Just to repeat, this is a work in progress.
At some point I will give it a drive shaft etc. However for the time being I've just given it a stand so you can spin the ring wheel by hand till your hart's content :)
The photos are out of date. Check out the stl of the assembled parts for the most up to date view.
I'm using four 3x10 screws to hold the frame together and one 3x20 to hold the two halves of the core together.
0.4 nozzle __ 0.2 mm layer thickness
The bottom part of the the gears are rather fiddly as only the very tips of the teeth make contact with the build plate. For this reason i have build a supplementary support structure into the stl file itself (see JPG). You will obviously still need slicer generated support structures for all other overhangs, use "touching build plate" rather than "everywhere".
For the gears I would also strongly recommend using a "brim" (single layer thick raft, NOT a true raft).