[muchzill4]

Hi,

I've been struggling with an issue for a while now.
My quad makes all these annoying sounds when flying forward. I've swapped one of the motors (cobra 2300) but that did not help much.
I've tried retuning pids and lowering them a bit - did not help either.
I've tried different props (dal v1 5040 and gemfan 5040) - nope.

This is footage before I got rid of the "broken" motor:
<- it still sounds similar to this (first 2 sec)


Can you advise on what I can do to make this noise go away? When I watch videos of other people their quads seem to sound much healthier (and I'm not talking about the triblades)

[TheOtherCliff]

I hear three different sounds:
- A beat frequency when motors are at different speeds.  This is mainly vibration from two different slightly unbalanced props.  It may be bad bearings too.  I have some motors with bad bearings.  I keep them oiled (maybe every 20 flights?) and they have not failed, just noisy.
- A slight PID oscillation.  Maybe that PIDs are too high.
- A high pitched screech that is either related to ESC firmware or bearings.  You could put one tiny drop of motor oil on each bearing of each motor.  I use a toothpick with a drop of oil on point to put it exactly where it should go.

If you wiggle the prop and shaft to feel for bearing play, to you feel any?

I always oil the motors at least when I first put them in a multicopter.

[muchzill4]

Thanks for the reply.

No play at all right now when wiggling.
I will try to oil the motors (need to buy some spare circlips first), before I take them apart.
Will try and do some prop balancing.

[TheOtherCliff]

I don't bother to take them apart.  Just be careful with a toothpick and a tiny drop of oil.  The bottom bearing is easy.  The top one requires a steady hand.

The circlips are a pain.  If you take them apart that way, you may not get the circlip back on.  There are often set screws (grub screws) at the top.  Taking them out is a different way to disassemble it.  Use a TINY bit of Locktite when you put it back.

[muchzill4]

Heh, I might need to clean them up after today anyway. I've crashed in mud and some of it is inside the motor now.

Unfortunately new cobras don't have grub screws, so the only way is to remove circlip.

You've mentioned something about the firmware too. I'm using blheli. Any particular setting I should look into?
If PIDs are too high, do you think it's any value in particular? (I've used easytune on not extremely aggresive settings)

[Mateusz]

• Hope you know it. It's not good to test motors with high throttle without props. You might damage or lose magnet that way.
  
• High pitch noise I had with SimonK Afro ESC and enabling COMP_PWM, my motors sounded horrible and vibrated, but otherwise all worked fine. Although it's not BLheli but maybe similar issue, discussion with the SimonK author here https://github.com/sim-/tgy/issues/42
  

[muchzill4]

@Mateusz

I did not know that. Every day is a school day, eh?
I've just tried playing with equivalent setting in BLheli, but it rendered no results - actually motors sounded worse when I disabled that.

[muchzill4]

I've managed to get rid of the noises.

It appears that buttons in my mobius were quite loose, plus there was some movement inside. I've taped everything and now rattling is gone!

[GrumpyMonkey]

I was delivered a new motor with a rumbly bearing which sounded a bit like one of the sounds I can hear.

I had to send the ebay seller a video so that he would agree to replace it (which he did):

[GrumpyMonkey]

@TheOtherCliff - what oil do you recommend for the motors?