I built a 440 FPV Quadcopter from plans that were sent to me by one of Red20RC’s Instagram subscribers. It’s a really nice little quad that would be an ideal introduction for anyone wanting to try out multirotors on a budget…
Realising an idea…
A lot of the photos on my Instagram feed lately have been of frames, plates and components cut on my CNC machine. To quote one my other subscribers these CNC cut products are “total eye candy” and they always draw attention.
A couple of months ago I was approached by a young chap called notalP. He was on the other side of the world but he had designed a quadcopter and was trying to find a way to get it cut. He had already become part of the “Maker” scene and was waiting for a CNC machine to become available but wondered if I wanted to take a look.
440 FPV Quadcopter
The design is simple enough. A basic “X” frame with an extended fuselage designed to provide plenty of space for camera and FPV gear. The overall appearance reminds me of the “Cinetank” by Flying Cinema and even features a similar clean/dirty plate separation. I was particularly interested by the motor mounts that clamp around the square carbon or wood booms rather than having any permanent attachment.
Time to fire up the CNC cutter…
The whole frame fit easily onto two 400 x 250mm 1.5mm G10 plates and the toolpaths were simple enough to cut in a single file with the same 2.5mm end mill. In a little over an hour I had a complete set of plates cut and sat on my office floor.
The plates are very light with all the holes in them. In 1.5mm G10 there is a fair amount of flex but this can normally be “designed out” of a frame with well placed and spaced fasteners and standoffs.
Assembling the frame
I love building multirotors. There is something about the plates, screws, bolts and standoffs that takes me back to my childhood and toys like Lego and Mechano. This is pretty much the sole reason you will never see me with a DJI Phantom or some other RTF monstrosity!
The first thing I did was put together the main frame so that I could send some pictures to notalP. The whole thing went together really well. The only modification I made was to add another pair of vibration mounts to reinforce a slight flex in the center of the frame.
The whole thing sat for a couple of weeks whilst I worked on other projects but when I came back to it I completely dismantled everything and started again so I could fit the electronics.
One of the nice things about this frame is the size. Even though it is only a 440mm wheelbase there is enough room in the “dirty” section to fit a power distribution board and four ESCs. This keeps the frame really clean, which is something you don’t often see on a quad of this size.
Not having any 10mm carbon tube laying around, I decided to make the booms from 12mm Tasmanian Oak. This is light and strong and very similar to the booms seen in many of the Flite Test multirotor kits.
I was a little worried about mounting the motors as I had only used the same 1.5mm G10 for the motor plates. Because I was using 12mm booms instead of the 10mm in the design I couldn’t use four motor bolts without drilling the booms. This was something I wanted to avoid for both simplicity and I didn’t want to compromise the boom strength.
In the end I use only 2 bolts on the 19mm holes. Doing this meant I could twist the plates slightly giving not only perfect alignment but also allowing the motors cables to run straight along the booms. I was amazed at how well these plates worked. On the wooden booms they gripped tightly with minimal effort, just don’t over-tighten then bolts to the point it distorts the plates.
I did have an issue with the holes in the center of the motor plate being slightly too small for my Turnigy cans.
I put them all together on a couple of bolts and tightened a nice new 10mm bit into my upright drill press. I didn’t have anything that would clamp such a small piece so I got a good grip and plunged the drill. The top plate jumped a bit in my hand making me swear and stop what I was doing.
At this point the smarter man would have stopped and thought. I just gripped harder and plunged the drill once more…
This time the drill locked in the plate completely. The whole thing jumped, twisting my hand and running the drill bit up my thumb and forefinger. My forefinger had a chunk out of the first knuckle and ribbons of skin hanging from it’s full length. The thumb had a deep gash running across the knuckle. I ran into the house, wrapped a dishcloth around my bleeding hand and headed for the local Emergency Department, which fortunately is only a two minute drive away…
Fortunately there was no nerve or bone damage. Although there was a lot of blood it was decided stitches wouldn’t help so a bit of sticky tape and some bandages later I was sent home feeling pretty stupid!
On with the show…
Rather than risk more injury I eventually binned the original motor plates and cut some new ones on the CNC machine. This also gave me change to cut notalP’s new extended landing gear that is held in place simply with zip-ties making a nice weak point in the event of a harder than planned landing.
With everything hooked up I strapped a 3600mah 3S to the top deck and fired her up.
Initial results were good. The motors were more than powerful enough and the 9×4 Gemfan props seemed to reach a 1:1 power/weight ratio at around 45% throttle. Impatient to wait for some daylight I tried a quick hover in the workshop and even with my dodgy thumb the frame seemed very stable. With the props running about as close as they can get to the frame I did have to dial down the PID’s on the KK2.1 a bit to prevent over-control but the Steveis 1.17s Pro firmware is a wonderful thing!
Out into the wild!
The next day was sunny but very windy but I didn’t want to wait. With all the cameras charged up I decided to try a little flying out behind the house. notalP had contacted me overnight, concerned that the props would show in shot on the front-mounted GoPro. I tended to agree but rather than try to extend the plate forward, upsetting the CG, I simply mounted the GoPro upside down under the frame. I knew those longer legs would come in useful.
There was a fair bit of jello in the onboard footage. I have since taken another look at the frame and those cheap vibration mounts are actually quite stiff and don’t allow for much movement. I would like to try it again with some softer mounts and see if that helps as it would be really great if this budget frame worked well with the lower end HD cameras like the Turnigy and SJ4000 that can only run at 25 frames per second.
You’ll also notice that I didn’t actually have any FPV gear installed. Well, expensive experience has taught me that things like gimbals and video transmitters are best left off a frame until you have it sorted. In time I will fit some FPV gear and give it a go so you can see the results.
All up this is a nice little frame. It’s compact enough to take with you anywhere yet large enough to feel stable in the air for beginners. I really like it. As I mentioned in the video, if there is enough interest I’ll consider doing a run of these for sale through the Red20RC store.
Nice work notalP. I think you have a winner here!