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Old 01-13-2011, 11:51 AM
casdave casdave is offline
Join Date: Mar 2000
Posts: 8,125
There are two forms of wheel balancing, or rather mechanical rotor balancing.

The first is static, the rotor should not come to rest in the same position eveery time it is allowed to run freely down to a stop.

The other form is dynamic balancing, this is the one where typically you make a chalk mark and use a timed strobe light, you can then measure the vibration in the shaft. The chalk mark is there simply to give you a reference point.Changing weght dirstibution will change vibration, however you do have to be careful about this as you can get resonances that you can balance, and yet at perhaps twice the speed you get another imabalance - this will be at the natural harminics of the system.

You add or remove weights to counter both of these unbalances - the rotor need not be round, the idea is to get the mass around a centre distributed evenly.

There is no guaruntee at all that these free moving objects will collect int he most suitable places, n fact they may well end up at one side of the wheel and exarcerbate the problem - if you think of a washing machine and a bunch of heavy wet towels, you get the idea about what could happen at certain speeds.

Closest I have come to an active dynamic balancing system is in very large industrial washing machines, where you have a drum easily big enough to sit inside. This is divided into three radially separated compartments into which the washing goes. Inside each of these compartments is a small balance pocket, and should the machine tend to pull off centre due to unbalanced loads - such as for water retaining items in one compartment compared to another, then water is injected into the relevent balance pockets.
These machines have a very high spin speeds and are made out of seriously significant pieces of metal, like 3/4 to 1inch plate steel for all the main structural components.It has to work or things will break quite badly.

You'll note that there are three balance pockets and they must be seperate, it just would not work in a full round pocket such as a car tyre, at best it would be neutral I would think.

There is the possibility of the fluid, or golf balls circulating at a differant rate to the wheel, but good luck in doing the calculations for that.