COuld it be possible that it is stray generated voltage? You have tons of magnets spinning around and I'm wondering if any outside voltage is crawling around your gadgetry. Kinda like a radio signal. I hope I'm making sense as I'm not an electrician. I work around commercial electricians all day long (harassing them about circuitry for powering up all my pumps and timers, I'm always on about lighting questions) and also know a few things about alternators and dyno's from motorcyles and cars. From what I understand the internal voltage flows through the wiring as it should and you could say it spins with the directions of the magnets. But there is a small interferrence voltage that can build up in the opposite direction on the outside of poorly insulated devices. That's why when you install a nice stereo in your car but do not get it grounded correctly it can whine with the pitch of the alternator.

It's just a theory as you say that almost each of your spinning motors is creating a small amount of "leaking" voltage.