The problem with leg movement is that as the leg moves forward or backward it also needs to go up to prevent dragging it's foot on the floor. The wheel has all the correct motions built in and it is just a matter of attaching the leg to the wheel in such a way as to take advantage of that range of motion (using crank/slider mechanism).
The build log is just a generalized discussion of photos of my build as everyone's use of materials would probably be very different.
1. I plan to add a knee joint to the leg that will lift the foreleg or bottom of the leg up as the thigh moves forward or back thereby making it easier to step over obstacles..
2. It would be really cool to add a solenoid to lower and raise the pivot point of the leg. This would reduce and enlarge the leg stride on the fly making a way to increase and decrease the efficiency of the robot leg while it is moving.
3. It would also be interesting to put 6 of these legs together and see how a robot can move without using computer control to coordinate the legs movements.
4. Put a shoe on the leg - noticed it is slipping a bit on the carpet.
Step 1: Mount Motor on Tether
After that I drilled and bolted a spacer which is the plastic box (gotten from half of a power supply box) to the bottom of the ruler or tether.
Onto the spacer I bolted another short piece of acrylic ruler which will serve as the mount for the leg pivot point.
Step 2: Build Leg Pivot Point
The second picture shows that the leg is a slotted piece of ruler which will slide up and down on the pivot point or pivot bolt.
Step 3: Add Leg Drive Bolt to Wheel
I put the outside nut on loosely and then added a glob of hotglue so that the nut would not come off or tighten itself up.
Step 4: Build the Leg
Drill one hole towards the top end to mount to the motor wheel.
Cut a slot in the leg about the length of the wheel diameter. To do this I just drilled a bunch of consecutive holes, took an old soldering iron and melted the holes together until I got a rough slot. Frankly, I am amazed this thing works as well as it does with such a crude slot. It could be more efficient if I smoothed out the slot so that the pivot bolt would slide back and forth more easily.
Putting washers on both sides of the leg, mount it to the wheel and to the pivot point bolt.
Step 5: Build the Tether System
The first picture shows a piece of jump rope handle that I cut and then put a bolt through to attach the ruler that supports the motor.
Attach this plastic bearing about the middle of the support tether ruler.
The second picture shows a piece of old metal mop handle that will sit inside some weights to hold it vertical.
The plastic bearing sits inside the piece of metal mop handle and allows the tether to rotate.
The third picture shows how it should all look put together.
Add some counterweight to the other end of the tether to take some weight off the leg and to make smoother rotation of the tether.
Step 6: Add a Support Leg (peg-leg)
For this I used a hollow piece of fishing pole cut a little shorter than the fully extended leg. I put some wire shrinkwrap on the bolt so that the support leg would fit tightly but so that I could take if off if I need to disassemble the unit.
And that is it, your robot leg is complete and ready to operate