[TowerTalk] congrete filled steel for tower base

[K7LXC at aol.com]

In a message dated 11/3/2007 8:57:41 A.M. Pacific Daylight Time,  
towertalk-request at contesting.com writes:

>  Hi all, I have a tr ex 51' crank up I am going to srrect. I  live a long 
way from any concrete supply and am looking for a way around the  big expense 
of delivery. Earlier, I salvaged  a large steel tube 24"  across with 5/8" 
walls by 20' long. from another project. It is already filled  with concrete. My 
plan is to auger a 24" hole in the ground as deep as  possible (6 to 8') , cut 
the tube,  insert it and use it for my base. I  would weld brackets  directly 
to the 5/8 plate on the top to bolt the  legs to. I could mix enough concrete 
for a shallow pad  around it. What  do you think of this idea? the tower would 
be directly grounded through the  tube right into the water table. Is there a 
concern for lightning strikes in  the base or any other potential problems 
anyone can see? It would certainly be  grounded well ! ...any guidance 
appreciated.
 
    I expect that this tower needs something  like 4-5 yards of concrete in 
the base (an educated guess). How many  yards of concrete are in the pipe? (I'd 
attempt answering that but I  don't remember the formula.)
 
    If there's enough, having 1/3 of the pipe per  anchor bolt (like a pier 
column) would be a start. 
But the engineering instruction is to have the concrete in undisturbed  earth 
so you'd need to drill them with an auger before dropping them in the  hole. 
At 4000 pounds per cubic yard, there's a bunch of handling involved  just in 
getting the pipe pieces where they need to be. 
 
    WARNING: I'm not an engineer so let's see what  real engineering types 
have to say.
 
    Grounding OTOH is pretty straightforward. 
 
Cheers,
Steve    K7LXC
TOWER TECH 





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