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
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|