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  #21  
Old 07-01-2022, 06:50 PM
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DanH DanH is online now
 
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Quote:
Originally Posted by scsmith View Post
I wonder about introducing some actual damping into this system.
Clean all the parts so bonding is good. Carefully align the leg fairing, duct tape the bottom, pour it full of room temp cure urethane rubber.
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  #22  
Old 07-01-2022, 07:11 PM
David Paule David Paule is offline
 
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The idea of the stiffeners is to eliminate the fore-aft motion if the gear leg as far as is reasonably possible.

With no motion, there can't be damping - damping requires motion to work.

And using an elastomer as a bond agent merely introduces flexibility when that's not desired.

The whole idea of this sort of stiffener is to add a structural element that's integral to the gear leg. Making a mechanism out of it, even a fancy one, is not consistent with that, and by its nature, lets motion occur - it's exactly that motion that's not desired.

Dave
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  #23  
Old 07-01-2022, 08:00 PM
FinnFlyer FinnFlyer is offline
 
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Quote:
Originally Posted by David Paule View Post
The idea of the stiffeners is to eliminate the fore-aft motion if the gear leg as far as is reasonably possible.

With no motion, there can't be damping - damping requires motion to work.

And using an elastomer as a bond agent merely introduces flexibility when that's not desired.

The whole idea of this sort of stiffener is to add a structural element that's integral to the gear leg. Making a mechanism out of it, even a fancy one, is not consistent with that, and by its nature, lets motion occur - it's exactly that motion that's not desired.

Dave
I still have concerns about this method. Now you have a much stiffer arm and the fore/aft forces are transferred more directly to the engine mount (gear leg mount tubes). The early RV-3 engine mounts cracked because of those forces and the two additional mount to firewall bolts were added. Wouldn't this much stiffer system require additional strengthening of the engine mount? Or was there some other reason those two attachment points were added?

Finn
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  #24  
Old 07-01-2022, 09:01 PM
PilotjohnS PilotjohnS is offline
 
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Quote:
Originally Posted by FinnFlyer View Post
I still have concerns about this method. Now you have a much stiffer arm and the fore/aft forces are transferred more directly to the engine mount (gear leg mount tubes). The early RV-3 engine mounts cracked because of those forces and the two additional mount to firewall bolts were added. Wouldn't this much stiffer system require additional strengthening of the engine mount? Or was there some other reason those two attachment points were added?

Finn
Since I went to the TLAR engineering school and I stayed at a Holiday Inn Express last night, I would think a shimmy leg would be worse stress on the mount than a constant force. As long as the stiffener does not tie in to the fuselage, I dont see any harm. But what do i know, I am getting kicked out of my hotel room due to non payment...
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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Last edited by PilotjohnS : 07-01-2022 at 10:57 PM.
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  #25  
Old 07-02-2022, 07:27 AM
David Paule David Paule is offline
 
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Adding the stiffener has no effect upon the forces at the top of the gear leg where it meets the engine mount. But eliminating the shimmy removes that undesirable dynamic load, and that's got to be good.

I watched mtnflyer's video showing his RV-6a main gear shimmying, and found it hard to believe that the gear stayed on.

Dave
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  #26  
Old 07-02-2022, 08:36 AM
Larry DeCamp Larry DeCamp is offline
 
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Default Antisplat on the right track.

The video for the nose wheel gets to the heart of the matter. The steel clamp on the MIDDLE of the of the steel rod is the critical ingredient . This is the end game for the Adel Clamp uncertainties. Time may prove Ironflights approach is totally satisfactory. If found to need more coupling security over time, the Antisplat approach might be a potential improvement.

The challenge appears to me to be the fabrication of a clamp that fits the tapered gear leg and does not crawl down the taper. A lot of smart people here, lets solve this problem and end the RV shimmy. Antisplat will probably kit it because the market is much bigger than nose wheels.

PS, anything that absolutely controls the deflection of the gear leg over its distance, Will concentrate the bending moment at the mount as previously challenged. This will creat a new unknown.
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Last edited by Larry DeCamp : 07-02-2022 at 08:48 AM.
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  #27  
Old 07-02-2022, 10:24 AM
Larry DeCamp Larry DeCamp is offline
 
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Default An afterthought

Using the engine cylinder head bolt preload principal, you could stiffen the rod leg with the backing bar to resist the maxlmum deformation expected ( reasonably practical ) and it should act like RV8 gear �� if it doesn’t break off at the motor mount ��
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  #28  
Old 07-02-2022, 10:33 AM
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Ironflight Ironflight is offline
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Appreciate all the comments guys - and I’ll report back when the whole thing falls apart. But I should point out that I am not the first one to do this - I stole the idea from guys who have been flying with the same thing for years. I’m just giving it some visibility for those that want to try something different, but which has some significant history. And lest you worry, there is a bit of engineering consulting behind it as well.

As for the P-shaped Adel clamps versus a symmetrical design, that’s also a question I have. I might end up fabricating some new clamps in the future, but we’ll fly this for now, and see how it lasts. I know of at least one plane with this design that has been in regular use for over ten years without a problem.

YMMV of course …. This is experimental after all!

Paul
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Last edited by Ironflight : 07-02-2022 at 12:11 PM.
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  #29  
Old 07-02-2022, 02:54 PM
PilotjohnS PilotjohnS is offline
 
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Default Alternate

Quote:
Originally Posted by Ironflight View Post

As for the P-shaped Adel clamps versus a symmetrical design, thatís also a question I have.

Paul
I think the originator alternated orientation of the P clamps along the leg. Is there any reason to alternate orientation as opposed to all the same way?
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

Dues paid 2022, worth every penny

RV9A- Status:
98% done, 2% left to go
Structure done (less gear)
Electrical/Panel done
Firewall Forward 95% done
Fiberglass 90%
www.pilotjohnsrv9.blogspot.com
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  #30  
Old 07-02-2022, 07:14 PM
FinnFlyer FinnFlyer is offline
 
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Quote:
Originally Posted by PilotjohnS View Post
I think the originator alternated orientation of the P clamps along the leg. Is there any reason to alternate orientation as opposed to all the same way?
Getting the alum bar centered so it will fit in the gear leg fairing?

Finn
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