I've asked my self this question. How is it that when you spin a bicycle wheel in a vertical plane while holding the axil only on one side that the whole essembly doesn't comes tumbling down. OK, now I know how that is possible. What I'm wondering now is if you take that essembly and rotate it as fast in a horizontal spin as well. My though process to this would be to imagine it suspended by a cord from above that could spin it in a horizontal plane. Do the same principal apply but on two planes?