Tippy Top --- so simple!

thingiverse

Gene Chao, chair of Berea College's psychology department, crafted an exceptional hardwood lathe-turned baby rattle for our newborn son that turned out to be a masterpiece. Years later, when it broke, we observed that spinning the end of the rattle caused it to flip over, revealing how the frictional torque from the table alters the angular momentum and propels the heavier side to the top! To replicate this phenomenon, I designed a 3D printed version of that rattle. The walls of its top are intentionally asymmetrical, which actually enhances the inverting process compared to a symmetrical one. Printing it is easiest when done with the cylindrical side facing down and the curved side up.