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Old 04-29-2020, 05:51 PM
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Question
MKS Servo Buzz

I'm using MKS HV747 servos on the flaps on my jet build, with the flaps up tight were they should be, meaning even with the ailerons. My servos buzz a lot and loud. mid flap is fine and full flap has buzz. If I sub trim each till the buzz stops, my flaps are down a few millimeters from the aileron. Tried adjusting arm lengths and what not to get rid of it but it wont go away. I assume its from holding it up tight. First time trying these servos. Is this normal, and is this going to cause excess battery drain to a degree that I should be worried. Any suggestions would be help full as I normally use hitec for their programing features.
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Old 04-29-2020, 06:50 PM
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you are overdriving the servo. use the travel adjust to reduce the travel and the servos should be happy. there have been a few recent threads on setting up flaps, you might try and find them.
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Old 04-29-2020, 07:01 PM
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Setting up the flaps with a lot of differential in the servo arm can reduce or eliminate the full up buzz problem. As FGNewbie stated, there have been several threads on this but sorry I can't point you to a link. Basically, when the flaps are full up, you want the servo arm to be nearly parallel with the linkage. This only works with conventional flaps that don't have to go up any amount.
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Old 04-29-2020, 07:05 PM
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Check your flap position, with no servo attached to it. Is the flap free in the full up position, or do you have to push it up there? Kinda like a bind.......
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Old 04-29-2020, 07:10 PM
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Quote:
Originally Posted by Bunky F. Knuckle View Post
Check your flap position, with no servo attached to it. Is the flap free in the full up position, or do you have to push it up there? Kinda like a bind.......
It's free moving, no bind
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Old 04-29-2020, 09:39 PM
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Im sure you already tried to adjust you linkage and servo position to eliminate the servo hum.

Does the servo mount to the hatch plate or into the wing? Is there any part of the servo arm or ball link (presuming ball link) touching the hatch? Again, I'm sure you have already checked this, never hurts mentioning if no.....
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Old 04-30-2020, 07:20 AM
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Quote:
Originally Posted by Bunky F. Knuckle View Post
Im sure you already tried to adjust you linkage and servo position to eliminate the servo hum.

Does the servo mount to the hatch plate or into the wing? Is there any part of the servo arm or ball link (presuming ball link) touching the hatch? Again, I'm sure you have already checked this, never hurts mentioning if no.....
Its mounted to the hatch plate, and no it does not touch the plate when full up, I'm going to zero out sub trims and all that again this weekend and see what I can do. they recommend 70mm of flap for landing and I am only getting 60mm before the arm bottoms out in the slot on down flap, but still have plenty of slot left when flap is up, that's why I'm confused. Its a T-1 mini I'm building. May have to pull servo and re ajust the horn a bit. Not sure, but going to tear into it over the weekend, may need a longer arm, hate that buzz
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Old 04-30-2020, 06:02 PM
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OK, worked on flaps tonight, raining like a bitch here in the north east, so figured I'd Get R Done, working good now, thanks for the advice guys.
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Old 04-30-2020, 09:59 PM
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If set up correctly, the servo delivers almost zero torque to keep conventional flaps up and locked. Its simply a matter of linkage geometry.

Flaps that also serve as ailerons are another matter and require more conventional linkage geometry similar to ailerons, but conventional flaps are a different matter.
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