Make a Large-Scale Star Wars AT-AT Walker

3/11/18 Update: This project was featured in an article on the Star Wars Blog!

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A few weeks ago, I found myself in need of a large prop for a four-week event at the church where I work. Since Star Wars was part of the fun, I began to imagine what kind of colossal Star Wars reference we could place in our building. While there were many worthy options, I couldn't get past the idea of having a 17' AT-AT in our lobby.

For this particular build, I knew that we would want to avoid having to place any anchors in the wall, and I knew that floor space would be limited, so I had the idea of half of an AT-AT (just an AT?) protruding from the wall.

I also knew that I would want to put most of the weight in the feet and lower legs and keep things as light as possible in the upper parts of the statue to keep things from tipping over.

With just the faintest idea of how things might progress from there, I decided to scour the internet for reference images. Fortunately for me, I quickly stumbled upon Seamster's amazing wooden AT-AT Instructable. While Sam built his 20" tall, I figured the plans could be scaled to suit our needs of making it about ten times as large. In retrospect, I'm happy to say that this worked well and was a huge help in roughing out the main pieces.

Before I proceed any further, I have to say that this was a shared labor of love. Several people contributed in significant ways by helping on multiple days of the build, and we also had teams of volunteers who were a huge help and encouragement along the way as well. This was a team effort, and I'm incredibly grateful for all who helped bring this crazy project together.

Here's a quick overview of the materials we used:

• 95% of the machine was built from extruded polystyrene (XPS), also known as foam insulation boards. We used various thicknesses.
• Loctite foamboard adhesive after we realized that Liquid Nails wasn't holding well
• Plywood for the inside layers of the legs and the bottoms of the feet
• 4"x4" posts for stabilizing the legs

Unfortunately, foam boards are not cheap, so neither was this project. All told, we invested about $1K in materials.

As always, your likes and votes on this post are super encouraging! Thanks for being an incredible community here.

But enough about that, let's get building!

Step 1: Cutting Out Basic Shapes

The first challenge was how to enlarge Sam's plans. We could have used a digital projector, but I decided to go old school: I printed them off on transparency film, and I and a team of people started the process of projecting the plans onto the wall and tracing them onto sheets of foam insulation board.

As you do this, it's helpful to have a notebook full of reference photos on hand so you can quickly choose which parts should be traced on thicker or thinner pieces of the foam board.

While parts were still being traced off, some of our amazing volunteers started the process of cutting out the pieces using a jigsaw. This part is incredibly messy, so you'll want to make sure you're working in an area that is easy to clean. You will be covered in the stuff.

Alternatively, we also tried using a heat knife to cut out the shapes, but for most of the cutting we found that we got better cuts with the jigsaw.

Step 2: Working on the Feet

Sometimes it's difficult to know where to start on a large project, but we decided to begin with the feet. Beginning with a sheet of plywood and then adding pieces of foam board to match the overall shape, we quickly realized that while the plans we had were a helpful starting place, we would have to adapt things constantly to make sure we achieved the look we wanted.

Again, we tried using the heat knife to add some shaping, but ultimately, our orbital sander ended up being the easiest way to taper and round our edges.

Once things were looking good, we cut away the inside of the feet with a sawzall (we should have made these hollow from the start), and installed the upright posts into the center of the legs, but we later decided to offset these posts a few inches so that the legs would be in the center instead.

Step 3: Building Out the Legs

Once the feet were mostly done, we did a rough fit for the legs. We had the option to build the legs out of foam board around the 4"x4" posts, but we ultimately decided to use plywood sheets inside of the upper and lower leg pieces to add a bit of thickness and create the stability on which everything could hang. This also gave us something sturdy to secure to the posts when we were ready to decide on the position of the legs.

The half inch pieces of foam board were perfect for adding greebles and details, and we also used the heat knife to indent lines. These built out and cut away pieces were a huge part of making the sculpture look realistic.

As we finished up the legs, and stood them up for the first time, we finally had some hope that this project might actually work. And yes, we had to tell every person who walked by that it wasn't going to be pink forever. :)

Step 4: Fashioning the Undercarriage

Next, we started piecing together the undercarriage. We build it somewhat hollow to save on foam, but mostly this part was a pain. Once we stood both legs next to one another, we finalized the distance between the legs and built out the undercarriage and hips to fit that width.

Though this part isn't the most exciting, it was helpful to have some solid areas of foam to provide structure and strength for the body to set on.

Step 5: Shaping the Head

When we started working on the head, we realized that things were both going to get more fun and more difficult. Honestly, getting the initial shape and holding it together long enough for the glue to cure was the most challenging part.

It wasn't until we started working on the body that we realized we could secure the foam together with sheet wall screws. That discovery was a game changer for us, and it allowed us to do more each day without worrying about the whole thing collapsing because of uncured glue.

Step 6: Building the Body

When we started construction on the body, we really started experimenting with using screws to hold pieces together as we worked. As a result, I was able to hand off this entire section to a team of volunteers who finished roughing things out that evening.

One of the most rewarding parts of the whole build was being able to work with volunteers - many of whom had never met one another and had never used power tools before. It was a blast to show people how to use the tools, give them an opportunity to use them as a team, and then encourage them with their results. It was way more fun than doing this whole thing alone!

*Pro Tip: If you're building outside, make sure you're able to get the body through the doorway before you put it together or else you're going to have some sad times. :D

Step 7: Adding Details

Like any project, things really begin to get fun when you add in the small details. As you can see in these photos, the little details and rounded or chamfered edges really made the legs look much more finished.

The guns were also a bit of a mystery to me, but I ended up using some large dowels and pieces of pool noodles along with some scrap pieces of pvc board to cobble together the large guns. It looked pretty junky until they were painted and installed into the head.

The air intakes under the head were great to work on too. Unfortunately, I worked on these before we figured out the sheet rock screw technique, so instead it was just a mess of painters tape.

Step 8: Painting and Detailing

We used three different shades of latex paint (spray paint will likely melt your foam), but we probably could have done fine with two. For the darkest, we tried to follow the look and feel of the reference images, so those areas were applied with a dry brush.

Goodbye, pink foam! Hello, awesome!

Step 9: Putting It All Together

The final installation began with getting the legs in place and securing them together and installing the undercarriage. Once those were in place, we kept the undercarriage supported by a person on a ladder. In retrospect, it would have been great to go ahead and tie off the back of the undercarriage to the ceiling at this point.

After that, we added the body, secured it to the undercarriage, and used metal rope to suspend the back of the sculpture from the ceiling.

Lastly, we secured a protruding 2" x 4" out the back of the head and then connected that to the pieces inside the neck hole in the body and suspended the head with metal rope. Easier said than done, but after a few minutes, we had everything connected.

Step 10: Finishing the Neck

Of all the weird things that gave us trouble, finishing out the neck was a bit of a pain. After trying a couple of things, I finally wedged a few strips of cardboard around the neck inside the head and body holes, and we used the cardboard as a structure to which we affixed pieces of pipe insulation.

It wasn't a perfect solution by any means, but it worked.

Step 11: Finishing Touches

With the AT-AT complete, we finished out our lobby with thirteen Star Wars cardboard cutouts, several nice costumes (I got to be Darth Vader), and free popcorn and sodas for everyone who attended.

Without a doubt, this build has been the largest and most complex prop I've ever made, and I'm especially grateful for the great friends and volunteers that helped make this idea become a reality.

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Got any great tips for working with extruded polystyrene or building large props? I would love to hear from you in the comments!

And like always, if you enjoyed this tutorial, please give me a like or a vote in the contest. Thanks!