Makerbot Tractor Upgrade Testing

Well, the humans have been really busy trying to complete my Tractor Upgrade so they can share it with the rest of the world.  They've posted pictures and a video of their first proof of concept test here:

http://vimeo.com/1438374

The idea was to eliminate as many exotic parts as possible, use as many printable parts as possible, and keep costs down as far as possible.  I think they achieved their goals.

They are in final build and testing and will be posting full STL files and build instructions by end of the week.

Requires less than $30 in parts, can be printed and assembled in a night, using standard tools (a drill, and a makerbot)   Should also work on a Makerbot HBP.