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Re: [TowerTalk] Tower ACCIDENT, engineering

To: "'jeremy-ca'" <>, <>
Subject: Re: [TowerTalk] Tower ACCIDENT, engineering
From: "Daron J. Wilson" <>
Date: Wed, 27 Jun 2007 13:51:25 -0700
List-post: <>
> If you are more concerned about potential liabilities then I suggest that
> YOU hire a lawyer and a PE to examine all documents and be present at your
> installations.
> In the meanwhile those of us that care more about THEIR personal safety
> than
> legal BS use a more common sense approach to THEIR specific install.

I'm concerned about folks getting misinformation, inaccurate information and
dangerous installation tips.  Common sense is wonderful when appropriate,
but dangerous when incorrect.

> I also suggest that you take some time to read a Rohn manual and then tell
> me how many average installations violate those specs, especially about
> 25G wind loading but yet are failure free. 

Sorry, I just don't have the time for that exercise.

> Then tell me how "legal" it is to use
> 1/4" EHS on 25G even tho it makes for a steadier tower. And then there are
> the torque arms which are in and out and in of the catalogs at the whim of
> some corporate legal slime ball.

I can't speak to the legality of using the wrong guy cable, but I can sure
speak to 'common sense'. Rohn specifies 3/16" cable for guy wires.  If 1/4"
is better, is 3/8" better yet?  How about 3/4"? How about 1"?  What would
happen if I used 3/4" EHS for guy wires because it is way stronger and will
give me a 'steadier tower'?  At some point, the increased weight of the guy
wires will outweigh any benefit of the increased strength.  I suspect that
the trade off occurs at 3/16" cable, hence the design engineers chose that
product for their solution.

The entire tower structure design takes into account the guy tension,
downward pressure, wind loading, bending, flexing, etc.  ANYTIME you change
those parameters, you change the structure, and if you can do the
calculations then you can demonstrate the 'over engineering'.  However,
simply using bigger parts hardly qualifies.  Why not drill out the holes and
use 1/2" bolts?  They're bigger, heavier duty, must make it stronger huh? 

> I over engineer my installs, within reason, based upon personal
> conversations I had with Rohn back in the days before litigation became a
> national sport. Ive never had a bit of static from any inspector or PE. A
> well known fact among serious installers is that 25G is actually designed
> at
> 2.5 times the specs since they knew that hams would always push the specs
> over the limit.

Simply increasing the diameter of one of the components is hardly 'over
engineering' unless you do the required engineering to the rest of the
structure!  Using your theory, I bet I could 'over engineer' a tower with
larger guy wires and turnbuckles until it buckled under its own weight!

> It is well known that galvanizing is self healing and flows to an injured
> section to a degree. Rust from an untreated point will not migrate under
> the
> galvanizing. There are plenty of methods to treat bare metal against rust.
> My favorite is ZeroRust  since it was developed
> for use in a salt water enviroment. The automotive restoration field has
> many other speciality coatings available.

The folks that have unmodified hot dipped towers rusting from the inside out
must be experiencing some other phenomenon I guess.  I'm trying to follow
the logic, but if the inside of the tower legs CAN (and do) rust after being
hot dip galvanized...somehow drilling holes in the material and using zero
rust will prevent that?  I live a few blocks from the Ocean, hot dip
galvanized stuff is good, but definitely not flawless.
> > If you drill a hole in the leg of a tower, you have decreased the
> strength
> > and made a weak spot.  Couple that with the lack of galvanizing
> protection
> > where you drilled the hole, and you are creating a failure point.

> Maybe in your dreams but in the real world a 1/4" hole will have no
> detrimental effect. The Rohn base plate legs  have holes drilled in it for
> water runoff.

If you can get a reputable PE to concur, I'll send you a free breakfast
coupon for your local Piggly Wiggly.  I'm not an engineer but I'll bet you
breakfast that ANYTIME you drill a hole in a piece of structural tubing, it
will have a detrimental effect to the structural strength of the material.
It is common sense.  Will drilling 1/4" holes in a Rohn Tower leg decrease
the strength enough to make it a hazard?  I don't know, I'm not an engineer,
and neither are you.  Unable to accurately determine the answer myself, I
guess I'm stuck trusting someone with a PE after their name that designed
the product...or...Carl the Ham down the street that talked with the factory
several years ago.  Yes the base has a 1/4" hole near the bottom right by
the weld, as well as a hole in the metal plate.  They could have used
thicker wall tubing for the base pieces to compensate, or the proximity to
the weld and steel plate may make some compensation, again, it was
engineered that way.

> > "If house bracketed then a minimum of 2 brackets is required."
> >
> > I'm unable to locate any of Rohn's engineering drawings that support
> this
> > either, perhaps you have something you can share to support it.
> Then I suggest that you keep reading. Rohn requires 2 brackets for
> anything
> 40' or higher.

Ahh, that is not what you said the first time, thanks for changing your
statement.  I was having a hard time believing that my 20' tower against the
peak of my single story house needed two house brackets.

If you have Rohn drawings showing this, I'd love to get a copy.  I'm unable
to find that in the current online drawings or my old Rohn catalogs.

73 N7HQR


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