"Doubowden" Double Hobbed Bolt Bowden Extruder Assembly

This is a dual hobbed bolt bowden style extruder for more grip on filament. This is for 1.75 filament only, so far. I made custom hobbed bolts for this.

Materials:

4 - 688zz bearings
2 - 608zz bearings
2 - 8mm X ~40-50mm (5/16" may work)
2 - 8mm Nylon insert Nuts (5/16" may work)
4 - 3mm X 8mm bolts
2 - 3mm X 18mm bolts
4 - 3mm X 50mm bolts
7 - 3mm nuts
4 - 3mm washers or more if wanted
4 - compression springs for idlers. Not sure what size exactly.
2 - 8mm X 15mm drill rod (5/1