[TowerTalk] Rotating tower failures ?

[N4ZR]

I believe that was the failure mechanism in the wind-induced collapse of 
K4JA's 200-foot AB-105 tower used for his stack of 40M beams.  I worked 
(in a minor way) on the replacement with heavy-duty AB-105 which was 
finished just minutes before the start of a major contest a looong time ago.

73, Pete N4ZR
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On 9/9/2019 7:17 AM, Jim Thomson wrote:
> <PiRod does not approve of rotating towers (the steel tower cork screws) -
> <which is a significant problem. Rohn towers (pipe vertical legs) are worse.
>
> <73
> <Tim K3LR## Has a rotating tower ever  collapsed because of  the  tower....corkscrewing,  or  been  permanently twisted ? The  guy  wires are not  attached to  the tower, but  to the  rings. The  tower isfree  to  corkscrew  all it wants to.   It  would be  like  having a 100-200 foot long driveshaft on a car. I  only  heard of  one  case  where the  wind  was  trying to  rotate the  yagis..clockwise....  while the op  was  trying  torotate the tower  counter  clockwise.   Base of tower rotated 20 degs CCW....meanwhile the top yagi had not  moved an inch ! Finally,  the  top  yagis caught up..and had  rotated 20  degs.  ## What  does the  entire  array look like, when  in a 80-100  mph  wind?   With  all  the  yagis  mounted to the  same tower face, youalready  have an  offset  load. With yagis mounted at their CG, and no  tq  comp  sail  installed,  and  wind  broadside to  the  booms,you  will  end  up  with an absurd amount  of  TQ  at  the  base of the  tower.  Jim   VE7RF
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