[TowerTalk] How much concrete to set a pole?

[David Robbins K1TTT]

You have a 40' tower and can get at least 22' from the base for your poles.
Then you are going to have to dig a hole.  Then you are also going to back
guy the poles 3-4' from the tower from the tower you are out to 25-26'....
so just how far from the tower can you possibly put in an earth anchor?  I
would prefer guying to screw anchors 22' from the base of a 40' tower over
trying to kludge together some kind of elevated anchor.  Heck a 40' tower
only needs one anchor 32' out from the base to meet rohn specs so you are
almost there anyway.  I would guy it at the 30' level and if I could get the
anchors out 25' that would be more than enough.  To properly design back
guyed elevated anchors for a 40' tower you are going to have to pay some
engineer way more than the whole tower cost, and the materials and labor are
probably much more than that!


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Frank N. Haas
> Sent: Monday, November 07, 2005 18:58
> To: towertalk at contesting.com
> Subject: [TowerTalk] How much concrete to set a pole?
> 
> Dear TTer's:
> 
> I am about to set 3 poles to secure elevated guys for my 40 foot Rohn 25
> tower. I am trying to determine how much concrete to use (and how big/deep
> a hole) to set the poles.
> 
> The 40 foot Rohn 25 tower was originally erected as a free standing tower
> atop one (1) cubic yard of high strength Sakrete. After the first
> hurricane
> blew through Florida in 2004 it became apparent that guying the tower is
> necessary.
> 
> Due to the tower's placement on the lot and its proximity to the house,
> elevated guys are required.
> 
> Three 21 foot long, 2.5" OD galvanized steel pipes are ready to go into
> the
> ground approximately 22 feet from the tower. The limits of the lot force
> this shorter than preferred distance.
> 
> The pipes have been drilled at 2 feet and 3.5 feet from the bottom to
> allow
> four 1/2 inch x 2 foot rebar to be put through the pipe to minimize twist.
> The current plan is the sink the pipes 5 feet deep into square holes dug 2
> feet by 2 feet. The holes will be filled to the 4 foot level with High
> Strength Sakrete mixed onsite. Dual eyebolts will be installed at the top
> of each pipe to accept the guy wire from the tower and allow guying the
> "back side" of the pipe to 2 earth anchors.
> 
> Each of the 3 pipes will be guyed to a pair of 5 foot long, 6 inch
> diameter
> earth anchors 120 degrees offset from the guy wire that comes from the top
> of the 40 foot tower. The earth anchors will only be 3 or 4 feet out from
> the pole.
> 
> To fill the holes (2 x 2 x 5 feet) most concrete calculations dictate 30
> 80
> lb bags of concrete. (2400 lb of concrete)
> 
> To fill the holes to the 4 foot level (2 x 2 x 4 feet) most concrete
> calculations dictate 24 80 lb bags of concrete. (1920 lb of concrete)
> 
> A suggestion has been made to use only 15 bags of concrete (1200 lb) to
> secure the base of the pipes.
> 
> Question 1: Given the size and type of pipe being used,  what would be the
> ideal dimensions of the hole (and thus the amount of concrete required)?
> 
> Are there any published guidelines for elevated tower guys? If so, where
> can I find them?
> 
> The tower will not be heavily loaded. It is hope that a 3 element SteppIR
> yagi and a single dual band VHF/UHF base station antenna will be installed
> at the top. A pipe for a pulley to support the center of a 135 foot wire
> antenna will also be installed at the top of the tower.
> 
> Any help appreciated. Thanks.
> 
> 73,
> 
> Frank N. Haas KB4T
> Florida
> 
> 
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> 
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