On reading people suggesting multiple rotors, I understand that normally if you have magnets on each rotor, it is more efficient to have two large rotors with more magnets, then 3 or more rotors with less magnets each.
But it got me thinking what would happen if you had 3 rotors, but the middle rotor was something like wood with magnet shaped iron cores to channel the flux? Would this allow more of an air gap with the same set of magnets?
My gut tells me that you would be able to get slightly more turns, or the same number of turns with a slightly thicker wire (if you add the turns of the two stators together), but its unlikely to be that much more than just a normal dual rotor of the same size, and hence not worth the effort.
What do you guys think?
