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Re: [TowerTalk] Rohn 25

To: "Al Williams" <>,"towertalk" <>
Subject: Re: [TowerTalk] Rohn 25
From: "Jim Lux" <>
Date: Sat, 29 Jan 2005 09:11:42 -0800
List-post: <>
----- Original Message -----
From: "Al Williams" <>
To: "towertalk" <>
Sent: Saturday, January 29, 2005 8:54 AM
Subject: Re: [TowerTalk] Rohn 25

> > I had 70' of Rohn 45 up, unguyed, at one time, and it was scary.  I
> got it
> > guyed right away.  Rohn 25 would be scarier.  73 - Rich, KE3Q
> >
> What in the design and construction of crankup towers allows them to be
> free standing
> whereas the others requiring guying?   Intuitively, it would seem that
> just the opposite
> would be true;  or could be made true with a change small change in the
> design?

For a given load handling ability, the crankup will be bigger across the
faces, making it stronger.

Bear in mind also that moving isn't breaking.  A tower can potentially flex
a pretty substantial (and scary, if you're up on top) distance without
failing (and, in fact, that flexing is essential to avoid stress
concentrations).  Perhaps this is one of the reasons why you're not supposed
to climb the crank up?  Aside from the guillotine effect that makes it
"really" unsafe, it probably sways a whole lot.  And, if you put a big mass
at the top (like that 100 kg ham with all the gear and the antenna), and it
starts to deflect, the mass is offcenter, which will aggravate the tendency
to buckle.


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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