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Non-wood anti-shimmy gear leg fairings?

Wear and tear on the stiffeners

Yes that may be an option. Im not sure how the wood stand up over time. Does it crack, does it loosen up from the gear leg from all the harmonics and lose effectiveness?

Once I get the fairing off it may be glaring obvious whats happening:D, or not.:confused:
 
If it's properly wrapped with fiberglass at a 45 degree angle, it'll probably hold up fine. Otherwise I suppose it could crack from the shear load, if the carbon alone were on it.

Dave
 
Wittman Gear

The round spring gear was designed and patented by Steve Wittman in the late 40's early 50's. The first plans built Wittman Tailwinds first flew in 1955. The landing gear was relatively short and the airplanes were considerably lighter that the RVs except for the RV3.
Very few airplanes in that era had any kind of shimmy dampener. Those that did used a hardwood stiffener. One common method of attachment was the banding straps used to build wooden shipping crates. Much later it was common to fabricate a gear fairing with a larger piece of wood on the trailing edge and a couple wraps of fiberglass around the gear leg and wood.
I have metal gear leg fairings so I was able to make the aluminum bar fit inside the fairing. My gear may very well toe out at heavier weights.
The angles on the gear legs are a guessing game on a taildragger. If the camber is set in the three point position as the tail is raised the gear toes out/or any toe in decreased.
If the angles are set at gross weight the gear will toe in at reduced weight. Wittman specified 1/16" toe in measured in length of axle but did not specify attitude or weight when setting this.
 
Antisplat

I'm surprised that Alan at Antisplat hasn't designed a complete kit for using a metal main gear stiffener. He usually is far ahead of the fray!


Chuck Brietigam
RV-6XXL
 
Using chromoly tubing for gear leg stiffeners

I am considering using chromoly tubing that I could run the brake line thru and Adel clamp it to the gear leg. RV4 long leg no shimmy but more bounce! Any and all comments appreciated
 
My fiberglass and carbon fiber

FinnFlyer,

I did what you were originally asking about in your first post. Check out my builders pages in KitLog.com. The link is in my address. Plane has 250 hours so far with no problems with the install.

Paul
 
I am considering using chromoly tubing that I could run the brake line thru and Adel clamp it to the gear leg. RV4 long leg no shimmy but more bounce! Any and all comments appreciated

Ought to be effective, I suppose, but you can do your own calculation of the combined inertia to be sure. 4130 has a modulus the same as the gear leg and about 2.8 times that of aluminum.

Dave
 
just me

I like the aluminum plate idea the best. I think this is what I am going to do. But please keep the ideas coming. i am waiting for the airfoil shaped titanium replacement gear for the 7/9 class planes. cant be that expensive; still gotta be cheaper than a 14.
 
You might not want titanium... it has 55% the material Young's modulus, or stiffness, of steel. Might feel too springy.
Dave
 
wood to the metal

I'm wondering if anyone has gone from the wood to the metal and if there was any improvement?

Thanks
Tim
 
I'm wondering if anyone has gone from the wood to the metal and if there was any improvement?

Thanks
Tim

I just finished doing this on our -3, and with only one test flight in the box, I can still give a pretty definitive “yes” to the question. Our wooden stiffeners were on there from day one, and with almost 800 hours, they had become loose, and were doign very little. The truth is, we have always had a shimmy with these spindly RV-3 legs - we just controlled it with lower tire pressure, braking, and avoiding certain taxi speeds.

Installing metal dampers was probably a total of about six hour’s work - I spread it out over a couple of days, but it was straightforward. Based on notes from Dave Paule, I used 1/8” x 1-1/2” aluminum, and seven Adel clamps. I removed the rubber from the Adel clamps, mostly because I was worried about the outside diameter affecting the fit of our gear leg fairings. Largest Adel is -18, smallest is -12, and they are spaced to where they are naturally tight on the gear leg for their diameter - note that this is NOT evenly spaced. There’s a single wrap of Gorilla Tape under each clamp, just to seat them better.

Spacers were required between the clamp and the metal bar stock to put the center of the bar stock through the center of the gear leg. Screws are low-profile #10 Allen heads, 1” long, and fastened with low profile nylon lock nuts. Washers and s machined bushings were used for spacers, and there was approximately a single washer difference between adjacent clamps. The existing gear leg fairing fit right back in place!

CC34C4DD-749D-40A8-96B1-4A4025774BD9.jpg
 
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Shimmy

On my Wittman Tailwind the problem has always been the left gear. I tried the metal strip, no rubber padding, no gorilla tape. It seemed to help at first, then revferted back to not quite as bad as before.
I am now installing the wood strips with double wrap of 2" fiberglas tape with epoxy resin.
The shimmy occurs at relatively low speed, around 25 statute on the gps. It is not terrible but certainly annoying.
This is my second Tailwind which gives me 58 years total experience with the Wittman round gear.
 
Another cause and fix for the shimmy

During my annual I decided to look deeper into my shimmy. Pulled the gear leg fairings on my short gear RV4 to find that the fiberglass wrapped wood had dropped down a good 1.25 to 1.38 inches on the tapered gear so they were a little loose. I tapped them back up into position until they were tight. Put a couple of hose clamps into position to prevent them from sliding down and went for a flight.

I was even brave with running 25 psi in the tires and low and behold the 3 runways that would almost shake me off the runway it was now smooth. Once I thought I felt a slight shudder but then it was gone. So a dozen landings so far and I would say its cured.

I was even able to leave my larger 380 tires on. I'm sure that down the road I will find a runway that will initiate the shaking but it will have to be a real rough runway.

Later this fall I will make this a little more permanent so I can remove the hose clamps.

Tim
 
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