High Frequency Whine on 700XF-455G3

[AndrewJHawes]

I am getting a high frequency whine on my 700XF-455-G3 motor.
I am running a Cool Kosmik 160A with the motor, and when running over about 55% in the Kosmik with 13 tooth 7HV gear set-up transition from a quiet run to a high speed whistle/whine.
This motor is brand new with only about 10 flights so far. Do I need to disassemble and re-pack bearings, or can someone explain this noise please?
Regards,
Andy

[PHANTMXR6]

Are you sure it's the motor and not another part of the drive train?

[helicraze]

The cooling perhaps from the motor?

If it always did it just fly it and check for vibes

[AndrewJHawes]

This is a helicopter with a belt drive, and the only component of the helicopter that I can think of which operates at a sufficiently high frequency to cause this high frequency whine is the motor.
It might be the 'fan' on the KDE motor, but unfortunately it sounds very much like a dry bearing. I was hoping that someone else might confirm that their 700 XF motor makes the same sort of noise to reassure me that it was the fan drawing air and whistling at the same time.
Regards,
Andy

[taoY]

Thinking out loud here. If the sound is from dry bearings, you should get the noise at all speed. Louder at higher speed.

My G3 505kv does not have abnormal noise. I have a Pro 750 whines loud at higher speed but normal at lower speed. Could be the sound from the fan as pointed out earlier.

[thenewguy]

To test your ideal of an issue with the motor you "must" take the whole drive system out of the loop. Just spin the motor up by it's self and you'll know right away if the noise is coming from the motor and not part of the drive system.

Don't guess, isolate each system and test it. You basically have 3 systems that would have to be tested. The motor it's self, the main rotor, and then the tail drive system.

You should be able to just run the motor, then add the main rotor in the loop, and then the tail system in the loop. Of course you do this with out blades on.

[AndrewJHawes]

Thank you theNewGuy, you are correct of course - just wanted to pick other users experience first. Just a bit on edge with this new machine at the moment before I learn all of its little idiosyncrasies.
Regards,
Andy

[thenewguy]

I completely understand bud,


Just take your time and take it step by step. You'll figure it out.

Thanks,
Chris

[HeliTor]

Just installed a 550XF-1200-G3 in my 550. I also get the high frequency whine when I spin up, but just for a second... I believe it happens while at approx 50-60% throttle. My guess is that the sentrifugal fan is going into some kind of sound resonance... It does not matter because I'm working at 80-85% throttle.
Try changing your pineon size to change the rpm of the engine. Try a smaller one to get more engine rpm.

[AndrewJHawes]

HeliTor, I think you are right, it occurs at transition between 50% and 60+%. I too believe it may be a resonant issue associated with the motor fan, and not a great problem. Its just that I have been doing some low head speed stuff at about 1100 rpm with my 700XF-455-G3 and get this only when I spool up to Idle1 at 1300 - 60%, and Idle2 at 1450 - 70%. beyond which it is mostly gone.
The motor is brand new and only completed about 10 - 20 flights. I am however, eliminating all the other possibilities in the mean time.
Trouble is I enjoy the low head speed, but also like doing some more aggressive work, and the pinion is spot on at the moment.
Regards,
Andy

[AndrewJHawes]

Somebody at my club suggested that they thought it was my Kontronik Cool Kosmik making this noise, probably associated with the freewheeling circuit.
I only got the whine atthrottle percentages up to about 60%. I had oiled everything I could think of, changed belt tensions etc., but nothing really solved the whine.
The day before yesterday I thought I would try one more thing before giving up, and mounted a single 6S pack in the 7HV which then at about 90% throttle was silent!
I guess I will just try to steer clear of the lower throttle percentages!
Andy

[Frostwick]

My 550g3 motor has the same whine around 55% throttle.

[AndrewJHawes]

Frostwick, what sort of speed controller are you using?
It certainly seems that the Kosmik running below about 60% whines like that, and probably other esc's too, if they use freewheeling circuitry.
I overcame this by flying 6S on the 7HV at 100% throttle in a separate setting - I use Idle3 on the Futaba 14FG, and works extremely well, without whine.
I think ultimately this noise is symptomatic of the freewheeling facility on the speed controller, rather than the motor per se, although the motor/speed controller/throttle combination may be pivotal. It seems that the noise is generated by the current fluctuation during this freewheeling. May be some of the electrical engineers may be able to elaborate here a little.
Regards,
Andy