At 02:44 PM 8/19/96 -0400, you wrote:
>
>
>I have been trying to determine the effect of ice
>on a tower such as Rohn 25G. Rohn gives antenna
>wind loading sizes with and without ice for their
>freestanding 25G but not for bracketed or guyed.
>
>I emailed Rohn about obtaining the max antenna
>size with ice for their 25G and 45G towers for
>a bracketed installation.
>
>The next day I received a phone call from a
>gentleman from Rohn explaining that ice is not
>really a problem with high wind speed because
>the wind blows the ice off the tower. He went
>on to say that Rohn installed a tower in
>my area (Cleveland/Medina, OH) for a utility company
>and that they used the non-ice wind loading
>numbers for the installation. He said that
>the reason the ice numbers do exist in the
>documentation for the freestanding tower
>versions is because marketing wanted it.
>
>Is this really true? What are the real effects
>of ice on a tower?
>
>Gene
>WD8OZL
>
>
>
I am no PE, but common sense tells me the weight of the ice is going to
account for something. If the ice is thick enough...and in Kansas we can
get a coating of ice 1 to 3 inches thick...the weight and the added surface
area of the tower tells me that non-ice specs are thrown out the window.
Several years ago, I lost a TH7DX because of three inch ice. I about lost
the tower, but the large guys I used saved it from coming down, but the
tower had torqued and rotated the tower when the wind whip the TH7DX around
to the north in the wind. That action took out the brake in the HAM IV
too....not the wedge, but the ribs on the inside of the Bell housing of the
rotor. Took out a 1;4 turn of the bell housing and then it froze up and
twisted the tower.
That same ice storm took down a newly erected 1400 foot TV tower in Topeka
Kansas and sent the station into receivership. What a mess. The tower
wrapped around the transmiiting building as designed leaving the $1,000,000
xmiter untouched. The tower was designed for 1" ice coating...and it had
three inches on it.
So, that is my horror story about ice. I don't like it and I get worried on
those nights ice hits.
Vy 73
Lee
k0wa@southwind.net
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