My office chair has legs made of plastic which has broken numerous times in the walls around the shaft of the wheels. I designed this brace to fill the gaps around the shaft as a repair for broken shafts and reinforcement for those not yet broken. It was designed specifically for my model of office chair, but it may fit others. Compare visually and you could maybe print a test piece to see if fits yours.
Print with strong settings (more walls, more top/bottom layers, more infill, higher temperature, shorter layers, wider extrusion width, slower speed, etc etc). I printed on it's side (as pictured in orange) so that the "spokes" would be stronger with just enough snug supports to achieve decent bridging. It doesn't have to look perfect, just be strong. I also lowered the model a bit on the plate to get better adhesion which gave it a flat side, which is fine.
I used plain-old PLA (Tangled's "Pretty-Good" PLA black) as I have a lot of it and PLA does good enough bridging. While we want strength, most of the stress is compressive, so it doesn't have to be steel strength. If you use PLA+ or something stronger like PETG, just be mindful of the bridges.
To install as remove the wheel and check orientation as there is an circle cutout that matches an extra mold mark it fits around. Rotate to match and slide the brace in, then replace the wheel. This should be good enough for ones that have not broken yet, but a few drops of glue/epoxy wouldn't hurt especially around the base of the spokes, just keep it off the wheel itself. If already broken you will want to check to see if any pieces of the original shaft walls remain and can be glued back in place before installing the brace. On mine a large piece was missing, so instead of using glue I used 2-part epoxy-putty so I could shape it to fill the space where the missing piece was.
The included .blend file has two previous versions with worse tolerances and missing an additional hole in the base which gives better fit, but I left them in the file in case it assists anyone with further modifications.
Copyright (C) 2024, Jonathan Hull, Creative Commons 4.0 By-NC-SA. Please message me if you would like to discuss commercial licensing.