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Help in analyzing the log file,arducopter v 3.6.9 -copter crash

(Sudipta Bir) #1

This was second flight, copter crashes after take off within minutes, 2 17-07-2019 16-57-44.bin (313.3 KB)
here is the .bin file.
Pixhawk 2.4.8
Ublox M8N gps+compass, external compass used only
Compass mot test - interference - 11% at 60% throttle.

(Dave) #2

That craft has severe levels vibration on all 3 axis with Z particularity bad.

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(Sudipta Bir) #3

how to correct it, i did all the calibrations before flight

(Harald Schmid) #4

Please send a photo of your copter then we can make some proposals in addition to „balance your props“

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(Sudipta Bir) #5

Here is the link , file size too big to upload here :slight_smile:
https://drive.google.com/open?id=1tx4WV1P68irS5iiCriq6R4sbQE0th9eK

(Dave) #6

Vibration has nothing to do with calibration. How is the flight controller mounted to the top plate? Are the props balanced? Those cheap frames are notorious for being flimsy and vibration prone. I have built a couple quads using them. They can be tamed though if everything is balanced and the FC is isolated.

Edit: I see you used a ball mount plate. Those typically work pretty well. Did something come loose?

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(Sudipta Bir) #7

I cannot find any loose ends, everything is strapped ,tapped, all ports connected. I replaced an arm after it broke during a previous crash, this arm seems to be less rigid, what i mean to say is this replaced arm bends a little more than the other three, elastic. Could this cause vibrations??
I am a newbie, i just bought a prop balancer today, haven’t tested the props for balancing. Will checking the motor rpm using tachometer help??

(Dave) #8

Yes, there seems to be 2 plastic materials those F450 arms are made from and one is more flexible and prone to vibration that the other. But you always need to balance props in any case so start there. Motor RPM is controlled by the flight controller, that will tell you nothing.

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(Harald Schmid) #9

Hi

Your mounting is pretty well. So damping is not an issue. But the arms you are using are very elastic and can cause a lot vibrations especially also with these cheap motors. For this kind of setup I would use first of all better motors, for example air gear 450 or air gear 350 (t-motor).
This will be an improvement you will see. Another improvement would be aluminium armes
https://www.goodluckbuy.com/dji-f450-f550-aluminum-alloy-arm-26-4cm-length-red-2-pack.html
Or
https://www.mhm-modellbau.de/part-TM-EA001.php

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(Dave) #10

Harald makes a good point about the motors. Are those collet style prop adapters? Some cheap motors use those. If so those will be impossible to balance right.

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(Harald Schmid) #11

Dave, they are. I had them also once several years ago, they are a nightmare. They vibrate like a power drill

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(Jeff) #12

What type of adhesive did you use to mount the FC to the ball mount and the ball mount to the frame? If you didn’t use zeal, you might try it as it’s cheaper than replacing the motors or frame

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(Jeff) #13

Also - double check that all your frame connections and motor connections are tight, and that the frame is level. And that the propellers are balanced, as has been suggested.

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(Dave) #14

Zeal is good stuff but collet prop adapters do not belong on a multirotor. It will be futile trying to balance those. Scrap the motors, or save them for a plane, and replace them with proper motors for a multirotor. You will need new props also.

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(Sudipta Bir) #15

Thanks for the help, i changed the arms with more rigid glass fibre arms, and it is giving me better results, also mounting the dampening pad with double sided tape helped i guess, instead of tying with plastic ties, i 'll upgrade when i save some $,

(Jeff) #16

Zeal really works - I have a similar frame as yours but do not have vibration problems. When you can, use a 6mm square piece under each corner of the FC and the ball mount (8 pieces total). And also consider better prop mounting nuts (which are cheap on eBay etc), and also better props if nec. One lesson you can take from all this is really cheap parts often don’t work, so shop accordingly.

Good luck!

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