Bike (2021 update)

I've made this little bicycle to be relatively strong, with movable parts.

You can watch a little video here: https://www.youtube.com/watch?v=tLqkvyrPnc8

I bought some common rubber bands (n. 8 here in Brazil) to use as a chain, with a diameter of approximately 25mm. Worked well! Usually rubber bands degrades in time (latex). But I think it's possible to find better quality rubber bands, more durable, something like o-rings...

Tried to use TPU as a chain but it doesn't work, too smooth and not so stretchy as rubber.