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.

Step 1: Mount Motor on Tether

The motorized wheel comes from a toy construction truck. I mounted the motor on an acrylic ruler by drilling two holes through the ruler and into the motor gear box. Be careful that you do not drill into the gears. Then use self tapping or wood screws to attach the ruler, which serves as the tether, to the gear box. Note I hotglued and zip tied the motor wires to the gear box so that they don't get pulled out.

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.
<p>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 </p>
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<br>As I said in the instructable, it is just a generalized build, your parts will vary from mine.
<p>not being mean or anything</p>
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 ^_^
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. <br>Am more interested in mechanical motion than actually utilizing it for some specific purpose.
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.
I must say that is a very cool concept, good job!
Thank you for your kind words.
You are very welcome, and keep up the great work, or should I say Fun?
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.
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?
This is a neat design and clear writeup. Thanks, I learned a lot from it!
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.
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. <br>Noone ever 'got it' when I describe this simple little leg to them.
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.<br>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.
That's quite a simple design ... I like it.
Thank you - I'm not much of a hardware programmer type so lean towards the simple and reuse of stuff around the house.
It's simple... but mesmerizing!! You gave me some cool ideas!! Thanks for sharing! :-)
Thanks for watching. I will be posting another video sometime that shows the same mechanism skipping for lack of a better word.

About This Instructable




Bio: I am an American teaching English at Shangluo University, Shaanxi. I like making machines that do interesting but fairly useless things - I call them Quixotic ... More »
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