On 3/15/21 4:54 PM, Al Kozakiewicz wrote:
I appreciate all the suggestions.
I don’t think isolating the tower from the house is possible. Yes, I can slip
some rubber or other material between the bracket and the house, but I probably
over-engineered the anchors. They consist of threaded rod passed through the header in
the gable end of the house along with two of the roof trusses. It is rigidly fixed
with nuts and washers on each side of every member the rods pass through. The bracket
is bolted to the rods.
In general, you're better off preventing the oscillation in the first
place than trying to isolate it once it's there.
Rope through the elements sounds like the way to go.
Rope around the elements (on the outside) is far more effective at
killing the vibration. Inside just damps it, but the forces are still
driving it and the mass just changes the resonant frequency. Around the
outside stops the oscillation.
Do you have an estimate of the vibration frequency? That can help you
figure out what is vibrating.
F (Hz) = 3.26 * V(mi/hr) / d (inches)
For instance, a 1" diameter tube in a 10 mi/hr wind will shed vortices
at about 33 Hz
Typically, aeolian vibrations are most noticeable in mild winds (10
mi/hr) - when the speed gets up higher, you often have turbulence or
gustyness so it can't excite the "resonator" as well.
However, anyone who's been in a high wind (>40 mi/hr) can tell stories
about wires and cables singing (or screaming), during the gusts too..
0.25" at 40 mi/hr is 521 Hz - and that's pretty noticeable.
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