Tested and working - open source, quick, simple, standard (2" PVC connector available at any hardware store). Used when your filament comes on a crappy cardboard spool. Print 2 sides and use PVC glue to glue sides onto a standard 2" PVC pipe connector. 180mm in diameter and takes a full 1kg of filament, rolls easily on 3/4" PVC pipe. Needs an 8x8 bed. If you scale it down, it won't fit the 2" PVC connector. I use a battery powered drill and a bolt glued into a 3/4" PVC pipe, taped up, to respool from a cardboard spool. Works well and I no longer get jams from the cardboard sides spreading and the filament falling into the crack.