Solution：On the one side, use laser cutter to cut a black frame to fasten gears.
On the other side, add parts needed, use a washers to stop it from falling, and use screws to fasten it.
2 how to connect linkages and gears
maybe add this part to gears. GLue it?
3 gear directions should be different
solution: use four gears in a row.
4 frame and linkages don’t hit each other