Mast Strength

[Mike Rhodes]

No idea about the specs but seem to remember a recent post about a
significant load an appreciable distance above the top of a tilt-over tower
and the bad things that happened because of it as it was being lowered! The
quad probably doesn't weigh much but the mast probably does and the quad
will make that mast into a pretty good lever! Steve, how do you approach
things like that?

73 de Mike / W8DN    
weightdn@bright.net

----------
> From: K7LXC@aol.com
> To: towertalk@contesting.com
> Subject: Fwd: Mast Strength
> Date: Monday, December 02, 1996 5:20 PM
> 
> 
> ---------------------
> Forwarded message:
> From:	bkennamer@arrl.org (Kennamer, Bill, K5FUV)
> To:	K7LXC@aol.com (K7LXC)
> Date: 96-12-02 15:14:20 EST
> 
> 
> Nay Nay Steve, the M200 is too light weight. He needs at least an M200H 
> which is .125 wall.
> 73
> Bill K5FUV
>  ----------
> From: K7LXC
> To: abowen
> Cc: towertalk
> Subject: Re: Mast Strength
> Date: Monday, December 02, 1996 12:40PM
> 
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> 1996 12:40:55 -0500
> Date: Mon, 2 Dec 1996 12:40:55 -0500
> Message-ID: <961202124054_1252827798@emout02.mail.aol.com>
> To: abowen@nettally.com
> cc: towertalk@contesting.com
> Subject: Re: Mast Strength
> Sender: owner-towertalk@akorn.net
> Precedence: bulk
>  ----------------------------------------------------
> In a message dated 96-12-02 09:59:34 EST, you write:
> 
> >I am erecting a quad antenna at the top of a Rohn 45, tilt over tower.
To
> >clear the top guy wires, I need to extend the  mast some 6-7 feet above
the
> >top of the tower. The mast I intended to use is a Rohn M200, which is 2"
> >outside diameter with a 16 ga. wall (.065). It appears to be mechical
steel
> >tubing, low carbon, electric welded (seam visible inside). According to
the
> >specification books at hand, it would be either hot rolled or cold
rolled,
> >but since it is galvanized, there is no way of even guessing. This is 
> tubing
> >designed for mast service, not conduit or pipe.
> >
> >Question: Is this mast adequate for 6 sq feet (35#) of antenna, 7 ft
above
> >the thrust bearing? Location is north Florida, Wakulla cty, about 15
miles
> >from the Gulf of Mexico.
> 
> Hi, Ink --
> 
>     You want the bad news or the good news first?
> 
>     The bad news is that you are in a 100 MPH TIA-222 wind zone AND
within
> 100 miles of hurrican oceanline so you need to use 100 MPH values for
your
> calculations at the minimum.
> 
>     Eight square feet of antenna load six feet above the top of tower
with
> 100 MPH winds exerts a force approximately 79,500 psi on the mast.  I
think
> the mast you described is the same one sold by Texas Towers.  If so, it
is
> rated at 87,000 psi.  The good news is that this mast should be okay
> according to the aforementioned assumptions and calculations.
> 
>     Congratulations for doing your homework before embarking on this
course.
> 
> 73,  Steve   K7LXC
> 
>    TOWER TECH -- professional tower supplies and services for amateurs
> 
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