I made a machine for respooling sapphire fiber. Mytake-off tension control was
made with a standard shaded pole motor, a 12 volt DC power supply controlled
with an LM317 voltage regulator connected to a dancer pot. The 120 VAC shaded
pole motor acts as a very smooth viscous drag when supplied with a small amount
of DC. Try it on a bench test. About as simple as you can get.

Earle Rich
Mont Vernon, NH