[TowerTalk] Crank Up Slop....MORE

[John KK9A]

Aluminum towers are much more flexible than steel ones. Your largest section
is 18" and smallest is 9" which seems really small for a 96' freestanding
tower.  If you look at Universal Tower's catalog of aluminum towers you can
see how large the sections of a 100 foot tower are and how small the
windload spec's are at that height.  I am not a mechanical engineer, but to
me this tower looks too weak for any HF antenna.

John

----- Original Message -----
From: "Steve Narducci" <w9sn at comcast.net>
To: <towertalk at contesting.com>
Sent: Monday, April 21, 2003 00:40
Subject: [TowerTalk] Crank Up Slop....MORE


After installing a 100 ft crank up this week, I noticed that it moves
>  around at the top.  How much
>  is to be expected swaying in light wind with no antennas on top?

    I've never seen a figure like you're asking for but by the time you
add
up all the cumulative tolerances in the sections, it's probably 6-12
inches
limit to limit.

    Absolutely nothing to worry about though. (As long as you're within
the
manufacturer's specs.) Just enjoy it.

Cheers,
Steve     K7LXC

Thanks for the several replies.  I guess I opened up more than I
bargained for.  Let me put more information here.
This is a homemade aluminum crank up (made by a toolmaker in a machine
shop 15 years ago).  It is 96 ft to the
Thrust bearing when erected.  I notice what looks to be about 8-12 inch
sway at the top in about 15mph winds with nothing but the
bearing, rotor and mast on it.  I think I have come to the conclusion
that I am going to put one set of guys on it 75% of the
way up.  Here is a link to show you the entire installation this week
showing the tower and all.
http://www.yorktownhouse.com/crankup.htm This all went up this past
Tuesday and I cranked it up for the first time yesterday, empty.
I can leave it cranked partially down but that would put stress on the
motor drive (brand new) and the manufacturer suggested taking
The load off of it long term.  He said long term with a load should
cause it to fail.  So I installed bracing on the tower for the top
sections
To rest on a ¼ inch piece of steel instead of the motor.  There is a 5'
overlap in the first section, 6' ft overlap in the mid section, and 7'
overlap
In the third section.  The sections are 27' long each.  The whole tower
weighs about 600 lbs total.   My goal here is to install the new 4
element
SteppIR yagi with possible force12 two element 40 meter yagi above it.
However, being new to this stacking and crank ups, I am a little
Nervous about doing this so it will stay up.  Thank you for all the
help...
_______________________________________________

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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