hollow clock

for hollow clock project (https://hackaday.com/2022/01/08/hidden-shaft-and-gears-make-this-hollow-clock-go/#:~:text=The%20Hollow%20Clock%20has%20no,to%20hang%20in%20the%20air.)

for 3d printing https://www.instagram.com/p/CYcCt1RN2Lf/