Motors vibrating/wobbling, balancing issue ?

[uneasy]

I built my first drone, 450 size it does fly, but I've noticed the arms are going wobbly sometimes, and I am afraid that it can snap the arm (3D printed).

Arms are not very very solid, you can slightly twist them with a hand, but I don't believe that's the build/print issue.
I was thinking it could due to unbalanced propellers? But I wouldn't expect it to behave that bad.

It happens on all 4 motors, it's kind like resonating issue.

Well question is, what do I do next ?

Here is the video of the situation:

 

[wafflejock]

Yah it looks too wobbly for my liking too agree with you there. Wondering what plastic and settings (mainly infill) you used. Also agree probably imbalance in the prop or motor contributing to the resonating. Believe this is called frame resonance broadly. I guess options are pick more rigid material to print with, go higher infill if possible or alternative make some cross beams to connect the arms in a square so is a more rigid triangle holding each of them in place (although then one might contribute to shaking another). Disclaimer I flew my first quad with 3D printed frame and CC3D and some other now ancient stuff and it did still fly but was always a bit wobbly but not this wobbly (was also only 5" size so had less leverage to deal with)

 

[uneasy]

Infill is 30% still more than required. I print with PETG since its stronger than ABS, but maybe its more flexi than abs and that could be a potential issue. In the other hand, I've seen same. Size frame to buy for pretty good money.

I did print from some well recommended project on thingieverse and nobody reported issues like that, so I am not really sure at this point what to do.

I am, afraid it could be print, as when it stands on the ground its pretty wobbly not sturdy enough.
Bummer.

 

[uneasy]

Yah it looks too wobbly for my liking too agree with you there. Wondering what plastic and settings (mainly infill) you used. Also agree probably imbalance in the prop or motor contributing to the resonating. Believe this is called frame resonance broadly. I guess options are pick more rigid material to print with, go higher infill if possible or alternative make some cross beams to connect the arms in a square so is a more rigid triangle holding each of them in place (although then one might contribute to shaking another). Disclaimer I flew my first quad with 3D printed frame and CC3D and some other now ancient stuff and it did still fly but was always a bit wobbly but not this wobbly (was also only 5" size so had less leverage to deal with)

I think after all, it is something to do with propellers, I took them off, balanced slightly and it seems to be better. One thing I noticed, my propellers "base" where the shaft goes, is pretty high, so top of it ends on the thread and it can be moved to the side.

Is there an option for flat propellers base, I thought the ones that actually screw into the motor with 2 bolts and that would be ideal I think, but just out of curiosity.

 

[wafflejock]

Yah mostly what I've seen is the smaller quad use the little screws to hold down the prop on either side of the motor shaft, but anything around 5" size uses the single nut on the threaded motor shaft to lock the prop on there (my tarot motors that are big for the hexabeast does have screws on either side for 13" props). From what I've seen usually the motors do have a flat just above the rotor and not so tall/offset from the actual rotation... some of these motors (especially smaller ones) may have only a single bearing supporting the motor shaft and so could get some "wobble" induced into them from the prop being up so high away from where the bearing is actually holding the shaft (usually on bottom of the motor at very least). I'm glad to hear you've made some progress on the issue though if it doesn't occur with props off then I wouldn't be too worried about the motors themselves and perhaps just need to look at really fine tuning the balance on the props.

Also maybe worth noting you might not need all that throttle to get into the air, usually I cruise at about 50% throttle, it does take a little blip to get things in the air but then after that need 50% or less on most things I've flown (granted usually very light and high thrust to weight stuff)

 

[uneasy]

Thank you for the info, yeah it looks much better. The only think I was worried, is that it can start shaking so bad and get some bad resonance and snap, but also Ive seen some bad vibrating on whole frame so that wasn't ideal either.

But like you said, nothing is happening with props off. I will have to give props close look, besides I think those are cheapest Chinese props so I will look into something better.

I didn't go to full throttle yet, I am still fine tuning before I properly lift off, I am scared of losing it in my first serious flight

I need to set return to home or something.
Anyway, let's the fun begin

 

[Dugdog47]

Try some 7 inch tri blades, might solve some vibration issues. Those cheap bi blades are horribly unbalanced.

 

[wafflejock]

Yah I was just thinking with tri blades might be less likely to have such a bad imbalance too since any little imperfections that are further out will cause more wobble plus with three blades just seems less likely to create a resonant frequency like that.