This is an entry for the Gada Prize
PolyBot spawns from a few key design concepts. 1) Simplicity of assembly 2) Ease of modification and repair 3) Reduced Parts count 4) Reduced number of different part types 5) As printable as possible
As a fantasy goal, PolyBot strives to be buildable in one form or another, by someone who does not have access to much more than a basic set of tools, and some raw materials. The structure is an endoskeleton, therefore it does not rely on any materials but its frame for basic support.
The basic frame structure is that of a tetrahedron. The reasoning behind this structure is that it is self supporting. Compared to rectangular forms, it does not require additional cross bracing in order to deal with sheer forces.
Additionally, it is a three armed parallel robot. This gives a fairly large usage of the build area, limited primarily by the lengths of the arms, and the size of the endoskeleton.
The design is easily expanded, without having to completely redesign the entire robot. Increased accuracy can be gained by replacing various joints to tighter tolerances. Weight can easily be improved by changing the material used for the arms (wood dowels vs carbon fiber tubing). Speed and accuracy can be improved by replacing the driving motors.
There is a set of pictures and explanation on Thingiverse: PolyBot
PolyBot - Cranberry Edition 1 Feb 2011 This was the first released form of a completed robot. It has all the pieces necessary to start a moving robot. It is lacking the electronics and control software.