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Wheel Balancing

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kboatright1(at)comcast.ne
Guest

Posted: Fri May 19, 2006 5:39 pm Post subject: Wheel Balancing

After another couple of landings this week with noticable shimmy, I've 

decided I'm tired enough of this problem to actually do something about 

it.



Here are the four issues I usally see when the subject of shimmy comes 

up:

   

    - Wheelpant balance.  I balanced 'em before the first flight, so I 

have no idea if the balancing helped or hurt. 

    - Gear leg stiffeners. Don't have 'em. 

    - Wheel/tire balance.  I have noticed that the gear seems more 

shimmy resistant on new tires. This may be a roundness or a balance 

issue. 

    - Air pressure - I keep it at 22-24 lbs, so reducing it more isn't 

practical.



My plan is to:



    1) Balance the wheels and see if this helps. 

    2) If not...New tires (balanced). This should take roundness out of 

the equation.

    3) If that doesn't work, I guess I'll pull off the gear leg fairings 

and add wood stiffeners.

    4) If *that* doesn't work, I'll remove the wheel pants and related 

hardware.  If that helps, I'll try a new set of wheel pants without 

balancing 'em.



Anyone got a better plan?  I'm all ears on this one.



By the way, how do you balance aircraft wheels?  I don't remember any 

suggestions on this.



Thanks in advance,



KB

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ronlee(at)pcisys.net
Guest

Posted: Fri May 19, 2006 6:07 pm Post subject: Wheel Balancing

I already posted about this a few months ago.



Check for tire roundness and then balance the wheel/tire

assembly.  Also applies to nosegear.



My A&P has a balancing tool.   Balance with motorcycle lead weights.



Previous post may have been Nose wheel shimmy topic.



Ron Lee

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pitts_pilot(at)bellsouth.
Guest

Posted: Fri May 19, 2006 6:22 pm Post subject: Wheel Balancing

Kyle, you need to define shimmy, and where it's from.  I think that 

technically, the nosewheel (or tailwheel) can have shimmy, but the mains 

cannot.  Shimmy is the rapid back/forth movement of a wheel located 

behind a pivot point. Like a shopping cart.  Another vibration can come 

from the Whitman - style main gear, which I call 'walking' for lack of a 

better term.



OK, what to do about shimmy.  The pivot axis needs to be as vertical as 

possible.  As the top of the pivot axis moves forward, the more prone to 

shimmy the wheel becomes.  The second thing is the drag on the nosewheel 

fork.  My Grumman has a castering nosewheel, and shimmy prevention is 

due to the pressure on the belleville washers.  Belleville washers are 

cupped and you can nest and stack them for more drag as the spindle nut 

is tightened.



As for the 'walking' of the mains .... well, the only knowledge I have 

is what's been on the list .... stiffeners on the gear legs. 

 Personally, I hate the Whitman gear.  Watching the wheels lurch fore 

and aft is just plain painful from an aesthetic point of view.  Just my 

opinion.  I'd much rather have a spring gear on my -10.  Blasphemy, I 

know, but I'm going to consider it.  Call it an experiment.  But I 

digress.  I can see 'walking' occurring from bent discs and/or dragging 

brakes or even bad bearings ...... but I don't think tire balance or 

fairings contributes to either 'malfunction'.



Here's what I'd do.  Go fly.  Just after liftoff, see if the vibration 

goes away.  If not, stomp on the brakes and see if it goes away.  If it 

goes away, then you have an unbalanced tire on the mains.  That leaves 

the nosewheel.  Have someone watch you as you takeoff and land ..... 

they'll be able to spot the shimmy or the walking.  Work from there.



As for balancing, jack the tire off the ground and loosen the axle nut a 

little.  Spin the tire a couple of times and see if one place 

consistently ends up on the bottom.  Aviation wheel weights are stick-on 

..... cut an inch or so and stick it on the inside of the rim on the 

high side.  Trim or add weight until the tire stops on a random spot. 

 That's all there is to it.

Linn

do not archive

Kyle Boatright wrote:



 	  Quote: 	
		  



After another couple of landings this week with noticable shimmy, I've 

decided I'm tired enough of this problem to actually do something about 

it.



Here are the four issues I usally see when the subject of shimmy comes 

up:

   

    - Wheelpant balance.  I balanced 'em before the first flight, so I 

have no idea if the balancing helped or hurt. 

    - Gear leg stiffeners. Don't have 'em. 

    - Wheel/tire balance.  I have noticed that the gear seems more 

shimmy resistant on new tires. This may be a roundness or a balance 

issue. 

    - Air pressure - I keep it at 22-24 lbs, so reducing it more isn't 

practical.



My plan is to:



    1) Balance the wheels and see if this helps. 

    2) If not...New tires (balanced). This should take roundness out of 

the equation.

    3) If that doesn't work, I guess I'll pull off the gear leg fairings 

and add wood stiffeners.

    4) If *that* doesn't work, I'll remove the wheel pants and related 

hardware.  If that helps, I'll try a new set of wheel pants without 

balancing 'em.



Anyone got a better plan?  I'm all ears on this one.



By the way, how do you balance aircraft wheels?  I don't remember any 

suggestions on this.



Thanks in advance,



KB

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kboatright1(at)comcast.ne
Guest

Posted: Fri May 19, 2006 6:39 pm Post subject: Wheel Balancing

---

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ronlee(at)pcisys.net
Guest

Posted: Fri May 19, 2006 7:14 pm Post subject: Wheel Balancing

Kyle, here was the first post:  http://tinyurl.com/zqt2r



And this:   http://tinyurl.com/ku5uh



To check for out of round just spin it with a stick or suitable object

close to the tire (front or back).  Look for even distance between the

stick and the tire as it rotates.  It is obvious if significantly out of round.



Ron

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