>From: "Patrick J. Jankowiak" <email@example.com>
>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
>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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