Picture of Build a Simple Walking Robot Leg
Here is probably the simplest robot leg that allows forward and backward and up and down movement. It only requires a toy geared motor and some other miscellaneous stuff  to build. I didn't have to buy anything to build this project.
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.

Future modifications: 
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.

cchk829 months ago

could you tell us actually what to get at the store so we can build it? it's kind of hard to make it if you don't know what to get at the store don't you think

JimRD (author)  cchk829 months ago
No offense taken. The problem is that I just built this with junk I had lying around so is difficult to say to go buy this and then buy that. Hopefully you can see the principles involved and make it with junk you have lying around. Mostly I used acrylic rulers, the motor and wheels from a toy truck, some chopsticks and nuts and bolts.I
As I said in the instructable, it is just a generalized build, your parts will vary from mine.
cchk82 cchk829 months ago

not being mean or anything

mcabuenos2 years ago
nice work ^_^.its possible on two robot leg two but its very hard to maintain its balance @_@.im a fan of your work bro thank you for this concept ^_^
JimRD (author)  mcabuenos2 years ago
Thanks for the kind words. Yeah, it would be difficult to implement. I lost interest as soon as I got this far and am now working on some other stuff. I like to build and fly foam rc planes and that takes a lot of my time, plus teaching plus always thinking about how to use my junk box parts to build something else.
Am more interested in mechanical motion than actually utilizing it for some specific purpose.
JimRD (author) 2 years ago
I have a couple more projects in mind but I am waiting for a couple of 360 degree - heavy duty servos. Hope they pan out.
danny592 years ago
I must say that is a very cool concept, good job!
JimRD (author)  danny592 years ago
Thank you for your kind words.
danny59 JimRD2 years ago
You are very welcome, and keep up the great work, or should I say Fun?
SCIENCEPAL2 years ago
Its an easy and simple design! Great instructable.... I like it!
JimRD (author)  SCIENCEPAL2 years ago
Thank you. I don't know how useful it is - I am trying to use it to build a little radio controlled bot but without using the pegleg for support, it moves pretty unsteadily. Am working on some different ideas - also rather useless - but interesting.
JimRD (author) 2 years ago
Sorry, don't know what the deal is - I posted my video to ipikz.com because I am in a country currently that has blocked the usual video sites. And now this site has suspended me for some reason. Will try to post video to youtube if I can ever get there.
judas792 years ago
Neat simple design. I can't view the video (if it is a video) from site5 though. Can you put up a link to see it in action?
marhar2 years ago
This is a neat design and clear writeup. Thanks, I learned a lot from it!
JimRD (author)  marhar2 years ago
Thank you. I really was too lazy to take it back apart for really clear pictures so I am happy you got something from it the way it is.
Graytail2 years ago
Back when Robotwars was on the TV in the UK, I designed a robot that used this type of leg to take advantage of the 150% weight limit allowance for walking robots. Same general idea, but instead of a wheel I used a cam with arms at 0,120,240' so it had three legs to one motor, though thinking back perhaps six legs each side at 60' turns would have given a smoother run. I was going to give it a flywheel like Hypnodisc, either drop more weight into that and the drive motor, or use two flywheels that rotate in opposition to counter the 'hit and fling' effect of a flywheel with a blade on the edge.
Noone ever 'got it' when I describe this simple little leg to them.
JimRD (author)  Graytail2 years ago
I looked around to see if others had used this design and I did see two similar examples: one where the wheel is at the bottom and the sliding shaft pivot is on the wheel. This gives a pendulum motion that slowly moves the leg back and forth but still causes the scuffing and dragging feet problem. The other used the wheel to drive 3 legs on each side but I didn't see a video to see how well it worked.
I really see this leg motion as just a curiosity and don't know how useful it can really be but hope someone can make a useful robot using it or if someone can post an example of a working robot already using this type of motion.
jolshefsky2 years ago
That's quite a simple design ... I like it.
JimRD (author)  jolshefsky2 years ago
Thank you - I'm not much of a hardware programmer type so lean towards the simple and reuse of stuff around the house.
M.C. Langer2 years ago
It's simple... but mesmerizing!! You gave me some cool ideas!! Thanks for sharing! :-)
JimRD (author)  M.C. Langer2 years ago
Thanks for watching. I will be posting another video sometime that shows the same mechanism skipping for lack of a better word.