Steve Maki wrote:
> Roger (K8RI) wrote:
>
>> Hmmm This was supposed to go to the group, but apparently I hit the
>> wrong key...again.
>>
>>
>> K7LXC@aol.com wrote:
>>
>>>
>>> In a message dated 11/3/2008 12:45:53 P.M. Pacific Standard Time,
>>> towertalk-request@contesting.com writes:
>>>
>>>
>>>
>>>> This subject has been debated before. Your analysis of
>>>> self-supporting
>>>>
>>>>
>>> towers and guying is another example of misinformation! Let me suggest
>>> you obtain the facts next time you post or other wise state that it is
>>> your opinion. The company that manufactures the self-supporting towers
>>> I use, RECOMMENDS guying ... fact!
>>>
>>>
>>>
>> Angles are the angle between the tower and guy line.
>> You can get the same answers by using the Sin of the angle between the
>> guy and ground.
>> Top guys on 100' 45G 3 @ 660# tension. Cos(30)*660 = 571*3 = 1715 rounded
>> Middle guys 3 @ 440# Tension Cos(45)*440=311*3= 933
>> Bottom guys 3 @ 440# Tension Cos(60)*440=229*3=660
>>
>> Tower sections 70# X 10 = 700.
>> Base section 35#
>> Antennas and mast 300#
>> Rotator 45#
>> Coax and control cables 100#
>> Guy bracket assembly 23# X 3 = 69#
>> Total = 1249 Give or take a 100.
>> Were I to use EHS guys instead of Phillystran I could easily add another
>> 300 to 600# while the Phillystran weights well less than 100# per 1000
>> feet.
>>
>> That means they guys on my tower exert an additional 3300# on the base.
>> That is well more than double the total tower and antenna system
>> weight. Free standing, or Self Supporting towers are build
>> considerably stronger than guyed towers as they have to serve the
>> function of those guy wires internally. Some are designed to allow
>> guying as well. The question them becomes, If permitted how does guying
>> the self supporting tower affect the wind load and weight support
>> ratings. Guying a tower with properly tensioned guys can easily add
>> more than twice the load to the base. So a 1500# tower could end up
>> with 4500# on the base structure.
>>
>
> Now figure the leg compression (unguyed) during a strong wind. You will
> find that it's MUCH greater, and concentrates on the downwind leg(s),
> and the conclusion is that reasonable guying will invariably increase
> the wind load rating of any reasonable tower. It's not surprising that
> most manufacturers do not recommend it though - it negates the advantage
> of the self support structure...duh.
>
>
Of course the self supporting structure is far heavier and more
expensive than the guyed structure. It also takes a lot more concrete in
the base. OTOH it takes up far less space, too. Were I not retired and
still working at my old job I'd have a pair of them up. Crank up AND
self supporting.
Roger (K8RI)
> Steve K8LX
> _______________________________________________
>
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>
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