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little flyers

p.o. box 657, kearny, az  85237

16 airport drive, kearny, az. 85237

(520)-363-5175         1-800-262-9644        fax (520)-363-5178

dynamic wheel balancing

it is a common assumption that if one assembles a light aircraft yellow stripe on tube wheel with the yellow stripe (heavy spot) on the tube with the red dot (light spot) of the tire the assembly will be reasonably in balance.  from our experience even with installing 1st line tires we have found that only about 5% are reasonably in balance.  hardly anyone would consider installing new tires on their personal vehicles without balancing them.  some aircraft maintenance shops have �static� balancers that they use if an obvious problem arises.  a few, such as us have invested in an electronic dynamic wheel balancer.         

some of the benefits of dynamic wheel balancing

1.         practically eliminates nose wheel shimmy if nose gear and steering are

properly maintained and adjusted.

2.         greatly slows the wear of landing gear components especially torque links and their attaching hardware.

3.         wheel brake components do not wear as quickly, especially torque pins and torque plates.

4.         usually less brake chatter during taxi operations

5.         wheel fairing life is greatly extended

6.         gyro instruments last longer particularly if their mounting is rigid

7.         take off and landing rolls are smoother

8.         less likely to develop �wheel hop� during heavy braking

 

prerequisites for dynamic wheel balancing.

wheel assemblies to be balanced are to be clean inside and out and clean and inspected wheel assembly not cracked, broken, warped, distorted or corroded.  correct wheel / brake disc hardware is to be installed and properly torqued.   brake discs are to be serviceable and wheel bearing cones secure.  tire is to be in good serviceable condition, true and without severe flat spot(s).  no loose material rolling around in inner tube (rubber balls) and of course properly inflated. 

 

balancing process

            wheel assembly without bearings is mounted on dynamic balancer mandrel and appropriate information such as wheel diameter and wheel width are entered into the balancer�s computer.   the wheel is then spun by hand and during coast down balance data is collected and processed by the unit.   the wheel is then turned until weight points are indicated along with necessary corrective weight.  location and weight are then marked on the tire.  wheel is wheel with balance weight then removed from the balancer and the weights are installed using pressure sensitive adhesive.  rarely do equal weights get installed opposite each other.  the wheel is then remounted and checked for balance; if ok the process is done, if not necessary corrections are made.  occasionally a wheel will require more balance weight than there is room to mount it.   sometimes one can reposition the tire on the wheel and bring it into a balanceable configuration. balance pad in tire sometimes it becomes necessary to install a balancing pad inside of the tire and then complete final balance on wheel rim area.   

see dynamic wheel balancing: an example

  situations that dynamically balancing may not cure

  1. flat spotted tires

  2. out of round tires

  3. tire tread separated for carcass (not always evident)

  4. poor quality recapped tires

  5. tubes with loose material inside

  6. bent / distorted / cracked wheels

  7. brake disc thickness varying, usually the result of excess brake disc brake run caused by improper torquing of wheel halves. the only reliable solution to this that we found is the replacement of the wheel / brake disc assembly.

weights

  • adhesive mounted weights have their limitations but are relatively easy to use.

  • mounting area must be absolutely clean, finish well bonded.

  • weights must be perfectly formed to mounting area.

  • weights must not be repositioned once placed.

  • double stacking of weights does not work.

  • heat from brake disc may loosen adhesive.

  • weights mounted in brake disc may not clear brake components.

  • various cleaning solvents may loosen weight adhesive.

  • aggressive braking wheels after take off may throw the weights.

balance pads

  1. time consuming to install.

  2. stay in place if tire casing is properly installed and adhesive is used as directed.

when should i have my wheel dynamically balanced?

            whenever new wheel, brake disc, tire, and or tube are installed.

            when the tire is flipped around on the wheel due to more wear on one side of tire. 

            whenever a flat spot is scuffed on the tire not requiring replacement.

at annual or 100 hour inspections. 

how long does it take?

about 10 to 15 minutes per wheel if done at tire or wheel component change or done in conjunction with an annual or 100 hour inspection.   

if your aircraft is brought in for wheel balance only it takes considerably more time.  the aircraft has to be jacked, wheel fairings, brake components, and wheels removed for balancing and then reinstalled. 

you may carry in your wheels (without bearings) for dynamic balancing.  we can usually accommodate a set without an appointment.  cost for carry-in wheels per balance is $20.  call us at 1-800-262 for more information.

 

other information

dynamic wheel balancing example

 

 

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last modified: march 01, 2007

 

 

 

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