Help with finding solutions for getting an AT-AT walk cycle like in the movies.

[bruh]

Just found this topic. Very interesting!

If you cut up part of a rubber balloon, and stretch it over the bottom of the foot, that will help with grip so the foot doesn't slip when walking.

[Nelson]

I'm still ironing out some issues with the mechanics, but thought I'd share this building technique using bars and round plates. It doesn't look as nice (or as screen-accurate) as the inverted tile pieces I had cladding the legs previously, but it's seriously tough. If you use this technique, get it right the first time because it's quite difficult to deconstruct!

 

 

[Toastie]

23 minutes ago, Nelson said:

but it's seriously tough

Wow! I am not into AT-AT's at all (but follow this thread with close attention), however, this is a very cool technique making strong connections! Have to remember that - well, it is copied into my "this is how you do it right" folder!

Thank you very much for sharing!

Best
Thorsten 

[2GodBDGlory]

That is cool!

And again, I love the perseverance displayed in this thread

[Nelson]

Here's the latest. It's been torturously frustrating trying out several time-consuming concepts only to discover the model runs worse than before. Each iteration takes most of a day to redesign, tear down, rebuild, and test. I'd say this version is about as good as the last video I posted. It's really tricky getting the legs to not interfere with each other as they flex from their own weight. I'm going to take a few weeks off and see if diffuse thinking offers any revelations.

Abridged-Terrain Awkward-Transport

 

Edited January 2 by Nelson

[Nelson]

So much for taking time off. I woke up with a few ideas to try out. I was perusing BrickLink yesterday and ran across part #28974. (https://www.bricklink.com/v2/catalog/catalogitem.page?P=28974#T=C)

A quick test with a minifig backpack confirmed this is a great part to shim various areas where you need just the tiniest bit of spacing. For my model, it will help get a touch more lift height in the legs. Obviously, I won't use the brown minifig backpack shown in the photo once I get the more appropriate parts, but you get the idea. There was just a touch of un-utilized gap at the peak of the leg lift cycle, but it was too small to add even a thin bushing. Now the crank can get that little extra lift it was missing before. That tiny shim gains me about 2/3 stud in height once the distance is amplified at the end of the liftarm raising the leg.

 

[Toastie]

1 hour ago, Nelson said:

great part to shim various areas where you need just the tiniest bit of spacing

Great!

When I ran into similar issues (on much, much simpler builds!) I used the #42446 bracket - simply because I have a couple of those.

I have to admit though that I usually use very thin 5 mm id metal washers and stack them up till it fits. Yeah, I am on the dark side, I know ... you can also make such washers by drilling 5 mm holes into other thin LEGO parts such as panels and so on ...

Actually, I also know this "need to take a few weeks break" feeling very well! And regularly it just turns out to shrink to one night. Not so much of a surprise as time is relative. A night of good sleep (at warp speed) seems to be the equivalent of a few weeks of trying harder (at snail speed). It also seems that seriously threatening the deep areas of the brain with "taking a few weeks off" gets things rolling much faster ;)

Keep up the good and creative work! Cross my fingers!

Best
Thorsten   

[Nelson]

I'm trying my best to keep the model pure, using only genuine Lego parts that are "currently" available. I'd like to eventually sell the instructions on various platforms and that usually means not using non-Lego or out of production parts.

[Toastie]

1 hour ago, Nelson said:

I'd like to eventually sell the instructions on various platforms and that usually means not using non-Lego or out of production parts.

Absolutely! And I bet there will be quite a number of people who will be interested/purchasing! That would include me ;)

How about a little cheating only during the (very complex) construction process, consisting, as you said, of many teardowns and new starts, modifications (be it only a fraction of a plate height), and so on? Maybe you could get more swiftly to a "test rig" instead of browsing BL and other LEGO resources? I'd even go to using screws, if things need to be held in place, but so far there was no way of doing it in pure LEGO world. And then, when the result is satisfactory or considered a step forward, refining it to get it "pure"?

I do that in research a lot. One example: Ultra-high vacuum (= ultra clean) environments we are monitoring on weird industrial sites do never tolerate any kind of glue, plastics, grease, etc. However in the lab, when we are “constructing” ("figuring out by trial and error" is a much better phrase) these metrology machines, 3D printed plastic parts are all over the place, superglue here and there ... Once the thing seems to do what it is supposed to do, we go to our machine shop and have it made of stainless steel, millable ceramics, and so on.

Well, just my odd and most probably totally stupid ideas.

Best
Thorsten

  

[Nelson]

I did do a bit of "cheating" early on in development, using non-lego springs, rubber bands, etc. But at this point, I'm down to two general model concepts (currently working with concept #2), so I typically start with a test mechanism that's all Lego. It's just one leg or quadrant stuck on a 19x11-stud technique panel (https://www.bricklink.com/v2/catalog/catalogitem.page?P=39369#T=C). It's kind of a pegboard where I can try out different geometries and timing. Unfortunately at this point, there's no replacement for actually putting it all together and firing it up. The concept is fairly proven, but it's really touchy in the overall build. IE: Last night I found out that kicking the timing of the rear legs forward one gear tooth caused total failure of the entire system! I admit that I still don't fully understand what makes one model work while another almost identical one fails even though I've been at this over four years now! Heck, NASA sent men to the moon only eight years after Kennedy's speech!

Edited January 2 by Nelson

[Toastie]

23 minutes ago, Nelson said:

Heck, NASA sent men to the moon only eight years after Kennedy's speech!

True.

But: "Moving as in the movies" AT-ATs don't exist in 2026. I may be wrong. But for sure not in LEGO universe. NASA had uncountable men and women working on the Apollo mission; according to Googles AI 400.000. As far as I am aware, you guys are down to two individuals, at least in this EB thread. So it may require some ... years. I truly believe it is worth the effort - as long as you have some sort of fun - or energy supply. 

Personally, I love this project.

All the best
Thorsten  

[BrickBear]

Looks like you’re getting on a treat Nelson! I’m away from my Lego at the moment (working on a graphic novel) but I whipped up this brainwave I had in Stud.Io. I traced a line of how the at-at’s leg moved from some footage and figured out this shape of cam is about right for the forward and lifting motion. My initial problem was I was looking at the current unbending, single lift arm legs of my AT-AT and thinking the point of the knee was equivalent to the point of the foot

This is the path the pin hole where the knee would be takes with the current setup, mind it was a little confusing as I took photos of my computer at different angles so it might be better, might be worse in reality, I’ll see if I can redo it with snipping tool instead.

Here is the path an at-at walk takes at the knee and foot: the red line above is the current path of my actual physical walker. I would say I’m much closer with the brick link version. 

 

30 minutes ago, Toastie said:

True.

But: "Moving as in the movies" AT-ATs don't exist in 2026. I may be wrong. But for sure not in LEGO universe. NASA had uncountable men and women working on the Apollo mission; according to Googles AI 400.000. As far as I am aware, you guys are down to two individuals, at least in this EB thread. So it may require some ... years. I truly believe it is worth the effort - as long as you have some sort of fun - or energy supply. 

Personally, I love this project.

All the best
Thorsten  

I can’t speak for Nelson but I can say I am nothing if not tenacious. And just think we’ll be making history, nobody has done this before, unless you count JK brickwork’s gingerbread AT-AT that has the right cycle but is stuck in place (the mechanism is in the ground). If successful I’m going to make a journal from the perspective of a kuat drive yards engineer with all sorts of drawings and such with instructions too if life finds me time for it. 

[Toastie]

12 minutes ago, BrickBear said:

And just think we’ll be making history

Yes, you will. 

I love this. Making instructions, selling them (why not), writing a book, whatever serves as documentation. After all, this effort is materializing a - thing - from a galaxy far, far away - in this world, hey, even more focused, in LEGO world. The more you spatially focus, the less well-defined is time or energy ... OK, that is just nerd talk. But it is true :D So far.

I am watching the progress here in awe.

All the best for both of you, make it - in one way or the other - just happen.
Thorsten    

[Nelson]

@BrickBear I'm not quite following your post, but it seems like you feel your current leg motion isn't as close to the ideal line as you'd like. I'll look forward to seeing updates when you get back on the project! I love how differently we think about the same challenge and how we utilize different tools to assist us in our quest. I imagine Lord Vader and General Veers hanging out in a conference room hashing out the AT-AT's design. Vader is pushing the intimidation features of the vehicle while Veers is concerned about its fuel economy.

I'm "satisfied" with the gate of the version in the video below. This concept design will always have a bit of shuffle from the feet on the ground. It's just the way the geometry works. I've minified it as much as possible. I could go back to concept #1 (and may someday), but I think #2 is more stable, robust, predictable, and will be more conducive to creating instructions for laypeople to build.

I've got clearance between the toes now! (Barely!) No hang ups. That may change as weight is added. I've attached the aesthetic "shoulder" pieces and love how the look is coming together. (I'll worry about articulating the upper legs later.) I'm going to try to get the side cladding on this weekend and see how it handles that weight.

@BrickBear One issue I've noticed in this thread is that we don't have adequate language to describe our model's mechanical features. I created this image and will use the terms shown in it moving forward.

And here's the latest video:

 

 

[BrickBear]

16 hours ago, Nelson said:

@BrickBear I'm not quite following your post, but it seems like you feel your current leg motion isn't as close to the ideal line as you'd like. I'll look forward to seeing updates when you get back on the project! I love how differently we think about the same challenge and how we utilize different tools to assist us in our quest. I imagine Lord Vader and General Veers hanging out in a conference room hashing out the AT-AT's design. Vader is pushing the intimidation features of the vehicle while Veers is concerned about its fuel economy.

I'm "satisfied" with the gate of the version in the video below. This concept design will always have a bit of shuffle from the feet on the ground. It's just the way the geometry works. I've minified it as much as possible. I could go back to concept #1 (and may someday), but I think #2 is more stable, robust, predictable, and will be more conducive to creating instructions for laypeople to build.

I've got clearance between the toes now! (Barely!) No hang ups. That may change as weight is added. I've attached the aesthetic "shoulder" pieces and love how the look is coming together. (I'll worry about articulating the upper legs later.) I'm going to try to get the side cladding on this weekend and see how it handles that weight.

@BrickBear One issue I've noticed in this thread is that we don't have adequate language to describe our model's mechanical features. I created this image and will use the terms shown in it moving forward.

And here's the latest video:

 

 

Very nice Nelson. You may sooner reach the goal than me. My line of thinking is that if I can use a cam to push the leg forward and have both the knee and the foot follow the line of motion that will lead to the most accurate and stable movement. I also noticed something yesterday with the AT-AT’s gait. When the AT-AT moves, the legs are direct opposites in how far they move. So the front legs when stepping forward move out to the front as far as the rear legs move out to the back, the angle at which both move inwards is steeper. This gives me an idea which I’m just experimenting with in stud.io. Regarding lights try “light my bricks”. A very small and easy to implement solution. As they aren’t a part of the actual mechanism and would not need to be incorporated into instructions I feel it’s acceptable to include compact 3rd party lights in your own personal version.

[Nelson]

Thanks for the lighting tip @BrickBear! I will investigate. And I think I'm following you a bit better now. I'll have to look at some video to see about your observations with the gate. If you feel it would be useful, draw up a image like the one I recently posted with naming conventions for the mechanics of your model. Perhaps we can even agree on some names for portions of our models that are similar or serve the same purpose.

Edited January 4 by Nelson

[BrickBear]

10 minutes ago, Nelson said:

Thanks for the lighting tip @BrickBear! I will investigate. And I think I'm following you a bit better now. I'll have to look at some video to see about your observations with the gate. If you feel it would be useful, draw up a image like the one I recently posted with naming conventions for the mechanics of your model. perhaps we can even agree on some names for portions of our models that are similar or serve the same purpose.

I’d need an intact model first. Mines a bit bitty. I don’t have access to the Lego for another week so it will have to wait a bit too. I have come up with a mechanism to replicate the movement of the legs forth and back differences: 

The orange cam rotates and pushes the grey and white liftarms back and forth, the leg would in theory be connected to the grey one. Due to the shape of the white liftarm it is pushed further. So you could basically make two of these and rotate it 180, attach them together and have an accurate forward back movement. I managed to make it so they lift up and down while still accepting drive. I’m curious to build it and see if it works. The up down mechanism would require synching with the forward and back of course.

The black L connectors connected to the dark 7L vertical liftarms are where the hip hinges.

[Nelson]

I will study this image a bit. As for reaching goals, I try not to think of this as a competition (although that can be motivating). My idea of success is different than yours. A model with true bending legs is integral to your vision, while I'm bypassing that feature. I would not be where I'm at in this process without your contributions in this forum. The current concept #2 design is a direct offshoot of this conversation. I only hope my contributions are helping you reach your goal. I had a sizable head start on this project, two years at least if not three. 

[Nelson]

Some tests on various substrates. I didn't notice the upper leg on the right rear had separated while I was setting up. It may have altered the motion slightly, but is probably not responsible for the mechanical failure at 1:00, even though it's on that leg. The loose terry cloth really bound things up. I think if it had been pulled tight, it wouldn't have been a problem. Still. This baby won't be tackling any loose dirt or gravel any time soon. Watch the rod on the right rear flex like crazy before finally breaking the crank ankle.

 

Edited January 4 by Nelson

[BrickBear]

6 hours ago, Nelson said:

I will study this image a bit. As for reaching goals, I try not to think of this as a competition (although that can be motivating). My idea of success is different than yours. A model with true bending legs is integral to your vision, while I'm bypassing that feature. I would not be where I'm at in this process without your contributions in this forum. The current concept #2 design is a direct offshoot of this conversation. I only hope my contributions are helping you reach your goal. I had a sizable head start on this project, two years at least if not three. 

I’ll admit to not fully quite understanding how yours works, but it’s inspiring and like you say motivating to see someone who’s achieving successes in the small field of Lego AT-AT engineering. And I will say that your design has made me more cautious about the strain I put on my parts having been witness to things breaking on your model, it makes me question my use of hard springs. I agree our goals differ here and there. I’m hoping to get it walking outside if my designs remain having decent ground clearance. 
 

Also petition to rename the crank angle the crangle? 🙋‍♂️

[Nelson]

@BrickBear Crank Ankle. "Crankle"

[BrickBear]

52 minutes ago, Nelson said:

@BrickBear Crank Ankle. "Crankle"

Ah! Yes, I misread it. 

[Nelson]

I completed my goals for the weekend: test the model on various substrates and see how it deals with weight. Mixed results in both departments. I really love how the side panels look, but man... they need to lose some weight. The chassis and legs alone are 1.25kg. The side panels bring it up to 1.38kg. That's over 3 pounds. I can't imagine how heavy this thing's going to be once I add the top and end panels along with the head! I just hacked together a method for attaching the sides, so you see them gracefully falling apart in the video. Aside from the idea I mention about angling the legs out a bit toward the front and rear, I wonder if reducing the camber on the ankles/feet might help it not pitch around so much. Here lies the next challenge! Honestly, it performed better than I expected. I didn't think the feet would even get off the ground.

 

Edited January 5 by Nelson

[BrickBear]

6 hours ago, Nelson said:

I completed my goals for the weekend: test the model on various substrates and see how it deals with weight. Mixed results in both departments. I really love how the side panels look, but man... they need to lose some weight. The chassis and legs alone are 1.25kg. The side panels bring it up to 1.38kg. That's over 3 pounds. I can't imagine how heavy this thing's going to be once I add the top and end panels along with the head! I just hacked together a method for attaching the sides, so you see them gracefully falling apart in the video. Aside from the idea I mention about angling the legs out a bit toward the front and rear, I wonder if reducing the camber on the ankles/feet might help it not pitch around so much. Here lies the next challenge! Honestly, it performed better than I expected. I didn't think the feet would even get off the ground.

I think the problem lies in the weight balancing as it takes its rear steps. As you can see when it takes its front steps, the at-at leans backwards and the opposite when the back legs raise I think due to the angle of the legs. I don’t know if you’d be able to implement that. Also perhaps a properly filled out head would be helpful. And if you want to test your mechanism while adjusting weight I suppose you could try attaching balloons to the thing, using those to adjust the weight could allow you to determine how much you need to shave off.
 

 

 

 

That all said though, it’s impressive that is indeed moving with the weight.

[Nelson]

If I could create more organically-shaped cams, that type of balance shifting might be possible. Unfortunately, I've yet to find a way to pull that off. I'm going to try stretching the length of the chassis out a bit to see if getting the legs closer to the front and rear will help. I'm also going to experiment with reducing the camber on the feet, making them more perpendicular to the legs rather than pitched slightly. I may let it all sit for a week while I catch up on some other projects. I have to portion out my obsession in metered doses!