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Home✈️Aircraft🚁HelicopterAerial Photography and Video › Wicked Shake/Wobble on Mount when Spooling Down
10-24-2006 03:48 AM  13 years ago
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c130pilot

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Windsor, CO

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Wicked Shake/Wobble on Mount when Spooling Down
Been getting a Bergen EB Gasser up and running. Flies great. Put the camera mount on it and it shook a little when spooling up. I flew it around and all seemed ok. But, when I landed and took the throttle down, the thing darn near shook itself apart when the RPM's started dropping off! What's the deal here???

Tim
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Help! I'm umop apisdn
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10-24-2006 03:59 AM  13 years ago
h2jringo

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Redmond Oregon

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How loose are the main blades? is this a new build or bought it used? a little wobble is normal on spool up and down. Excessive wobble is not. My Predator did this when I had my main blades too loose but I had smooth hover and flight with no shakes. If its shaking on hover I would check blade balance, main shaft and spindle and make sure flybar is centered.Quad copter and Camera mount design
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10-24-2006 04:05 AM  13 years ago
c130pilot

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Windsor, CO

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I could tighten the blades a little more, I suppose. The thing is that it does not shake like that when it's not on the mount.. that's the weird part. And to answer your question, I did not build it, but it was pro built. I am certain it is not main shaft etc.

Tim
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Help! I'm umop apisdn
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10-24-2006 04:18 AM  13 years ago
waterskier

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Crosby, Texas

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Probably shakes a little off the mount, the mount just exagurates it... you sure it is is not new.... flown it since the wobble w/o mount?Greg
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10-24-2006 04:28 AM  13 years ago
NitroSpazzz

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Knoxville, TN

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My EB does this as well but not too bad, I have the blades pretty tight. I can still move them by hand but it takes a bit of force. On the initial spoolup of the day it takes some time for the blades to align but once they do its smooth. The mount just makes any and all vibrations more noticable so you'll see everythingBlake
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10-24-2006 04:31 AM  13 years ago
GMcNair

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Birmingham AL

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Tim, hit throttle hold as it is spooling down, and gradually increase the collective until the rpm's drop way off and you've found the "sweet spot" where it spools down completely without causing the resonance. Trust me on this one. Been there, done that, feathering the collective on spool-down will overcome it every single time.
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10-24-2006 04:36 AM  13 years ago
Flyingeye

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San Diego, CA, USA

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While you're spooling down, switch to throttle hold and gradually bring collective to maximum (being careful not to lift off). That will get your head speed down through resonance rapidly and the oscillations won't have as much time to build up. Fiddle with the collective as it's spinning down and see you find a place where the oscillations go away. Your mileage may vary. You will also find that different surfaces (pavement v.s. grass) will behave differently. I find that grass seems to absorb the energy where as things seem to bounce around on pavement.
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10-24-2006 02:34 PM  13 years ago
NitroSpazzz

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Knoxville, TN

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GMcNair and FlyingEye are right, I forgot to mention thats what I started doing. Just raise the collective SLOW...I have had more than one accidental lift off from going too quickBlake
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10-24-2006 11:53 PM  13 years ago
FLAP

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Michigan

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don't see any photos of your setup. Hopefully you are not landing on hard surface without any padding on the skids. You will get wobble not matter what you do with unpadded skids on hard surface. If this is not the case, the throttle hold recommendations in previous threads should sort you out.
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10-25-2006 02:18 PM  12 years ago
c130pilot

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Windsor, CO

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Throttle hold did the trick. Also, talking to Bergen, they suggested adding flybar weights since I have been running larger than standard main blades. Will try that too.

Tim
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Help! I'm umop apisdn
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10-26-2006 12:00 AM  12 years ago
FLAP

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Michigan

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you were running with no flybar weights?! That makes a huge difference in sensitivity of the bird. Not sure how it affects your wobble. Be prepared for the differnce in feel (forgive me if you already knew this).
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