You may have seen my X-47B build log a few months ago. While my latest project isn't nearly as elaborate, it's certainly a lot of fun! I've been experimenting with 3D printing lately, and think it's a great tool for R/C. While printed plastic parts aren't quite light enough for airplanes, they make great multirotor frames. Since I'd been wanting to get into mini FPV racing, this seemed like a great way to do it. Plus, I could easily print and sell kits afterwards if the design was successful. There was just one issue - mini quads are everywhere, and I wanted something more unique. My first multirotor build was David Windestal's RCExplorer tricopter design back in 2010, and I always liked the way it flew. I eventually moved on to other configurations, but thought it'd be fun to have a tricopter again. So, I decided to design a mini tri from the ground up, specifically for FPV racing and with 3D printing in mind.
The first step was to CAD the design. Since the printer is driven directly by the CAD model, it needed to be as precise as possible. Plus, I wanted to keep everything enclosed for a very clean-looking design. This meant modeling every single component, from the motors and propellers right down to each individual screw. Fortunately a copter this small has fairly few parts, so it only took a couple of weekends to complete the design. Here's the result:
And here's a transparent view:
As you can see, everything's packed nice and tight inside the center body. The battery is enclosed as well, with a slide-on top hatch. The design has been optimized for 3D printing, with flat surfaces and chamfers placed so that every part could be printed without support material. This means that no clean-up work is necessary once the parts come off the machine. Next step - making parts!
The first parts I printed were the arms. I originally used white ABS plastic, but later switched to black PLA. It's more rigid and the layers adhere better. Each set of arms takes about 2 hours and 30 minutes to print.
Next came the center bodies. There's a top half, bottom half, battery tray, and hatch. In total, it's about 6 hours of printing time. I let the printer run for a weekend, producing the first "batch" of kits. I bought an assortment of filament colors to add some variety.
Assembly came next. The frame is held together with screws, and no glue is required. This makes for easy assembly, and one of these can easily be put together in an afternoon.
Then it was time to add the electronics. I'm using the following components:
- SunnySky 2204 2300kV motors
- Gemfan 5x3 Props
- Magic 12A ESCs with SimonK
- Glacier 3S 1000mah Battery
- HS-55 Tail Servo
- Panasonic CX-161 Camera
- HobbyKing TS5823 Mini Video Transmitter
My first build used an APM 2.5 flight controller. This was quite big, and took up a lot of space inside the frame. I couldn't even fit some of the FPV gear!
To solve this problem, I switched to the Naze32 flight controller. This is much smaller, and is a popular controller for minis. Plus, I could use an Orange satellite receiver by itself, saving even more room. Here's what the inside looks like now. Even with all the FPV gear and ESCs inside, there's some empty space left over for cooling airflow.
After that, it was only a matter of screwing on the top of the frame and adding the battery hatch. Here are completed pics of both my first and second builds:
And close-ups of the tail servo mount and battery:
Time to fly! The Naze32 was rock solid right from the start, and the tri handles great. The APM version did fine too, though it required a bit more tuning. FPV is a blast, and I'm looking forward to giving racing a try.
Finally, a pic next to a friend's mini quad for scale:
That's it for now, hope you guys found this "mini" project interesting! I love how this design turned out, and would like to get it out there for other pilots. If you've got 3D printer access, you'll find the design files on Thingiverse free of charge: http://www.thingiverse.com/thing:526082. I also make kits to sell, since I might as well put my 3D printer to work! They go for $40 plus shipping - feel free to email me at ericmaglio (at) cox.net if interested.
Thanks for reading!