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## [Towertalk] Tower Buidling 201

 To: [Towertalk] Tower Buidling 201 n4kg@juno.com (n4kg@juno.com) Tue, 3 Sep 2002 08:07:10 -0600
 ```Roger, I politely suggest you do the CALCULATIONS to determine EXACTLY how much benefit there is in 4 guys vs 3 guys. At 5 degrees off line, the IN-LINE wire carries 99.6% of the load. NOT much help from the side wires IMHO). (I assume you do know how to resolve a force vector into orthogonal equivalents as it is rotated). Further, I suggest you do the calulations for a 70 ft tower guyed 3 ways at 50% of the tower height. I'm sure you will find that the loads placed on the tower are WELL within the R25 ratings and the guy wire ratings assuming a nominal antenna load under 12 sq ft. There are many thousands of towers that have withstood the rigors of weather for many decades, all using 3 WAY guying, testifying to the soundness of this approach. If 4 way guying was so much better, then why don't ANY of the BIG tower designers use it? I expect that if all the guys in ONE direction were removed from a guyed tower, the tower would still FALL DOWN, whether it was guyed in 3 or 4 directions. BTW, Percentages of wind direction is MEANINGLESS. Any guying system MUST be capable of supporting the tower 100% of the time. RUN the NUMBERS. It's the RATINGS that count, not the number of directions the tower is guyed. Tom N4KG On Mon, 2 Sep 2002 Roger Borowski" writes: > With 4 guys at 90 degrees apart there are only 4 degrees out of 360 > degrees > when one guy is holding the whole system up. With a 3 guy system at > 120 degrees > apart, there are 90 degrees out of 360 degrees when one guy has all > the tension > to support the whole system. This is the engineering reason for > closer in > spacing with a four guy system. The three guy system has each guy > individually > capable of providing for supporting the entire system 25% of the > time the wind > is blowing whereas the four guy system has each individual guy > providing for > support of the entire system less than 1% of the possible wind > directions. All > other than these 4 degrees out of 360 degrees there are two guys > doing the wind > load support work. This was quite an extensive tread about 4-5 years > back and I > guess some non-believers then still think its OK to use Rohn's > guying standard > for the fold over series of towers, which needed four guys to clear > the > backbone strut, on a conventional system using three guys. NOT! > -=Rog-K9RB=- > > ----- Original Message ----- > From: > To: ; > Sent: Monday, September 02, 2002 5:26 PM > Subject: Re: [Towertalk] Tower Buidling 201 > > > > Do you consider 15% to be a SIGNIFICANT increase in strength? > > I don't. > > > > Worst case for a 3 way guy arrangement is at 30 degrees > > to any one of the guys. Force in the guy is equal to the > > in line force divided by COS 30 degrees (= 0.866) = 1.155 > > or 15.5% more tenstion that an inline force which is the worst > > case for 4 way guying. > > > > The old 80% guying guideline applied to the FULL rated height > > of the towers (200 ft for R25). At 70 ft or less, the tower can > take > > more of the load from close in guys since it does NOT have to > > support the weight, guy tension, and resolved wind load > > of a tower extended to the full rated height. > > > > Tom N4KG > > > > On Mon, 2 Sep 2002 08:53:46 -0400 "Roger Borowski" > > > writes: > > > > > > ----- Original Message ----- > > > From: > > > To: > > > Sent: Monday, September 02, 2002 3:01 AM > > > Subject: Re: [Towertalk] Tower Buidling 201 > > > > > > > > > > > > > > Note that for tower heights under 70 ft, Rohn shows a 35 ft > (50%) > > > > guying radius for their (discontinued) fold over tower > > > intallations. > > > > > > > > Tom N4KG > > > > > > > That is because the fold over series must be guyed with FOUR > guys, 90 degrees > > > apart, which is a significantly stronger method of guying vs. > three > > guys at 120 > > > degrees apart. There was a tread about this about 4-5 years ago. > > > 73, -=Rog-K9RB=- > > ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/web/. ```
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