Some decisions I've maybe made:
1. Motor and Electronics will be mostly enclosed
2. Will use a belt (silicone tubing), driving the spool. The pulley will be attached to the spool end. I may have to add some sort of belt tensioner, not really sure yet. 2:1 drive-gear;pulley ratio. This should allow for 4.5-5k rpm speeds, which is pretty fast for a spinner. Maybe too fast for this thing.
3. Both spool ends will have pushfit printed geared bearings (fallback plan is to print bushings for 608 to fit)
4. The brake will be around the flyer's shaft. There will be a knob in the front panel that allows one to adjust the scotch brake.
5. The flyer will be in a geared bearing. Working on the details of this part (such that the spool is easily removable). The threaded metal rod will be attached directly to the flyer. Its other end will be, of course, in a geared bearing.
6. Somewhat trapezoidal threaded-rod and printed plastic frame.
Version 2:
Add BMS/PCM circuit with a lifepo4 battery at 14.4v and make it mobile.
Version 3:
Add NC socket w/ 3dp foot-pedal thing to pause spinner temporarily.