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

[Nelson]

I put together a new version of the "slide piston" chassis over the weekend. It answered my question about one motor being enough...I believe it is, even with the slightly taller gearing I used. Unfortunately, because of the design modifications to accommodate gearing change, the build was not as rigid and wasn't an overall improvement. I've made up my mind that I'm going to try my older mechanical concept with the newer drivetrain style. I think that the older concept has a more accurate walking motion to the film and fits within the body better. The drawback it that it's more complex and touchy than the newer "slide piston" concept. Considering my end goal is to sell the MOC, this is a risky decision. But if it ends up giving more accurate motion and aesthetics, it will be worth it.

[BrickBear]

16 hours ago, Nelson said:

I put together a new version of the "slide piston" chassis over the weekend. It answered my question about one motor being enough...I believe it is, even with the slightly taller gearing I used. Unfortunately, because of the design modifications to accommodate gearing change, the build was not as rigid and wasn't an overall improvement. I've made up my mind that I'm going to try my older mechanical concept with the newer drivetrain style. I think that the older concept has a more accurate walking motion to the film and fits within the body better. The drawback it that it's more complex and touchy than the newer "slide piston" concept. Considering my end goal is to sell the MOC, this is a risky decision. But if it ends up giving more accurate motion and aesthetics, it will be worth it.

Ooh. So you’re selling the model as like sets or as a one off? Or just the instructions on rebrickable?

[Nelson]

@BrickBear My hope is to offer it as both instructions or as a full set. I'm not sure how many sets I'd put together. Some of the parts I'm currently using are out of production. I'm hoping I can make design updates to get all the parts current, but that will be challenging. I received an insane amount of positive feedback and requests to make the instructions available after I posted a FB video of the current design taking a few steps. I think I could easily put together a dozen or so sets and there would be ample buyers. But first things first. I need to actually finish the thing! And generating instructions will be no small task. I'm easily a year away from putting anything out there. I'm also stocking a new BrickLink store, so lots to do.

[BrickBear]

39 minutes ago, Nelson said:

@BrickBear My hope is to offer it as both instructions or as a full set. I'm not sure how many sets I'd put together. Some of the parts I'm currently using are out of production. I'm hoping I can make design updates to get all the parts current, but that will be challenging. I received an insane amount of positive feedback and requests to make the instructions available after I posted a FB video of the current design taking a few steps. I think I could easily put together a dozen or so sets and there would be ample buyers. But first things first. I need to actually finish the thing! And generating instructions will be no small task. I'm easily a year away from putting anything out there. I'm also stocking a new BrickLink store, so lots to do.

Interesting. My goal is to offer instructions and because i like making books, i might make a sort of haynes manual inspired book on the process and mechanisms that contains the instructions too with handrawn bits and pieces too. It’s a whole creative project for me.
 

 

Edited May 14 by BrickBear

[Aurorasaurus]

3 hours ago, Nelson said:

And generating instructions will be no small task. I'm easily a year away from putting anything out there. I'm also stocking a new BrickLink store, so lots to do.

Good luck with this. I recommend you to do instructions for a couple other models (maybe smaller ones) before you start on the instructions for this, if you dont intend to do multiple re-releases and updated versions of this model. I've made instructions a few times and theres no shortcut to getting it right.

I recommend you to use lots and lots of submodels when you're building, and also convert small ones to callouts to keep the page length from getting out of hand. Also, 6 steps on one page is fine on a big screen, but less is better for people on a laptop, phone, ipad IMO.

I guess what I'm trying to say is, if this will be a one off masterpiece, take the time to learn how to make good instructions first.

[Nelson]

@BrickBear All good advice, especially the bit about trying some smaller models first. I'm in no hurry. I'm using Studio at the moment. Would you consider that the best option or have you tried others that are better?

[BrickBear]

15 hours ago, Nelson said:

@BrickBear All good advice, especially the bit about trying some smaller models first. I'm in no hurry. I'm using Studio at the moment. Would you consider that the best option or have you tried others that are better?

It’s @Aurorasaurus that has all the know how nelson. 

[BrickBear]

installed xl motor in back of AT-AT,  you’ll notice the orange 2L beam can rotate to allow the motor to move such that the weight distribution mechanism can still work. Theres enough play in the gears to allow this. 

Although it balanced really well pre motor it’s clear that the head really does need to be attached to act as a counterbalance to the back. Once done then hopefully hopeful hopefully i can get it to if not walk then shuffle.

[BrickBear]

Yesterdays progress included knee bending mechanism. Unfortunately a bit too wibbly so they buckle. Also i know the head isn’t quite secure, i need to build at better attachment 

 

 

This morning i’ve adjusted the motor so it isn’t part of the body shifting mechanism as yesterday under test the direction of the active motor was causing upset in the balancing mechanism. 
 

Going to unbend the legs for now i think

[BrickBear]

ugh. So the xl motor kept coming loose because the strength of the surrounding structure wasn’t good enough so that’s a setback and so everything was getting out of sync (thank goodness for the gearbox system i introduced to resync stuff). I’m considering redesigning the feet so the ankle joint is actually at the base of the foot, it’s not canon but it might be more stable that way as the feet otherwise catch when they move forward. What matters is that it looks roughly accurate. 
 

regarding the leg bending i think i might try bending the body armour instead of the mechanism to give the illusion of a bent knee if I can’t come up woth a better alternative. I’m curious about my previous attempts with the sliding bending function but we’ll see.
 

 

 

 

[Nelson]

Sorry I haven't checked in recently. Looks like you're still making progress, @BrickBear. A couple weeks back, I did work on a version of my old chassis design, combining it with the newer, more direct motor and drivetrain designs from my later chassis. Unfortunately, I ran into issues where moving parts are hanging up at various points in the cycle. This has been something I've encountered often and it can be tough to predict. The smallest .025mm ridge between two "flush" mating parts is enough to catch a rotating liftarm and bind the whole mechanism. I'm getting a few parts on order to combat this. Sometimes it's as simple as using a part with a rounded vs. squared end so that the liftarm is subtly directed over that catch point. Other times, it means reevaluating the whole design. Have you encountered this issue? It can be challenging to create clearance areas when the available space is so limited.

[BrickBear]

Ok, so I’ve returned to the old bending function because I never had the problem with the bucking feet in that. It only bends a teensy wee bit but it’s noticeable enough. Should give plenty more room for the motors and battery box too. The legs aren’t too wobbly either luckily. 3 more legs and the motor then I can test it again.

On 6/4/2025 at 9:02 PM, Nelson said:

Sorry I haven't checked in recently. Looks like you're still making progress, @BrickBear. A couple weeks back, I did work on a version of my old chassis design, combining it with the newer, more direct motor and drivetrain designs from my later chassis. Unfortunately, I ran into issues where moving parts are hanging up at various points in the cycle. This has been something I've encountered often and it can be tough to predict. The smallest .025mm ridge between two "flush" mating parts is enough to catch a rotating liftarm and bind the whole mechanism. I'm getting a few parts on order to combat this. Sometimes it's as simple as using a part with a rounded vs. squared end so that the liftarm is subtly directed over that catch point. Other times, it means reevaluating the whole design. Have you encountered this issue? It can be challenging to create clearance areas when the available space is so limited.

I think I get what you mean, I’ve had parts catch on others but i’m quite good at compact building and so not had too much of a problem.

[BrickBear]

tada

FYI I’m not holding it up, the balance is pretty good, unfortunately I had to lock the steering so I don’t think we’ll see a proper RC version, although time will tell.

Edited August 8 by BrickBear

[Nelson]

@BrickBear It's alive! Great to see it scooting along. What's next? Is there a way to get the legs up off the ground a bit more? Maybe control that front leg splay?

[BrickBear]

20 hours ago, Nelson said:

@BrickBear It's alive! Great to see it scooting along. What's next? Is there a way to get the legs up off the ground a bit more? Maybe control that front leg splay?

Yeah I need to have a play around with counterbalancing and fixing that snapping motion the front legs do

[BrickBear]

Ok, so i came up with an attachment to the shoulder/hip movement mechanism that works to shoft the weight of the battery box at the back and needs to be connected to the head. Which was much like how the OG lego walking at-at worked.

Edited August 30 by BrickBear

[Nelson]

Cool! I've been occupied with repairs to my condo, but that's wrapping up. Once I get back from my upcoming vacation, I'm planning on getting back to my model. 

[BrickBear]

 

My latest problem with the legs is their propensity to slide with the weight, this mechanism has the correct cycle but without that issue. I just need to figure out the front legged version