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motor makes grinding sound w/heavy load

Old 02-10-2009, 07:04 PM
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Default motor makes grinding sound w/heavy load

I have a 4250-650 brushless outrunner with a 4400MAH 4S 20C battery and 60A ESC. Everything is a minimum of 60 amps.
With props 13X8 and 14X8 I get about 30 and 45 amps. Up to 600W and 91 ounces of thrust. When I switched to a 15X8
got a max of about 51 amps but picked up a loud grinding noise when I advanced the throttle quickly. The grinding noise
appeared whenever I applied full throttle. Changed to a 14X7-13 Zinger and same thing, a loud grinding noise at full throttle.
Changed to a 13X8 prop and no grinding noise at full throttle. Is this a bad motor or is the ESC timing set wrong or what????
Old 02-12-2009, 10:34 PM
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Default RE: motor makes grinding sound w/heavy load

Hey Griesel
It sounds like you may be over loading your motor. I had a similar thing happen to me with a 400 size outrunner that I used as a replacement for a geared brushed unit. I put on the prop off of the old moter (a 9x7) and it made the same grinding sound at full throttle. As a last resort I got out the spec sheet and lo and behold the largest prop I was supposed to use was a 9x4.7. After changing to this prop the noise was gone. Hope this helps-oemflyer
Old 02-21-2009, 03:58 PM
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Default RE: motor makes grinding sound w/heavy load

Our brushless DC motors are really brushless 3 AC phase motors.

So if they get too big of a load on them they will SLIP OUT of SYNCHRONAZATION. That means the ESC is shooting the current at the windings out of phase. It will shake the plane apart eventually.
Old 02-27-2009, 11:21 AM
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Default RE: motor makes grinding sound w/heavy load

hi there from Toledo:

The grinding noise is indeed a timing issue between the ESC and the motor for the prop of interest. I had a similar issue with a ccphx60 and an AXI 413016 a while back. The great guys at CC told me to set the ESC timing at minimum (or low) timing, the issue went away. Every thing has worked great since. If you can adjust the timing for your ESC then by all means do so.

ciao -rjf

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