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Re: [TowerTalk] Q on guyed rotating towers

Subject: Re: [TowerTalk] Q on guyed rotating towers
From: <>
Date: Thu, 28 Feb 2008 12:29:59 -0600 (CST)
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Rotating towers tubular/cantilevered like berthas or triangular trussed like 
Rohn with rotating guy rings need to have some point fixed against rotation 
somewhere in their height to develop the resistance to allow the mechanism that 
rotates them to work. This is also the place that resists any torsion applied 
to the tower system by external forces,i.e., eccentric wind load on the 

The torque is usually resisted by the rotating mechanism be it a gear and chain 
or direct coupled system. This is the fixity that both resists the torque and 
allows the tower to rotate.

The tower structure itself (tube or triangular trussed section) has to transmit 
this torque force say from the antenna location to the point of resistance. 
Tubular towers do it thru hoop stress and trussed triangular towers thru the 
diagnol members.

Dick Weber, K5IU, published a paper a while back in QEX, I believe, on the 
effects of torsion on towers and how to mitigate it.

IF you dont have a mechanism to resist the torsion created in the tower, it 
would not turn or it would spin like a top.

I don't know of any brake mechanism that is utilized at the rotating guy rings 
to keep the tower from rotating.

Lonberg Design Group, Ltd.
H.S. Lonberg, P.E.,S.E.

>Date: 2008/02/28 Thu AM 11:56:17 CST
>Subject: Re: [TowerTalk] Q on guyed rotating towers

>Comments bottom-postedFrom: "Arthur Trampler" <>Subject: 
>[TowerTalk] Q on guyed rotating towers<snip>From what I understand part of the 
>strength of a guyed tower is that torsional movement is converted into down 
>force by the guy wires tightening as they attempt to cover a greater distance 
>(as the tower twists).With a rotating guyed tower, is there some sort of 
>locking mechanism between the bearings and tower, at least in a given "parked" 
>position to allow this phenomenon to occur?  Otherwise it would seem that this 
>benefit is lost as the guys are not attached to the tower, but to the bearing 
>rings.Help me out...maybe the difference in strength is inconsequential or 
>mitigated by other factors.Art, K?RO-0-The strength of the tower is the 
>strength of the tower, based on the materials and design.  LOADING on the 
>tower comes from mass and surface area, as the wind works on the structure.   
>Loads are transferred into vertical compression by the guy system.  Torsional 
>loading on a triangular tower indeed does add to the down force somewhat, but 
>this is quite small compared to the other loads.   Thus, a tower which rotates 
>inside a ring-coupled guy system is simply relieved of whatever torsion 
>loading might otherwise be imposed upon it.   It is neither stronger nor 
>weaker as a result.Make sense?n2ea
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