And so the fourth little piggy built his house out of carbon fiber. With some 5 inch props, the wolf never saw it coming.
Worker Bee #3 was not happy with the frame selections currently on the market so I set out to design a pure X racing frame myself.
I got started with drones in the first place because at the time, everything was so poorly designed and everyone was flying the same thing. Fast forward a year or two and the choices are now endless. Not only that but there is a lot of actual thought being put into the current products on the market.
I wholeheartedly support every designer out there putting in the effort to make a superior product (we have purchased and flown many of these frames), however for me designing and cutting out your own frame is just that much more satisfying than unpacking and assembling a frame from a box that UPS delivers. Still not as much fun as flying though!
So without further delay, let's layout the design goals:
- Small and lightweight - I wanted a smaller frame. I have enough larger frames and more ZMR frames (in various states of assembly/disassemly) than I know what to do with. So I settled on something around 190mm.
- Customize-able - There a bunch of extra parts laying around here which is great for replacing broken components, but only if you can use them. Everyone likes options so I decided that this frame should support up to 5 inch props and 2208 motors.
- Inexpensive - This is a bit harder to determine right off the bat, but bolt on replace-able arms along with no excessive curves and material help. Less excess carbon fiber and symmetric design with similar parts led to deciding on an X-frame.
- Easy assembly - Building and flying quads is like standing in line at an amusement park, you spend 6 hours building and setting it up for 5 minutes of flight time. Less parts for easy assembly/disassembly means less time standing in line. Minimal bolts and pieces.
So this is how it started:
This is about as close as you want to put 4 spinning props together. Resulting in a roughly 190mm frame. To avoid back pressure from the props against the frame, which cancels out some thrust, I wanted as little surface area as possible on the arms and for the body to not interfere. This reduces total surface area and drag. If the arms are too thin though, they will just snap, so this a good compromise. A straight line is the quickest way to the body so that's what I went with.
So here is what it looks like with just the base and the arms. There are vents on the arms to cool the ESC's as well as a small slot to secure a zip-tie (this also serves as a crumple-zone). Additionally the arms come together to distribute forces in the case of a crash. Two points define a line so that's really all we need in terms of bolts in this case.
Now its beginning to look like a quad! 2206 motors, ESC's, PDB, and a flight controller. lets add some five inch props and see how much room I have to work with.
Hmm, not much room to work with so we have to go up and get up over those props. We need room to mount things on top and need the top to be slanted for the fpv camera and the run camera.
After cutting out the window for access to the flight controller it kinda looked like a house, so why not add a little chimney? It is after all, a "house" frame for testing. It can serve as stabilization and protection for the run camera. Ah, so this is how we ended up with such an ridiculous design. Somehow I love it.
Here's what it looked like with a battery and the rest of the parts mounted. Let's cut it out and see how it flies!
I'm using Solidworks with HSMworks. This is what the tool path looks like for two sets, after it's all laid out. I cut out this prototype with our mini CNC machine. I'll go over CAD/CAM and machining/printing in another blog post.
Here's the first prototype of this frame! We're still getting this CNC dialed in so we cut on top of some cheap wood for quick prototyping purposes. I'm not sure what to do with these, I think they look pretty cool. Maybe I'll frame them and put them on the wall or something. Maybe we can do a give away or something =P
Here's the frame put together and the frame on the operating table. The frame snaps together with no screws, nuts, or bolts. Of course you want to bolt it down when really building but it's pretty neat that it can hold itself up. We learned a couple little things when putting this frame together that we will change on the next iteration. Building such a small quad definitely takes a lot of skill and attention to detail.
Decked out with some 4in triprops and a runcam. We flew a couple different configurations on this frame, some flew better than this one but this one definitely looked the best.
After extensive crash testing, we got tired of having to take the whole frame apart just to fix one broken arm. So I updated the arm design to be more easily replaceable as well as harder to break. The arms are now slotted for the second hole and I have moved the vtx towards the rear to allow more room for a bigger camera. There are now a grand total of only 10 bolts, 8 nuts, and 1 spacer to hold the whole thing together. It can still be optimized further, especially for production, but our pilots love this thing and I always have to fight to get it back to work on it. Here's a half built v1.2
Look for our pilots flying this frame around San Diego! If you see it, ask to give it a whirl and let them know what you think!
- Worker Bee #3