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Wheel Pants

TheBebo

Member
Hey Everyone,

Recently picked up an RV3B. LOVING it.

I have the dreaded shimmy. Tires are pretty far out of round/balance. Brakes are worn. I have a bit of work ahead of me. Thankfully the fear legs already have a wooden dampener.

Interestingly, without the wheel pants I have no shimmy at all. I have the "stock" wheel pants, they look... huge on this plane. The extra weight at the end of the gear can't be helping the shimmy, even if I replace brakes/tires.

What wheel pants are everyone else running on their 3's?
 
I have an RV6 but I am running James wheel pants. I assume you also have 500X5 tires, so they would be the same for you. If you put on new tires and balance them it should help a lot.
 
Our -3 has standard pressure recovery pants, and they work fine. One thing that can affect shimmy is tire pressure - for us, lower pressure reduces it, higher pressure enhances it. Short of a major rebuild of....something..that is a quick way to reduce shimmy.
 
Been tinkering with lower vs higher pressure. 25psi seems to be the best place for my current setup.

New tires and tubes are going to be on order after the holiday for sure.
 
They are narrower, not sure if they're lighter. I installed the James cowling so I bought a set of wheel pants to. When I got them it was Sam James and his son making them. The business got sold the new owners are still making them and the cowlings.
 
Is the shimmy dangerous? I have it as well but I just slow down and it stops. I wasn't going to worry about it. I don't notice it at all on takeoff, only on landings when I use the brakes to slow down. It only last for a couple of seconds when on the brakes. I then taxi with no issue.

Chris
 
Just wondering - shimmy is nothing more than non-aerodynamic flutter. Our weapon against flutter typically is mass-balancing. Would the same work on wheel pants?
 
My RV-3 has just a tad bit of shimmy as I decelerate to taxi speed. It only happens for a 5-7mph range between about 30 and 25-ish. Once I'm below this range, it goes away. I never noticed it on the takeoff roll... only on landing rollout.

My 3 is out of service getting an engine rebuild and I took the opportunity to have Allen at Anti-Splat do the main wheel bearing mod as well as mounting and balancing new tires and tubes. I did the bearing mod to get rid of the old fashioned trailer bearings, but if the shimmy ends up disappearing because of the balance job, that'll be a bonus.

I have the new style Vans pressure recovery wheelpants. The initial break-in flights for the new engine will be conducted without wheelpants to keep me from exceeding redline on the airframe. This may be a good opportunity to see if the wheelpants are contributing to the slight shimmy. It'll probably be several weeks before I'm flying again, but I'll try to report back with results. Of course there's a good chance that the AntiSplat work will eliminate all the shimmy (with or without wheel pants) so I may not have anything to report! :)

My shimmy was never so bad as to be dangerous or really even annoying, but it was there.

Just another data point.
 
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Same 'ole thing guys...natural frequency, exciting frequency, damping.

Regarding the OP's comment, removing the pants is a mass reduction at the end of the pendulum, re, guaranteed to change natural frequency.

Exciting frequency is anything which can drive the structure with periodic motion. Tire out of round, a tread separation, brake disk warp, and vortex shedding are all examples. Get rid of the driver and there is nothing to excite the natural frequency.

Here damping is being added by using low tire pressure. The energy dissapated heats the tire and tube. I don't know how much. It works, although heating is not the only reason to call it a miseable shimmy solution.
 
Just wondering - shimmy is nothing more than non-aerodynamic flutter. Our weapon against flutter typically is mass-balancing. Would the same work on wheel pants?

There have been a few reports here on VAF from people who tried it and found that it worked.

Since that adds weight, it would be worth adding the balance incrementally, testing as you go. You might not need complete mass balancing.

Dave
 
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