Revell At-At WIP

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.


Hagoth

Sr Member
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.
4fWWGBS.jpg

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!
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Hagoth

Sr Member
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

Active Member
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.
yaYEKS1.jpg


Then the file
YpK03fF.jpg


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.

d7Pru5t.jpg

TgXdUqy.jpg



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.
TA0fxhq.jpg

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

Sr Member
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

Active Member
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
 
Last edited:

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Sym-Cha

Master Member
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?

AT-AT.jpg


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?

Revell AT-AT.jpg


AT-AT-joint.jpg


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
 
Last edited:

Hagoth

Sr Member
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

Active Member
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

Sr Member
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.

Joint Motion.jpg


Hope this makes it more clear what is going on. :)
 

Your message may be considered spam for the following reasons:

  1. Your new thread title is very short, and likely is unhelpful.
  2. Your reply is very short and likely does not add anything to the thread.
  3. Your reply is very long and likely does not add anything to the thread.
  4. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
  5. Your message is mostly quotes or spoilers.
  6. Your reply has occurred very quickly after a previous reply and likely does not add anything to the thread.
  7. This thread is locked.

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Top