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3 versus 4 guys

To: <>
Subject: 3 versus 4 guys
From: (Stan Griffiths)
Date: Fri, 14 Jun 1996 00:25:06 -0700 (PDT)
>In a message dated 96-06-11 11:40:24 EDT, you write:
>>I would say that the quadrature guying is because of the space required for
>>mounting booms on the tower top while on the ground.  I don't know what
>>forces you are talking about as there would be no rotational twisting forces
>>the tower (in the plane of the earth) while folding it over (assumes no
>>I don't see that having quadrature vs triangular guying improves things at
>>base of the tower while folding it over.  The hinge guys must resist the
>>introduced by the folding action and 3 guys work as well as 4.
>Hi, Bob --
>      Actually I sent that post without checking my Rohn book.  The specs
>call for 4 guys over the entire structure.   I was in error and apologize for
>any confusion.
>    IMO the reason that four guys is used is is because of the potential for
>larger torsional stresses both in the lowering/raising mode and in the
>upright position.  As you know, some beams are not symetrical in terms of
>their mechanical balance.  If you have an unbalanced load such as this on
>your foldover tower, there will be a torsional load on the mast exerting some
>twist to the tower.  Also, even though the section at the hinge is pinned, it
>is not connected 100% to the rest of the tower like a regular section is.  It
>is also a weak link in the ability of the tower to absorb  these torsional
>forces.  Therefore, having 4 sets of guys gives the tower additional twist
>resistance to make up for the design compromises of the hinged tiltover
>design.  Like I said, this is my opinion based on my observational experience
>in working on towers.  BTW, I've rarely seen a tiltover section that wasn't
>bent or broken at some time in its history.  Don't overestimate the
>mechanical strength of any tiltover fixture.  73,  Steve   K7LXC

Hi Guys,

I think the answer is really much simpler than what I read above.  If you
guyed a tiltover tower in the normal three ways, the tilting boom that the
cable attaches to would interfere with the guy on that side of the tower as
the tower is raised.  In order to move the guy out of the way of the boom,
it is simply split into two guys leaving a gap for the boom.  Since there
are now four guys, the other two are moved a little around the tower to keep
things symetrical and take advantage of the additional strength of the
fourth guy.  I think you could guy the top in the normal three ways, but it
would require a new set of guy anchors since the first set was spaced for
four guys.  Much easier to use four guys on the top also.

My two cents worth.


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