[TowerTalk] Guyed self-supporters (was "Concrete suggestions")

Sat Apr 19 13:32:49 EDT 2003

Taking one's breath away is a measure of psychological effect. Inches
is the physical measure and can be seen with a transit on the ground.
These are not self-contradictory statements.

The movement of even an inch profoundly "stirs up" some folks' juices,
others seem impervious (K7LXC has no nerves).

The human body does not like falls, and normally has autonomic
responses against losing one's balance. Think about how you feel
walking if your foot unexpectedly slides an inch, and the instant,
un-thought-out response to it, including a quick adrenalin pump.

A guyed tower DOES move in a high wind. And for a lot of us, that's a
considerable pucker factor.

I don't need a PhD expert to tell me what I've experienced and felt
and seen. Don't need to find it in a book. I'm completely confident
what anyone will find if they check it out themselves. Except being up
the tower in a sudden windstorm, and deciding it's smarter to hold on
belted up and ride out the gusts instead of trying to climb down,
ain't exactly what I'd recommend as entertainment for my friends.

The Trylon tower is a pyramid that is 48 inches across at the base and
angles to as little as nine inches across at the top. It is not a long
thin cylinder like Rohn 25, etc.

There is no question that the Trylon is far less flexible in the wind.
The difference is like standing with your feet spread well apart or
standing with your feet pushed together. The Rohn will move under wind
force until the guy changes shape (stretches - if you must - or
un-droops) to what it would have been in zero wind if it was first
tensioned to the sum of design AND the wind-induced tension.

Just from remarks heard over the years there is not a general
appreciation for how much force a 50 mph wind exerts on a tower and
antennas. Perhaps all that means is that most folks are smart enough
not to be up there in such a circumstance, and happily don't have any
gut-wrenching personal experience with it.

The tension on the guys IS the point of the design, not the shape. Out
at classical WCPE FM in Wake Forest, NC, the 1200 foot guyed tower
there has enormous droop in the guys. It stood up to Hurricane Fran.

The station's general manager, a friend of mine, who was out there
with some of her crew during the night riding out the hurricane and
keeping the station on the air during the power outage, said she could
plainly see the lights up top waving around. The engineer in her said
that's the design, the gut-lurch in her said it's coming down any
minute now. Engineer won, happily.

73, Guy.

----- Original Message -----
From: <w3wv at att.net>
To: "Guy Olinger, K2AV" <olinger at bellsouth.net>
Cc: <W2fca at cs.com>; <towertalk at contesting.com>
Sent: Saturday, April 19, 2003 12:49 AM
Subject: Re: [TowerTalk] Guyed self-supporters (was "Concrete
suggestions")

> Yes, of course the EHS guys are not stretching (noticeably), but
that's not
> really the point (although it was the original question).
>
> It seems to me that the physical extent of the catenary is pretty
much
> irrelevant for what we are discussing here (a person on the tower
wiggling
> around).  It seems that it's the tension in the guys that counts.
In other
> words, the tower doesn't know (or care) whether the "droop" is two
inches or
> two meters; what it does know is that some force is pulling on it at
some angle.
>
> Of course, as the tower moves from its "steady state" (sorry--I'm an
> electronics man, not an ME) condition, the increase in tension will
occur less
> rapidly if there is a pronounced catenary rather than none at all.
>
> In your latest post you say that the movement is a few inches,
whereas in the
> earlier one you say it "will take your breath away."
>
> Now, I'm not trying to be argumentative here; I'm just trying to get
at the
> facts--how much does a typical properly installed guyed tower really
sway . . .
> and how much does a typical properly installed free-standing tower
really
> sway?  Does a guyed tower really sway all that much more than a
free-standing
> one?
>
> Several years ago, I was talking with a man who makes his living
trimming
> trees.  At that time, he was taking a break from working in some
120-foot
> trees.  He said that he recently had been asked to replace a lamp at
the top of
> a (guyed) radio tower.  He allowed as how he felt _really_
uncomfortable on
> that tower as it swayed, but the movement of the trees didn't bother
him.  So,
> yes, I do believe that the things actually move!
>
> Comments from professional tower people?
>
> Thanks.
>
> Jim, W3WV
> > No, EHS guys are not stretching to give this effect.
> >
> > The guys are not tightened to make them straight, they are
tightened
> > to present a certain designed tension on the tower.
> >
> > If you sight down them, you will see that they are not pulled
> > "straight-line" taut. They have a certain "bow" to them. This is a
> > function of the weight of the guy pulling down in the center
against
> > the design tension trying to pull it straight, and the gradual
loss of
> > leverage to lift the middle by pulling as the line becomes
straighter.
> > The higher the tension, the less the bow, the smaller the tension,
the
> > more the bow.
> >
> > The higher the guy point the more obvious the droop because of the
> > length of the guy, both adding to the weight and to the
opportunity
> > for droop.
> >
> > Pushing on the tower away from the guy adds tension to the guy,
and
> > lessens the "droop". AND the tower moves away from the guy point
by
> > the amount given up by the lessening of the droop.
> >
> > This will give you the inches drift in the wind that seems like
feet
> > when amplified by the tower top pucker factor.
> >
> > 73, Guy.
> >
> > ----- Original Message -----
> > From: <W2fca at cs.com>
> > To: <towertalk at contesting.com>
> > Sent: Friday, April 18, 2003 8:21 PM
> > Subject: Re: [TowerTalk] Guyed self-supporters (was "Concrete
> > suggestions")
> >
> >
> > > In a message dated 4/18/03 13:12:19 Eastern Daylight Time,
> > > olinger at bellsouth.net writes:
> > > << I have been at the top of guyed towers, and my own
self-supporter
> > in high
> > > winds, and the movement in the wind at 100' on a guyed tower
will
> > take your
> > > breath away. I never have felt that at the top of the Trylon. It
> > simply does
> > > not move like a guyed tower. >>
> > >
> > > Does that mean that on a 100 foot tower guyed with 3/16 EHS at
the
> > > recommended tension that those guy wires will be stretching on
the
> > order of
> > > several inches or more?
> > >
> > > Frank
> > > W2FCA
> > > _______________________________________________
> > >
> > > See: http://www.mscomputer.com  for "Self Supporting Towers",
> > "Wireless Weather Stations", and lot's more.  Call Toll Free,
> > 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> > >
> > > _______________________________________________
> > > TowerTalk mailing list
> > > TowerTalk at contesting.com
> > > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> > _______________________________________________
> >
> > See: http://www.mscomputer.com  for "Self Supporting Towers",
"Wireless Weather
> > Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with
any questions
> > and ask for Sherman, W2FLA.
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk at contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers",
"Wireless Weather Stations", and lot's more.  Call Toll Free,
1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
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