Hi Phil -
"The folks on this board originally used laminate backing also. When the dual magnet
rotor concept came around, it seems everyone dropped the laminated stators.
They were hard to wind, labor intensive, heavy, and silicon steel was not readily available.
Cogging also seemed to be a problem in some cases."
When I was using laminates, I'd press the coils over the top of the laminates - so hopefully the coils would be very thin. The laminates existed behind the coils - not inside, so cogging was not a problem. Cogging could become an issue when we slot the laminates and put the coils inside them - kind of tricky to do that, but he benifit is a much smaller airgap and much less magnetic material required. The drawback there is more work - and possibly issues with cogging. Also - in a single rotor axial flux machine with laminates the magnet rotor is always 'pulling hard' against the stator, and when current is flowing, the stator will vibrate. The bearing is always under some load. This makes it a bit stiffer to turn I think, and unless the stator is very rigid and attached very well I would expect it to either warp, or come loose enough so that the magnets could rub on the stator.
"question 1
If the same amount of magnetic material, as used in a dual rotor machine,
is mounted axially on one rotor, with a laminate behind the stator, would there be more power generated than a dual rotor system?"
I haven't really tested this too much, but yes - I think it would be similar, assuming that the coils are the same thickness, and the laminates exist behind the coils, not around them. The last laminated machine I made had 1.8" diameter x 1" thick magnets on the rotor, a 1/2" thick stator, and laminates behind the stator. Shortly after that I made some dual rotor machines (with identical stators) and each rotor had 2" dia X 1/2" thick magnets, and the dual rotor machines were slightly more powerful at any given rpm, but they had just slightly more magnetic material in them (2" diameter instead of 1.8" diameter).
"question 2
If steel laminate is cut to fit around and/or through the center of the
individual coils, then poured in resin to make the stator on a dual rotor machine,
Would the output be higher than just using magnet wire in the stator?"
Yes - but you'd be hard pressed to come up with something that didn't cog. The vibration of the stator might be fairly intense. You'd have iron losses again, though they may not be too big an issue. I think it would be tricky, the forces of the rotor pulling on that during assembly might be hard to deal with. It'd be fun to see someone do it though, it might workout fine once some things were figured out. We only figure out by doing...
"question 3
Are there other more efficient alternatives I'm overlooking?"
I tend to think laminates are very nice in some cases. Coils cool better when surrounded by steel, thats one big advantage - although overheating has not yet been a problem with stators of only copper and resin. I tend to think laminated stators are very nice/handy in radial flux machines - it's tricky
in axial flux machines.