Steven,
Lets look at the 190' tower you quote.
A 190 footer has a guy load of about 4000 pounds
in no wind. Using the 9800 pounds you quote from
Rohn the wind/no wind is 2.45
Now follow the usual thinking. A 190 foot tower
is a big tower. It really needs stronger guys
than Rohn uses. I want a strong tower. Thus guys
tensioned to 1200 pounds are installed replacing
the nominal Rohn guys. The no wind load for these
would be about 12000 pounds. The load with wind
would be about 30000 pounds. This exceeds the
25350 pounds the three legs can carry.
Bottom line: If you are not going to do what the
manufacturer says, the you better be prepared look
at the numbers and determine things are OK. This
is consistent with Steve's advice to always do
what the manufacturer says.
Your conclusion "for short towers" is probably
valid but again, check or have some PE check the
numbers.
73 de Brian/K3KO
Steven H Sawyers (n0yvy) wrote:
>
> The Rohn book says 25G will handle 8,450 pounds on each leg. I am assuming
> this means properly
guyed with the guy spacing under 30'.
>
> The 90 MPH chart for a 190 foot tower shows a base reaction of 9,870 pounds.
> This is the base
load under full wind load. A 190 foot tower has 6
guy levels for a total of 18 guys 3/16 dia.
>
> The section is designed to take compressive loads and appears to do a pretty
> good job of it. So over
sized guying on shorter towers (under 100 feet)
should not be a problem.
>
> de n0yvy steve
>
> At 09:15 PM 8/24/99 +0000, alsopb wrote:
> >
> >By the way, these 6 guys put a downward force of
> >1500# on the tower.
> >Those considering heavier guys (hence higher guy
> >tensions) ought to consider the impact. Doubling
> >guy tension will double downward force.
> >Do you really want to do that?
> >
> >73 de Brian/K3KO
> >
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