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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>See http://www.mscomputer.com
>
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