Printrbot Simple Metal Retro Feedwheel

I really liked the design of [ei8htohms](http://www.thingiverse.com/ei8htohms/about) "Olde Timey Spur Gear for Printrbot Extruder" ([thing:163975](http://www.thingiverse.com/thing:163975)) so I adapted it for the Printrbot Simple Metal.

Made it a bit smaller and thinner, because it's now just an accessoire.
Also added a mount for the shaft of the extruder. (Holes are actually a bit too big in the files, but came out just right with my simple metal.)

Printed in colorFabb Traffic Red PLA/