P1 v1.1.1 grounded due to progressing vibration

[JKDSensei]

Not sure this on again off again vibration sound is motor related... the changing sound is low frequency (low pitch) and not a high frequency (high pitch) that I would normally associate with high speed motors. If motors were going bad, the vibration would probably be bad (constantly) and not waiver as much as I'm hearing.

You could be picking up a vibration caused by something related to how your camera is mounted. If some attachment point loosened up, you could easily get this type of waivering sound as the P1 motors changed speed to maintain level flight.

Double check how your camera is mounted and make sure there are no loose connections.

Wretched sound huh?
Okey dokey. Checked all camera mounts. Gooten-tight.
Have not changed anything with the camera mount since day one. I should upload a clip from the first 30 flights for comparison. TOTALLY smoother sound.

The thing that makes me think it's motor related is two things...
1). One motor has twice the vibration of the two that are smoothest (measured with a vibrometer)
2). Lubricating the suspect motor smoothed it out nicely...for about 3 minutes.

That said, I can not feel any shaft free play in any direction AND...the motors only have about 50 flights on them.
But if the bearing races were bad or one of the ball bearings went bad, I think this vibration could be the result.

I also did check the prop balances. Perfect. (Did I already say I did this?)

But one other thing I need to rule out is that I added a GPS locator about 20 flights ago. I suppose it's possible that thing is vibrating. I'll check it out. (But that doesn't explain away the bad vibration of the motor with the vibrometer).

Thanks

 

[JKDSensei]

 

[Pilot_FML]

Wretched sound huh?
Okey dokey. Checked all camera mounts. Gooten-tight.
Have not changed anything with the camera mount since day one. I should upload a clip from the first 30 flights for comparison. TOTALLY smoother sound.

The thing that makes me think it's motor related is two things...
1). One motor has twice the vibration of the two that are smoothest (measured with a vibrometer)
2). Lubricating the suspect motor smoothed it out nicely...for about 3 minutes.

That said, I can not feel any shaft free play in any direction AND...the motors only have about 50 flights on them.
But if the bearing races were bad or one of the ball bearings went bad, I think this vibration could be the result.

I also did check the prop balances. Perfect. (Did I already say I did this?)

But one other thing I need to rule out is that I added a GPS locator about 20 flights ago. I suppose it's possible that thing is vibrating. I'll check it out. (But that doesn't explain away the bad vibration of the motor with the vibrometer).

Thanks

I can't argue, that if adding lube to the motors alleviated the problem (at least temporarily), that its points to a motor(s) as being the problem. I mentioned the possibility of other loose connections because both the pitch and consistentcy of the vibrations didn't seem to track to only a motor problem. You may have more than one source of vibration...

Depending on where a second source of of vibration is coming from it could very easily find itself moving more easily through one arm than another.

This vibration stuff is a tough nut to crack and usually only gets resolved by a lot of experimentation...

 

[JKDSensei]

Agreed. I wonder if rubber dampers under the motors would help?

Also, if not the motors per se, what about resonance instead of simple vibration? I've been thinking that maybe since there are 4 motors, the chances for a resonance to occur might go up.
The resonance might originate from a minor motor or propeller vibration, but then become a resonance induced by other motors. Once that magic frequency is hit....boom...resonance.

 

[Pilot_FML]

Agreed. I wonder if rubber dampers under the motors would help?

Also, if not the motors per se, what about resonance instead of simple vibration? I've been thinking that maybe since there are 4 motors, the chances for a resonance to occur might go up.
The resonance might originate from a minor motor or propeller vibration, but then become a resonance induced by other motors. Once that magic frequency is hit....boom...resonance.

Finding the right material (i.e. too hard, too soft, etc.) would probably be a long effort with little if any good results. Much better to spend time looking for the source of vibration...

You're getting into a pretty complicated area when you're thinking about resonance. Resonance comes about because every object has some "natural" resonant frequency. Its caused by follow-on vibrations adding in such a way that vibration amplitudes get increasing higher and higher until the object breaks apart. Look up "galloping gertie" and/or why soldiers always march out of step when crossing a bridge for some interesting facts on resonance.

I doubt resonance is causing your problem because if anything, the different vibrations of the each motor would more than likely interfere with how vibrations add together and in the process stop resonance from occurring. Resonance only happens when follow-on vibrations are exactly in step with the objects natural resonance....

 

[JKDSensei]

Finding the right material (i.e. too hard, too soft, etc.) would probably be a long effort with little if any good results. Much better to spend time looking for the source of vibration...

You're getting into a pretty complicated area when you're thinking about resonance. Resonance comes about because every object has some "natural" resonant frequency. Its caused by follow-on vibrations adding in such a way that vibration amplitudes get increasing higher and higher until the object breaks apart. Look up "galloping gertie" and/or why soldiers always march out of step when crossing a bridge for some interesting facts on resonance.

I doubt resonance is causing your problem because if anything, the different vibrations of the each motor would more than likely interfere with how vibrations add together and in the process stop resonance from occurring. Resonance only happens when follow-on vibrations are exactly in step with the objects natural resonance....

You may be right. But to my ear it doesn't behave like a vibration.