Have you guys seen this fellow's design?
http://digilander.libero.it/tornadoblu5/en/index1.htm
video: http://youtu.be/HEPxcoX7ivk
It is utterly brilliant, eh? Not easy to build, but brilliant. I've seen nothing in four years of looking that a DIY'er has surpassed for simplicity and originality. VERY low wattage requirements and silent. And, like the JoyRider, a gimbal'ed movement is second best for realism. You want your center of gravity at or below rotation axiis; never above (unless your goal is opposite motion ...