[TowerTalk] Re: BPH25G

[Stan or Patricia Griffiths]

Hi Tom,

I have never seen a number for this given by Rohn in any of their
publications.

If you think about it, it depends on a lot of different things:

How are you tilting the tower up?  Are you pulling it up with a
crane above it?  Are you pushing it up from underneath?  At what
points on the tower are you pushing or pulling?  All of this is
important because it will determine how much shear will be on the
hinge bolts and how much force will be trying to lift the base out
of the ground.

If a failure occurs, will it be shearing of the hinge bolts or will
the base lift out of the ground?  Maybe a weld will fail or one of
the hinge bolts will pull through one of the holes?

If it is a typical situation involving a tower on a hinged base, 4
or 5 guys will try to push it up and as it gets closer to vertical,
the pushers will get closer to the base.  Therfore, the push up
"contact point" on the tower varies as the tower goes up making it
VERY hard to calclulate the stresses and estimate if it is safe or
unsafe.

A more important question is, "Why would you ever use a hinged base
($186.30) and push up a 50 foot assembled tower instead of erecting
the tower with a gin pole 10 feet at a time?"  (Maybe the cost of
the gin pole?)

Stan
w7ni@teleport.com

n4kg@juno.com wrote:

> Do any of you know the maximum height of R25
> that can be tilted up using the BPH25G base plate?
>
> One of the locals is planning to use such a plate for
> a 50 ft tower which has me concerned.  He will place
> the rotor and antenna AFTER the tower is erect and guyed.
>
> de Tom  N4KG
>
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