[TowerTalk] Self-supporting Tower

[Jerry K3BZ]

I sure hope you are not at the mike when that tower comes down onto the
power lines. Your has to be one of the riskiest installations I've ever seen
described on TowerTalk. How did you ever get approval from your local
authorities?
 73 and may the good Lord protect you,   Jerry K3BZ

----- Original Message -----
From: "Tom Martin" <tmartin at chartermi.net>
To: <towertalk at contesting.com>
Sent: Monday, April 11, 2005 12:18 PM
Subject: [TowerTalk] Self-supporting Tower


> I have been following this thread with a vested interest.  I have a 72
foot Heights tower located in the only place on the city lot where the XYL
would allow it to be erected.  It is in the back of the lot next to the
garage and 25 yards from the utility lines that run parallel to the tower
down the alley.  The tower is also 20 yards from my two story house.  There
are no guys but I increased the size of the concrete base (4X7), added
square tubing at each joint with 8 inch bolts running vertically to safe
guard the "egging" problem with the bolt holes at each leg joint, and added
extra horizontal struts where each section joined.  The original design
didn't have any horizontal bars.  All of this extra welding was done by a
professional aluminum welder.
>
> Only 9 months after I erected the tower, we had a F2 tornado go through
the area.  It thankfully veered east two blocks from my QTH and I didn't get
hit with the major winds.  However, the top 30 feet of the tower did suffer
a slight "twist" which is noticeable.  The southwest wind must have had
enough sustained force to drive the 5 element 20 meter beam and 2 element 40
in clockwise motion causing the twist.  The TX2 brake was damaged but there
wasn't any windmill effect.  I was out of town that evening and missed
witnessing the damage.  I would have been a nervous wreck, if I had to watch
the tower and beams in that storm.  At least there wasn't any buckling of
the tower.  I had to replace the rotator and repair the 40 meter reflector.
>
> If the worst comes and the tower does ever buckle, I hope it occurs at the
48 foot level.  Otherwise, I have the choice of taking down the power lines,
or having the antennas come crashing through the roof.  Since the most
damaging winds come from the southwest, it looks like the former.
>
> I have slopers on the tower but they would not be effective as safety
lines.  I think I will consider the copperweld idea with decent insulators.
I think the XYL will go along with that scenario.
>
> In conclusion, some of us do not have the luxury of acres of land for our
antenna systems.  Also, we don't want to operate with a low dipole, or
vertical with a few short radials.  We have to be diligent and design our
towers with safety in mind...all within reason.  Excellent insurance
coverage is also a plus!
>
> Tom W8JWN/V31TR
> _______________________________________________
>
> 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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