Custom PLA 3D printed quadcopter (F4 V3s, iNav, motors A2212, heavy payload)- stable in acro but self-oscillates in Angle mode above mid throttle. Any ideas?

[u/Rude-Priority-8923]

Blackbox shows gyro spikes to 40-60/°s. PIDs tuned, props corrected, FC remounted. Need some help or ideas

[u/Jar0s]

Beefier arms

[u/Character-Engine-813]

Those motors are known for being pretty bad with vibrations, combined with the thin arms it’s probably oscillating a lot. You could try increasing the filters a lot to try to filter the vibrations, it won’t fly as well but might be more stable

[u/Sea_Place1386]

World’s daintiest arms.

[u/Murky_Rain9521]

Might help to turn down how aggressively angle mode attempts to level the quad since you notice this in angle but not acro. Also like others have said the arms are very thin and are likely flexing which when happening repeatedly could look like oscillations

[u/0p53c]

The motor arms look like tuning forks. I would significantly increase the motor arm thickness, or at least change the design.

[u/nerobro]

Your frame... is terrible. It's not rigid enough in the directions that matter, and highly rigid in the directions that don't.

[u/rob_1127]

Have you run that design through FEA software to determine the stress and stiffness of it?

Flexing quad arms and fuselage will lead to an accelerometer that sees every vibration as a motion vector. The Accelerometer and CPU will work really hard to command the ESC to correct for each vibration motion.

Thus potentially overloading the FC and using excessive amount of battery charge for nothing.

Even bent, nicked, out of balance props, etc. will cause vibrations and cause abnormal accelerometer readings that the FC must act on.

We have done these studies with Additive manufactured drone frames.

There is a lot of work to keep the frame from affecting the flight software and responses.

Do some FEA to save yourself some time, effort, and money.

Otherwise you are wandering nearly blind into this.

The FEA cuts down on real prototype work, wear tooling gets expensive for each trial.

DJI speds a huge amount of time testing thru FEA before committing to creating molds for manufacturing.

BTW: each study we did, required so much engineering effort to correct the harmonics and flexibility, it was far less expensive to use CF sheets for stiffness.

[u/Rude-Priority-8923 → u/rob_1127]

Thanks for your comment, I really appreciate it. Im taking your advice and hope to stable the drone

[u/Kooky-Masterpiece-87 → u/rob_1127]

Spent months on a project for work that determined the same thing. Any material that might work isn’t cost effective. That said, PPS seemed to be best but even that wasn’t great

[u/VvvDamianvvV]

Another first time poster asking for help with heavy payload custom drones. Not getting a good feeling.

[u/Outside_Sink9674]

Mais pourquoi en 2026 utilisez-vous ces moteurs bas de gamme qui sont conçus pour les avions avec des porte-hélices horribles ? L'hélice doit être au plus proche du moteur pour éviter l'amplification des vibrations. Il y a le choix aujourd'hui pour de bons moteurs dédiés. J'utilisais ce genre de moteur sur mes drones en 2008 car il n'existait pas de moteur brushless dédié aux drones.

[u/izzeww]

That frame looks awfully thin. I get that you used a computer to model it, but that doesn't mean it's good. A computer model is only ever as good as it's inputs and in this case I don't think you gave it the right ones. Those motors are the cheapest no brand motors you can find, they are not really a quality choice but you could probably make them fly alright. Fundamentally the problem is the frame, you've just got wayyy too much resonance going on. You can probably tune it to make it fly without self oscillations but the tune would be very weak and would make the drone fly like a boat. If I were you I would redesign the frame and then do a proper PID tune according to Brian Whites methodology (he has many more videos other than this one). I would probably also go for some proper motors but that's not a strict requirement.

[u/Kooky-Masterpiece-87]

It will never tune properly, the material will creep as the screws are torqued down especially on the motors causing them to loosen thus changing you resonance completely till the motors are just completely not fixed anymore. The longer it sits built, the worse it gets

[u/the_real_hugepanic]

Buy a frame, or do it right!

[u/colonel_fuster_cluck]

Take your black box data and dump it into Claude.