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  #11  
Old 01-16-2017, 06:11 PM
Dvalcik's Avatar
Dvalcik Dvalcik is offline
 
Join Date: Jul 2011
Location: Ellsworth, ME
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Check the fiberglass layup on the canopy. I modified a part in my panel and canopy did not close all the way in the front and I got a harmonic vibration until i made an adj, fixed. ONLY A GUESS FROM WHAT I READ FROM YOUR POST. Good luck finding it.
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  #12  
Old 02-20-2017, 09:43 AM
bernsbm bernsbm is offline
 
Join Date: Nov 2015
Location: Mequon, WI
Posts: 22
Default Vibration

Thanks all for your many helpful suggestions. Thought I would provide an update on finding the cause of the vibration in my RV12. As background:

Pitched prop blades, identical to 0.1 degree
Carbs balanced by experienced Rotax repairman
Carb floats checked and all found to be ok (2.9gm each)
Gear box removed, checked and reshimmed to Rotax specs
Removed nose wheel fairing (no difference noted)
25 hour Rotax inspection completed with no problems found
Prop dynamically balanced
Checked Engine Isolators per Van's Notification 16-08-10 and found to be correct.
Prop blades returned to Sensenich and balance checked

Based on suggestions:
Removed nose wheel fairing and jacked up front of plane. Spinning nose wheel at a high speed (placing the edge of an orbital polisher on the tire) elicited a vibration that was transmitted throughout the airframe. The nose wheel was found to be both out of round and out of balance. Replaced tire and balanced nose wheel. Vibration could no longer be elicited by spinning the wheel, but vibration in flight was unchanged.

Completed installation of Van's weather proofing/seal kit, including canopy frame

Identified an area of "tin canning" on right fuselage side skin near firewall. Added stiffener eliminating tin canning.

I continue to experience vibrations in the rudder pedals but can also feel it in the canopy frame and panel. The vibration is strong enough that is is uncomfortable leaving my feet on the rudder pedals! Noted in flight only, seems more pronounced at cruise (not climb out), and somewhat less (but present) when operating at <5000 RPM.

Engine seems to be running smoothly, and after 35 hours on the Hobbs, I'm very happy with the way the plane flies. Any other thoughts on potential causes or approaches to identify a source would be greatly appreciated.

Barry
Mequon, WI
2017 Dues Happily Paid
RV12 N12BB Flying
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  #13  
Old 02-20-2017, 10:50 AM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,535
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To confirm that the vibration is from moving air and not the engine, climb up high and close the throttle. While descending, note the vibration at various air speeds. Have the Matco wheel bearings been adjusted per specs that require a certain amount of drag? Have you tried pressing the brakes while flying?
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  #14  
Old 02-20-2017, 10:52 AM
RV Jerry RV Jerry is offline
 
Join Date: Jan 2009
Location: Chino, CA
Posts: 152
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I know you have had a lot of suggestions so here's one more, sometimes something Attached to the engine can be touching motor mount or airframe transmitting vibration, could be something like a hose clamp or exhaust support it easy to check.
Jerry
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  #15  
Old 02-20-2017, 11:54 AM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
Posts: 615
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Following up on Jerry's suggestion -- On the RV-12, potential vibration/touching-the-cowling points include: 1) the left front exhaust spring, 2) a left-side rocker box cover, 3) the exhaust pipe where it exits the cowling, and 4) a floppy lower-right-side oil line.
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  #16  
Old 02-20-2017, 02:29 PM
jsenft jsenft is offline
 
Join Date: Aug 2013
Location: Burlington, WI
Posts: 161
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Barry,
I sent you a PM. Fly your plane to KBUU, I can check it out.

Jim
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  #17  
Old 02-20-2017, 02:50 PM
greghughespdx greghughespdx is offline
 
Join Date: Nov 2011
Location: Hillsboro, OR
Posts: 398
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Will be interested to continue to hear updates on this one. Did the problem change at all when flying without wheel pants vs with them, after the wheel balancing?
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  #18  
Old 02-20-2017, 03:55 PM
jrich jrich is offline
 
Join Date: Apr 2012
Location: Arnaudville, LA
Posts: 59
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Quote:
Originally Posted by DHeal View Post
Following up on Jerry's suggestion -- On the RV-12, potential vibration/touching-the-cowling points include: 1) the left front exhaust spring, 2) a left-side rocker box cover, 3) the exhaust pipe where it exits the cowling, and 4) a floppy lower-right-side oil line.
I agree with 4. above if DHeal is referring to the oil reservoir vent line. But, i would also check the hose vent line from the weep/drain off of the mechanical fuel pump. I had a similar sporatic vibration. Then, during an annual, I made a thorough inspection of all hoses, lines, etc. for abraision and saw how one or both of these vent lines were wearing at contact points against the firewall. So, I put some zip tie offset combos. and RTV where applicable between the lines and all possible contact points and have not noted recurrence of the vibration.
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  #19  
Old 02-20-2017, 05:42 PM
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DonFromTX DonFromTX is offline
 
Join Date: Oct 2010
Location: La Feria Texas
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Another suggestion, a friend had a similar problem, turned out to be oil canning of the floor directly behind the baggage bulkhead. Mine was doing the same thing so we fixed it with a couple of strips of aluminum angle.
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  #20  
Old 02-21-2017, 06:26 AM
bernsbm bernsbm is offline
 
Join Date: Nov 2015
Location: Mequon, WI
Posts: 22
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Thanks everyone, greatly appreciate the thoughtful suggestions and offers of help. I'll follow up on the possible sources of vibration and report back!

Barry
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