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Old Jan 15, 2007, 08:56 AM
DaleM is offline
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Dale Lindsay

CX2 motor sounds strange

I noticed here recently that the upper rotor motor has started making a strange noise in the midrange. It's the speed about what it takes to hover at eye level. When coming off the throttle the motor makes a buzzing noise. When under load (as in throttle up to climb) the sound stops for a moment and eventually comes back once the load has lessened. It also seems to affect the gyro somewhat as I get a slight nose left twitch as I throttle down.

When holding the CX2 and powering up with right rudder I can get the sound. I've checked the linkage, nothing is binding, etc. Is this a sign that the brushes/bushings are already going out? I've had this since Christmas and fly a good bit, but not excessive and let things cool down between flights.

Just curious if anyone else has experienced the same noise.
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Old Jan 15, 2007, 09:20 AM
Rob Hair is offline
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Have you checked to see that the motor mounting screws are tight?
Old Jan 15, 2007, 09:37 AM
DaleM is offline
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Dale Lindsay
Yes, I checked the screws and made sure the gear lash didn't seem tight by 'slightly' loosening them and then retightened.
Old Jan 15, 2007, 03:22 PM
venomoussvt is offline
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mine was making a similar sound.... I took the lower gear out and removed the inner shaft. Checked everything and put it back in being careful to pay attention to detail as I put it back together. It stippoed after that. I am not sure exactly what the issue was but I think when I installed my aluminum inner shaft and aluminum bearing I didnt line the keyway up with the screw at the base of the shaft where the gear goes on. I think it was trying to spin freely and was skipping over that keyway making a grinding noise.
Old Jan 15, 2007, 07:24 PM
Lou is offline
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#define answer_universe 42
Tough to say, but a source for some noise can be found in the two screws that retain the lower rotor head to the outer shaft. In some cases the screws will protrude far enough into the inner shaft that they will be touched by the spinning inner shaft. This is particularly so if the inner shaft has a slight bend to it.

If you are confident that the mechanics are good, you can try reversing the motors to see if the noise moves with the motor. These are brushed motors and as the brushes wear they tend to change their 'sound'.

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