A couple of other thoughts: You could put at least 50% more magnet on that rotor.
It was too dang hot to do anything else today so I loaded the thing in the back of the Dodge Cummins and went to the motor shop with it. I showed my buddy that owns the shop what the deal is. He says, well, why not make it air core? All the new high-efficiency electric motors are air core, not laminated steel anymore.
So I got a new plan I'm going to try. I'm going to cast a non-magnetic core out of SmoothCast 300 plastic and using N50's instead of N42's on the rotor. I checked, and I can get them N50's with 1/8" holes pre-drilled for like 7 bucks each. It'll be a little time consuming making a mold to cast the plastic but I think it will be a fun experiment.
Here's the deal - I pulled the rotor out of the core, put some iron powder on a piece of plexiglass and held the plexiglass 6" from the magnets, between two poles. Even at 6" the flux "arranges" that iron powder on the plexi. Rotate the rotor while holding the plexi above it at a distance of 6" and it really does some cool stuff to that iron powder.
So if I throw enough flux at it, why do I even need a magnetic core?
--
Chris