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  #1  
Old 11-21-2021, 02:43 PM
WingnutWick's Avatar
WingnutWick WingnutWick is offline
 
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Location: Fresno, CA (KFCH)
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Default Cowling vibration - oversized piano hinge.

Hello,

So I have been trying to isolate some rather annoying vibration on the new 10 that can be heard during taxi and in flight at certain power settings. I believe I have isolated it to the top part of the cowling where, with the engine running you can see it vibrating significantly. Upon further inspection it looks like the piano hinge is significantly larger than the wire itself which results in a lot of play and the allowance for the cowling seam/hinge to vibrate causing the noise. I took a video of it. Also in flight you can see the play allows for the cowling to lift from air loads. Measuring the top cowling wire it is around .0815 and the hinge is about .14'

Writing to see if this is normal to allow for east of the wire to curve around? Has anyone else experienced this? Any smart solutions out there? Using a .14' wire seems to be quite a thick wire but maybe this is the easiest solution. Replacing the hinge would be a task and require repainting.

Thoughts, insights, comments, suggestions always welcome!

Thank you!

VIDEO: https://youtu.be/IyOau94ymhs
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  #2  
Old 11-21-2021, 02:49 PM
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rv6n6r rv6n6r is offline
 
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Default

On my -6 I have an oversized pin, tapered a fair ways back (sander & scotch-brite wheel) where the bend is sharpest. As I recall that was in the plans but it may have been something other builders had just figured out. Don't really recall as it was 21 years ago (!) The pins and hinges, while worn, are still original.
I do rub some Boelube wax lubricant on the pins every time they go in, otherwise they'd be very hard to get in and out.
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Last edited by rv6n6r : 11-21-2021 at 02:56 PM.
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  #3  
Old 11-21-2021, 03:15 PM
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You can buy hinge pin material in pretty much any diameter from McMaster-Carr. Get a variety and give them a try to find what works best.

I made two sets of hinge pins. One with the original pin size from Van's that came with the hinge, then one slightly smaller. I'm still using the slightly smaller one, since it is much easier to insert and remove.
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  #4  
Old 11-21-2021, 03:18 PM
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mfleming mfleming is offline
 
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Hopefully others more experienced than me will reply but that doesn't look right at all. I'm guessing a smaller pinned was used to ease pin installation. Looks like that needs to get fixed ASAP.
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  #5  
Old 11-21-2021, 03:28 PM
Richard Connell Richard Connell is offline
 
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The Vans design specifically uses 0.090 Stainless pins for the top cowl hinge.
These replace the 0.120 pins the hinge is designed for.
the lower diameter pin is to get around the curve, but allows a 0.015 up and down play along the flat top which is noticeable.

I think you will find it difficult to get a 0.140 pin around the bends unless the hinge is already significantly worn. Even getting the 0.120 pin through is tough on a new hinge.

Id think about the tapered pin idea. I think ill try this as well in time. Im not flying yet but my RV7 top cowl pins became a lot easier in time so perhaps try bruces suggestion and get a few different sizes but maybe err on the side of thicker as they do loosen. lube the pins.

cheers
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  #6  
Old 11-21-2021, 04:01 PM
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Carl Froehlich Carl Froehlich is offline
 
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I got a couple of the larger pins from Vanís (SSP-120).

On the first RV-10 I chucked up a pin in the drill press and used a angle grinder with to taper 10Ē or so. This as a pain as the SS was difficult to taper - but it worked. I finished the pin off with some sandpaper while still in the drill press. Once done the part of the pin in the chuck was trimmed off and the pin cut to length (leaving in a margin to make the end bends for the locking device). The tapered part the pin of course goes into the hinge curve. A couple of drops of oil and all is good.

On the RV-8 I did the same, but twisted Tom Doranís arm to do the taper in his laythe.

Happy with both applications, and recommend it.
Carl
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  #7  
Old 11-21-2021, 04:54 PM
Ralph Inkster Ralph Inkster is offline
 
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I had similar vibration at the top center cowl on my latest 6A where I used a similar pin locking plate. I riveted a tab to the bottom of the center plate which hooked under the firewall flange. This stopped the top center cowl vibrating. Also, the cowl used to bulge there in flight, the tab fixed that too!
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  #8  
Old 11-21-2021, 06:24 PM
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WingnutWick WingnutWick is offline
 
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Ralph, trying to visualize this. Do you happen to have a pic?

Quote:
Originally Posted by Ralph Inkster View Post
I had similar vibration at the top center cowl on my latest 6A where I used a similar pin locking plate. I riveted a tab to the bottom of the center plate which hooked under the firewall flange. This stopped the top center cowl vibrating. Also, the cowl used to bulge there in flight, the tab fixed that too!
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  #9  
Old 11-21-2021, 06:34 PM
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WingnutWick WingnutWick is offline
 
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Ok, looks like I'll be trying the tapered pin method, starting the taper at where the bend begins. The six pins on this cowling definitely make me appreciate the quick releases that my 8 and 6 use. If I ever do a repaint I may retrofit the 10 with these.
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  #10  
Old 11-21-2021, 07:49 PM
Ralph Inkster Ralph Inkster is offline
 
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Default stabilizing vibrating cowl

Sorry, a drawing will have to do. The plane is 20 miles from here.
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