Stumbled onto a design for a 3D printed Jansen Linkage on Thingiverse.  A Jansen linkage is a mechanical linkage system for creating a complex gait that is actuated by a single servo. To create a full walking robot 3 leg pairs are needed.  I was intrigued and tried to print out several Thingiverse designs but couldn't get anything that was low enough friction to actually be functional.  The Thingiverse designs were also lacking a servo harness and instructions.  I created a new design that uses radial bearings and a MG996R servo that looks very promising (see the video).  Unfortunately I ran out of bearings, so I couldn't finish the robot (more bearing on order now).  I might post the parts if anyone is interested.  Could be fun to try and design a mechanical linkage for some portion of a bipedal leg.  Check out the TED talk that Theo Jansen gave where he shows off his beach walking robots ... interesting for the walking mechanism and simple mechanical "intelligence".  Also found an interesting site that compares the Jensen linkage with a Klann linkage.