Project: Revell AT-AT Walker

rbeach84 · Feb 3, 2016

Perhaps the rubber band is involved with keeping the pistons in tension upwards and the cam drives them down. But what drives the cam? Perhaps the cam is in a fixed orientation so as the leg is moved, the pistons go up and down in response (this would make the stop motion much easier as the pistons would position automatically & consistently.)

This makes me wonder that the modelers must have been thinking "everything should move as needed when I move the foot" - in short, the spatial position of the foot would index the movement of the rest of the "limb". Because the slot & pin features makes me think this is part of the design. Still, it must have been very difficult to pull off this "walk".

BTW, the advantage to a rubber band is it is thin, can go around corners and is easy to adjust the tension (just use different sized bands.) On a display piece however, they lack durability.

R/ Robert

Sourdoh · Feb 3, 2016

This is getting rather complicated, isn't it?

anamorphicWayne · Feb 3, 2016

I think you're right, rbeach84, about adding tension. It looks to me that the rubber bands may have been wrapped around the core of the cam a few times. I believe there has to be an arm or wire connecting the cam to guide pin. And it's at the right angle as not to get stuck within the channel. The cam appears to have 'posts or connectors' on each side. If you look at the leg on the left, the pistons are in their extreme positions and cam is rotated to line up with them.

VFX Freak · Feb 3, 2016

Wow! I haven't had time to visit in a while. Insanely great job! With the emphasis on insane. I truly admire your skill and dedication.

Sent from my iPad using Tapatalk

Junk Pilot · Feb 3, 2016

From what I've seen the pistons connect directly to the cams through those small pins on the cam itself.

I'm also starting to believe the pistons were animated by hand and aren't connected mechanically and that the rubber band was there just to prevent slippage during filming. This is because I'm almost sure I've seen the pistons in different positions when the legs of a different AT-AT were in the SAME position. Could I be wrong about this?

anamorphicWayne said:
I think you're right, rbeach84, about adding tension. It looks to me that the rubber bands may have been wrapped around the core of the cam a few times. I believe there has to be an arm or wire connecting the cam to guide pin. And it's at the right angle as not to get stuck within the channel. The cam appears to have 'posts or connectors' on each side. If you look at the leg on the left, the pistons are in their extreme positions and cam is rotated to line up with them.

View attachment 586692

swmodelfan1977 · Feb 4, 2016

Junk Pilot;
Hand-animated piston might be happened as even broken piston rod was shown on film as you may know. And probably same AT-AT has lost leg-tension part. I assume speeder attack made them.

Wayne;
As you noticed on my design, guide pin is linked to half-moon cam by one linkage to drive the cam. While struggling about the rubber-band(?), I am re-shaping of linkage in order to avod exposure from the C-shape slot. I am still on virtual field but not started to cut styrene sheet other than prototyping.

anamorphicWayne · Feb 4, 2016

Junk Pilot said:
From what I've seen the pistons connect directly to the cams through those small pins on the cam itself.

I'm also starting to believe the pistons were animated by hand and aren't connected mechanically and that the rubber band was there just to prevent slippage during filming. This is because I'm almost sure I've seen the pistons in different positions when the legs of a different AT-AT were in the SAME position. Could I be wrong about this?

I thought the same Junk Pilot. But then how could Cinefex, Berg, Tippett and ILM make it all up. Just to glamorize their profession, not likely. I think they had the pistons run mechanically, but sometimes things don't work out as plan. And when you're in crunch time (during animating), you have to fudge it so you can finish the shot. These shots could take a whole day to do and you're dealing with film on top of that.

Who knows, the rubber bands could have been for a quick fix for something. But it looks like the Fly Wheels on the Knee Capos were done by hand. They sure don't look like it.

swmodelfan1977 said:
Junk Pilot;

Hand-animated piston might be happened as even broken piston rod was shown on film as you may know. And probably same AT-AT has lost leg-tension part. I assume speeder attack made them.

View attachment 586913

Wayne;

As you noticed on my design, guide pin is linked to half-moon cam by one linkage to drive the cam. While struggling about the rubber-band(?), I am re-shaping of linkage in order to avod exposure from the C-shape slot. I am still on virtual field but not started to cut styrene sheet other than prototyping.

View attachment 586915 View attachment 586917 View attachment 586918

Aaaa, that's coming together swmodelfan1977. I never thought of using a curved arm to run the cam. Excellent.

I've discovered, while test assembling the legs, that outer Knee Cap should be permanently attached to the Lower Leg. Otherwise, it'll be rotating around as the leg bends.

So, that leaves the inner Knee Cap/Bracket to apply the tension needed against the two leg parts.

swmodelfan1977 · Feb 5, 2016

I agree with you for outer knee cap. It must be fixed.

Sourdoh · Feb 20, 2016

Two weeks and no new posts? Did this die?

joberg · Feb 21, 2016

Good work swmodelfan1977...yes, that knee cap has to be fixed. I still believe that those pistons are with springs inside them and the the weight of the model is enough to maintain that half-moon flat on one piston, then on the other when the leg is changing angle/position.
As far as animating those piston frame by frame? Too much work!! Should I start to explain what's involved animating those? Don't have time to do so, 'cause it's way complicated (and loooonnnng)!

anamorphicWayne · Feb 21, 2016

joberg said:
Good work swmodelfan1977...yes, that knee cap has to be fixed. I still believe that those pistons are with springs inside them and the the weight of the model is enough to maintain that half-moon flat on one piston, then on the other when the leg is changing angle/position.
As far as animating those piston frame by frame? Too much work!! Should I start to explain what's involved animating those? Don't have time to do so, 'cause it's way complicated (and loooonnnng)!

Thanks joberg

, but I'm aware of the laborious and painstaking task of stop motion. :wacko It's probably why ILM went thru a mechanical means to move the pistons as oppose by hand. It appeared they had their hands full with just getting the legs to pose that they didn't need to worry about that.

I'm working on the Piston mechanism as I'm prepping all the legs for a test fitting, so I should have something significant soon. Thanks for your patience everyone.

swmodelfan1977 · Feb 21, 2016

joberg said:
Good work swmodelfan1977...yes, that knee cap has to be fixed. I still believe that those pistons are with springs inside them and the the weight of the model is enough to maintain that half-moon flat on one piston, then on the other when the leg is changing angle/position.
As far as animating those piston frame by frame? Too much work!! Should I start to explain what's involved animating those? Don't have time to do so, 'cause it's way complicated (and loooonnnng)!

Oh my post was bit late.

(Edited)

Hi joberg,
Thank you very much for your comment. Yes, piston movement was made by link and cam automatically following leg animation according to Cinefex as Wayne quoted too. Also it was talked in other thread. And the mechanism was not robust unfortunately at that time. It is fun to chase it as well as looking at other people how they are realizing.

I am still in drawing phase but have to go biz trip for a week.

Hi Sourdoh,
As long as RPF server and its data still alive, two weeks won't be no matter. (Too old thread might be archived probarbly.)
He(Wayne) will be back:cool when he become ready.

anamorphicWayne · Feb 21, 2016

Opps. Double post....

swmodelfan1977 · Feb 21, 2016

anamorphicWayne said:
Opps. Double post....

anamorphicWayne · Feb 21, 2016

I know this isn't significant, but at least it's something for now............

THE LEGS Part XVI

The Toes.

Okay, for all the 16 Toes. I thought I'd make them out of 3/16 small aluminum blocks and then mill off 2/3, so they can be easily inserted into the Toe Shells.

Afterwards, I drilled the joint holes and tap them with a 4-40 tap.

The Toe Shells were basically made from styrene.

All were cut from a template.

I had each Shell line up with its corresponding metal Toe.

From there, I basically built around it using more styrene and putty.

After that, I added details, scribed the panel lines and gave them all a priming.

Each Toe will eventually be epoxy to each Shell.

TazMan2000 · Feb 21, 2016

Sourdoh said:
Two weeks and no new posts? Did this die?

https://m.youtube.com/watch?v=grbSQ6O6kbs

TazMan2000

anamorphicWayne · Feb 21, 2016

THE LEGS Part XVII

Misc Stuff.

The Leg Tensions are made from 3/16 aluminum and are basically cut and shaped by hand.

The Flywheels (top) were cut from a 1mm sheet of aluminum. They'll need to refined to into the Upper Leg Caps and outer Knee Caps

The Guide Pins are cut from 3/32 and 7/64 rods.

I had to make 'T' Head Bolts as they were non-existent to find in my area. They're comprised of cut 4-40 bolts and small 2mm thick aluminum bars.

I also needed something as a shock absorber in the Foot Chamber. I found this at the dollar store, A Snake in a Flashlight. Go figure.

For Tie Downs, I thought of using Easy Key Release Key Chains. Because they have a hole on the top 'clip in', they can be secured to inners of the foot via an allen bolt.

anamorphicWayne · Feb 21, 2016

TazMan2000 said:
https://m.youtube.com/watch?v=grbSQ6O6kbs

TazMan2000

Ooooooooooo!!!!! :eek

anamorphicWayne · Feb 28, 2016

THE LEGS Part XVIII

The Foot Shells.

Thinking the Foot Shells would be too labour intensive to make, I thought I try casting them instead. Never done it before so it goes.

I started with a master. Basically made out of layered styrene, fitted over the Foot Chamber to ensure a proper fit.

The only mold making material I had available was EasyMold Silicone Rubber. It seem pretty straight forward to use.

I made a fence out of corrugated plastic, glued on a wooden base.

I poured in the stuff and waited over night.

The master popped out without any problems. Next, I poured in polyester resin. I didn't have anything available, so I took a chance the resin wouldn't shrink too much.

Well, it did. By a millimeter or so. They didn't line up with the Foot Caps. Errr! Luckily, they only shrunk on the outside, so they still fitted over the Chambers.

My only options were to recast them with a better resin or use what I have and add a layer of styrene. I choose the styrene option.

It wasn't too much of a hassle to do. By the end of the day, I had them all done and primed.

The next step was to make up the drainage greeblies, which wasn't a big deal.

anamorphicWayne · Feb 28, 2016

THE LEGS.

Another test fitting.

I managed to get all the leg parts milled, drilled and tapped, so I could do a test fitting with all four legs.

Unfortunately, I found issues with some of my joints which is forcing me to do some changes. More work is needed.

Project: Revell AT-AT Walker

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