| Re: [GMCnet] Wheel Balancing Beads (Part III) [message #78608] |
Tue, 30 March 2010 15:15  |
Gary Casey
Messages: 448
Registered: September 2009
Karma:
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Senior Member |
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I've been following this thread with some interest and have an "explanation" of my own: Every system (collection of stuff) has a resonant frequency determined by the mass (weight) and the spring(nothing is perfectly rigid) that supports it. In this case the dominant mass is the hub, knuckle, wheel and most of the tire. Pretty heavy. The spring is the tire itself reacting with the ground. The resonant frequency, has for most of eternity, just happens to be at the wheel rotation frequency corresponding to a speed between 55 and 75mph, depending on weight, tire pressure, etc. Assuming the tire is round at speeds below the resonant frequency the tire just rotates smoothly and the unbalance has little or no effect - the tire rotates about the axle. But when it approaches the resonant frequency or beyond, the wheel tends to rotate about its center of gravity, which is NOT the axle. So what happens is that the axle orbits around the CG and that's what
you feel. This happens at all speeds above the resonant frequency, but the motion is amplified at the resonant frequency. Since the tire is rotating about a point that is not at its center the tire now has a different radius in different directions. Turns out the light side of the tire is further from the center of rotation than the heavy side. Consequently, the loose beads migrate to the light side until the rotation goes back to being at the axle. At least that's the explanation. Do I buy it? I'm not sure. But my question is, if they work so well, why doesn't everyone use them? The idea of balancing beads has been around as long as I can remember (it's only my short-term memory.....) and that is a LONG time :-). The idea has hung on forever, but never made it mainstream. Why not? Maybe part of it is that the tire has to rebalance itself every time it comes up to speed - does that take time? Does it shake for a little while? Does a bump
in the road disturb the balance for a while?
Gary
'73 23' that needs 4 new tires :-(
After exhausting my mental avenues, very easy to do these days, I thought
> that I would did around in the internet and do it the easy way and I did
> come up with a hit.
>
> Would link not display in Firefox, I had to use IE.
>
> http://www.innovativebalancing.com/HowItWorks.htm
>
> I still have to do some thinking on it but it is an explanation.
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