[TowerTalk] Update on 40' non-guyed tower question

[john at kk9a.com]

I just drove home from Chicago and I'm catching up on towertalk.

The manufacture's site that I linked does state various heights above the
top bracket and corresponding wind rating. With a little common sense I
think you can safely make minor bracket changes. It also shows the
recommended concrete base size for a bracketed Rohn 25 tower, why guess? 
My point is, I would use the Rohn information over someone saying I did
this and that and it didn't break so it is OK.

John KK9A

To:	john at kk9a.com, towertalk at contesting.com
Subject:	Re: [TowerTalk] Update on 40' non-guyed tower question
From:	TexasRF--- via TowerTalk <towertalk at contesting.com>
Reply-to:	TexasRF at aol.com
Date:	Thu, 5 May 2016 15:30:27 -0400


John, in this case the Rohn design will not work. The 40 ft Rohn  design
calls for a bracket at 15ft and 30ft.

Common sense says other bracket locations would work but there is no
manufacturer's data to support that.

The safe moment of restraint for 25G has been published in the past but not
 in recent documents. It was about 7,000 ft lbs back when. The old
documentation  also stated a wind load of about seven pounds per lineal
foot of
tower just for  the tower sections alone, at 70 mph wind speed. One can take
this information  and derive a rational conclusion about wind load and wind
speed but there is no  supporting documentation and you are out on your own.

Since the Rohn design can't be used, it becomes imperative to find a
competent engineer to do the proper calculations to derive some credible wind
load and survival data.

Note that there has been no mention of the desired antenna wind load or
survival wind speed. Both of these are critical to determine what can be done
safely.

This is a classic example of projects that can go awry and cause property
damage or worse yet injury or even death to an individual.

73,
Gerald Williamson, K5GW
GM Texas Towers









In a message dated 5/5/2016 2:04:27 P.M. Central Daylight Time,
john at kk9a.com writes:

I would  do what the manufacture says: http://www.rohnnet.com/bracketed

John  KK9A


To:    towertalk at contesting.com
Subject:   [TowerTalk] Update on 40' non-guyed tower question
From:   Rob Matherly <jimrob at gmail.com>
Date:    Thu, 5 May  2016 11:08:56 -0500


A couple weeks ago I asked about  self-supporting a 40' Rohn 25 tower.
After input from the list and a  no-vote from the Missus on guy wires strung
across the yard, I've gone back  to my original plan to house bracket it.  I
have a two-story with 10'  ceilings, so there's plenty of house to hold it
up.  (There is some  concern regarding my metal roof, but less than I'd have
to deal with if I  were to anchor a guy wire in a flower bed.)

Question #1 - I've read at  various sources that I can go 16' above the
bracket.  Is this  correct?  Assuming my rough estimations of the house
height are  correct, my top bracket will be at about 30'.  I will also have
a  bracket in the 15' area.  I should be safe with about 45' of total
height
including my mast f I understand the Rohn data correctly.  Let  me know if
this is incorrect, please!  I will also be sistering the  studs to help
spread the weight out a bit.

Question #2 - I'm going  to homebrew the house brackets since I have the
equipment and know-how to  build it correctly (and not some hobbled-together
mess of metal.)   Does anyone here have dimensions and specs on the
materials used?  I  believe the angled pieces are 2x2x3/16 galvanized, but I
am not 100% on  that.  I do not have any information on the thickness of the
flat  steel.

Question #3 - It is my understanding that, since it is bracketed  to the
house, the concrete base does not need to be as large - 2x2x3 as  opposed to
3x3x3.  Is this correct?  I don't want ground heave to  damage my house.

Thanks again, folks!

Rob,  w0jrm