Compact Bowden Extruder (Geared Motor Version) for 1.75 filament

This is a variant of [scarou's](http://www.thingiverse.com/thing:669459) and [0110-M-P's](http://www.thingiverse.com/thing:1132201) Compact Bowden Extruder. It's been designed for use with 1.75mm filament and a Nema 17 Planetary Geared Motor with a 8mm bore hobbed drive gear.

Tolerances are very tight, so I don't know if this design can work with a different hobbed gear and/or a different geared stepper motor.
Here is the link to the ones I've used:
* [Kysan Nema 17 Geared Stepper Motor (P