Go here for original description and the rest of the STL parts: http://www.thingiverse.com/thing:1123139
Needed to print out a bunch of kits so I redesigned the body to reduce material and printing time.
Allows all components to remain visible (better as a teaching tool, easier to troubleshoot)
Additionally, made revisions to the cut outs to be able to use the same size screws for all three axles on the body.
Works identical as the previous version, ON/OFF switch now located on the bottom side
Holes for the ON/OFF switch may fill in on you because of the cutouts for the batt contacts. A 1/16th drill bit will clean them out fine for you and still leave enough material to bite into.