Author Topic: Once again in 3-part (phase) harmony  (Read 19667 times)

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Mary B

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Re: Once again in 3-part (phase) harmony
« Reply #66 on: December 11, 2017, 05:46:32 PM »
You could bolt an angle iron bracket across the bottom of the plate. If it is the source of the vibration it would change the frequency. But I suspect you are hearing the tower legs vibrate. My house brackets Rohn 25 antenna tower makes a heck of a racket in high winds as it vibrates.

MattM

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Re: Once again in 3-part (phase) harmony
« Reply #67 on: December 11, 2017, 08:32:17 PM »
I remember the location of guy wires playing a big role in vibration.

SparWeb's suggestions would help diagnose the source of you could record wind speed, too.  Each rotation of the turbine disrupts airflow each time the blade passes in front of the mast.  An out of balance turbine would have a similar frequency, but a different trough pattern. Sound forms might suggest something altogether out of sync with the turbine. Knowing the frequency would pinpoint more specifically the type of vibration.  It could be something as simple as a broken  allowing tangential rotation of an isolated segment of the tower.

kitestrings

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Re: Once again in 3-part (phase) harmony
« Reply #68 on: January 15, 2018, 04:22:05 PM »
I haven't been able to follow up on this - most of the fixes are best in summer weather anyway...

A curious thing though... we had a freezing rain, sleet, snow event late last week.  Temp's were at record highs ~50 degF Friday, and then back to -10F last night.  The blades, tower, mount all had a thin frozen layer of ice, but I started the turbine on Saturday morning.  It had been lulling about, so there didn't seem to be any imbalance.  The output was a bit diminished I'd say, but the blade whistle was totally gone!  And, the plate vibration was also negligible.

On Sunday I scampered up to look it over.  The plate and tube were sort of welded together with a seal of ice.  The blades had a smooth, but irregular coating.  There was virtually none on the leading edge, heavier near the thickest cord section; spottier on the trailing edge.  (Should've had my camera).