Introduction: RC Crawling Bot
Technically this is not a robot as it has no sensors and is not autonomous, but it could be roboticized. It is really just an investigation into robot type motion and it was easier for me to accomplish that using radio control rather than microprocessor control.
The crawling bot, whose pet name is Ratchet, was built using an acrylic ruler for the chassis along with a few pieces of perforated metal bracket for the tail section, and the arms.
Two servos serve to move the arms 180 degrees and the one-way wheels allow only forward but not backwards rolling of the wheels. This is what gives Ratchet his traction, otherwise he would just spin his wheels forward and backward with no forward motion of the body. Only a two channel radio is required to make Ratchet move.
The ratchet or one-way wheel is constructed by gluing a four arm servo horn to an axle shaft, and making a pawl out of plastic tubing which only allows the axle to turn in one direction. A spring is attached to the pawl and the axle holder to keep tension on the pawl against the servo horn. I looked for a toy that had working one-way wheels but had no luck finding one so had to resort to my own clunky implementation.
As you can see from the video, forward motion is accomplished by moving both arms forward and back or independently. Turning is a little trickier and requires moving one arm forward, the other back and swinging the tail up and around. I still haven't got it down very well. Sometimes I will pull forward too fast and Ratchet ends up on his nose doing a headstand.
I think one can figure out how Ratchet is working from the photos. It would be interesting to try and create a real robot from Ratchet.