Dynamic Diameter Spool Holder

As it's name states, this is a self adjusting spring loaded spool holder. It expands in order to fit most common spools inner diameter.

This is something I have been thinking for a while as an upgrade to my previous spool holder http://www.thingiverse.com/thing:770657 and during my previous researches stumbled upon this site/reference (http://richrap.blogspot.com/2014/03/universal-3d-printing-filament-spool.html) where they're also tackling the issue in their way.

I accepted the challenge