空心鐘 Hollow clock 2 - silent and smooth by shiura Februar

from https://www.thingiverse.com/thing:4761858Silent and smooth : stepper motor version of "Hollow Clock", https://www.thingiverse.com/thing:4747403Easy operation : super-easy time adjustmentEasy print : printable without supports (except optional cover.stl)Easy assembly : gears can be set by just sliding inCheap : used stepper motor is very popular and cheap (around 3USD with amp circuitry)A bit smaller than original "Hollow clock" (rotor diameter : 200mm vs 160mm). Now it has no air gap between rotors.Update Feb 24, 2021