[TowerTalk] Request for Advice - Rohn 25 vs TRI-EX HZN 471

[Mark Robinson]

I am not a mechanical engineer but why don't you put the tower in the ground 
and the building next to the tower.


Mark N1UK


----- Original Message ----- 
From: "Bruce Ward" <Bruce at IPIntel.com>
To: <towertalk at contesting.com>
Sent: Saturday, 18 February, 2012 6:53 PM
Subject: [TowerTalk] Request for Advice - Rohn 25 vs TRI-EX HZN 471


>I am setting up a tower (my first) to get internet service.  The
> antennas will be less than 2 square feet of wind loading combined and
> could be even less using 2 11x14" grid antennas.
>
> My plan is to build a 10'x10' 9' to 10' tall block building on a slab
> that is larger in all directions.  This building will will have a
> concrete roof with rebar and wire in all concrete.  The blocks will have
> rebar and concrete in every cell.  The structure will use 12  to 15
> yards of concrete plus 400 concrete blocks providing an over 45,000
> pound base for the tower.  I have a civil engineer friend who will be
> involved in the final design of the building.  The building is dual
> purpose, it will provide a secure home for my servers and a stable base
> for the tower.
>
> Now for the difficult part, I do not have room for guy wires.
>
> I am trying to decide between two options
>
> 1. I have 9 full and a top section of Rohn 25G in my yard waiting to be
> be installed.  Currently Rohn rates the 25G for freestanding use up to
> 40' with 1.4 square feet of wind loading.  From reading online it sounds
> like Rohn 25s have been used for decades even higher without guy wires.
> I do not want to risk stretching beyond Rohns specifications.  I have
> access to 40' lengths of 8" pipe. If I go with the Rohn 25G my intention
> would be to embed a  40' section of the 8" pipe into the building and
> bracket to that pipe up to 35' or so then have the tower extend another
> 35' to 40' above the pipe.  All the metal would be isolated from the
> ground and properly guided with a ground rod to avoid corrosion issues.
>
> 2. There is a TRI-EX HZN 471 available locally.  I would have jumped on
> this one earlier but it is worth more the the current owner than it is
> to me.  This is a 70' (71'?)  crank up tower with a motorized winch. The
> motor is broken and would need to be replaced.  The tower is free
> standing with the exception of three diagonal pipe braces that connect
> from the top of the bottom of the 4 sections to the ground around 10'
> out.  I like that this tower is freestanding and I believe I could do
> away with the braces if I bracketed the tower at the same location to a
> sufficiently strong structure.  If I used this tower I would likely
> build a 3'x3' column of solid concrete into my building and place the
> tower on top.
>
> I would very much appreciate any suggestions and advice.
>
> Thank you.
>
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