Walking AT-AT

Hi folks, this is just a heads up for a long term project. I'll be working on it here and there in between other work. Over the past few years I've been looking into ways to create a mechanised walking AT-AT. There is a youtube video of one that Adriano Kenobi made a few years back, and it is amazing:


I got in contact with him and as I guessed, he wanted to keep the mechanism a secret. Don't blame him really. All I really know is that it is a clockwork-type mechanism, presumably made with a central motor and a cam/sprocket system. I spent a LONG time trying to work out such a mechanism for myself. Here is a video of my experiments!:


I got reasonably far with this but figured the skills involved machining small parts would be a complete nightmare, not to mention trying to keep all of the actions in perfect synch. I'm going to work on a servo-based system instead. This will have the added advantage of being able to move legs independently, and to refine the walking gait as part of the process.

I tried with sub-micro servos embedded in the legs first, but still ran out of room. Also, the torque generated just wasn't strong enough. I also tried a design where the servos were held inside the hull, with pushrods and control cables to transmit the motion. It worked okay, but again the torque needed to move the legs would have been too difficult to transmit through all of the joints. I didn't want to do any cheats with the design, it all had to look exactly like the filming model.

So... what to do?

Well, I'm going to go bigger and attempt to double the size of the Revell. This will mean a scratchbuild of approx. 1/35 using the revell kit parts as a starting point. I should then be able to find servos with sufficient torque which will still be able to fit within the legs. This should be completely doable. I tried a servo from a small Walkera helicopter and it had just enough power to work... when it comes to buying the servos I'll be upping the power considerably!

I cannot tell you how many sleepless nights this has caused. It is completely maddening, but I am determined!

I'll post updates as and when, but this will be a slow build!

Wow! What a quest!
Your video looks really complicated, you must be a real engeneer!!
This is really interesting!

Wish you all the luck for the project, Keep at it and I'm sure you will have a working mechanism :thumbsup

I can't wait to see how you do this... It looks amazing

LukaFilm said:

Wow! What a quest!
Your video looks really complicated, you must be a real engeneer!!
This is really interesting!

Click to expand...

I'm really not an engineer - I failed maths first time at school. All this is trial and error

Yep, I spent sleepless night after seeing the video of that AT-AT walking! I wish you luck and eager to see you succeed in your project.

This might be a good starting point if you can get a hold of it.

https://www.youtube.com/watch?v=DqDHsy0bOFw

Chris, from the sound of it the motor and mechanisims may have come from a toy "pet" like a walking dog, cat etc. Don't know if it would help to find one close and take it apart, then reengineer for your own purposes. Don't get one that does backflips or barks!!!!! Great work, you really like your AT ATs!!!!!!!

That would be my guess too. Take an existing walking pet product and adapt it.

Thanks for the options, but the lego walker's gait is completely wrong, and I'm not going to be working from existing toys... I may add a backflip though? - The walker needs three points of articulation for each leg so the servo route is gonna be the best option. Like I said, this will be a long term thing

Adriano Kenobi's sounds and walks exactly like a Zoid! Seems like it could be around the right size too.

How about this?



Cheap to run, but you might have to clean up after it once in a while...

Rob

ROFLMFAO! , was so not expecting that lasts picture, drink out of my nose!! Good luck with the project will be watching

This will be an AWESOME project! :thumbsup Will be following!

Hi again, I thought I'd add an update. No pictures I'm afraid, just me writing away.

I purchased a Pololu Maestro servo controller and some servos. The controller comes with a servo sequencer where you can almost program the servos frame by frame. I hit a major snag though. The software likes all the servos to be running at the same speed from point A to B, and the AT-AT's walk gate has a lot of acceleration and deceleration. Pololu, whilst being very helpful told me I could alter this by changing scripts. I am not a programmer and whenever I tried to learn I realised my backup knowledge was not sufficient enough for me to progress. It was becoming a nightmare! Plus, I had misgivings about servos burning out and generally how complicated the whole thing was getting.

So, I went back to Algodoo (physics simulator) and went over my designs with a fine tooth comb. I also scoured the internet for mechanisms which would help get the walk correct. The biggest hurdle is getting the movements at the right speed at the right time.

You can split each leg movement into 4 quarters. The forward lurch of each leg happens in the first quarter, it moves forward from the extreme back position to the extreme forward position in one quarter of a cycle. The remaining three quarters is the leg moving slowly towards the extreme back position. Each leg begins its cycle a quarter later than the previous one. Hope this makes sense! So at any given time you have one leg lurching forward while the other three are moving slowly back.

Anyway, I managed to find a specific gear mesh which alters its speed along a cycle which will allow this timed motion. When you put four of these gears together with separate timings the leg motion is perfect! So, with a revised design I'm going back to the idea of using one geared motor to drive the 4 legs.

The bonus of the cogs and gears system is that it can be kept small, so I could still utilise the existing Revell AT-AT and modify it. I currently have 2 revell AT-ATs, one for messing around and testing ideas on, the other for the final build. I've started building a mockup of the system and the motions do work very well.

The main snag I'm finding is I'll need to get some steel pushrods laser cut as well as getting some gears made as well. The pushrods will need to be very thin as some will have to fit inside the hip joint and provide transmission to the legs. I'll need to go with steel so they don't flex at all. This pushrod system will be almost hidden, the only thing you'll see is a bit of thin metal exiting the hip at the top. For me, it is not perfect, but look at Adriano's walker and you can see little cheats here and there.

So, I suppose the question is - can anybody laser cut steel?! I've tried getting some quotes, but it seems like unless you are planning to order 50,000 parts for a jet they don't want to touch you!

I keep wondering how much of this build I should share, as I've put years (literally) into devising this system. I've decided I will show everyone the mechanism, but only when I've finished the build.

Still gonna be a long term project, so don't expect miracles any time soon!

Thanks,
Chris

For laser cutting steel, you could try checking metal supply/fabrication companies around you. I found a company near me (Northern California) that'll do single parts if needed. They charge a basic set up fee plus a fee per part. Hopefully you can find one in your area.

I found another video on the AT-AT and that said Adriano had help from Carlos "FocaYoda". Maybe he can help you out what mechanics were used.

https://www.youtube.com/watch?v=JVl4fV2g1jQ

Thanks I'll try and get in contact with him. I've already been in contact with Adriano and he is keeping tight-lipped. Fair enough too

Best of luck with this, I've had the same project idea in the back of my head for a long time now. I would love to see how you pull this off.