As the name implies, this spindle has collapsible hooks to facilitate quick change of filament spools.
Print 1 hub, 3 hooks and 1 hanger. Bolt the hooks as shown in the pictures. String a rubber band through the C shaped channels and it is ready. Turn all hooks upright for loading. The hooks will stay that way unless one of them flips the other way; they are just over an unstable equilibrium point. Once the spool is in place, flipping one of the hooks into position will make the others follow.
The hanger snaps in the hub. You can now hang the spindle to the Ultimaker. Sorry for delaying the availability of the hanger.
Improvement suggestions are welcome and appreciated.
Inventor files (*.ipt) are now available.