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

[Carsten Svendsen]

This is really cool. I wonder if you there is any inspiration to get from the old 9754-3 Dark Side Developer Kit (Halfway down the page)
LEGO 9754 Dark Side Development Kit Instructions, Technic: Mindstorm (brickinstructions.com)

[BrickBear]

On 4/21/2024 at 2:41 PM, Carsten Svendsen said:

This is really cool. I wonder if you there is any inspiration to get from the old 9754-3 Dark Side Developer Kit (Halfway down the page)
LEGO 9754 Dark Side Development Kit Instructions, Technic: Mindstorm (brickinstructions.com)

Thanks, though i’m afraid from what I can tell the gait is the same as the other lego motorised AT-AT. But I have news. So I ran into a problem where the positions of the feet were not at an angle such that all feet that were supposed to be on the ground at a point in time were not flush. I have since changed that, the mechanism remains similar otherwise. I believe I am on the last stretch though to getting a moving machine. I intend to use the head turning left and right for balance too so that mechanism will have to be made. Progress though, is happening.

[BrickBear]

It is great to finally be adding bodywork where the shape and design is somewhat a good compromise between accurate and possible (what with the gears and movement being quite limiting). Admittedly I did not work very much on it this weekend as I was working on another non lego project. So this much progress in such a short time is good. 

[Carsten Svendsen]

We still haven't seen it walk though... Does it actually function? The bodywork won't matter now, if you have to rebuild it later.

[BrickBear]

14 hours ago, Carsten Svendsen said:

We still haven't seen it walk though... Does it actually function? The bodywork won't matter now, if you have to rebuild it later.

It breaks up the monotony of redesigning the system each time I run into an obstacle. But also as the key problems have been fixed (the feet that are not raised being flush with each other on the floor, the strength of the springs to hold up the weight) it (the mechanism) is essentially finished, in the pic below you can see it was nearly there before I had to fix the aforementioned issues. I reckon i’ll get it walking next weekend. 

Balance ✅

Strength ✅

Bend ✅

 

[BrickBear]

Okay so I added/am adding a feature that enhances the mechanism somewhat, this required removal of the legs but essentially makes calibration of the lego positions much easier:

As i’m sure you’re all aware, working with worm gears requires keeping them strongly held within a tough frame, unfortunately however that means it’s a pain to adjust their position if you find something isn’t quite right. Now, with this small gearbox system allowing me to unite and separate the drive from one of the pairs of legs, I can freely rotate one pair to adjust their positions slightly and perfect the movement of the legs relative to each other without taking things apart to adjust things. Perfect. Secondly it has caused me to strengthen things even further and thirdly it does not take up much more vertical space. Win win.

Edited May 18, 2024 by BrickBear

[Bluehose]

On 5/18/2024 at 6:45 PM, BrickBear said:

I can freely rotate one pair to adjust their positions slightly and perfect the movement of the legs relative to each other without taking things apart to adjust things.

That's a neat idea !

[BrickBear]

20 hours ago, Bluehose said:

That's a neat idea !

Thanks, I was motivated by the tedium of reconstruction :D I should add it has made the top of the structure a little wider but this is not a worry as it only 9 beams wide and does not affect leg movement or bodywork, in fact it actually provides more attachment points, hoping it makes things easier as a result

[BrickBear]

Progress of today, finalised the connection of the gearbox, built the rear panelling around it for a more compact length, attached the legs and began adding the stoppers in a different position. 
 

 

Once I attach the head mechanism for balance, the xl motor and AAA battery box it should be ready for testing next weekend or possibly the one after that. Final stretch!

 

[2GodBDGlory]

Good job persevering!

[BrickBear]

5 hours ago, 2GodBDGlory said:

Good job persevering!

I am nothing if not dedicated to my goal of destroying echo base. 

[BrickBear]

Ok so having worked on it some more I am being defeated by balance. Naturally it’s a little wobbly and when a leg lifts up it has a tendency to lean towards that direction. I’ve attempted to counteract that by experimenting with the head placement and so far landed on this angle as the way to support a lifted front leg. I was hoping to add a head movement mechanism which alternates the way the head is facing to shift the weight when one side has a leg lifted, unfortunately this angle is not ideal nor realistic. Note this problem is only a problem with either one of the front legs raised. A less extreme angle is enough for the back legs.

the head

 

The feet position.

 

[Jeroen Ottens]

Balance is tricky on such a spindly leg vehicle. Can you use an internal (boat)weight that moves left and right for balance? That will sacrifice some internal space of course, not sure if that is compromise you are willing to make.

I would love to see this thing walk

[BrickBear]

3 hours ago, Jeroen Ottens said:

Balance is tricky on such a spindly leg vehicle. Can you use an internal (boat)weight that moves left and right for balance? That will sacrifice some internal space of course, not sure if that is compromise you are willing to make.

I would love to see this thing walk

I’ll order one (or a few) and see, if it turns out not to work I may just consider it an acceptable “loss” for the project. After all it still stands up and likely walks (once motors are in place) it just leans. 

Edited July 6, 2024 by BrickBear

[BrickBear]

I have succeeded in reducing the balancing issues by simply placing a 2x1 plate with rail underneath the innermost toe of each leg, this offsets the legs lean somewhat but it’s still precarious. Of course this means that the feet aren’t completely flat on the ground, it’s a cheap and easy fix, might have to place rubber pieces in the feet too as they tend to slip on smooth ground.

I’ve also been working on the neck bending so it bends in two places, this is nearly finished and has significantly increased the rigidity of the head and assists with the balance.

All that remains is to install the motors and place on the bodywork then hopefully it will work. The springs appear to be able to support the weight, let’s hope they can support some more.

[oracid]

I have found this very good old video. May be it can help : https://youtu.be/GUsOouwjsL4?si=6RoTRfLsZ3mw1EF6

 

[BrickBear]

On 8/1/2024 at 6:41 AM, oracid said:

I have found this very good old video. May be it can help : https://youtu.be/GUsOouwjsL4?si=6RoTRfLsZ3mw1EF6

 

This is exactly the video I’ve been referencing for the entire project it’s been a massive help.

[Nelson]

Man. I have been itching to get in on this thread. The registration verification takes a long time for this site. I also have been trying to create a Lego AT-AT that walks one leg at a time for about 4 years. I have had varying degrees of success. This is my best effort to date. I'm intrigued by your use of gearing, quite advanced. I too started with the legs and worked inward, which ultimately was not the best direction in my case. I quickly realized that the chassis supplying the power was just as critical. Everything in my design has hinged on stability. Just as important as the motion of the lifting leg, is the rigidity of the non-lifting legs. This balance of letting components be free to move, then locking them down, has been incredibly challenging. I ended up going with more of a cam-based design than a gear-based design. Lego gears just have too much lash. When the legs aren't moving, they must be solid, and the gearing just allows too much movement. But I'm really excited to see if you can figure out a way to make it work. I feel like I'm so close, but the final issues are difficult to solve.

https://www.youtube.com/shorts/uTedbcHywWU

Edited October 28, 2024 by Nelson

[LegoTT]

On 7/6/2024 at 6:48 PM, Jeroen Ottens said:

Can you use an internal (boat)weight that moves left and right for balance?

I think it would need a lot boat weight or a lot of displacement to stop the lean, so maybe it woult take less place to just move the rechargeable battery box.

[Nelson]

@BrickBear Did you get your AT-AT walking? It seems like things trailed off without resolution. If you’re on a path similar to mine, you got about 90% of the way there, then realized the final 10% was going to be brutally difficult. I’d love to team up on the challenge. I feel like I’m very close. 

As it’s been said:

“With our combined strength, we could end this destructive conflict and bring order to the galaxy.”

[BrickBear]

On 10/28/2024 at 7:18 PM, Nelson said:

@BrickBear Did you get your AT-AT walking? It seems like things trailed off without resolution. If you’re on a path similar to mine, you got about 90% of the way there, then realized the final 10% was going to be brutally difficult. I’d love to team up on the challenge. I feel like I’m very close. 

As it’s been said:

“With our combined strength, we could end this destructive conflict and bring order to the galaxy.”

I’m still here, life and educational has temporarily got in the way. I should be able to get back to it in a few weeks, in the meantime i’ve been having ideas. Believe me, I won’t stop working on this. As it stands right now my main concern is actually fragility, the 5L half beams  that connect the legs to the cams are too fragile so i’m going to have to replace them with an alternative. 
 

Please also feel free to use this topic to discuss your own project and what got in the way and such. There may be designs that can come from the discussion.

[BrickBear]

Interestingly I learnt about tightrope walking through a novel which as part of the story explained how the physics of it works. Basically you can stay relatively stable if you place the weight further down which makes sense as a low centre of gravity is also what keeps double decker buses stable but it’s fascinating that it helps even on a thin wire. I figure if I experiment with boat weights towards the middle and slightly below the hips then it might help maintain the balance, it should provide a big help to the spindly legs.
 

 

Edited October 30, 2024 by BrickBear

[Nelson]

Glad to hear you're still keeping the project alive. As for the lower weight distribution, early on I decided to sling two Power Functions large motors underneath, at the bottom of the chassis, to both get the weightiest part as low as possible and also replicate the look of the film version engines. I also went with the small size battery box with super light lithium AAA batteries since in my design, that box ends up at the top inside the body. I've been tinkering with some new cam designs, but haven't had much luck. I'm going to try reverting to the build I had in the earlier post's video and see if I can refine from there. I have a few new ideas.

 

Edited October 30, 2024 by Nelson

[BrickBear]

2 hours ago, Nelson said:

Glad to hear you're still keeping the project alive. As for the lower weight distribution, early on I decided to sling two Power Functions large motors underneath, at the bottom of the chassis, to both get the weightiest part as low as possible and also replicate the look of the film version engines. I also went with the small size battery box with super light lithium AAA batteries since in my design, that box ends up at the top inside the body. I've been tinkering with some new cam designs, but haven't had much luck. I'm going to try reverting to the build I had in the earlier post's video and see if I can refine from there. I have a few new ideas.

 

Mmm, I might redesign the main chassis. It’s beautifully compact but yes, it probably needs an adjustment to account for the weight.

[Nelson]

Here are a couple more ideas that may help your cause. I too have the same issues with balance/leaning and sought to get some compensation in the feet and legs. I came up with a way of mating the external legs to their internal connecting rods with a small ball/bar piece wedged in between a stud-pin and round 1x1 plate to create a bit of negative camber (Image 1). I also utilized the ankle strut feature seen in the film models to get more negative camber from the leg to the foot. I made the struts just a bit too long for the distance so they push the feet out a bit crooked (Image 2). Also note that the feet/ankles on my model have very limited movement, probably less than 10 degrees. I found this essential to keep the model from pitching forward or backward and falling on its face or butt if the feet slid. Finally, you can see in image 3 that the model is quite rigid at all points during its cycle. If I hold it sideways, the legs barely deflect at all. My early versions all started out pretty loose and I had to really lock things down. Of course, we are taking somewhat different approaches, which I find really intriguing, so these features may not be as necessary in your design. There was a post earlier in this thread that suggested a cam system that is very close to the concept I'm using (although I had already tried and failed with the parts he suggested and used a different method of creating cams.)

Edited October 30, 2024 by Nelson