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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › How to tell if you have a High Freq Vibration
01-16-2006 03:40 AM  13 years ago
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mcoccia

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Central Jersey

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How to tell if you have a High Freq Vibration
I have heard the phrase "High Freq Vibration" but how do you tell if you have one? I have yet to see one nor would I know if I had one.

Can someone explain this to me?

Thanks
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01-16-2006 03:48 AM  13 years ago
Kokamo

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Liberty Hill Tx

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You would see ALOT of foaming of the fuel in the main tank, prolly the verticle and horizontle fin look like a blur and you may possibly hear it, it just depends on how bad.


Joe
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01-16-2006 03:49 AM  13 years ago
Rcer22

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Somewhere In The Adirondack Mountains

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Looking for trouble?
If you had it you would know it. Commonly you would see the tail shaking up and down very quickly at high RPM or high head speed. Most likely due to a bent crank shaft or out of balance fan or anything that spins at engine speed.
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01-16-2006 03:49 AM  13 years ago
TMoore

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Cookeville, TN

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It usually manifests itself in a buzzing or frothing of fuel in the fuel tank or buzzing of the tail fins at the extremities.

This sort of vibration can be attributed to the engine.

TM
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01-16-2006 03:50 AM  13 years ago
mcoccia

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Central Jersey

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If this happens at idle but goes away once you spool up I guess that would be good then or no?
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01-16-2006 03:56 AM  13 years ago
dkshema

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Cedar Rapids, IA

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Watch the tail fins, the skids, and the fuel tank. A high frequency vibration is exactly what it sounds like.

If the tail fins are a blur, the skids are a blur, and/or the fuel tank is foaming like mad, you've got one. Watch for these at hover, or just as you're getting light. Watch the tail boom, especially near the end, and the boom supports. The higher frequency vibe generators on your heli are the motor, clutch bell, fan, and flywheel, and the tail rotor assembly. The parts that are shaking are moving fast (appear as a blur) and the movement is usually small.

The high frequency stuff can cause rapid parts failure (fatigue fractures), parts coming loose, can affect the operation of the gyro, can cause your receiver to glitch (if it's not well isolated from vibration using foam rubber), can cause fractures in solder joints in the servos, gyro, receiver, governor, and can cause premature battery failure.

Lower frequency vibrations are usually associated with the main rotor system. These are more like shakes, and the movement associated with the shaking parts are larger (and slower).

High frequency vibrations are cured by properly balancing the tail rotor assembly, the clutch, flywheel and fan, and by making sure the runout in your start shaft is minimal.

The lower frequency vibrations can generally be cured by balancing the main rotor system -- head, MR blades, flybar, and by using MR blades whose centers of gravity are well matched, and by getting your tracking adjusted correctly.

Dave
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01-16-2006 04:07 AM  13 years ago
Rcer22

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Somewhere In The Adirondack Mountains

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The high frequency stuff can cause rapid parts failure (fatigue fractures), parts coming loose, can affect the operation of the gyro, can cause your receiver to glitch (if it's not well isolated from vibration using foam rubber), can cause fractures in solder joints in the servos, gyro, receiver, governor, and can cause premature battery failure.
You forgot to mention that it can also eat all the food in the refrigerator and drink all your beer. It has also been known to eat candy.
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01-16-2006 06:28 PM  13 years ago
mcoccia

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Central Jersey

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Ok all is good.


Thank you
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