Making a Mad Max R/C Car Part 1: Building a Custom Body Shell

By Bill Doran, Punished Props

I've been jonesing to mod an R/C car for a long time and this project turned out to be a massively fun challenge.

I'm sure I'm not the only member of the Tested community who grew up with an R/C controller firmly planted in my hands. At one point or another, we had every manner of radio controlled vehicle under the sun on our workbench. It's been a good 20 years for me, but I figured it was high time I got back into the hobby and let me tell you, it's never been a better time to start playing with R/C vehicles!

As a way to justify dumping money back into this hobby, I decided it would be fun to modify an R/C car to look like something that pulled off the Fury Road. That's right, I'll be making my little car look like something Max Rockatansky would be proud to drive through the wasteland. The victim for my little experiment is the LaTrax Teton 1/18 scale truck. As an entry level vehicle, this little fella is a really impressive beast!

This build will be a multi-article adventure over the next couple of months, as there are many facets to the project. I'm starting with the body shell, since it'll be the platform on which the rest of the build is constructed. Most R/C car bodies are vacuum formed plastic shells that are perched on the chassis using pegs. I figured I'd build my new body in the same way.

To get started, I knew I would need some good, properly scaled reference photos of the stock car body shell. So, I put the car against a cutting mat with a grid on it and took a handful of reference photos. To ensure that my photos were as useful as possible, I used my longest lens (200mm) to cut down on focal distortion.

These photos were dumped into Photoshop so that they could be scaled appropriately to one another and lined up, all pretty like! This left me with some nearly perfect orthographic shots of the car body, from which I could start to construct the 3D model of my new design.

Using references from the Mad Max movies and video game, I whipped up my own car design on paper. It isn't any one particular car from the series, just something I thought looked kind of neat.

With my design roughed out, I got to modeling. The 3D model for this project was done in Fusion 360. I put my reference photos into the 3D space, scaled them to the appropriate size, and fleshed out my custom form right on top of the reference images. This is the same way I did my Mister Handy robot model and it ended up being fairly accurate, so I was confident that the sizing on my model would print out at least pretty close to what it needed to be to fit on my R/C truck body.

This body was too big for my 3D printer, so I cut it in half and printed the two parts out separately. The prints came out fairly tidy, but definitely needed some cleanup work, especially on the nose and rear end of the body. Every square millimeter of the PLA print was sanded down to a 220 grit. Some of the more rough areas were filled with an air drying spot putty and then sanded down.

I'll admit that my 3D model wasn't exactly what I had intended to make. I hit the border of my skill level on some parts and resorted to "fixing it in post". That is to say, I let the 3D printer do it's job and then planned on cleaning up or adding to those parts with traditional model making skills later in the build. For example, the inset window areas had some really whacky overhangs. I filled them in with Bondo and sanded them down, creating a much nicer bevel.

At a certain part of the refinement process, I decided it was time to mate the two parts of the car body, so they were superglued together. This left a little bit of a seam, but that was quickly remedied by filling it with more super glue and sanding it flush.

To save on printing time and plastic, I printed the body with the negative space below the car completely empty. To mold or vacuform this part, that area would need to be filled in. The quickest and easiest way to achieve this was to cut out a quick support structure from insulation foam. This was made even easier with the employment of my trusty band saw, Jabba the Cut.

At this point I got a little bit impatient. I wanted to pull a copy of the form on my vacuum former, but I had a hunch the 3D printing material wouldn't hold up so well. I also really wanted to see if the form would fit on the car chassis. So, throwing caution to the wind, I formed a thin piece of styrene over the 3D print, getting a decent copy… and also melting the roof. Just like I would on a real car, I fixed up the indentations with a little bit of Bondo and a lot of elbow grease.

This first pull was actually pretty good and it told me a couple of important things that I needed to change. The rear of the shell was running into the rear bumper. I trimmed it so that it would go over the bumper. Also the wheel wells were a little wide, especially in the front where the steering motion caused the tires to scrape the shell. A little bit of bandsaw work thinned our 3D print just enough to give it clearance.

Confident that this updated form would produce an appropriately shaped shell, I set about adding a little bit more detail to the body. Using some half round pieces of styrene, I added some runners to the roof, hood, and sides of the car. The rest of the details would be added onto the shell after it was vacuum formed.

To avoid melting my 3D printed master again, I decided to turn it into a solid hydrocal vacuum forming buck. This was done by claying up the sides of the model to make them nice and smooth, making a quick mold box around the part, and then covering the entire piece in alginate. Alginate is a quick, cheap way to make a one-time use mold.

I've made some decent molds in my day, this was not one of them. I cast the positive copy from my alginate mold using hydrocal and allowed it to set overnight. The copy that popped out was pretty good, but pockmarked with many imperfections, caused by bubbles in the alginate. A little bit of cleanup work later, however, and we had a nice, pretty buck! I also took the chance to carve in some grooves for the hood and door gaps.

With my buck all ready to go I could finally pull a copy of my final part! I went with a thin styrene plastic for the final part, because I have a lot of it lying around. I'm pretty sure the original shell out of the box was done in polycarbonate, but I didn't have any on hand.

Overall the pull came out well enough that I could work with it. I definitely need to build a better vacuum forming machine and ditch my disassembled toaster rig, but that's an project for another day! I trimmed the part from the stock material and cut out the windows. I'm pretty stoked with how it turned out and I'm really looking forward to adding more details!

So far this has been an incredibly satisfying build. I've been jonesing to mod an R/C car for a long time and it's turned out to be a massively fun challenge. I'm really looking forward to building more tiny parts for this thing and getting some paint on it. Thanks for reading and I'll see you all in the next part of the build!