The magnet count and size, and wire size, are all a given.
Just need to go with the basics for how they are commonly assembled.
That's less than one cubic inch of neo. Not much to work with.
The 1/8" thick is the killer.
Almost require an iron core to get anything out with magnets that thin.
Problem is the iron core needs to be within about 1/8" of the neo's face, which does not leave room for much wire and mechanical clearance.
If the 1/8" gap opens more than about 1/8", then the flux drops off fast.
With an air core, the turns more than 1/8" from the magnet face do not count for much power, but they add resistance.
I'd be tempted to make an air core stator with the coils 1/8" thick, kind of splitting the difference to hope for the best.
If they can do and measure 3-ph, need to go with something like Ed's coil arrangement above.
Could use a plywood ring where Ed uses the laminated ring, for a single disk air core.
Magnet spacing will be important. 1/2" dia should be 1/4" apart for 3-ph. Willib's files are something to look through.
Then the coil size too,
for 3-ph with overlapping coils, 1/4" wide legs, 1/2" hole, 1/8" thick. That's about 8 turns wide legs x 4 turns thick.
for single phase, 1/2" wide legs, 1/2" hole, 1/8" thick. That's about 16 turns wide legs x 4 turns thick.
There is enough wire for a 3-ph, and Way Too much for single phase.
I have a feeling most people run into the idea of using ALL the wire, which lowers the output.
Need to have the neos on iron to do anything. Maybe a 3" knock-out disk?
Getting 20W is past what I personally would hope for without an iron core. Gosh, seems like a lot even with an iron core (unless he wanted to do a mini motor conversion- yikes).
G-
