Revell At-At WIP... finishing up!

[Hagoth]

About the pulley system moving the hydraulic pistons up and down in the upper leg... the metal skeleton picture shows a circular pulley type system inside the upper leg that seems to be connected by cables to the main leg and hip joint. I suspect this is connected to the hydraulic piston shells moving them up and down as the lag rotated in reference to the hip movement. So I think this is the precise repeatable movement Analyzer deduced with the quote. I have been thinking about what links might be needed and how to duplicate the motion automatically in my 3D printed project version. It will have as many automatically moving parts with leg motion as I can figure out.

You can see what I think is the pulley system here on the front leg that is missing the lower part.


Nice! That leg extension pivot point above is just what I was looking for. That tells me that it would be precise and repeatable as well and I think you are dead on Starks that this is a motion limiter. Also, because it provides three contact points including the hip pivot point that do not have a linear relationship to each other it might automatically help hold the leg in position once moved. Looks like the Cam could lock it. Clever! Now I want to duplicate it and make one myself to see the mechanics of it.

Definitely going to look up that book Chaïm. Thanks for the lead on it.

That animation is pretty darn good. I've seen that before but never paid really close attention to the actual individual movements of the various parts It is missing some of the relational movement we see on screen like the separation of the travel limiters (leg extensions) and the movement rates and timing are off to be tied to the repeatable pulley drive system mentioned. however, it shows well the majority of parts that have movement.

Really fun stuff here guys!

 

[Hagoth]

Oh, one motion in the animation I had not noticed before is the tops of the feet, or ankles, move in and out of the foot pad like a shock absorber. I just watched some Rouge One footage and the "Shock absorber" action is present on the AT-ACT foot movement. Same thing on sequences from the battle on Hoth in ESB. Interesting. Another motion action to capture.

I've always like the walkers, as one of the more interesting mechanical vehicles (and practical props to boot) of the original series. All these little details being discovered and explored here are just making me love them that much more. The models makers did an absolutely fantastic job with these.

 

[starks]

Oh, one motion in the animation I had not noticed before is the tops of the feet, or ankles, move in and out of the foot pad like a shock absorber. I just watched some Rouge One footage and the "Shock absorber" action is present on the AT-ACT foot movement. Same thing on sequences from the battle on Hoth in ESB. Interesting. Another motion action to capture.

I've always like the walkers, as one of the more interesting mechanical vehicles (and practical props to boot) of the original series. All these little details being discovered and explored here are just making me love them that much more. The models makers did an absolutely fantastic job with these.

I agree it is amazing how much effort they went to, to portray the walkers as being a real thing. And I think even though you don't automatically pick up on those things and little movements, your brain registers them all and that all adds to making it believable. The only thing that ever lets the Hoth scenes down from a special effect perspective is the overlaying of separately filmed models and at times... especially against a white background that stands out a bit. But the filming and models themselves stand up even better than a lot of modern day CGI. they have a real feel to them because they are real... not just a well rendered cartoon.


So on my continuing journey of this build a few things bug me on the hips. I want to see that diagonal slot, I want to add the leg extension and the locking tab for the hip to leg joint is totally inadequate and really want to see the cam behind.
Oh and to boot when looking at placement of the diagonal slot for the hip I noticed the hips are too long. By about 10mm, maybe just a bit more.
you know what that means... new hips time. But screw it lets make a working cam and hip.

Working off measurements on the Revell model and overlaying placement onto this file.

Then the file

and the pieces with the leg. I need to adjust and recut the cam as the slot came too close to the edge but the plan here will be to dremel out the leg center, glue the cam in place and screw the hip through to the cam locking tab which will give the correct articulation and I will have to work out the mounting of the leg locking extension. I might fatten that piece up and recut it as well.

You can see on this inner picture the cam locking tab has the 2 fixing screws... obviously the rear screw with the washer being for leg movement.

so this idea of having a centralised joint in the hip to a centralised hole in the leg is wrong. The leg rotates further back to the end of the hip. Looking at that Mira kit was wondering if they addressed this but it seems more a case of a centered hole but with a cam and locking tab on top for aesthetics.

I need to perfect this file a bit more then find some very tiny screws it seems.

Im really keen to see some thoughts on the designs here.

cheers,
Josh

 

[Hagoth]

That is a great start on parts for proper motion but you will have several potential issues with the current design.

Your rectangular piece with the slot in it will need to have its pivot point in the center matching that of the circle with the crescent shaped cam path in it. It should not be matching the pivot point to the hip. Otherwise you will not be able to rotate it in the fixed circle that it overlays. The small rectangular center pin (does not rotate) provides the rotation point for it. What this does is force that part to move in a repeatable fashion in relation to the leg pivoting around the rotation point at the hip. The cam slot pin is fixed to the hip blade. This means the crescent shaped cam slot in that center circle of the leg should have the same center point as the leg attachment to the hip so the arc can move over the cam pin. The motion limiter leg extension will need a round pivot point to fit in the hip slot since it will not always be parallel to the slot in the hip as the other end attached to the leg rotates around the hip joint.

Hope this makes sense. I'll see if I can draft up some overlays of the relationships later tonight... if I can get a chance. Wanted to alert you to the potential problems before you went too far.

 

[starks]

That is a great start on parts for proper motion but you will have several potential issues with the current design.

Your rectangular piece with the slot in it will need to have its pivot point in the center matching that of the circle with the crescent shaped cam path in it. It should not be matching the pivot point to the hip. Otherwise you will not be able to rotate it in the fixed circle that it overlays. The small rectangular center pin (does not rotate) provides the rotation point for it. What this does is force that part to move in a repeatable fashion in relation to the leg pivoting around the rotation point at the hip. The cam slot pin is fixed to the hip blade. This means the crescent shaped cam slot in that center circle of the leg should have the same center point as the leg attachment to the hip so the arc can move over the cam pin. The motion limiter leg extension will need a round pivot point to fit in the hip slot since it will not always be parallel to the slot in the hip as the other end attached to the leg rotates around the hip joint.

Hope this makes sense. I'll see if I can draft up some overlays of the relationships later tonight... if I can get a chance. Wanted to alert you to the potential problems before you went too far.

I follow what your saying.
The pivot point IS central to follow the camshaft curvature. You can see the marking on the left side of the rectangular tab. I was able to determine that new ' center' in Corel.

Edit: I misunderstood, seems I didnt follow what you were saying cleary enough haha. Im going to alter the design and recut! Thanks Hagoth

The mounting points for the leg extension I still need to work out.

Cheers,
Josh

 

[Sym-Cha]

I'm not an engineer so perhaps someone can explain with visuals what you guys are refering to? Here's a picture that could be used as such?

That said I took your new design for the hip replacement and in Photoshop made a 50% overlay over the Revell kit part, as seen in the Revell instructions, and then virtually 'cut' the Revell hip layer and moved the back part forward to accomodate your design. You'd only need to shave some plastic of the sides and would end up with the same part that you scratchbuild, would it not?

Also I found that Blue Moon has made an accurizing kit for this 1: 53 Revell Kit : AT-AT Accurizing Kit, Blue Moon do we know what that kit contains and if it's still available?

Chaïm

 

[Hagoth]

I follow what your saying.
The pivot point IS central to follow the camshaft curvature. You can see the marking on the left side of the rectangular tab. I was able to determine that new ' center' in Corel.

Edit: I misunderstood, seems I didnt follow what you were saying cleary enough haha. Im going to alter the design and recut! Thanks Hagoth

The mounting points for the leg extension I still need to work out.

Cheers,
Josh

Sorry Josh, I was afraid the wording might be hard to follow. Looks like you might have recognized the pivot point issue.

And per your request Chaïm, and for any others following down this rabbit hole I'll post a 3D layout of the motion and constraints shortly.

 

[starks]

I'm not an engineer so perhaps someone can explain with visuals what you guys are refering to? Here's a picture that could be used as such?

View attachment 1458270

That said I took your new design for the hip replacement and in Photoshop made a 50% overlay over the Revell kit part, as seen in the Revell instructions, and then virtually 'cut' the Revell hip layer and moved the back part forward to accomodate your design. You'd only need to shave some plastic of the sides and would end up with the same part that you scratchbuild, would it not?

View attachment 1458272

View attachment 1458273

Also I found that Blue Moon has made an accurizing kit for this 1: 53 Revell Kit : AT-AT Accurizing Kit, Blue Moon do we know what that kit contains and if it's still available?

Chaïm

The blue moon kit I chased up at the very beginning but no longer seems to be available Chaïm.

And you're right, I could shorten the Revell hip. I considered cutting around the front circular joint and moving it back and reattaching. I decided to laser new hips because thats easier with making the slot for the leg extension.

Cheers,
Josh

 

[Hagoth]

Here is the basic motion configuration.
NOTE: These shapes are not model dimension accurate. This is just a quick sketch to show the relative motion of the parts.

Key points of reference.
The leg does not pivot through its center but rather around the orange pivot point to the left end of the blue hip blade.
The green cam pin is attached to the hip blade
(We can see these two features and relative positioning on the images of the resin model posted above)
The small dark rectangle and post at the center is part of the leg and rotates with it around the orange pivot point.
The light blue larger rectangular part with the slot spins through its center around the post in the circle of the light grey leg.
The purple motion limit stop pivots around the lower pivot point attached to the leg.
The upper pivot point slides in the slot on the blue hip blade. (The slot is not at the right angle but the point is made)

As the leg is rotated back and forth the large rectangular shape with the slot will always spin in the same way and the motion limit stop will separate from the leg automatically. The animators would not have had to pay any attention to setting these.

It occurs to me that a linear drive stepper motor in the slot would be all that is needed to move the leg. This could be motorized.

Hope this makes it more clear what is going on.

 

[Sym-Cha]

So ... in other words ... most of the modelkits in any size have been wrong by pivoting around the center point in the leg and hip blade except Bandai :

I don't have this kit yet, so it just dawned on me to check out the information on scalemates.com and there it is ... working as it should.

Chaïm

 

[Sym-Cha]

The blue moon kit I chased up at the very beginning but no longer seems to be available Chaïm.

And you're right, I could shorten the Revell hip. I considered cutting around the front circular joint and moving it back and reattaching. I decided to laser new hips because thats easier with making the slot for the leg extension.

Cheers,
Josh

So ... we can expect a Starks Enterprise Ltd. AT-AT Upgrade Kit in the near future

Chaïm

 

[Hagoth]

So ... in other words ... most of the modelkits in any size have been wrong by pivoting around the center point in the leg and hip blade except Bandai :

View attachment 1458342

View attachment 1458343

I don't have this kit yet, so it just dawned on me to check out the information on scalemates.com and there it is ... working as it should.

Chaïm

Bingo! Bravo Bandai!

Those Bandai instructions show it pretty well. Nice find. Didn't think to look for those. I also don't have the kit yet but I'm on a waiting list for it. One remaining question for me is where is the upper pivot point on the motion limiting leg extension? Where does that pin sit in the hip slot at the neutral leg position? I've watched several build videos of the kit but have not seen the back side of that part clearly enough to determine. I'm pretty sure it is lower down than where I put it in my motion example layout.

 

[Analyzer]

Yep, the Bandai kit captures that movement perfectly. It is amazing how faithfully they recreated the animation parts with the exception of the pistons. They just give you the option of various static positioned parts to use that have them in a choice of 3 combinations

They even modeled all the little thumb screws and stuff use to hold the parts in position during animation. I really wish they would do a 1/72 version. That would be a grail kit for me

the little pin is supposed to go in that long oval slot for the rectangular piece. That causes it rotate when the leg is moved
Here Sometime it pops out since if you move it too quick since it is only loosely fitted here

Here it is in in different positions when the pin in is the right spot. You can also see the bit on the back of the leg that travels though the slot in the hip

And speaking of the hip, It pivots out as well as up and down. Something I did not fully notice until the Bandai kit

It's the only commercial kit you can position for this scene without doing major work on it

 

[Hagoth]

Oh yeah, I would love to have a 1:72 scale Bandai kit. It's been a struggle just to get a 1:144. My grail kit would be a 1:35 Bandai quality kit.

So Analyzer, given that you have the kit how hard would it be show a picture of the back side of the motion limiter leg extension? From the pictures I would guess that the pin that slides in the hip slot is about 1/3 of the way down from the top? I can barely see a hint on it in one of the pictures from the inside of the hip blade. These are great pictures of the kit and its motion range.

It's impressive the amount of motion that Bandai captured. I remember comparing my MPC kit to what I saw on screen, especially that last picture you posted with the hip extended out and wondering "how did they get that movement out of this". I also have a distant recollection that the leg did not rotate on the hip through its center point but didn't pay much attention to the difference at the time. At the time I thought it must be an animation error. Now that this has become a focus for me I find this is all very fascinating now.

 

[LadyFerry]

I took the liberty to grab these pictures from that youtube feature I posted earlier. Perhaps someone can get these same images from a 4K resolution source?

View attachment 1456558

View attachment 1456559

View attachment 1456560

View attachment 1456561

Now it's very likely and possible this was the largest AT-AT which the ILM folks had build, so it may differ slightly from the smaller ones made ... perhaps someone can enlighten us?

Chaïm

Hi, have you seen this website for 4K screen caps?

Star Wars: Episode V - The Empire Strikes Back (1980) [4K] - StarWars Screencaps.com

Screencap Gallery for Star Wars: Episode V - The Empire Strikes Back (1980) [4K] (4K 2160p Quality, The Movies). Luke Skywalker, Han Solo, Princess Leia and Chewbacca face attack by the Imperial forces and its AT-AT walkers on the ice planet Hoth. While Han and Leia

starwarsscreencaps.com

 

[starks]

So ... we can expect a Starks Enterprise Ltd. AT-AT Upgrade Kit in the near future

Chaïm

Surely people wont buy my chook scratch lol


Ok I have been playing with the file. I still need to get to looking at the leg extension but the center is working as I think it should however the angle of the rectangular locking tab doesn't line up with what I see on screen so I need to set the leg pivot point in the hip higher, but it is on the right track. By changing the leg to hip angle (closer to the second photo) and setting the leg mounting point higher that locking tab will rotate downwards.

I was thinking about mounting the hip to the body and I have decided to graph in the end of the Revell hip so it uses the models factory mounting point and ball in socket locking system to keep things simple. I can shave down the Revell body mounting post for the hip mount and I have made caps to go on top. Needs screw heads but the cap will make this appear as the studio model.

Cheers,
Josh

 

[swmodelfan1977]

Hello, please allow me to jump in.
Hope this thread would help or give you some hint but 7 year old.

Project: Revell AT-AT Walker

Hello Everyone, The planning stage is done, so it's ready to start on my rendition of an Imperial (AT-AT) Walker. I'll be using the Revell AT-AT kit #1859 and my goal is to construct an accurate stop-motion replica of the onscreen miniature in 1:72 scale. My intention is to use as much of the...

www.therpf.com

He did great job.

 

[Analyzer]

Hello, please allow me to jump in.
Hope this thread would help or give you some hint but 7 year old.

Project: Revell AT-AT Walker

Hello Everyone, The planning stage is done, so it's ready to start on my rendition of an Imperial (AT-AT) Walker. I'll be using the Revell AT-AT kit #1859 and my goal is to construct an accurate stop-motion replica of the onscreen miniature in 1:72 scale. My intention is to use as much of the...

www.therpf.com

He did great job.

Sure did!

And this post here from you really sheds some light on a possible solution for the pistons as well as a great shot of the rubber band thing

Project: Revell AT-AT Walker

THE LEGS Part XIV The Caps and Panels. Being such misc parts, I found some of the caps quite challenging. The problem was how to mill the outer impression. I couldn't mill them while they were on the sheet because of the lack of clearance I had. And I prematurely cut them down too short for...

www.therpf.com

 

[Hagoth]

Hello, please allow me to jump in.
Hope this thread would help or give you some hint but 7 year old.

Project: Revell AT-AT Walker

Hello Everyone, The planning stage is done, so it's ready to start on my rendition of an Imperial (AT-AT) Walker. I'll be using the Revell AT-AT kit #1859 and my goal is to construct an accurate stop-motion replica of the onscreen miniature in 1:72 scale. My intention is to use as much of the...

www.therpf.com

He did great job.

Thank you for the heads up on that thread! Huge help! Fantastic project and detail captured there. Confirmed for me where the pin on the motion limiter leg extension that slides in the hip slot is located.

Looks like you have a lot of insights yourself as you have already traveled down the road we are headed. Any additional insights you can contribute would be very appreciated.

 

[starks]

Hello, please allow me to jump in.
Hope this thread would help or give you some hint but 7 year old.

Project: Revell AT-AT Walker

Hello Everyone, The planning stage is done, so it's ready to start on my rendition of an Imperial (AT-AT) Walker. I'll be using the Revell AT-AT kit #1859 and my goal is to construct an accurate stop-motion replica of the onscreen miniature in 1:72 scale. My intention is to use as much of the...

www.therpf.com

He did great job.

That things insane! Fantastic work by the OP.
And thanks for sharing.

I can see myself going down this route as a scratch build when I get a few more projects accomplished. I dont know about metal though haha.
Interesting the pivot point for the leg is so large.

Cheers,
Josh