Fully Printable Modular Wheel

I made a fully printable wheel consisting of four parts:
1. Top part
2. Wheel
3. Spring
4. Lid for spring.

You can scale it down or up as you please. The wheel cannot rotate though. I am planning to make a rotating wheel put for that I am planning to use steel bearing balls. I would like to get comments for design improvements and interesting projects to use these wheels for. I have also made another wheel design but I do not know what to use it for. Please comment on that project also.