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Hover vibration/noise

Old 06-18-2020, 02:30 AM
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Nick80
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Default Hover vibration/noise

Hey all. Fontana 90 converted to electric with 120 size motor and HV servos ball links on both side of control rods so tight with no play, straight level flight or vertical at any speed itís smooth and quite but in a hover/torque roll as soon as I add enough throttle to hold or pull out a vibration which sure sounds like a flutter appears until moving again then goes away. Was worse with higher pitch prop. Prop is also balanced and tight with cotter pin hinges on all surfaces, sealed gaps. Iíve setup around 10 airframes before with out this problem and enjoy the setup dial in airframe process. Any thoughts on my hover noise?
Old 06-18-2020, 03:19 AM
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ahicks
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Could you actually have a Funtana? If so, what a blast. Have a bunch of time on a couple of gas versions of that plane.
Cowl rattling against something? Maybe try it with the cowl off? Motor bearings?

Old 06-18-2020, 08:48 AM
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Default Vibration


Thatís her, original owner around 15yr old Motor really smooth but cowl idea seems very possible and will test if I can get CG without, currently locked in with neutral CG and flying well or how I like it.
Old 06-18-2020, 01:13 PM
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daveopam
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Best guess is a linkage issue. When it's in a hover all the surfaces are more or less unloaded. You might be able to isolate it. Hover with full aile deflection one time. Next time add rudder for a split second to see if it stops , then try elev the same way. Some early production Funtanas's were lost due to aile flutter. The early run had a weakness in the aile mount. The later run of birds they boxed in the aile mount and cured the problem. You aren't getting flutter in a hover but a little bit of play on a surface that big can be a lot of movement.


David
Old 06-18-2020, 04:28 PM
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Nick80
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Default Vibration

Another great idea will try in the a.m. not counting anything out at this point. Thanks all been struggling with it for while now. I had 18x10 prop on it then dropped down to 8 pitch and seem to almost go away but noise gradually returned. Just remembered that for minute thought I had it.
Old 06-18-2020, 05:45 PM
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speedracerntrixie
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I recently changed from a soft mount to a hard mount on my Divergent oattern airplane and now it does the same thing. Not only in hover but to a lesser degree in knife edge flight as well. It did not do this with the soft mount. I suspect that having a large, light fuselage just happens to match the harmonics of the motor. I'm going to play with some ESC settings to see it it makes any difference.
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Old 06-19-2020, 12:11 PM
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Nick80
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Default Vibration

Well 4 flights this morning and sadly noise/vibration still there but only hover around holding throttle and little above until little momentum is built up then nothing. Motor and light airframe very interesting, if I hand spin prop thereís a hum that can hear coming from back into the fuselage, sounds like about were wing tube sleeve is at, every tight as far as I can tell. This light hum/vibration does sound totally different from hover sound tho but Iím not exactly hand spinning prop at speed so could/probably be amplified at higher rpms. Iím currently running zero motor timing and 12 frequency so maybe move to 16 which I herd is frequency above what humans can hear, so smoother? Idk
Old 06-19-2020, 12:12 PM
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Thanks again all for the ideas

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