Hi I'm in the middle of a similar but smaller project as yours, and I just wondered what it was that you bolted to each rotor (the thing with 4 bolts and a hole through it for the shaft). I'm interested because I have used mdf for my rotors, superglued the magnets on (they are weaker and smaller than yours though), and to transfer the torque I have used 8mm threaded rod as the shaft and attached "T-nuts" to each rotor - effectively making each rotor like a nutthat screws onto the shaft and can be fixed with a lock nut. However, I have run into problems with this method, as the rotor seemsto wobble and the t-nuts seem to be coming loose as they eat into the mdf every time I remove them (the magnetic force pulls them together at one side and then the other).
Having seen yours, I think that might solve the big problem with using mdf so I was wondering what they were called and where I could get them, and also if they had bearings inside? Because I'm hoping that they don't, so that I can find one with an 8mm diameter hole and tap a thread onto it. If they have bearings I might have to try to make something similar myself, which will be much harder as I don't have metal working gear except a hack saw and some files - I don't even have a metal vice at the moment!
I hope you can help me out a bit =]