For a week or so now I've been working on making a walker based on Theo Jansen's designs (Actually, after I couldn't get the legs right I based them off of someone elses' leg designs). After I made a simple four legged thing that just went forward and back, I wanted to make one that could turn and could be remote controlled. The problem is I just got back into technic after not touching legos for years (It was this project that brought me back), and I am very limited in the pieces I have. I have the mindstorms brain thing, but I'm not sure if I have the software to program it anymore, and either way I kind of decided that I would go without it anyway, kind of as a challenge.

So I have three Mindstorms motors driven by one of the large controls for the lego trains and some pneumatics. The first and second pictures attached show the little gear box thing I came up with so the robot would be able to turn.

The top gears in the second picture physically move forward and back to engage the gears in the first picture, giving two combinations, turning and straight. The gears are shifted by the piston in the third picture.

And now my question. The main problem with this is that occasionally when I'm trying to shift the gears the top two will get caught on one of the bottom ones that are unaligned, which then causes the piston to just snap the part it's moving, or the motor running the piston will just fall off. I'm wondering if anyone knows of any way that could keep the gears aligned so they don't get stuck when they are moving. Hopefully there is a way that doesn't involved purchasing anything or using any unusual parts.

have you this parts?

http://www.bricklink.com/storeDetail.asp?b...;itemIDseq=1528

http://www.bricklink.com/storeDetail.asp?b...itemIDseq=17040

http://www.bricklink.com/storeDetail.asp?b...;itemIDseq=1559

http://www.bricklink.com/storeDetail.asp?b...;itemIDseq=1524

in my humbly opinion this is the easiest way to syncronize the gears

Here's the story about Theo Jansen's Lego Walker: http://technicbricks.blogspot.com/2008/03/...heo-janson.html . It has a detailed description, videos, and pictures.

If I recall right, the walker of the picture above, only walk forward and backwards, and seems that Sternford is trying to do something a step forward, since he want that is walker be able to turn also.

I can't be of much help here, but I wanted to add something to the information given by efferman about the parts he mentioned, to say that you can see how they can be assembled and work at Blakbird's Technicopedia, in this particular page:

http://www.ericalbrecht.com/technic/1994.html

The image I'm referring to is this:

Good luck for your work.

Cumps

EDIT: Not that I've seen much, but here's the most complex gearbox I've seen so far (7 speed + rear), by Sheepo

http://www.mocpages.com/moc.php/180863

And as you can see, it uses the parts suggested earlier

Edited June 12, 201014 yr by Mortymore

I would concur, I think your best bet for avoiding the alignment problem is to use the clutch parts suggested above. I've also found that a problem with the 24 tooth gear to 12 tooth double bevel combo is that it tends to slip if you give it a lot of torque. In general with walkers, if the legs have to carry the weight of the battery box, you also need a good bit of gear reduction in order to get it to work without ripping itself apart somewhere.

Hope you post pictures when you're done, I'd like to see your implementation of Theo-style legs...

Efferman: Dang, I was afraid that those special gears would be the only way to do it. I wish I had them.

Mortymore: I already have it so it can walk and turn, I guess I'll just live with having to manually fix the gears when they get stuck. And also, I though Sariel's ten speed gearbox was complex, but I guess it doesn't have reverse

Telecasterman: It was done before this, I was just wondering if there was any way to fix this problem that didn't require the specially made gears. I tried to make legs myself but after a while of it not working looked around and went with this design. Apparently the problem was the legs I made didn't have the correct dimensions

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Thanks for replies

[Edit]Oh! While I'm here. There's a weird thing happening with the pneumatics in the walker. I used Sariel's pneumatic autovalve so I would only need one motor to control that (It takes two motors to make the legs move or there isn't enough power). It works well, but for some reason, when I run the motor one direction, the piston moves very slowly. It is fine in the other direction though. Very odd.

Edited July 6, 201014 yr by Sternford

if you want build a simple steerable walker you could possible try something like this

sorry for bad movie quality

detail pics

or something like this

detail pics

or in extreme like this

detail pics

the first needs one motor for walk and one for steering. a four leg version is possible

the second needs one motor on each side and is to steer like a tank

the last one needs one motor for walk and two to steer

Edited June 12, 201014 yr by efferman

@ Sternford: Perhaps you don't know that you can buy the needed "special gears" from the Bricklink.com links that Efferman provided you in Post #2 above. For US$10, you can the parts delivered to your door by a Bricklink vendor of your choice.

You could try a system that was used to steer a forklift in the 8082 technic universal set.

It uses two motors and no special parts to control 3 functions (you could use the same two motors to control any number of functions!)

For a detailed description of it's workings go to http://www.ericalbrecht.com/technic/8082.html (a very excellent website!) and scroll down to see the forklift.

@allanp, that is a pretty interesting system, but I feel like I'd rather have the engine not move.

I've set up a paypal account just so I could order the gearbox pieces (and some universal joints, because why not?). I hope within a week I will have them and can get it working

@allanp, that is a pretty interesting system, but I feel like I'd rather have the engine not move.

If you're referring to the fact that the motor platform moves, it doesn't necessarily have to be built like that. There are many possible variations of that concept. The setup used in 8865, for example, is similar.

For manual gearboxes, the red transmission rings work very well and let you have several speeds in a relatively small size. On the other hand, if the gearbox is supposed to be switched by a motor, then the 8082/8865 system of sliding gears is better (unless you only need two speeds/functions). The double bevel gears (which didn't exist back then) work especially well for this.

If you're referring to the fact that the motor platform moves, it doesn't necessarily have to be built like that. There are many possible variations of that concept. The setup used in 8865, for example, is similar.

For manual gearboxes, the red transmission rings work very well and let you have several speeds in a relatively small size. On the other hand, if the gearbox is supposed to be switched by a motor, then the 8082/8865 system of sliding gears is better (unless you only need two speeds/functions). The double bevel gears (which didn't exist back then) work especially well for this.

The 8865 gearbox is what mine is based on. The gears kept not being lined up right when I tried to change functions

Edited June 16, 201014 yr by Sternford

The 8865 gearbox is what mine is based on. The gears kept not being lined up right when I tried to change functions

Yes, the double bevel gears fix that issue to some extent. The angled teeth allow the gears to mesh gradually instead of abruptly like spur gears do.

Well the pieces I needed were finally delivered today so I was able to finish. Here's what I got

It can't walk on carpet.

Here's what one of the legs looks like. I didn't come up with the design, but I modified it to make it stronger.

The design I based it on was supposed to be modular, but I made some changes to make it smaller that also make it a pain to take apart. This is two leg modules connect. The walker is made of two of these. When both sides walk in the same direction, it goes forward; when they walk in the opposite direction, it turns.

In between the legs is the motor box thing. It is pretty heavy.

This is what I finally settled on as the mechanism to drive the legs, using my new gear pieces. One motor wasn't strong enough to power it so I just put another one in.

My solution to changing the gears. Originally, before my parts had arrived, I had designed something based on this, but as the person who made that noted, it took a lot of torque, and when today when I tried it my motor wasn't powerful enough.

The whole thing is run off of one of the train speed regulators, so in order to go from walking to switching gears, you have to physically switch the wires. It's inconvenient, but not enough for me to care. It works pretty well, considering how heavy it is. I hope to get a video some time soon.