Thanks everybody for your assistance !!!!.
GREAT idea Gerald !!!!...i think 4 guys is my best solution...i re-measure
the roof today and it is a little bit larger...it is 24.3 ft by 42 ft (it is
from hole to hole to anchors...about 1ft from the edge)...so,
calculating using guy angles 120, 60, 120 and 60...i have 24.3 ft from the
base to the anchor...guying the tower at 30 ft the anchor/height ratio is 81
% !!!!...guying at 28 ft the anchor ratio is 86.7 %...i think it is a good
and safety value.
I would like add a mast....maybe an 18 ft mast (1,5 or 2 inch OD) with 5 or
6 ft below the top of the tower and 12 or 13 ft up the top of the tower.
I am planning install an HD spiderbeam for 10, 15 and 20m only...it is very
light weight and very low wind load antenna.
Yes, it is a single story home...roof is about 12 ft up the ground level and
the concrete roof is about 4 inch thick (high).
Thanks again for your help.
73....Douglas, CO8DM
"No creo que haya alguna emoción más intensa para un inventor que ver alguna
de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer,
de dormir, de todo." - Nikola Tesla
----- Original Message -----
From: "TexasRF--- via TowerTalk" <towertalk@contesting.com>
To: <co8dm@frcuba.co.cu>; <towertalk@contesting.com>
Sent: Wednesday, August 26, 2015 11:22 AM
Subject: Re: [TowerTalk] How many tower sections i can install??
Hi Douglas, you can achieve a a greater guy point distance by using four
guys instead of three. You would not want the guy to guy angle to exceed 120
degrees in any case.
Your roof dimensions would allow guy to guy angles of 120, 60, 120 and 60
degrees. With the tower mounted in the center of the roof and assuming the
anchors are at the edge of the roof, a guy to guy angle of 120 degrees, the
distance would be 20.0 ft to the anchor. The distance between anchors
would be 34.6 ft, 20 ft, 34.6 ft and 20 ft.
So, in this case, you could guy the tower a couple of ft below the top and
three 10ft sections would have a anchor/height ratio of 66.66%.
We typically use an 80% ratio mainly because that is the number Rohn
specifies for all of their tower models. It is a good compromise between
load
capacity and space required.
Considering that these towers are used up to 180ft in height or more, it is
reasonable to move anchor points inward for reduced heights. The issue in
doing this is that Rohn has no published data for doing this. The wind load
rating has to be reduced and it takes engineering skills to properly do
the calculations. It is not rocket science however.
I would be concerned about possible roof damage as much as the tower surviv
al. It is conceivable that using the roof edge as a turning point for the
guy and then a ground anchor would be stronger. Something else that would
benefit from an engineers blessing.
73,
Gerald K5GW
In a message dated 8/25/2015 9:14:22 P.M. Central Daylight Time,
co8dm@frcuba.co.cu writes:
Hi,
I would like read your ideas.
I have few 10 ft section of a tower (it is like a Rohn 25G).
I would like install few section over some part of my roof...The roof is
concrete...as you know many house in the Caribbean has concrete roof ...it
is 24ft by 40ft...so, i have calculating and the distance from the base to
the guy anchors is 14 ft !!!
I know the distance from the base to anchor points is 70 % of the tower
height...so, 70% of 20 ft is 14ft, that´s mean 2 tower sections...right
??...Is it possible install 3 sections adding more guy´s set ???
Thanks,
73....Douglas, CO8DM
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