[TowerTalk] Crank UP

[kk9a at arrl.net]

There is a lot of debate on towertalk as to whether adding guys to a
freestanding tower improves it's strength.  I still believe that it does.
Adding guys to a crankup tower is a different scenario.   Unless the
sections lock together somehow adding guys adds a lot of stress on the crank
up cable and motor.  This tower is quite high with small sections so I would
be fearful of even mounting at Step_R antenna on it.   I have seen stronger
looking aluminum top sections shear off in strong winds.

John

----- Original Message -----
From: "Tom Martin" <tmartin at chartermi.net>
To: <towertalk at contesting.com>
Sent: Tuesday, April 22, 2003 03:18
Subject: [TowerTalk] Crank UP



It might be nicely made by the toolmaker, but it does not demonstrate
proper engineering. The legs that went into concrete, I assume were
steel, but they should have some cross bracing, I saw only straight
pieces, one bent?

I agree.  Also, there is no re-rod in the concrete base.  The straight
legs with no bracing and the lack of a cage in the concrete make for a
precarious situation without any guys.

Top section between the rotator and thrust bearing has no cross bracing,
which is a major no-no. No way you should have 40m beam on the top!!!
This thing would fold like a parallelogram right at the rotor plate.

Very true!  I have a two element 40 meter beam over a 20 meter
monobander on a 72 foot Heights self supporting tower with a 14"
reinforced top section and the top eight feet of the tower twisted a few
degrees in a 75 mph wind last fall.  I doubt if guys at the very top
would have stopped this torquing motion  Guys at 75% of the height of
this 96' tower will not stop the folding you suggest.  No way should a
two element 40 be atop this tower!

Go with the Step-R and guy the tower.  Add slopers, or a delta loop for
40 meters.

Tom W8JWN



_______________________________________________

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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