint is complete. A stainless steel cable will control the position and remove weight from the outer end.