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[Towertalk] Rohn 25G Bracketing

To: <towertalk@contesting.com>
Subject: [Towertalk] Rohn 25G Bracketing
From: wa3gin@erols.com (David Jordan)
Date: Wed, 02 Oct 2002 16:22:01 -0400
Jon,

Pin bases can be used with guyed towers.  The PIN base only has to keep 
the bottom of the tower from jumping around when the wind blows. 
 Imagine a 40ft 25G tower guyed at 20ft.  With the base resting on a 
flat tar pad or hard packed clay base.  With the beam on top and the 
wind blowing the guy point starts to look like an axis.  The guys do 
create a downward force and some of the wind load and the antenna is 
also tramsmitted as a downward force but some is still side moment and 
it could kick the base section out and flip the tower.

Now imagine a bracketed 40ft 25G in the same scenario...all the force of 
the windload is on those four lag bolts in the brick or the 3/8" bolts 
through the facia board and into the wall or studs with a plate on the 
back, etc. If that bottom section starts hoping around it could rip the 
bracket off the wall!

So, dump some concrete and bolt it down.  When I put up my 40ft 
bracketed tower 30yrs ago there was no mention from Rohn of using two 
brackets.

Enjoy,
dave
wa3gin

Jon Ogden wrote:

>on 10/2/02 12:59 PM, tongaloa at tongaloa@alltel.net wrote:
>
>>It's in the catalog...
>>
>>http://www.rohnnet.com/rohnnet2001/catalog/html/gtowers.html
>>
>>allowable loads for bracketed tower
>>http://www.rohnnet.com/rohnnet2001/catalog/pdfs/25G/25G-3.pdf
>>
>>self supporting loads for GT series
>>http://www.rohnnet.com/rohnnet2001/catalog/pdfs/25G/25G-1.pdf
>>
>>
>>
>>
>
>Sure, but like everything with Rohn, it's not completely clear why you  need
>two brackets.  There is no spec given for a single bracket installation.
>
>Then the other funny thing in ALL their specs is why they say "Pinned bases
>must not be used." Yet they sell the BPC25G base plate and pier pins and
>they even have some drawings for pier pin bases!  Now, perhaps the term
>"Pinned bases" is something different.  In general what they show on the web
>is somewhat sketchy at best.
>
>Jon
>
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Life Member: ARRL, NRA
>Member:  AMSAT, DXCC
>
>http://www.qsl.net/ke9na
>
>"A life lived in fear is a life half lived."
>
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