RepRap, 3D Printing, 3D Printer
This is http://www.thingiverse.com/thing:135368 This revision of the Tweety Extruder had a few small printing flaws but still works great. The main thing is the wider idler hinge and a stronger idler made out of PLA. Even with only one idler screw doing all the work there's plenty of force to grip the filament.