[TowerTalk] new member with tower question

[Patrick J. Jankowiak]

Jim Lux wrote:
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> *--*
>
> 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!!
>   
>>
>> 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.
> As you increase the tension on the guy (e.g. by bringing the anchor in 
> closer to the tower base) you increase the compression load on the 
> tower, perhaps above that which the mfr recommends. You also increase 
> the load on the anchor, tending to pull it out of the soil. And, of 
> course, the increased downforce on the tower tends to sink it into the 
> soil.
That is a very good point.

> An engineer can answer all these questions, tailored for your particular soil conditions, in about an hour or two.  The couple hundred bucks for the engineer will be well spent (and you might find someone to do it free or for the proverbial "sixpack".. check the ARRL Volunteer Consulting Engineer lists)
>
>   
Ok, I am convinced to hire an engineer first. Then, I will know what I 
can put up, and what I can't.

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)
>   
>> Is there a free downloadable calculator to help with the angles of the 
>> guys and design of the site? All advice will be welcome.
>>     
>
> Not one that I would trust....
>
>
> Jim, W6RMK
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>
>   

-- 
kind regards,

Patrick Jankowiak
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