thats hurting my brain a bit at the moment...
would that run as 3 phase, or 6 phase? Seems like it should work for 3 phase...
Thats a bit of an old project. I'd use better material for the laminates than I did... find some silicon steel, or perhaps tear down a big transformer and slice up the laminates for it.
I'd also be sure to cast resin over the whole thing if you make it from plywood, the pull of the magnets on the laminates is strong and I've seen a couple come apart.
I would wind that differently now too... it had a pretty low cutin speed. I would perhaps use heavier wire and 1 gage thicker if I made another single phase machine like that. It had a 7' prop or so, so it could've had a higher cutin speed, heavier wire... and it would've been more efficient. I would also say - as I built that, on that page, it had too much resistance for the 7' prop. If I used that same arrangement again, I think I'd go for a higher cutin speed, perhaps around 180 - 200 rpm, and run with a 7' prop max, maybe even a bit smaller.
A ballpark guess at the windings though, to get it to produce 12 volts at the same speed as the single phase machine, is simply to figure how many windings are in each phase. Mine was single phase - 18 coils, 18 windings each... so 360 windings got me 11 volts AC @ about 125 rpm. If 12 coils/18 magnets works as 3phase... (I think it will but 2 coils would be reversed on each phase?) then you'd have 4 coils/phase, so youd need about 360/4 windings per coil... about 90 windings per coil. Changing the shape, and size of the coil will affect things, but I suspect that would be close. Wire sizes have about half the cross-sectional area each time the size goes up by 3...
so if I used 16 gage and fit 20 windings, you could probably go with 21 gage wire and it'd be close.. keeping in mind that your coils would be larger.
It's very easy with an arrangment like this, to test a single coil. You should use the heaviest possible wire you can that fits enough windings in there...
Again - that's kind of an older project. If it were me... I'd build a dual rotor design ;-)
But - as we built it there, it did run for quite a while. I remade the stator once, and doubled up the magnets (so we were having a double stack of magnets and heavier wire w/fewer windings) - and encapsualted the whole stator in fiberglass mat and resin - and it's been running fine since. The newer stator has cold rolled sheet steel for lamintes... it takes a good 10mph wind for several seconds to get it spinning (mostly due to hystoreses losses which were even worse with the bandsaw blade). Once up and spinning though it does pretty well for a 7' 3" prop... but it takes a somewhat windy day for it to really run much or produce much. A better choice of steel for laminates would improve that greatly.
