Cut a hole in the filament feed tube.
Jam a star drive bit from an electric screwdriver into the hole.
The star screwdriver is basically a splined shaft - the hole is positioned to intersect with the filament guide. The splined bit cuts into the filament and drives it downwards.
Renor3 Extruder at 2.4v : Produces lots of filament very quickly.
At 3.6v tends to stuff filament too quick, stalls, and then chews a notch in the filament.
Can't drive it with the RepRap electronics at the moment.
Also, the large 3.6v motor needs too much current to run from the RepRap electronics. This could be a big problem.
My RepRap >