:::: Holy cow!
I never knew any of this stuff about guys.
It must be a miracle that the dozen or so guyed towers that I've put up,
over the fifty years I've been a ham,
have not come crashing down, especially considering the brutal mountaintops
I've lived on.
>From now on I'm going to have to consider the X an Y symmetrical sectors as
well as the ying and yang of every one of my towers :-)
BILL
----- Original Message -----
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
To: <wc1m73@gmail.com>; "Tower and HF antenna construction topics."
<towertalk@contesting.com>
Sent: Friday, January 15, 2010 18:08
Subject: Re: [TowerTalk] FW: Guy article in CQ
>
>
> Dick Green WC1M wrote:
>> TowerTalkians --
>>
>> In followup to my post about computing guy lengths over sloping terrain,
>> below is an exchange with W2RU that clarifies my approach and adds
>> important
>> information. Bud's question is at the bottom, my response at the top.
>>
> That makes it very difficult to follow.
>> 73, Dick WC1M
>>
>> Hi Bud,
>>
>> I agree that the tension must be the same in all three directions, but
>> not
>> only in magnitude. It must also be the same for the horizontal and
>> vertical
>> vector components of the force along each guy wire. I don't believe that,
>> for a given angle, simply duplicating the tension along the guy can
>> reproduce the relative proportions of vertical and horizontal force of a
>> guy
>> that's at a different angle.
>>
>>
> To be symmetrical the guys only need to leave the tower at the same
> angle and be under the same tension. Then the x and y vectors will be
> the same for all guys. Length does not come into play for this
> calculation as it does in resonance. Also symmetrical refers to only a
> tier, not that all tiers be the same.
>> I think you can visualize this by picturing a tower with two guys at,
>> say,
>> 45 degrees to the tower, and a third guy at 15 degrees to the tower. That
>> third guy can easily be set to the same tension as the other two, but
>> it's
>> going to have a much greater proportion of vertical (pull down) force
>> than
>> horizontal (pull out) force. I suspect there's no value of tension that
>> could be used to exactly duplicated the vertical and horizontal tension
>> vectors of the other two guys.
> That is correct. Hence you have to adjust the length.
> OTOH when if such a situation the important part is to keep the angles
> as close as possible and let the length fall where they may.
>> That proportion is a function of the angle of
>> the guy to the tower.
>>
>> Regardless of the physics involved, one of my objectives was to follow
>> the
>> Rohn-specified layout for the tower as closely as possible, on the theory
>> that the manufacturer knows best. Rohn specifies guy attachment heights
>> and
>> the distance from the tower base for the anchors, which results in a
>> certain
>> set of guy angles and horizontal/vertical vectors.
> That is on level ground so you are already not adhering to their specs.
>> I wanted to get as close
>> as I could to that and still allow clearance for the middle SteppIR. I
>> had
>> to push the anchors out about 5% to accommodate the middle SteppIR, but
>> that's within the Rohn-specified tolerance for the distance.
> IIRC the distance is there to indicate where the guy will hit at the
> given angle "on level ground", not that the length is a requirement,
> particularly on sloping ground.
>> Then the task
>> was to reproduce the guy angles and forces over my sloping terrain.
>>
> Just maintain the angles and tension which will mean additional guy
> anchors.
>
>
> 73
>
> Roger (K8RI)
> _______________________________________________
>
>
>
> _______________________________________________
> 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
|