The Nelson-Wiggen Co. used a system of rubber tire riding on the pump
wheel to drive the roll feeder.  The speed was controlled by turning a
knurled knob that moved the wheel with the tire farther from or closer
to the center of the pump wheel.  This is obviously different from the
Wurlitzer set up but works the same in principle.

The tire fits into a grove around the outer edge of the driven wheel.
When the one on my Nelson-Wiggen became stretched to the point where
it was loose on the driven wheel I simply replaced it with an "O" ring
obtained for a couple of bucks at the local machine supply outlet.

Hal Davis