Unit 3 - Develop the Doorbell

1. Change the shape of the handle for easier control.

2. Turn the bottom of the handle into a hexagonal shape as a way to lock the handle and gears so they can rotate together

3. Changing the rod length on the centre cross fixing piece reduces the contact surface and allows for smoother rotation

4. In accordance with the experiment of Unit 2, the cog teeth on both sides are staggered to achieve a linear reciprocating structure.