This re-spooler works on the general principal that the Filamentalist project uses but is adapted to work with the "Auto-Rewind Spool Holder for RepRack" and some inspiration take from the re-spooler in the 8-track project.
There are some challenges with using Filamentalist on the Reprack that required something a little different.
Due to the position of the conduit pipe that is core to the Reprack, using the larger wheels that Filamentalist uses is not really feasible. However, these larger wheels are important to the rewinding ratio to ensure that even on near empty spools, it rewinds fast enough for a tight wind. So we need smaller and faster rollers.
To combat this, the drive wheel (the wheel with the o-rings, driven by filament being pushed) is not directly attached to the roller shaft, but is instead positioned next to the roller shaft. This allows us to apply a gear ratio of roughly 1:2, making the roller shaft spin about twice the speed of the drive wheel.
The standard filamentalist feeds filament from the bottom of the spool and out the front. This is rather inconvenient to load a spool when there are other shelves above it. When used in a wall mounted Reprack, feeding from the front of the spool, going downward is more convenient.
The solution for the roller wheel size also makes way for the direction of feed as well. Effectively we need the roller shaft to spin in the opposite direction of the drive wheel. By having the drive wheel mesh with roller shaft rather than having an axial connection, the directions are reversed.
See Documentation.
I think the main potential issue I imagine running into with this is perhaps the longevity of the o-rings. I don't think tension on the filament when the wind is tight is enough to completely disengage the o-rings, so I suspect the filament drags across the o-rings and will slowly wear them out.