Z Anti-backlash add-on for Prusa i3

My own requirements were:

- No need to reprint existing parts;
- No loss of printable space;
- Use of the PLA property for the elastic force required for the system to work;
- Easy installation;

I think I've made it work... ;)

01-09-2015 Update
You may experience some wear on both the threaded rod and the nut (especially if you're using z-lift a lot). You can tell when the Z step motor start to skip step and have a hard time lifting the Y carriage.
I had to replace