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Feb 20, 2003, 08:59 PM
Thread OP

Mega 16/15/6 resonance


Hello,

I have a new Mega 16/15/6 driven by a TMM 18+3P controller. The motor is running a 7x5 APC E prop on 8-cells of KR600AE. The problem is some very noisy resonance points. It runs smoothly at most throttle settings, but as you slowly advance through the range, you will hit these resonance points. At it's worst point around 1/3 throttle it will make a loud screaching sound that definitely does not sound healthy. I have tried different props with the same result.

My Mega 16/15/5 with a Jeti 30-3P does not have this problem.

Is this a defect? Or a characteristic of the motor/controller combination?
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Feb 20, 2003, 09:09 PM
contact ken mizel at
www.megamotorusa.com
he is very great in helping mega users. One of the best customer services out there.
Feb 20, 2003, 09:12 PM
Micro-Turbine Superhero
henke's Avatar
mine has that sound too!!

TMM 18+3P 16/15/6 8x6 APC E 8x1100HE


trying 9x6 tomorrow

please tell if you find a solution

/Henke
Feb 22, 2003, 02:33 PM
Thread OP

Mega-Resonance


I spoke with Ken Mizel at Megamotorusa. He did not have an immediate solution. He was willing to look at the combination motor/controller. I told him that I would start with NeSail first to resolve the problem since that is where my money went.

I'll report back.

jc
Feb 23, 2003, 02:49 AM
Registered User
aau007's Avatar
Have you tried the Mega/Jeti setup with the /6 motor?
Feb 23, 2003, 10:29 AM

This might not help but...


I had the same problem with a S400 DD motor a few weeks ago. At certain throttle settings (close to full), it would screech like a stuck pig. I took the motor off and spun it by hand and found that the bearings were a little dry. Some lube on the bushings and the screech went away.
Good luck
Feb 23, 2003, 10:42 AM
I don't want to "Switch Now"
pmackenzie's Avatar
A possible source of this might be that the chopping frequency and the commutation frequency are in sync at this rpm, and the controller is not
handling this smoothly. This could be confirmed with a scope. The Jeti conntrollers I looked at (older ones) used a different method to chop the signal, which would not cause this problem.

Pat MacKenzie
Last edited by pmackenzie; Feb 23, 2003 at 10:45 AM.
Feb 23, 2003, 03:54 PM
Registered User
Might it perhaps be a harmonic frequency vibration from the prop, or does it do the same thing with other propellers too?

Bob
Feb 23, 2003, 04:09 PM
Micro-Turbine Superhero
henke's Avatar
no vibe with 9x6 APCE or GWS 8x6

/Henke
Feb 23, 2003, 08:00 PM
Thread OP

Some more Mega experiments


Quote:
Originally posted by Kiwi Bob
Might it perhaps be a harmonic frequency vibration from the prop, or does it do the same thing with other propellers too?

Bob
Bob,

Good question!

I have removed the power system from the airplane in case it was a resonance with the mount or structure. I also took off the prop. Same resonance while holding the motor in my hand with no prop. Of couse it was muted, but still there. I reassembled airplane and power system, applied a small amount of oil to the bearings, and resonance persisted.

Tried three props, identical behavior. The biggest resonance is at 1/4 throttle, with another popping up at 1/3 throttle. There is a muted one at maybe 3/4 throttle. One click of throttle (+/-) is about the width of the resonant areas.

These experiments rule out a prop or airplane structure interactions. It is something between the motor and controller. Not a big deal, but I want to look into it further.

Thanks for the ideas,

jc
Feb 23, 2003, 08:04 PM
Thread OP

The defining experiment


Quote:
Originally posted by aau007
Have you tried the Mega/Jeti setup with the /6 motor?
Yes, this would be the defining experiment. Unfortunately, the /5 turn uses the bayonet connectors that came with the Jeti controller and I don't have any more of them. So I can't connect the Jeti and the new /6 without soldering and desoldering.

We'll see what NeSail says when they get back from the WRAM show.

thanks!

jc
Feb 24, 2003, 03:10 PM
Registered User
aau007's Avatar
rc4metoo,

Looks like you WILL have to solder/de-solder the Jeti onto the /6 somehow to be sure. Do it now to get your curiosity over.

If NESAIL finds nothing, then it may be either you /6 or TMM controller and you will have to de-solder them to make sure.

IF NESAIL says yes, will you consider sending the TMM back and get a CC or Jeti? You still have to de-solder them to swap, unless you are willing to put up with a motor/ESC mismatch.
Feb 25, 2003, 06:02 PM
Thread OP

The latest


Here is the latest on the Mega resonance. I spoke with Sal at NeSail. He thinks it is a bearing in the mega. I will be sending motor and controller back to him so he can investigate.

I'll report back when the issue is resolved.

Regards,

jc
Mar 23, 2003, 10:55 AM
Thread OP

Re: The latest


Quote:
Originally posted by rc4metoo
Here is the latest on the Mega resonance. I spoke with Sal at NeSail. He thinks it is a bearing in the mega. I will be sending motor and controller back to him so he can investigate.

I'll report back when the issue is resolved.

Regards,

jc
NeSail replaced the Mega motor. Total turn-around time of 2-weeks.

jc
Mar 23, 2003, 02:53 PM
Registered User
Thomas Nelson's Avatar

How's the new Mega?


I am wondering about a similar noise with mine. Actually, I'd describe it the same, but perhaps not so loud.

Doesn't seem to be a performance issue, though. I can't detect a drop in RPMs as I approach the offending points.

16-15-5 with CC Phoenix 25 and MAS 7x4 and APC 7x5E on 9 Hecells. Not getting any worse or better.


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