The DeltaCELT https://www.physicsfunshop.com/search?keywords=deltacelt A new elegant rattleback design where the indentations create an asymmetry in the distribution of mass that leads to rotation reversals when spun: 1) If spun clockwise, after about two full rotations, a complicated combination of friction, precession, and instability induced vibrations transforms the rotational energy into into end-to-end rattling (energy of oscillations) and then into rotational energy in the opposite direct

The Chembongo http://physicstoys.blogspot.com/p/physics-toy-store.html Expertly crafted from African Blackwood this device prefers to only spin clockwise! If spun counter clockwise, a complicated combination of friction, precession, and instability induced vibrations transforms the rotational energy into rattling (energy of oscillations) and then into rotational energy in the opposite direction! This behavior is related to the asymmetric shape of the bottom of this kind of rattleback, it's somew