A
recent discussion of bouncing tops reminded me of this gizmo from last summer -- a dual-spin top with bouncing rotor. I call it "chained gyration".
The green octagonal "rotor" freely slides and rotates on the mostly black "spindle" carrying the stem, tip, and rotor stops. The gold chains connecting rotor and spindle transmit torque from one to the other while variously allowing and limiting relative motion between them. The whole thing's surprisingly durable.
When rotor and spindle angular speeds diverge, the chains wind up on the spindle, and the rotor quickly rises to the upper stop. When the top is still, or when rotor and spindle speeds equilibrate under chain action and bearing friction, gravity pushes the rotor onto the lower stop.
Dual-spinIn the spacecraft biz, "dual-spin" refers to a vehicle with 2 main components -- platform and body -- capable of relative rotation about a common axis. Typically, the body spins continuously to stabilize the common axis in space, while the antenna- or camera- or solar panel-bearing platform is aimed at various targets. Most communications satellites use dual-spin designs.
You can get some pretty cool mechanical and visual effects out of dual- and triple-spin tops. I've made well over a dozen now with many more effects yet to be explored.
