I got lazy. Instead of repairing my old Ender2, I ordered a new R3D Mini (aka CteateBot) printer. The advantage being it is fully enclosed including the filament holder. While the printer has room internally for a full 1Kg filament spool, the included spool holder limits one to 500 Kg or 250 Kg spools ... worse yet, it does not roll because of design flaw. This problem needs some serious redesign and this is a WORK-IN-PROGRESS.
REVISION "B": This revision strengthens the base (a lot), add alignment pens and provisions for 2 M4 x 75mm long socket head screws (and hex nuts) to hold the base together. You may not need those but I had rather have the possibility and not need them than to need them and have to start over.
The build platform comes down to within 35mm of the base and there is only 85mm between the steel frame and the build platform. That determined to envelope for the spool holder which is based on a pair of rollers running on R4-2RS Ball Bearings. https://www.amazon.com/dp/B09311SWMQ
The curve in the spool is supposed to make the spool self centering in the available 80mm wide space.
The original DWG files as well as the STL files for model are include. The recesses in the ends of the spool (two required) include 36 teeth that form a slightly undersized diameter for the bearings. Those bearings should SNAP into place on the base plates (two required) however I have also included a simple 3mm diameter pin (4 required) to lock the bearings in place.
This project and all included files are the exclusive, original work of the author and placed into the PUBLIC DOMAIN by the author in July of 2021. The author assumes no liability for the accuracy, fitness or application of the information or design herein.