The frame for a quadcopter has a number of requirements. It must be strong enough to handle the power of the motors, while also being light. For a 3D-printed frame, lightness directly corresponds to the amount of plastic used, and affects the print time as well.
It doesn’t have to be particularly aerodynamic. Since quadcopters tend to move slowly, aerodynamics is a secondary concern. All else being equal, having better aerodynamics is obviously good, but we don’t have to spend a lot of time chasing that goal.
A number of projects have shown up on Thingiverse, which can be used as a source of inspiration for the WumpusUAV. Many are under a CC-BY-NC license, which won’t work for the WumpusUAV because (per the Open Source Definition and the Free Software philosophy) commercial use must be allowed.
The PL1Q Vampire makes a good starting point. The author claims a complete frame being 230 grams. It’s a bit small–I’m not sure it’ll hold an Arduino, Raspberry Pi, and a battery. It looks like a solid starting point for comparison; there’s nothing particularly noteworthy about it, but it does seem to work just fine.
The Flone is meant to be controlled by an on-board smartphone. The motor mounts aren’t on long arms, as they are on the Vampire and the Parrot AR.Drone. They’re almost on top of the frame. The author’s pictures indicate a CNC (laser?) cut wood platform rather than a 3D printer, but from a casual look, everything looks 3D-printable.
One I think is really clever is the Micro H-Quadcopter. The reason it’s clever is because the frame is built out of symmetric pieces, which means a smaller 3D printers can build it in sections. It’s only bilateral symmetry, so there’s two distinct pieces to print. Full four-way symmetry would be more amenable to mass production, though not a big deal for 3D printers.
The WumpusUAV Prototype Frame
I didn’t start this project with the intention of innovating anything. I merely saw a number of ideas already out there and wanted to work them together into a cheap kit. Then I had one of those flashes of insight: nobody seems to be using honeycomb structures in model aircraft.
They’re used extensively in full-sized aircraft, but until 3D printers, there probably wasn’t a good way to make them in model kits. Most model RC aircraft kits were done by hand with balsa wood, and honeycombs are tricky to do that way. With 3D printers becoming more popular and accessible, we can change this.
The honeycomb structure promises to be both light and strong. The reduction in materials from a solid frame may also reduce printing time (though I’ll have to see if that works out in practice).
As a prototype frame, we don’t need anything fancy. A single honeycomb “block” will do. Here’s an OpenSCAD drawing of one:
The nice thing about OpenSCAD is that the details can be programmed in without much fuss. We can change the size, spacing between cells, and number of cells just by tweaking a few parameters.
From this, we can attach all the electronics we need to test out. Once we have that, we can use this prototype as the starting point for something more aesthetically pleasing. Electronics will probably need to be fully encased, but with a 3D printer, we can have the bottom layer of the honeycomb filled in.