[TowerTalk] Tower Base Technology

[Stan or Patricia Griffiths]

Hi Mike,

I know you don't want to hear this, but I feel obligated to tell you.  The Rohn
catalog clearly states that the BX series towers should not be used with
antennas that have boom lengths longer than 10 feet.  The TH11DX is WAY over
that.

Also, I have seen two BX failures and both of them were due to the tower
twisting somewhere in the middle about halfway up and folding over.  In both
cases the beam on top was a TH6DXX.  My real advice is to NOT put a TH11DX on a
BX tower.  I have never seen a BX tower uproot the concrete block and I believe
it would fold over first.

Guying it to prevent foldover is a bad idea, too, since that will put much
greater vertical loads on the tower legs and invite another kind of drastic
failure.  The BX tower was not designed to be guyed.

Stan  w7ni@teleport.com

Mike Foerster wrote:

> Guys,
>
> I'm new to the group, got a reference to ask the TowerTalk bunch my
> question.
>
> I just purchased a used (6 year old) 48ft Rohn HDBX 48, TH11DX and
> Tailtwister rotor.  Had to take it down and it was in dire need of some boom
> to mast repairs.  I've got that taken care of.
>
> Now for the question.  The mfg. specs call for a big block of concrete
> buried in the ground.  Brute force style.
>
> Has anyone done any engineering using some technology to help to keep the
> tower erect safely, other than just the big block?
>
>     *Something like digging post holes in the bottom 4 corners of a bit
> smaller pit and putting in some re-bar and then pouring concrete
>
>     *Or perhaps a "+" shaped hole to use more of the dirt/clay to press
> against vs the big block effect.
>
>     *Is one shape (square, round, tall, short,tapered, etc.) better than the
> others?
>
>     *Differences in the ground makeup (sand, clay, rock)?
>
> This (Rohn) tower technology is about 20 years old  (as is the book that
> tells me how much concrete is required).  There has to be a better way
>
> I know about following the mfg. specs, liability, warnings about twist, etc.
>
>     I'm just asking...
>
> Mike
>
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