Steve:
I am somewhat concerned over your comments, ref: item 5 below, where you
say that "cable clamps and Phillystran do not mix"!!
I recently put up a 15 foot Create tower on top of my house and have a
KT34-XA on top of it. Gerald at Texas Towers told me that the smallest
Phillystran (1200 lb. test) would be sufficient to hold this in 70 mph
wind. Further, Texas Towers' catalog says to use 4 cable clamps with the
smallest Phillystran and preform grips with all other sizes.
The "local tower guru" only used 3 clamps, and said I didn't need 4 anyway
when he helped me put up the antenna Steve, could you elaborate a little
on your comment? Am I at risk with only 3 clamps, considering the square
footage of tower and antenna? (Tower is rated at 23 sq. ft. @ 90 mph).
Also...I don't understand the statement 23 sq. ft. @ 90 mph......what does
it mean? How do you calculate what the windload is at 70 mph if its 23 @
90 mph?
To me a more definitive number is how many pounds of wind force are trying
to push the antenna and tower over. If I know how many pounds of force are
pushing then I can calculate the vector forces vertically and then
determine how much strength I need for the guy material. (Assuming that
the pounds of force are horizontally pushing on the assembly). I realize
that this can get very complicated since we need to know the angles the guy
wires make with the horizontal, etc. How do I calculate the force on my 9
sq. ft. of antenna at 70 mph? Someone told me it was 9 times 70 = 630
pounds.
Although I am an Electrical Engineer, I don't want a detailed mathematical
formula, just a rough rule of thumb. Well, I guess that is enough
questions for now (I have lots more...hi).
Thanks, Steve
Bill Haselmire WX8S
wbh3@daimlerchrysler.com
K7LXC@aol.com on 12/15/98 09:33:56 AM
To: mlowell@noclant.navy.mil, towertalk@contesting.com
cc:
Subject: Re: [TowerTalk] thimble size
5/16" EHS 1/2" thimble
> >
> >3) If 4000lb Phillystran is used with Preform Grips, the thimble is
> >7/16".
This is correct but you're not using Phillystran.
> >
> >4) If 6700lb Phillystran is used with Preformed Grips, the thimble is
> >1/2".
This is also correct but you're still not using Phillystran.
> >
> >5) If Phillystran is used with cable clamps (highly not recommended)
use
> >one size smaller than above.
Cable clamps and Phillystran do not mix anymore.
> >
> >In all cases the heavy duty version of the thimble is used.
Use the 1/2" ones as per above.
Cheers, Steve K7LXC
Tower Tech
Champion Radio Products
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