You're right about the steppers. With my small ones (ex 5 1/4" floppydrives) I can't get more than 22mA, no matter how fast I turn. Voltage goes way up, though.
The reason here is not resistance, but inductance: as you turn faster, the frequency of your AC increases. With higher frequency, the coils inside the stepper create more 'inductive reactance', a bit comparable to resistance, in that it limits your current.
Xl=2*pi*f*L
where Xl=inductive reactance (ohm)
f=frequency (Hz)
L=induction (Henry)
With axial flux generators without a core, your induction L is many times less than in a stepper, with its metal core, so reactive inductance is much less of an issue, whereas resistance isn't.
Willi, you may further reduce your (effective) resistance by wiring the coils in delta, as opposed to star; this reduces your internal resistance of the 3 coils by a factor 3. Made the calc yesterday evening, I wrongly assumed the difference was only 1.73;
My next projects will probably be made with two wires per coil, to reduce resistance. Another lesson learned from experience, when just listening to other people's advice could have had the same effect... I think that with more wires, you'll quickly get diminishing returns (you're reducing your coil resistance, but your other wiring & connecting resistances stay the same, unless you take measures for these too). At those high amps, a few tenths of an ohm quickly become losses of several volts, as I found out with the bike genny. Again, experience confirming what mr. Ohm had predicted. Another few lessons learned.
Good luck,
Peter,
The Netherlands.
