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Re: [TowerTalk] Tower "DROP ZONE" or "DROP RADIUS" for Rohn 25G&Trylon T

To: "John WA2GO" <>, <>
Subject: Re: [TowerTalk] Tower "DROP ZONE" or "DROP RADIUS" for Rohn 25G&Trylon Titan?
From: "Jim Lux" <>
Date: Thu, 13 Jan 2005 07:36:02 -0800
List-post: <>
----- Original Message -----
From: "John WA2GO" <>
To: <>
Sent: Thursday, January 13, 2005 4:53 AM
Subject: [TowerTalk] Tower "DROP ZONE" or "DROP RADIUS" for Rohn 25G &Trylon

> The Building Inspector is requiring my engineering drawings to specify
> he is calling the "drop zone" or "drop radius" of the tower.  He wants to
> see what is the radius of the circle it will all land inside when it all
> comes crashing down.  (perish the thought!)
> I couldn't find this figure in the Rohn catalog anywhere. The one engineer
> talked to didn't seem to know about it either.

It's fairly easy.. the approximate(!) radius of the circle is the height of
the tower(including mast and antennas) plus a bit of margin.

Sure, guyed towers often crumple at the base, but they also don't. (Take a
look at the pictures of the KFI or KSON towers... they're basically laid out
straight).  And, as loggers are well aware, depending on the failure, the
base might kick backwards from the direction of fall, causing the fall
radius to be a bit smaller.

If a guy fails and the tower starts to fall towards the remaining guys (the
most likely scenario), the other guys on the same side as the broken one
will probably also fail (lots of inertia there..)

No engineer is going to stamp a set of drawings that would show otherwise,
unless you had something like dual redundant guy wires (in which case
anything that's attached to the guy will land within the radius of the
length of the guy from the guy anchor).


See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

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