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Re: [TowerTalk] new member with tower question

To: "Patrick J. Jankowiak" <>,
Subject: Re: [TowerTalk] new member with tower question
From: Jim Lux <>
Reply-to: Jim Lux <>
Date: Fri, 30 May 2008 07:29:53 -0700 (GMT-07:00)
List-post: <">>

-----Original Message-----
>From: "Patrick J. Jankowiak" <>
>Sent: May 29, 2008 7:25 PM
>Subject: Re: [TowerTalk] new member with tower question
>Jim Lux wrote:
>> *--*
>> Why can't you put up the BX?  Talk to an engineer familiar with your local 
>> conditions, and they may agree with your assessment that caliche is 
>> comparable to concrete.  The BX wants a base that is heavy and large enough 
>> that a) the downwind side doesn't sink into the soil and b) that the upwind 
>> side doesn't pull up.  There's lots of potential concrete pads that can be 
>> created that are compatible with this.  One common strategy is to drill 4 
>> round holes, one for each foot (you see this on HV Transmission towers).
>The other reason is the BX has X-shaped braces instead of flat ones, and 
>no one wants to climb the thing because it is horrible to stand on!!

Well, there is that...

>>> Since this will be done in an enclosed area of yard that is only 40x40 
>>> FT, the three guy pipes will be placed so that they are sunk 5 FT into 
>>> the ground and extend 5 FT above the ground. We want to use 4" oil well 
>>> drill pipe for this. We can find the pipe because any piece with a crack 
>>> has to be discarded and they go to scrap. 
>> Of course, that crack indicates a failure of the pipe, no?  (unless you're 
>> talking about taking a 20 ft stick with a crack at one end and chopping a 
>> section out of the middle?)
>True. The wall of the pipe is 3/4" thick and the cracks are hairline and 
>discovered by X-ray (thanks Halliburton), I was told. I have yet to 
>inspect one of these to find the facts. Might be bogus info.

Even if the pipe is 3/4" wall, the bending loads are huge in this sort of 
thing, you need to calculate some stuff to see if it's going to work.  4" is 
pretty small.. you've got a 5 ft lever arm, so the the mechanical advantage is 
15:1.  A 1000lb load on a guy wouldn't be unusual, and that turns into a 
15000lb load on the steel at the base.  

You could also test it get a 10 foot length supported on two blocks, put a big 
weight in the middle and see if it bends.  The other thing is that if it bends, 
that's a failure from a structural analysis standpoint, but it's not like the 
tower collapses.

>I trust that a 25FT pole embedded 5' in the ground will be OK to support 
>an end of a dipole without the engineer's approval :-) (not to open 
>another can of worms)

why sure.. that's just a flagpole, eh?

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