Making an Enclosure

One of the more difficult things I've faced so far in this project is finding a good enclosure. I need something that will fit my electronics and will also fit in my RC car. I also want something that's fairly water resistant since it tends to rain a lot around where I live near Seattle.

I tried food containers (the round corners posed challenges), a Savox servo plastic box (the lid won't stay closed), and some project boxes that I got on Amazon (they're pretty heavy and tend to be too tall for what I need).

A few of the enclosures that I tried.

Nothing was working, so I looked into making my own.

Blast From My Past

Long ago I thought I wanted to be a mechanical engineer (I still think it would be a ton of fun). After high school, I worked in a metal fabrication shop at this place for a year before starting college, and again a few summers between semesters. Working there, I did everything from assembling hoppers and huge X-ray cabinets (used to inspect airplane parts), to TIG and MIG welding, to operating the mill and lathe, and a bunch of other odd jobs.

The engineers there knew that I was going off to college soon, so they occasionally invited me to show them what they did in the engineering office. Mostly, though, I helped out in the shop. I have very fond memories of listening to the machinists and welders bitch about how those dumbass engineers designed a part that can't physically be made. (Nobody there was dumb, they just each had their own skillsets).

It was a really great job, especially at my age, and I learned a ton of life skills and engineering skills to boot.

My Design

So when it came time to design something, I didn't hesitate to find a free CAD program, go through the 10 minute tutorial, and get to designing. I used Tinkercad, mostly because I recognized the company and it was the first one I landed on. It's a bit short on some features like rounded edges, but I managed to make do with the built-in primitives. A few measurements on the RC car and my electronics, and a few hours of intermittent work later, I had a design.

The custom enclosure that I designed with Tinkercad.

I was concerned that it would be expensive to have this thing made. Then I remembered that 3D printers are a thing now, and I found that there are even online services where you can have someone make your part! I used Treatstock, and I found the process to be very easy. Best of all, I only paid about $25 to have GRM3D manufacture and deliver the part to me!

Results

I am very impressed with the quality of the part. The measurements are accurate and precise, surfaces are smooth, corners are clean, and even the overhangs are clean enough (though I tried to keep them to a minimum in my design). I built in a 0.5mm tolerance where my parts interface with one another, and they exceeded my expectation. Based on what little I know about 3D printers, achieving good quality is sometimes tricky, so I'll definitely return to GRM3D for future 3D printing needs.

My part fits where the battery holder normally goes.

Everything fit together like a charm. "Measure 3 times, design once" paid off. My design allows me to layer my components into the box, one on top of the other. I also added some port holes so that I can reprogram the microcontrollers without disassembling everything.

9DOF IMU

Sparkfun GPS-RTK2

My main board mounts on the other end.

A Google Coral Dev Board mounts on top of the GPS and IMU. I may integrate this in the future for machine learning and/or computer vision.

The port holes lined up perfectly with the USB ports.

The hex nut recesses were a perfect press-fit.

Plugging in a USB cable through the port holes.

The port hole cover.

All assembled.

Mounted on the car with wiring in place. I mounted the receiver in the box.

View from the right side. The large cylinder is the GPS antenna. The bent antenna is for the LoRa radio.

View from the left side. Note that the car's receiver box has been removed since the receiver is now inside the green box.

Conclusion

Overall, I couldn't be happier with how my first attempt at this custom designed part turned out. There's a few minor things I would change if I do it again, like increase the screw hole diameter (because it's really hard to get a drill head down in there), and I wouldn't bother trying to tap the plastic holes but instead just use self-tapping sheet metal screws.

You may also note that my color choices are... terrible.