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[TowerTalk] Now What?

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Subject: [TowerTalk] Now What?
From: (Malcolm Clark)
Date: Tue, 14 Apr 1998 09:48:30 +0000
Mike wrote:


> The Idea of a 4-5 foot hole with the tower
> stuck in then 1 1/2 inch rock covering sounds nice.
> Will it handle the load of say 70 feet of Rohn 25?
> Or maybe Rohn 45 should be used?


The maximums for freestanding 25G and 45G are:

25G  40'  1.5 sfwl  @70 mph (2.4 yds concrete) 
45G  45'  2.3 sfwl  @70 mph (4.1 yds concrete)

The base of a freestanding tower has to be imbedded in a solid block
that is big enough and weighs enough to withstand the maximum
overturning moment that will be generated by the rated wind speed and
wind load.  Gravel cannot possibly do that.

With a bracketed tower, it is mainly the bracket that withstands the
overturning moment--not the base by itself.  You really should get a
Rohn catalog.  You can send them ten bucks or you can send Steve five
bucks.  Shouldn't be a hard decision.

You don't have to use the exact examples in the catalog.  Rohn cannot
possibly cover every situation.  But you do have to understand the basic
physics of your planned installation and design accordingly.  You also
have to check and find out what the zoning ordinances and building codes
require.  You probably will need a building permit for any substantial
installation--almost certainly if you are located anywhere in suburbia
or the big city.  And I would suggest you get your landlord's blessing
for anything concreted in or bolted to the house.

Good luck.

Malcolm KR4HP

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