[TowerTalk] Weak Link in Guy System?

[K7LXC@aol.com]

In a message dated 11/17/00 4:56:50 PM Pacific Standard Time, 
ray1965@hotmail.com writes:

>  I am laying out parts for installing Rohn 45 tower 100' high.  Details for 
>  90 MPH 100' are 1/4" at 91' and 3/16" at 61' and 31'. From the AnchorData 
a 
>  Rod No. of 303 is given.
>    The 1/4" EHS is rated at 6400# and the 3/16 at 3900# break strength.
>  The Rod 303 allowable load is only 7,330 #.
>  
>    If all three guys are connected to the single Rod, it would seem to be 
>  greatly overloaded.  Yet I have never heard of a Rod breaking, but have 
>  heard of numerous guy wires breaking.  I am puzzled as it, would seem the 
>  Rod would be the week link when connected to the 3 guys.

    This is kind of a gray area. Your logic makes sense but I'm not an 
engineer so I can't give you an engineering analysis.

    What I can tell you is that the tower/guy/anchor calcs have been done by 
qualified structural engineers and that since it is the Rohn recommended 
configuration that it is okay and in fact recommended (the LXC Prime 
Directive).

    Have I ever seen a failed one? Yes, but it had been holding a severely 
overloaded 45G in a spot where 160 MPH winds weren't unusual. I've never seen 
any other failed anchor in the hundreds of tower sites I've visited. 

>    Do I need to go to the 3455 with 17,670 at twice the cost ($57 vs 
>  $110)each or is the 303 safe as Rohn specifies?

    No, but I'll never discourage someone from over-engineering something. 
For a very small amount compared to the cost of the whole installation, you 
can get have the beefier ones. Look at it like this - when that first BIG 
storm comes rolling through and you're laying in bed listening to it, will 
you wish you'd put in the bigger rods? It's a matter of your comfort zone and 
accepted engineering that'll let you sleep at night. Either way is fine with 
me. 

Cheers,   Steve    K7LXC
Tower Tech 

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