Custom built APM mini quad.


Just want to share my scratch built FPV quad made with my new CNC machine :) Called "the butterfly" name picked by my Fiance 

This was my first CNC project I gave myself.. It has been a great learning experience learning all the different techniques required to design, and translate that design to a finished CNC'd product.

I wanted to make something very forgiving in crashes for teaching my friends, full featured flight controller, and capable of FPV flight. Just a pure training and fun flying helicopter.

The length of the quad arm end to arm end is 17 inches (including prop guard). I do not have an exact weight, but I can say it hovers at 40-45% throttle and has a flight time of 10 min. The arms are tilted inward 10 degrees on each arm to improve stability. The motors are mounted upside down to avoid prop-wash hitting the arms and creating drag.

The gimbal and video has not been tested as I'm still waiting on the video transmitter and rca-usb video input for tablet to arrive. The plan is to fly it from my surface tablet using a usb hub for video and data radio Tx. I also plan to design a small box for an antenna tracker. There is no traditional Tx/Rx used to control this copter.. It's all done through the data link. Flying this way took a little practice, but it's very nice using the PS4 controller's joysticks. This also helps save a little weight and frame real estate. There is no lag at all between my controller and the heli.

Crash durability has been extensively tested.. The frame is very forgiving in crashes. After many small bumps with objects, crashes, and even being stuck in a tree the props have not even the slightest nicks on them and no broken parts.

Overall I'm happy with the frame. The flight controller is giving me a few issues however. GPS positions jump allover the map frequently, and altitude hold is sketchy at best. I currently only fly in stabilize mode. I'm using the miniAPM flight controller.

3689615343?profile=originalOpinions and thoughts welcome.

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  • I have seen a few mutlicopters with the tilted motors, but have yet to see an explanation to the reasoning.

  • You might want to read up on Pendulum rocket fallacy and then remove that silly 10° tilt. You'll gain some extra flight time, reduce the complexity of your build and you won't be losing any stability. At all.

    Pendulum rocket fallacy
    The pendulum rocket fallacy is a common fundamental misunderstanding of the mechanics of rocket flight and how rockets remain on a stable trajectory.…
  • Check the IMU logs and I bet you find a they are high. Get some 3M foam double sided pads between the APM mini and the frame and I bet your issues go away. I would not even raise the compass unless the TLogs show that you have an issue. Your symptoms seem vibration related. Toilet bowling in loiter is usually what you get with compass issues.

  • I will turn on IMU logging to see what i can find there and raise the GPS, see if that helps. Right now the IMU is hard mounted, so I will try something different there if vibrations are an issue. Yes I'm in the US.

    Material is G10, actually many tiny screws and bolts to assemble. I didn't plan on selling any, it took all day just to cut the parts. More just for a self learning experience and sense of accomplishment :) 

    I didn't run into any problems using joystick control. Just used the joystick tab in mission planner. Assigned a button to arm and disarm, few flight modes, joysticks, and that was it. I plan to use the triggers to control camera tilt. I did have to adjust the bandwidth of the data radios to get rid of the delay between the controller and the heli though. 

    Thanks for all the comments!

  • Looks great. I agree a few more inches of height with the mag and vibration with the IMU, probably the latter, are behind your alt hold issues. Hard to tell how you have vibration dampened the flight controller. Is it hard mounted in the center tower? Maybe mount in on 3M pads instead if that is so. Have you looked at the IMU data flash logs?

  • Very nice! I've also wondered about using a joystick control. Does it connect via Bluetooth to the tablet? Does Mission Planner support that or did it involve a lot of hacks?

  • Great job! How did you manage to have the joystick control without R/C radio? AFAIK, it is an option in the standard Arducopter code but you must have the R/C receiver attached. Did you change the arducopter code?

  • I like it! What is your frame material? Construction technique? Any chance you'd offer a kit? It's going to be a while before my CNC router takes shape. Looking forward to hearing mor on this project and seeing some good pictures of your baby.

    Nice Job!

  • I wonder if you are vibro isolating that FC tower? and the GPS needs to be at least couple of cm above your motors, otherwise it catches their RF noise. 

    very good frame design though! are you US based? 

  • Looks nice, can't wait to see it fly :)

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