RE-balance it again. It is likely dirty and out of balance. Or
the balance moved over time. Oil can make some glues soft.

I've known fans that were on 12 foot extensions that were wood and
didn't wobble. I wanted them - old school designs for colleges. They
were junked and air condition was put in. Just as I stopped going to
that building. Such is life.

Martin

On 8/31/2013 10:19 AM, Phil wrote:
Low speed , it is quiet, higher speed , rattles, I balanced the wobble
out of it years ago, have a 18" down shaft on the fan, checked the blades,
pushed up and down on the fan blades, arms, in the center of the motor
and have the play there.