After printing and loving the simple elegant design of @MeisterEdel 's pull rod copter, it was inevitable that one of my kids lost the pull rod…

Instead of reprinting the rod I remixed the design to be used with a pull cord and elastic band. This way my kids won't loose the pull rods anymore…
The downside is that for my design you will need more than just a 3D printer, namely a piece of cord and an elastic band (although the latter might be optional if you want to rewind the cord manually after every pull).

So it's a bit less elegant , yet I'm very happy with the result.

And best of all the design is still compatible with all the original blade designs.