Toys & mechanisms

Trammel of Archimedes — Do-Nothing Machine Fidget

A classic 'do-nothing machine': a gloriously useless desk fidget. Crank the knob and the arm traces a perfect ellipse over an engraved groove — and that's it, it does nothing else, forever. Two dovetail sliders shuttle in perpendicular channels; a knobbed crank arm snaps onto both. 3 unique parts (print the slider twice), all flat, no supports. Honest heads-up: the motion is not glass-smooth — at the crossroad a slider can catch and need a tiny nudge.