[MOC] Imperial AT-ST

[Falcrum]

And there it is, the grand finale of my MOC miniseries; the pride of the Imperial Army, a machine spreading fear in the rebel ranks – the AT-ST. Also my Magnum Opus.

AT-ST by Falcrum by Jakub Grochowski, on Flickr

Although the walker appeared in the Empire Strikes Back for the first time, it’s most famous for its role in the Return of the Jedi. A handful of seconds we see it walking cost the animators whole 2 months of their time, but thanks to that the 39 year old animation amazes even today.

Shortly on the project’s history

The building started in August 2021 and lasted about a month, which allowed me to construct half of the head. It was only in this June that I took the project seriously. I had a first prototype ready for an exhibition in July – by that time I had spent 150 hours on the project. The event exposed multiple weaknesses of the model; I introduced numerous structural improvements, which gave me 50 further hours of headache.

Let’s talk technical details

I estimate the walker itself counts 1000-1500 pieces without the base (legs alone, without the feet, have around 400). The AT-ST was my first model which forced me to look at structural aspect of things, and not only the looks. Had the feet not been fixed at the base, the walker wouldn’t be able to stand on its own, let alone walk, since its centre of mass is almost directly above it’s toes, and the head would inevitably tip forward and collapse. At least I got a chance to use my engineering intuition.

Speaking of which…

The AT-ST legs, ah yes. I unironically think they could be studied at the first year of structural engineering, since they experience every single form of material stress possible – tensile, compressive, shear, bending, torsion and moment. Some of those physical quantities are bordering the ABS durability, a material which LEGO is made from. Torsion in the hips rotated the legs by roughly 20-30 degrees, which I didn’t know could be done. The tension in the  “Achilles tendon” is so high that only a rubber pneumatic hose provides enough friction to withstand it.

The reason behind the magnitude of the stresses are the legs, and their peculiar, impractical and convoluted shape and what they are holding – a 300 gram head, protruding far towards the front. Needless to say, this combo doesn’t leave a slightest bit of hope for any articulation.

Although my model is strong enough to stand on its two chicken legs (which took a while to achieve, as mentioned above), I decided to prop it on a strut to reduce the stresses the pieces experience. Since LEGO bricks are made of plastic, even despite its very high quality, its Young’s Modulus is still laughably low (it’s not stiff at all), which tends to be a problem in many structural applications.

The strut, then, is a stabiliser. Given stresses that high, any asymmetry in the legs or the central segment can lead to the latter leaning on one side, the head rotating, stresses redistributing and accumulating in the legs in the transverse direction (the direction of studs), which would inevitably lead to the machine collapsing. Proofing the model against such stresses is impossible in this scale, hence the strut, which doesn’t let this happen.

Attaching tiles to both sides of technic liftarms was achievable thanks to a flex cable – pneumatic hose combo, which put one over another has the diameter of one stud. I estimate there are ~65 of such cylinders inside.

The aesthetics

It’s not difficult to spot that the walker predominantly consists of Light Bluish Grey elements, a colour closest to the imperial grey. It was one of the primary requirements for the build, since all brick-built AT-STs I saw relied on Dark Bluish Grey to some extent.

A great deal of emphasis was put on the difficult aspects of the machine, such as he side profile of the legs, the hexagonal vents at the rear, the engine section detail and the feet. Moreover, I wanted the “face” to look “clean and clever”  –  not only to be recognisable, but also accurate. Above all, though, the main objective was fidelity – every single detail on the model can be found in the original (but sadly not the other way round :P) and is not a filler or a creation of my own.

Scale issues: they always arise. The LEGO man doesn’t have human proportions – my model is scaled to the minifig’s width; so if the stormtroopers wore 2 studs tall shoes, they’d observe the model to be about 9 metres tall, or as tall as the AT-ST should be.

 

Conclusion

I’m tired after this journey. As many of us probably know, the word LEGO has been formed from the Danish phrase Leg Godt – meaning play well. Attaining this level of accuracy and structural integrity has cost me 200 hours of work. However, I am pleased, and even proud of the outcome and I think the struggle was worth it all. No, the model isn’t perfect, but none is, and I’m done with correcting it – maybe in 5 years LEGO will have released another batch of revolutionary pieces and I’ll fiddle with the walker again. Until then it’s time to rest and get down to less demanding projects.

Edited October 8, 2022 by Falcrum

[MAVERICK26]

Wonderful job! Sounds like quite an adventure just getting it to stand up.

[Falcrum]

I can see the model isn't exactly breaking popularity records, so here's a little incentive:

And a little bonus:

[La Chupacabra]

Nice but that trans - clear column ruins all 

[Mr Ogel]

15 minutes ago, La Chupacabra said:

Nice but that trans - clear column ruins all 

easy words but not keeping general Lego brick physics in mind - gravity is always right.

[The Stud]

That looks amazing! It feels like it stepped right out of Return of the Jedi.

[Gremer2]

I actually really like it. It's probably the best AT-ST I've seen. I don't mind the trans-clear column, the AT-ST is so unstable that it's unavoidable.

[Falcrum]

Thank you all for the comments, guys, you are awesome :)

[LEGO Train 12 Volts]

Really impressive!