I put new tires on last year and used beads in each tire, the coach
drives as smooth as can be.
>
>>>
>> Centrifugal force will dominate and make them try to get as far from the center as they can and they will move TO the larger radius instead of away
>> from it. Making a bad situation worse.
>>
>> If there isn't a larger radius, they would evenly distribute and still accomplish nothing.
>>
>> They don't behave that way, and that's why it doesn't make sense to anybody. So the only possible explanation is supernatural black magic. Accept it
>> and move on.
>>
> Here is as good an explanation as I can come up with. I have checked several sites on the Internet to validate this:
>
> Short of a mathematical proof, the concept is valid -- the beads dynamically distribute mass to align the center of mass with the geometric center of rotation. Centrifugal force is not the cause of the balancing as we would normally assume.
>
> The following time steps are involved.
>
> 1. Tire at Rest: The beads rest on the tire floor due to gravity.
>
> 2. Tire in Motion: The beads distribute uniformly by friction as the tire begins to rotate, where they are held in place by centrifugal force (F=mv2rF=mv2r), acting perpendicular to the tire wall. Note that beads would remain in this state for a perfectly balanced tire. For completeness, gravity still acts on the beads but is small relative to centrifugal forces.
>
> 3. Heavy Spots in Tire: In this time step it is important to remember that the vehicle's suspension allows the wheel assembly to move vertically- Upward motion is resisted by the car's suspension (spring) while downward motion is assisted by the suspension (spring) and resisted by tire pressure against the roadbed. As the 'heavy spots' in the tire are rotated at higher velocities, their centrifugal (inertial) forces physically move the tire up and down- poorly balanced tires can literally cause 'wheel hop'! As the tire moves (up and down), the beads, with their own masses resisting motion, do not move rigidly with the tire's translation; they move relative to the tire. Note that without vertical movements, only centrifugal forces act on the beads and they maintain their new position on the tire wall.
>
> Imagine a bead when the tire moves up (ie. the 'heavy spot' on top)- Reversed when the tire moves down (ie. 'heavy spot' on bottom):
>
> At the top: As the tire moves up, the bead does not. No longer guided by the tire wall it maintains its tangential velocity until it reestablishes contact at a new tire wall location, further from the imbalance.
>
> At the bottom: As the tire moves up, the bead is lifted with the tire and does not change its location in the tire wall.
>
> On a side between top and bottom: As the tire moves up, the bead rolls down the tire, changing its relative location in the tire wall further from the imbalance.
>
> 4. Reduced Tire Oscillations: Each oscillation (tire movement, up and down) moves the beads progressively further from the imbalance ('heavy spot'), reducing the imbalance. Therefore, the tire becomes more balanced each oscillation until the tire is balanced.
>
> 5. No Tire Vibration: The beads are held by centrifugal force in their balanced state. Because no imbalance exists, there are no vertical movements of the tire to disrupt their positions.
>
> However, there are practical considerations worth mentioning.
>
> Because the beads are free-floating (unlike mounted weights), accelerations create transient imbalance. For example, until the beads are distributed, their mass actively contributes to wheel imbalance. Similarly, road bumps, braking or driving accelerations will disrupt the equilibrium state. In most cases it really doesn’t take long for the beads in the tire to balance itself.
>
> Because the mass is distributed furthest from the center of rotation, more force is required to accelerate the wheel assembly, resulting in decreased fuel efficiency (this is probably not measurable in our case). This effect is magnified by larger diameter tires. Additionally, more mass is required to balance the larger tire mass. (So, larger tires require more beads)
>
> Note: Tire balancing machines do not validate this method because they have a fixed axis, unlike the axis on a vehicle that moves. Without movement, the beads gather at the 'heavy spot'. To accurately measure the effect, the machine must allow movement.
>
> While tire balancing beads are a valid method to correct imbalance, their effectiveness depends on speed, tire size, and driving accelerations.
>
> Beads will not reduce “shimmy” or side to side movement of the tire.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
>
>
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--
Ray Erspamer
78 Royale - "The Great Lakes Eagle"
Center Kitchen TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMCRoyale
414-484-9431
Web Site:
http://ray-lisa.page.tl/
