Fully articulated 24" tall AT-AT adventure

[Searun]

Hagoth,
This is certainly one nifty project. Wife just caught me digging out my grandkids Fisher-Price Dinosaur out of the closet. Thinking about taking it apart. Has some rather clever leg and neck articulation. Will be watching this thread.

 

[Bauble]

Hagoth, this is amazing! I love your obsession with details. JediMichael's observation about the foot compression is amazing as well. That is one fine detail that the original crew put in that I suspect 99.9% of us missed if JM did not point it out.
There are a few engineering considerations that make a moving scale model easier than an actual AT-AT.
I suspect we can use put a electromagnet in the foot that can help 'pull' the foot down during part of the move. The ground would have to be metallic but we can easily hide it with the right surface cover. This approach will not only add 'weight' to the downward motion of the foot, it will also likely simplify the whole model stability as well. With three feet magnetized to the floor at all times, there is no risk of the model tipping over.

 

[Hagoth]

Hagoth,
This is certainly one nifty project. Wife just caught me digging out my grandkids Fisher-Price Dinosaur out of the closet. Thinking about taking it apart. Has some rather clever leg and neck articulation. Will be watching this thread.

Taking things a part to figure out how they worked was a childhood joy of mine. A favorite toy as a toddler was a wind up train engine with a bunch of gears inside that you could see moving as it would move across the floor. I took that thing apart dozens of times to the point that I could practically put it back together with my eyes closed. I think projects like this are in my blood. My X-Wing project still a surprise?

 

[Hagoth]

Hagoth, this is amazing! I love your obsession with details. JediMichael's observation about the foot compression is amazing as well. That is one fine detail that the original crew put in that I suspect 99.9% of us missed if JM did not point it out.
There are a few engineering considerations that make a moving scale model easier than an actual AT-AT.
I suspect we can use put a electromagnet in the foot that can help 'pull' the foot down during part of the move. The ground would have to be metallic but we can easily hide it with the right surface cover. This approach will not only add 'weight' to the downward motion of the foot, it will also likely simplify the whole model stability as well. With three feet magnetized to the floor at all times, there is no risk of the model tipping over.

Thanks for checking this one out Bauble.

See line number 7 of post #2
I didn't realize the feet had this shock absorbing motion till a couple of weeks ago when I saw an animation of 10 min of walker motion. Then I went back and poured over the shots in ESB and even Rouge One and there it was. Shock absorbing feet! How cool is that!
As I have been researching into this project and working out the reverse engineering I have been more and more impressed with the work that the original builders accomplished. What they accomplished 40+ years ago is an absolute work of engineering art. The realism of the movement and convincing simulation of a massive heavy machine walking that was captured in the stop motion photography is most impressive. This will be fun to take it to a new level.

As for duplicating the foot shock absorbing effect, if the ankle is weighted (not too much so as to not overpower the hip and knee joints) it will sink into the foot pad on a light spring and give the weighted heavy look I want to simulate. Since the weighted potion will be below the center of gravity it should act like a tight rope walkers balance bar to keep the walker stable with only three feet touching the ground at a time. That is at least the theory behind it. Now, your idea of electromagnetic feet...hmmm that's interesting. I wonder if that concept could be used for joints as well? A plastic model might be light enough for it to work.

Here is a picture of the parts for the original hero models laid out on a table. I would have loved to be part of that. This is what resulted from the prototype (See post #7 picture) that was mentioned in Starks history post.

 

[Hagoth]

The foot has an insert in the base and a large spring inside. The toes are fixed by pins and you will notice hinge up and down also. All 3 hero models were built in this configuration so your %100 correct, the foot does compress

And that walking walker is cool! They got the knees lifting. No cam movement that I can see but what an achievement!


This was originally posted by dsp5500 during his awesome build.
View attachment 1465755

Cheers,
Josh

That is a fascinating glimpse of history here Starks. Thanks for posting it. Really curious as to how those "Pop Pins" worked. I keep reading it and trying to imagine what was going on here. I wonder if those are the pop pins on the front edge of the table in the picture I posted above? What leg shaft are they talking about? How did these work?

 

[JediMichael]

Hagoth, this is amazing! I love your obsession with details. JediMichael's observation about the foot compression is amazing as well. That is one fine detail that the original crew put in that I suspect 99.9% of us missed if JM did not point it out.
There are a few engineering considerations that make a moving scale model easier than an actual AT-AT.
I suspect we can use put a electromagnet in the foot that can help 'pull' the foot down during part of the move. The ground would have to be metallic but we can easily hide it with the right surface cover. This approach will not only add 'weight' to the downward motion of the foot, it will also likely simplify the whole model stability as well. With three feet magnetized to the floor at all times, there is no risk of the model tipping over.

Although I cannot take credit for noticing it in the movie, as someone here had pointed it out to me. But I am glad to be able to now point out that interesting and totally missed feature.

Glad its being considered for this build, however you guys end up achieving it in the end.

And that pic with everything layed out, I don't think I've ever seen that before. Love those type pics.

 

[Hagoth]

Maybe this can help now that I think of it.
One thing that someone here on the RPF had mentioned years ago, (do not remember who) is how the feet compress into itself. I have never seen any model or person make a scratch build do this, but it WAS in the movie. I will take some screen grabs to illustrate best I can. And maybe you knew this already, but just incase.....as I would like to see a model do this, even if its the most little simple thing. Looking more into the scene, it appears not every one of the ILM models were doing this. At least one of the normal sized ones and the big leg for smashing Lukes snow speeder was doing it.

Three screen grabs. First frame the foot is not quite all the way down, but 2 and 3 it is, and you can see the top red line, on the 3rd frame, the top of the foot is ever so slightly down.
View attachment 1465710

See it a little better on the bigger foot, which I only recently found that they even had made this.
The camera does tilt down a little as well, and the top is cut off, but is you play the scene, you can tell.
View attachment 1465711
Hopefully I explained it well enough.
When I find out about little things like this, then when I see its not known or in any models or builds, I get obsessed.

....annddddd.......
Heres a motorized version I remember seeing many years ago, (video uploaded in 2008) and I was able to find it.

This is a great observation JediMichael and one that only until recently was I even aware of myself. This feature will definitely be included in this project.

After seeing that I started paying closer attention to the motion of the other parts in relation to the timing of the movement of the legs and noticed something else. The front and back legs are mirror images of each other and move in the same ways but the knee fly wheels spin the same way on both the front and the back legs. Not mirrored but in time with the pistons. So the linkage I'm designing for animating those with the piston flywheel needs to reverse sides half way down for the spin direction to match on the back legs with that of the front. Also they spin a lot faster than the piston cam so the gear ratio needs to be 1.5 to 1 on them at least.

So, when you say you get obsessed with little details that you notice and have not seen before on other models? Yeah, I get that.

And that motorized example... I can be done folks. So that puts the next chapter of this project completely in the realm of possibility.

Good stuff here!

 

[JediMichael]

I always forget they added the gif button on here not too long ago. Fun what you can find.

 

[Hagoth]

I just want to say to everyone following this thread that I really appreciate the interaction and information sharing so far even at this early stage. This is great!

 

[Hagoth]

I always forget they added the gif button on here not too long ago. Fun what you can find.

Ha! That's great!
The bottom one shows another thing I noticed. When the walker gets tripped and starts to fall in the close up shot the rear legs are bent forward but when the shot pans out to the one you show the rear legs are bent backwards.

Fun little fact I remember reading is that the big 4' model had electric clutches in the joints that were supposed to be released and make the Walker collapse. They kept failing so that is what led to the cable being used to drop it as shown in the picture Starks posted. However, now the legs were free to bend the wrong way. On the smaller models (20" tall for the history post?) there is a notch at the bottom of the knee that I think was a motion limiter for the lower leg range of motion. Anyone with insights on that feature?

 

[JediMichael]

I just want to say to everyone following this thread that I really appreciate the interaction and information sharing so far even at this early stage. This is great!

Oh of course. And to see it eventually all working correctly will be totally awesome. Through trial and error, I know you will get it to work out great.
Not sure if you have seen my collection......yeah, bit of a fan. haha
None scratched built. Way more than I could figure how to do. Most were bought already assembled and painted.

 

[Hagoth]

Oh of course. And to see it eventually all working correctly will be totally awesome. Through trial and error, I know you will get it to work out great.
Not sure if you have seen my collection......yeah, bit of a fan. haha
None scratched built. Way more than I could figure how to do. Most were bought already assembled and painted.

View attachment 1465948

Love it! Very nice.

Both of mine are in pieces or various states of re-construction to figure out how they might move and work. On the waiting list for a Bandi 144 to get something more studio accurate. What do you think the chances are that it will actually be assembled and used as a display piece?

 

[JediMichael]

Also, it was this shot, the closest walker to the frame, that when both front legs hit the ground, the foot does NOT compress in.
I wonder what the story is on that?
The two back ones are working correctly.

Funny that since I now pay SO much attention to this "foot feature", I actually have not noticed if the rest of the leg pieces are working/moving like they should be from shot to shot, or models built over the years by anyone.

 

[JediMichael]

Had to search for a few more.....I need to get to bed.

I could stare at this for an hour.....

 

[Duncanator]

That is a fascinating glimpse of history here Starks. Thanks for posting it. Really curious as to how those "Pop Pins" worked. I keep reading it and trying to imagine what was going on here. I wonder if those are the pop pins on the front edge of the table in the picture I posted above? What leg shaft are they talking about? How did these work?

I think the "Pop Pins" they were talking about were releasable ball detent pins. They use a spring loaded rod inside the pin that holds the balls out, or allows them to fall inside to release the pin. The ball detent pin would be shoved up through a hole in the table and into a hole in the bottom of the foot when the foot landed on the tabletop. The balls would pop out enough to secure the foot to the tabletop for animation. This was a lot quicker than the typical method which would be a screw or all-thread with a nut.

Here's a diagram of something similar.

 

[starks]

I think the "Pop Pins" they were talking about were releasable ball detent pins. They use a spring loaded rod inside the pin that holds the balls out, or allows them to fall inside to release the pin. The ball detent pin would be shoved up through a hole in the table and into a hole in the bottom of the foot when the foot landed on the tabletop. The balls would pop out enough to secure the foot to the tabletop for animation. This was a lot quicker than the typical method which would be a screw or all-thread with a nut.

Here's a diagram of something similar.

View attachment 1465953

So they're using this method to secure the foot/ model in place so there's no movement while animating the other components? Am I understanding that correctly?

Cheers,
Josh

 

[Duncanator]

So they're using this method to secure the foot/ model in place so there's no movement while animating the other components? Am I understanding that correctly?

Cheers,
Josh

Yes. Like I mentioned: the usual method was to use a screw from under the table, which takes a while to tighten or loosen. Something like these would have made it quick to pop in and out, making the already tedious animation process a little easier.

 

[starks]

As part of this upcoming build I have been trying to find as much information as I can on kits used. I have a list of kits but still need to identify which parts were used where. Hopefully as a collective we can put together a map as seen for the MF and X-Wings. This will help everyone, be it those using smaller kits for the smaller models, those wanting to create a studio scale replica and us for reference to make up-scaled replicas.
Heres a basic list of parts so far, just a few, and we know these but I think photos go a long way to help, especially for those who are still in even earlier stages of identifying pieces. Any additions to this will be greatly appreciated.

1/35 Flakvierling. or 1/48 suit Revell kit. I need to identify more parts as some are apparently used on the belly. The guns are used for the cheek guns (no photo yet) The armour plates on the rear. The rectangular pieces on body and feet, 2 other greeblies on the ankles.

The ankle greeblies. Note these are separate pieces on the 1/35 kit. theyre already molded into another part on the 1/48.

The armour plate. Im showing the pic of the 1/48. the 1/35 is slightly different and matches the studio model.

The rectangular greeblies body and feet:

1/24 Airfix Harrier Engines... I haven't included a walker shot... doesn't take much working out.

1/24 Stuka rear gunner window... theyre places upside down and I believe this to be the only Stuka part on the Model.

Further kits apparently used but still need to identify parts. I have copied and compiled these lists from old posts by other members. Quite a lot of time searching went into this information so I feel for the guys who spent time actually scrounging through kits to find the parts.
1/144 Apollo Saturn 5
1/35 Tamiya Sd. Kfz Leichter 222
1/35 Tamiya T34/76
1/35 Tamiya M16 Multiple gun motor carriage
1/35 Tamiya Chieftan Mk.5
1/35 Tamiya Leopard
1/35 Tamiya Matilda
1/35 Tamyia Marder 1A2 Milan
1/700 Tamiya Nelson Battleship
1/12 Tamiya F1 with Ford DFV engine
1/72 Hasegawa Morser Karl
1/700 Tamiya Scharnhorst

1/35 Tamiya flakpanzer Gepard No.3599 has underside parts
Kampfpanzer Leopard No.35064 for vents on the rear.

The chin guns are from an old tooling Tamiya 1/35 Sturmgeschutz III.

ROCO gepard (mini tanks)

1/35 Panther Sd.kfz 171 Aust.A
1/35 Sdkfz 232 (8rad)
1/35 British 25PDR Field gun
1/35 Churchill Crocodrile



And some interesting information regarding the studio model shown on the Modelers magic website

AT-AT Studio Model

As it is told to me, these are the photos MR had taken of the studio AT-AT from The Empire Strikes Back in the Lucasfilm Archives! As further told to me, and as you can see in the photos, the neck …

modelermagic.com

This has been an annoyance for me trying to work out where it is seen, the site states it being the studio model MR used when building their replica (they definitely copied the paint scheme). This has a few discrepancies and I thought may have been background use.

In the film there were the 3 hero's, the large walker and seemingly 2 smaller models.
The walkers in the background were photographs or some such.
These Resin copies were apparently made as executive gifts, 5 in total, one supposedly was a prize in a competition. So this never saw any screen time.

Cheers,
Josh

 

[Searun]

Hagoth, this is amazing! I love your obsession with details. JediMichael's observation about the foot compression is amazing as well. That is one fine detail that the original crew put in that I suspect 99.9% of us missed if JM did not point it out.
There are a few engineering considerations that make a moving scale model easier than an actual AT-AT.
I suspect we can use put a electromagnet in the foot that can help 'pull' the foot down during part of the move. The ground would have to be metallic but we can easily hide it with the right surface cover. This approach will not only add 'weight' to the downward motion of the foot, it will also likely simplify the whole model stability as well. With three feet magnetized to the floor at all times, there is no risk of the model tipping over.

Bauble,
Clever idea. My American Flyer trains in the early 50’s used to fly off the curved track If I did not slow down. Lionel train engines could go much faster since they had an electro magnet. Also, they could handle steeper grades without wheels spinning. Took me some time to understand this concept.

 

[Hagoth]

I think the "Pop Pins" they were talking about were releasable ball detent pins. They use a spring loaded rod inside the pin that holds the balls out, or allows them to fall inside to release the pin. The ball detent pin would be shoved up through a hole in the table and into a hole in the bottom of the foot when the foot landed on the tabletop. The balls would pop out enough to secure the foot to the tabletop for animation. This was a lot quicker than the typical method which would be a screw or all-thread with a nut.

Here's a diagram of something similar.

View attachment 1465953

Thank you! I get it now. These were going into the bottoms of the feet to hold them in place.