balance on the 'fly'

[kitestrings]

Just curious if anyone has ever used one of these type of balancing devices.  Probably expensive, compared to balancing blades, but seems pretty interesting.

http://www.centramatic.com/how-centramatic-balancers-work.rhtml

~ks

[ontfarmer]

Looks like a simple way to balance, never seen one before.

[joestue]

I've heard there is one in every front loading washing machine.

[Adriaan Kragten]

In the video you can see that the ring with balancing balls is situated at about the same radius as the imbalance mass. If you would balance a windmill rotor this way, the ring with balancing balls would be situated at about half the blade length. This seems practically impossible to me. Another problem is that the balls all move to one side if the rotor stands still or is moving only slowly. So the imbalance is not balanced at low rotational speeds and this imbalance requires a rather high starting torque of the rotor. I think that this way of dynamic balancing is only possible for fast rotating disk shaped objects but for those objects it is a clever way.

[ontfarmer]

The general motors two cycle diesel used a granular material in the harmonica balancer a
one time same idea I think.

[DanG]

Been there, done that, question asked January 23, 2007...

http://www.fieldlines.com/index.php?topic=139784.0

Ungrounded Lightning Rod had a reply that I believe nailed the reasons they would not work:

It depends on springs supporting the spinning wheel, which causes a phase shift between the angle to the off-center mass imbalance causing the vibration and the actual displacement of the wheel.  In a suspension this occurs because of the springs between the wheel mount and the car, and because of the springyness of the inflated tire.  In the engine it's because of the springiness of the engine mounts.

A mill has no springs.  It wobbles as it attempts to rotate around the center of mass.  So it may not have the phase-shift required to make the weights move properly (unless the gyroscopic effects produce it).

[kitestrings]

Thanks Dan.  That was an interesting read.

Let's hope we can always do better than the horizontal-axis washer.  Mine appears to be bouncing toward the door at times before it gets to a reasonable level of imbalance.

~ks