Walkabot - Gravity Powered Ramp Walking Robot

Walkabot is a gravity powered ramp walking robot. Place him on a shallow ramp, tilt him to one side, let go and he will walk down the slope. The robot makes a "walka-walka" sound as he walks.
See the video of him walking here: http://youtu.be/vgM6PPkw6cQ
Use a piece of straightened 1.75mm filament as the axle or print out the axle if your printer can handle the small diameter. Assemble the robot by positioning the legs inside the body and pushing the axle through the body and legs as shown i