my crude research with soft magnetic powders such as MPP and other nickel moly alloys leads me to believe that it might be helpful to mix into the casting resin of a dua rotor stator - MPP, nickel-iron, and sendust are available in powder form
windstuff ed's casting projects would be a wonderful sort of testing for dual rotor or maybe even single rotor, depending on the permeability rating of the powder - there have been poured stators of iron powder (windstuff ed), but MPP and insulated nickel-iron powders have far less losses
Whoooa! Dude.
I was mearly "suggesting the use" of saphire powder (aka AL02 or aluminum oxide)mixed in the resin epoxy or high temp epoxy ready mixes as provided as my preivious link.
Nevertheless, Wa's suggestion makes EXCELENT sense.
You couldn't pot the whole thing in soft magnetic material, of course, because it would route the flux around the coils. But you could mix up TWO batches of epoxy, one for the pole pieces with magnetic material, and one for the non-poles with sapphire or what-have-you. Both would conduct heat.
You could use a temporary dam to shape the pole pieces in any way desired, allowing you do design the transitions to minimize cogging, then pull it out while the epoxy is still soft so the magnetic and non-magnetic portions bond to each other, forming a single mass.
The powdered magnetic materials are way better than laminations at limiting eddy current losses. (That's why they're used in the inductors of switching regulators, where the magnetic fields are swapping around at kilohertz rates.) If they're not prohibitively expensive they'd make dandy pole pieces to eliminate the large gap in the radial alternator designs.
They'd also be great for making the one-rotor, slotted-disk style. Cast your slotted disk, insert your pre-wound coils, either pot them in with sapphire-etc-filled material or leave them open for ventilation. (You could also do a second casting of the magnetic material to make the crossbars of T-shaped pole pieces after the wires are in place.
So the questions are:
- Does anybody see anything wrong with the above speculations?
- Where can we get this stuff?
- How much does it cost?
- Is there any special technique necessary for working it?