Printrbot Simple Direct Drive Bowden conversion

Improved version at http://www.thingiverse.com/thing:305215

Parts to convert a PrintrBot Simple with a direct drive extruder (not aluminium) to make use of a Bowden tube. No changes to the Simple itself are required (no new holes etc.).

Motor and extruder are mounted on the Z axis support bars.

All parts are sized to be printable with a Simple.

UPDATE v2:

Redesign of extruder and extruder model support so that the extruder unit can rotate as required to alleviate pressure on the