If you're looking for a good place to start, I highly recommend reading Ben Katz' blog and thesis: Blog posts: "HobbyKing Cheetah" http://build-its-inprogress.

If you're looking for a good place to start, I highly recommend reading Ben Katz' blog and thesis: Blog posts: "HobbyKing Cheetah" http://build-its-inprogress.blogspot.com/search/label/HobbyKing%20Cheetah http://build-its-inprogress.blogspot.com/search/label/HobbyK... Thesis: "Low Cost, High Performance Actuators for Dynamic Robots" https://drive.google.com/open?id=0B2x3Di8kVjT3N3BkQzhSQ3FwTU0 https://drive.google.com/open?id=0B2x3Di8kVjT3N3BkQzhSQ3FwTU... (Edit to note: Ben's design uses gears and thus is not direct drive, but his bot still has lots of power and software-controlled "springiness".)