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Wheel Vibration at Low Speed

istrumit

Well Known Member
There is a speed range, about 22-25 knots, where the main wheel on the copilot side (or, maybe both sides, its hard to tell) vibrates significantly.

I don't like to stay in this speed range during takeoff/landing/taxi because the vibration is quite pronounced.

Outside of that speed range, there is no vibration.

It seems like it must be the tire, but wow, its quite a lot of vibration for a small tire at such low speed.

Perhaps someone in the past used fix-a-flat on it ?

Any theory/input welcome.

Scott
 
My guess would be wheel balance. Several have posted their experience here and when balanced require a lot of weight, especially the cheap, stock tires. I used Dynabeads on my original tire and left them out when I went to the Wilkerson retreads (they run them through a balancer before shipping. I have no vibrations. I do have the wood dampers, but I suspect my lack of vibration is due to proper wheel balance and not the dampers.

I have some experience with very large tires on a jeep. I couldn't get a good balance on them and they would occassionally develop a very bad shudder at a specific speed (35 MPH) and only at that speed. It required hard braking to stop it.

Larry
 
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There is a speed range, about 22-25 knots, where the main wheel on the copilot side (or, maybe both sides, its hard to tell) vibrates significantly.

I don't like to stay in this speed range during takeoff/landing/taxi because the vibration is quite pronounced.

Outside of that speed range, there is no vibration.

It seems like it must be the tire, but wow, its quite a lot of vibration for a small tire at such low speed.

Perhaps someone in the past used fix-a-flat on it ?

Any theory/input welcome.

Scott

....Three Possibilities!
#1 Most likely balance
#2 Tire out of round or flat spotted
#3 Glazed spot on brake rotor. This shake usually starts on roll out as brakes are applied.

....We can help you with any or all of these, just let me know.
Thanks, Allan...:D
 
How about a small, but noticeable nose wheel "shimmy" just after rotation that dissapears within a few seconds. Absolutely no shimmy on landing. :)
 
Vibration

I am fighting a left wheel only, very ittermittent, at times very severe vibration on my Wittman Tailwind. Balancing helped but didn't cure it. The top of the line Goodyear tire is badly out of round. I am going to try Michelin on the left side and later Lamb. Might try counterbalancing the wheel pant. After that I am out of ideas.
 
Vibration

My problem had only been on landing and taxi until the last flight when it vibrated badly on takeoff for just a second or two. The airplane is now grounded to fix another issue. 75 hours plus of experiencing the vibration perhaps one out of 20 takeoffs and landings. The standard Tailwind gear is 3/4" at the ankle vs 7/8" on most RV's. My gear is 13/16". Most RV's gears are also longer which makes the vibration more likely to occur. I have the Michelin tubes in the Goodyear tires, the left was badly out of balance. Balancing helped but did not eliminate the problem. This is a very old issue with the Wittman round gear. The stiffner's and balancing usually cures it but not in my case.
 
Balance

Make an arbor that fits the wheel bearings along with some collars to keep the bearings snug but not tight. Static balance the assembly by trial and error using 1/4 oz stick on motorcycle balance weights. You can also spin the wheel with a rubber backup sanding disc on drill motor. Again trial and error. Chalk to mark the tire on the bottom for static balance.
On the Baron the best Goodyear tire eliminated a horrible vibration in the nose wheel. No such luck on my airplane.
I was told by the motorcycle shop that the Harbor Freight balancers are a waste of money.
 
Can you take a airplane wheel to an automotive balance shop ?

If not, then where ?

I have not yet balanced my tires on my 6A, however, I have read posts from others that took their wheels to a motorcycle shop for balancing. I personally like dynabeads. When I put new tires and tubes on my motorcycle, I forewent the balancing and used dynabeads. They work very well and are very popular with the motorcycle crowd. Others on this board seem to think their bad and will rip your tires up. As I mentioned, I used them on my mains for 90 hours (original tires) and they are still in my nosewheel at 150 hours.

Larry
 
Harbor Freight balancer

I had a similar issue. First off, my mains were worn so I got some retreads.

Then, I got one of these cheap balancers and some stick on weights:

http://t.harborfreight.com/motorcycle-wheel-balancing-stand-98488.html

I ended up using some Amazing Goop on the weights just to make sure they stayed put.

Then, I took my drill motor and chucked up a sanding disk I found deep in my toolbox. Next, as a double check, I spun up the tire mega fast using the edge of the disk on the tire. If the tire didn't do a dance, I called it good.

I slapped them back on, problem solved.
 
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Main gear bolt in tower bottoms out

Hi Scott,

Another place to check is the gear retaining bolt at the top of the gear tower.

The plans call for only one washer and then torque. I have seen it twice now on RV-10's where the nut bottoms out on the thread allowing the gear to rotate a bit back and forth in the tower . Adding another washer and re-torquing reduced shimmy on that wheel.

Just another data point.

Cheers,
 
Hi Scott,

Another place to check is the gear retaining bolt at the top of the gear tower.

The plans call for only one washer and then torque. I have seen it twice now on RV-10's where the nut bottoms out on the thread allowing the gear to rotate a bit back and forth in the tower . Adding another washer and re-torquing reduced shimmy on that wheel.

Just another data point.

Cheers,

Could I get a pick of that ? I am having trouble understanding that location since I did not build myself. Also, thank you, I am always interested in other ideas.
 
Hi Scott,

Sorry, I do not have a picture.

You just remove the front seat and then the cover plate that covers the seat support frame.You will then have access to the top of the gear tower.

The way the bolt is installed means that the thread is facing down so that when builders torque that bolt,it is not so obvious that the nut has bottomed on the thread and not pulled up against the gear tower.

If the bolt has bottomed out and the gear leg and frame was reamed a touch oversized,the gear will be able to be rocked left and right.

Just something else to check,

Cheers,
 
OK...I will try that.

I suppose, since I will be jacking it up to check the tire balance anyway, then, if there is a loose bolt as you mentioned, I should be able to move the leg back and forth by force once its off the ground ?
 
Shimmy damper

I had a similar problem at 30 knots or so. Balancing didn't help much, neither did stiffening the wheel pant mount. I fabricated and attached wooden shimmy dampers on the back side of the main gear legs, which solved the problem. My shimmy dampers are very similar to those described in the RV 6A fairing plans.
 
If anyone on this thread has a jack stand they have built/bought or knows of one, and they are don't use it anymore, please let me know.

I'd be more than happy to purchase it and it and pay for shipping.
 
If anyone on this thread has a jack stand they have built/bought or knows of one, and they are don't use it anymore, please let me know.

I'd be more than happy to purchase it and it and pay for shipping.

I bought the larger hydraulic ram (made for their cherry picker, but with a flat base) from HF for $35. I put a piece of wood between it and the fuselage (right below the spar carry-through) and it lifts the wheel nicely. Not perfect, but cheap. I have also used a car jack by putting a worm gear clamp on the gear leg (a suggestion from the archives here).

Larry
 
I bought the larger hydraulic ram (made for their cherry picker, but with a flat base) from HF for $35. I put a piece of wood between it and the fuselage (right below the spar carry-through) and it lifts the wheel nicely. Not perfect, but cheap. I have also used a car jack by putting a worm gear clamp on the gear leg (a suggestion from the archives here).

Larry

Are you describing something like this ?

http://www.harborfreight.com/3-ton-super-heavy-duty-long-ram-hydraulic-flat-bottom-jack-36468.html
 

That's the one. Some have built a base for it to give it more stability, I just use it as is and am very careful. It is not very stable, but if you block 2 of the three tires it is managable. Some have also modified it to lift at the wing by making a mount that goes in the tie down threads.

Post #6 here wil give you an idea for using a smaller bottle jack or traditional car jack:

http://www.vansairforce.com/community/showthread.php?t=129435&highlight=jack+clamp+gear+leg

Larry
 
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That's the one. Some have built a base for it to give it more stability, I just use it as is and am very careful. It is not very stable, but if you block 2 of the three tires it is managable. Some have also modified it to lift at the wing by making a mount that goes in the tie down threads.

Post #6 here wil give you an idea for using a smaller bottle jack or traditional car jack:

http://www.vansairforce.com/community/showthread.php?t=129435&highlight=jack+clamp+gear+leg

Larry

I had not found that thread. Thank you. That's and excellent reference.
 
Tires

I had the same problem with my -4 when I bought it. I considered gear stiffners, but ended up living with it. Then one day I got a wild hair and bought two new tires and installed them. Problem solved!

Zem
 
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