The steeper the angle (smaller angle to tower) the more tension is
needed to provide the same horizontal restoring force at the connection
of the guy to the tower. The needed horizontal force is determined by
the total wind load and strength of the tower.
The limiting but informative end points are:
Horizontal guys - 1lb of tension equals 1lb of horizontal force and no
downforce
Vertical guys - 1lb of tension equals no horizontal force and 1lb of
downforce
As the angle decreases the amount of tension needs to increase for the
same horizontal force. At small angles it approaches infinite. Thus,
the force on rotating bearings increases with shorter guy baselines.
The amount of downforce is limited by the buckling and compressive
strength of the tower, a complex calculation for slender towers. The
downforce is total static weight tower + everything else plus vertical
load from all guys all levels at the maximum wind load when upwind guy
tensions are the maximum.
So for shorter than catalog guy base lengths and loads, better have a PE
do the calcs. (beyond my pay grade).
Grant KZ1W
On 7/27/2021 04:56, john@kk9a.com wrote:
In the U.S., the standard guy anchor distance is 80% of the tower height but
I have heard in Europe 60% is more common. Is that correct?
I have no answers to your questions but if you are using a rotating tower I
believe that a larger anchor distance makes it easier for the guy bearings
to turn.
John KK9A
Jari Jussila oh2bu wrote:
Hi ...
I'm sure these topics have been discussed earlier, but could not find
any thread ..... Sri ...
We are at our club erecting two towers. A rotating steel tower being 31
m high and a aluminium telescope mast 18+18 m = 32 meters.
B) The steel tower height is 31 m - it's a rotating tower - but the
upper bearing is at 23 m ( leaving 8 meters for the antennas) and the
lower bearing at 11 meters.
Whats the advise of anchor point distance? Some say, that the 60 %
(distance for the tower) should be calculating from the total height
(31 x 0,6 = 18,6 meters).
Some say, it should be calculating from the upper bearing (23 m x 0,6 =
12.8 m)
Whats your opinion?
Jari, OH2BU
For OH3AC Club Station
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