Strange vibes from motor on T-Rex 600E PRO

[glushkov]

After changing pinion (from aluminum to steel), strange vibes registered (see attached screenshot and vibe log). Main gear and lower KDE pinion support removed, so only motor with pinion tested.

SK-720 governor is active.

By touch, vibration level is minimal, but sk-720 shows extreme level. Most of vibes is Up-Down. Bad bearing or misbalanced motor should produce lateral or Fore-Alt vibes, IMHO.

Any ideas? Maybe, resonance?

Motor KDE 600XF-530

[Xrayted]

Motor timing in the ESC. Try other timings within reason and see if it changes. Also pull up on the motor can and make sure there is no up/down play of the can and shaft at the retaining clip and bottom can bearing.

[glushkov]

Thank you very much!
Now I have timing setting 0 (Low) and PWM 12. Low timing is recommended by KDE. I'll try to ask them for any other possible options for timing for this motor.
Can wrong timing setting damage motor or ESC?

[Xrayted]

Originally Posted by glushkov

Thank you very much!
Now I have timing setting 0 (Low) and PWM 12. Low timing is recommended by KDE. I'll try to ask them for any other possible options for timing for this motor.
Can wrong timing setting damage motor or ESC?

No, higher timing will make the motor more powerful, but less efficient, and possibly run warmer. Just change it on the bench as test to see if the vibe spike changes with the timing to confirm the suspicions that this is indeed the source.

I also run a KDE motor and have a motor spike of about 8 with my Castle set to Medium timing and 12kHz PWM. My motor runs very cool only hitting about 65C after sport flying.

Some motors just have this timing induced up/down vibe more than others, but its not enough to make the overall vibe score very high and does not trip the self leveling, so I don't worry about it. Its happening to many people out there and they don't even know it without the ability to see the vibe logging, and as you stated the heli doesn't feel like its vibrating when touched by hand. Also, sometimes just changing the RPM by 50 or so will make a big difference using the same timing, so some experimentation of various combinations may be needed.

What is the overall vibe score when you plug into the software and look under View/Last vibe score?

[glushkov]

Try to change timing.
Vibration level is almost same in all three cases. But with timing High (10) RPM "flow". But RPM registered by SK-720 are same (may be, because no load).
Then I try to set lower rpm for idle1 and idle2. Vibration reduced, from 22 to 15.
Vibe score in all cases - 0.1 (screenshot and all logs attached)

And no up/down play of motor can.

[Xrayted]

Originally Posted by glushkov

Try to change timing.
Vibration level is almost same in all three cases. But with timing High (10) RPM "flow". But RPM registered by SK-720 are same (may be, because no load).
Then I try to set lower rpm for idle1 and idle2. Vibration reduced, from 22 to 15.
Vibe score in all cases - 0.1 (screenshot and all logs attached)

And no up/down play of motor can.

Same as mine then. It appears to be much worse than it is from looking at the single peak on the graph, however the actual effect on the model and the overall score is nothing.

My overall vibe score in flight at 2000 rpm, sport flight is a tiny 0.3, and that is with loops, flips rolls etc.

My suggestion would be to check your actual flight vibes scores and make sure they are within range, and not worry about it if so.

There is only one mechanical way that the motor can move up/down and that is with play in the can, so there isn't anything mechanical to worry about since you have no play.

Its just magnetically induced vibes from within the motor itself, and you will need to live with it as long as the overall vibe level is low

[georgi UK]

=] really need to see a playback log to determine your GPS, the problem being is that you have changed parts outside of the known compass swing, this can play havoc with vibe recordings ( always in an upward readout ) which bear no truth to reality.

Re-swing the heli after any changes, I get the feeling you have changed more than the pinion gear, perhaps? And try again.

[Xrayted]

Interesting Georgi. I never heard of this before. I understand that adding or changing any parts requires a new compass swing calibration due to the change in metallic objects on the heli, but I'm not wrapping my head around how this would cause physical vibes detected by the FBL units accelerometers to change??

Not doubting you at all, but just not understanding the process.

[glushkov]

Hi, Giorgi,
Thank you for your answer. I can get playback log tomorrow evening. I really changed only pinion, but old was made from aluminum, new is made from steel. Can this change magnetic field significantly? And all tests performed inside room, so GPS can't lock satellites.

[glushkov]

Hi Georgi,
Please find attached playback log. There are two peaks during spool up and just after hold. RPM is about 2550 - no load on motor.

[georgi UK]

=] Hi and thanks for the log. what I was looking for was a huge discrepancy between vibe and playback vibration logging, the GPS proximity to the pinion and so on.

Nothing there to be found! my approach now would be to refit the ally pinion and bench log again, your gears are helical and slanted, it wouldnt take much for an up/down vibe if the mesh was out on the steel/metal version.

so we have to eliminate something to the point of running the motor with no pinion at all. The MX is notoriously bad for vibrations, mine wasn't perfect until I fitted the KDE adjustable upgrade mount which uses the larger counter bearing.

thats another area for you to consider, pinion to counter bearing float. again, eliminate by removing it for bench runs.

your settings look good, and needs an actual hover to see if the gearing is correct, I note a voltage drop mid-way into the log, any clues as to why?

best.

[georgi UK]

Originally Posted by Xrayted

Interesting Georgi. I never heard of this before. I understand that adding or changing any parts requires a new compass swing calibration due to the change in metallic objects on the heli, but I'm not wrapping my head around how this would cause physical vibes detected by the FBL units accelerometers to change??

Not doubting you at all, but just not understanding the process.

=] Tony hi! what I have seen is a perfectly low vibe 500 go to red light vibration shut-off on the self level 720 and gps side of things. when switching from play back to vibe logging the scores contradict each other. disconnecting the gps plug allowed me to continue on a green light.

I was testing added gear to the heli, and knew it was vibe sound! re swing time.......

[Xrayted]

Originally Posted by georgi UK

=] Tony hi! what I have seen is a perfectly low vibe 500 go to red light vibration shut-off on the self level 720 and gps side of things. when switching from play back to vibe logging the scores contradict each other. disconnecting the gps plug allowed me to continue on a green light.

I was testing added gear to the heli, and knew it was vibe sound! re swing time.......

Thanks Georgi and very interesting. Good to see you back around by the way

[Luvmyhelis]

I learn valuable stuff with both you guys. Hi Georgi! You have been missed bro.

[glushkov]

Today heli has been tested in the field. Before test changing timing or PWM (to 16kHz) had no effect. But when I turn SK-720 governor off and switch to the Castle governor, vibrations fell from 15 to 3. On full load vibrations was about 8 with 1 sec peak of 15...
But, SK-720 governor is much better than Castle one. I have governor gain 25 with Low Ramp=80, High Ramp=110 and Overdrive=100.
Maybe gain was too high? It worked good on previous firmware.