Robot Wheel-Leg (from "Making Simple Robots")

This is the final version of the wheel-leg project from the book "Making Simple Robots" by Kathy Ceceri, published by Maker Media in 2014. (http://craftsforlearning.com/makingsimplerobots.htm)
The project was inspired by the Mini Wheg research at Case Western Reserve University (http://biorobots.case.edu/projects/whegs/).