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Trey
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Fri Jun 16, 2006 4:37 pm

Train nut.
That is really wierd. Can T-bolts do it to? I'm guessing it probably has something to do with the fiberglass too, being that fiberglass is lightweight.

Jim_Ferer
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Fri Jun 16, 2006 8:12 pm

I don't recall who first posted it (Adam, Jason, Eric, and the usual suspects) but the Thunderbolt manual advised taking a hand scale, hooking it to the Thunderbolt horn, and tugging sideways on it until it rotated. It was a 35 pound pull maximum, IIRC. So the horn should weathervane if the lateral force on the horn exceeded that number, but I never saw it happen. I'm probably missing something, like the rotator being disengaged for this test or something. What they were testing for was the tightness of the clamping of the air tube.

Bshinn
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Sat Jun 24, 2006 4:16 am

I guess your question was already answered,
but yes, I have also witnessed Allertors being rotated by the wind. As a matter of fact, the siren in Lovettsville, Virginia (Loudoun/NOVA area) that i mentioned in the Washington DC post was doing this the day I shot photos of it back in 1999. It freaked me out just a bit, as I was standing under the horn at the time. The drive mechanism for rotation uses a chain and pulley. The fact that this is a pulley, and not a sprocket allows for some slippage of the chain, which can be tensioned via a bolt at the rear of the motor housing. This tensioning bolt is present on the Allertor, the Penetrator 10/15, the RM130DC, and the RM127AC sirens, FYI.

The "discharge" horn on the allertor siren is very large, and the larger surface does have similar properties to those of a weathervane (although this probably wasn't intentional).

Ben S.

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Sat Jun 24, 2006 6:57 am

I wonder if some sirens don't have a mechanism that once so much force is applied they begin to rotate to protect them from damage. I noticed one day a couple weeks ago on my way to work the Whelen that I go by was pointing one way but on the way home it was another. The weather was hot and sunny, no storms but windy as hell. There weren't any warnings and it wasn't the monthly test day either.

Jim_Ferer
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Sat Jun 24, 2006 12:05 pm

LtKernelPanic wrote:I wonder if some sirens don't have a mechanism that once so much force is applied they begin to rotate to protect them from damage. I noticed one day a couple weeks ago on my way to work the Whelen that I go by was pointing one way but on the way home it was another. The weather was hot and sunny, no storms but windy as hell. There weren't any warnings and it wasn't the monthly test day either.
It would make sense to do so. Wind pressure in pounds per square foot varies as the square of the speed. Wind load can be huge. (It's the largest load on tall buildings, for example, not weight).

Bshinn
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Sat Jun 24, 2006 3:47 pm

Some sirens that oscillate have limit switches at each end of the sweep. If the wind moves the horn far enough away from the "park" position (thus opening or closing the switch), with some models the rotation drive will activate, moving the horn back to the parked position.

As far as the Thunderbolt horn being moved by the wind, some of the "surplus" thunderbolts I have worked on that were being cannibalized for parts would have done it, as their friction bands had been removed. They moved so freely that you could give the horn a good shove with your hand, and it would spin back around and hit you if you weren't careful. For the units in the field, however, the band would have to be really loose, almost to the point of the nut & bolt being able to vibrate apart(which the spring might prevent).

Ben S.

thunderbolt1003kid
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Wed Jul 05, 2006 8:35 pm

we had a thunderbolt by our old apartment and on windy days i would watch the horn and it would always turn in the wind i`m alaways worried that it may fall over because it swings violetently on windy days

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