Date: Wed, 28 Dec 2005 16:05:30 -0500
From: "Mark A. Holman" <[EMAIL PROTECTED]>
Subject: Re: Re: Tower Installation
<Say AL W. I have a Q. what is the wind survival speed on a house bracket
<? just curious?
<most installs up here in MI. are cement our wind avgs. are 75 mph.
<non-straight line winds.
<mark h. ab8ru
Mark,
You probably would need to check with Rohn about the strength of a house
bracket. Anecdotally, I have a 50 foot Rohn tower bolted to the side of my
two story house with a big TV antenna on it. It's been there since 1979. A
few years ago a small tornado took out several large oak trees in the yard
and the TV antenna. Tower and house were unscathed. (House has been here
since 1850 but that's another story.)
The house bracket is through bolted to a 2 by 8 about eight feet long
inside the attic. The tower base is a regular Rohn 25 section buried about
18 inches in the ground.
I don't know anyone personally that's ever had a failure of a real Rohn
house bracket. I'm sure they occur, probably due to poor installation. I
have taken down many towers and several were put in with just two or three
inch long lag bolts, an invitation to disaster. I recommend a backing board
and bolts through the house bracket through the backing board.
A good rule of thumb is to never go more than twenty feet above the
house bracket (or top guy point), however, I violated that rule here by
about eight feet.
I am in east central Illinois and we seldom get winds more than sixty
MPH, although they do exceed that occasionally.
I did read a piece from Rohn once where they said that a house bracket
could actually weaken a tower in that it puts a bending moment on only two
legs of the tower. However, they were comparing the bracketed tower to a
properly guyed tower.
73,
Al, K9SI
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