A quick war story (the aftermath looked like a war zone). Several years ago
at a previous QTH, I had my AB-105 tower up, but no antennas on it yet. An
airborne tornado, yup, a funnel here in central Ohio, decided to alight upon
the top part of my tower. A top guy broke (11,000# Phillystran), the tower
began to twist and that's all she wrote folks. The tower crumpled down.
HOWEVER, the only sections that survived were the ones that I had double
braced (where antennas were to be mounted). The rest were a twisted mess!
So, I would suggest adding extra braces to the 2 non-step sides of your
tower, making the bracing an X as opposed to a Z. I used ¾ x ¾ x 1/8" angle
iron (didn't know about this reflector then or about a larger sheet metal
fabricator in my area that could make them (OEM style) for a very decent
price). You could order the braces from the company Frank mentioned (OEM) or
have them fabricated locally or even do it yourself (lots of holes to
drill!). Since you have two BIG antennas at the top, the extra bracing will
provide significant extra strength. The OEM's would be easier to just add
since they have the flattened ends. The angle braces must be alternated one
inside then one outside the tower to keep the angles from interfering with
each other. If you thought the AB-105 was sturdy before- solid as a rock
comes to mind for one braced in this manner. Just a thought. This investment
would be small compared to what you have in the air! Good Luck.
73's Bill WR8K
From: Hardy Landskov [mailto:firstname.lastname@example.org]
Sent: Tuesday, April 18, 2006 10:47 PM
To: email@example.com; firstname.lastname@example.org
Cc: Mark Smith
Subject: Re: [TowerTalk] AB105
Thanks for the specs. I have never have these numbers before. Mark asked me
if I had all the specs but I have about a dozen sheets that tell how to put
it together and that's it.
However, I have started having some cross bracing failure problems. They
start at about the 70 ft level and go to the 85 ft point. All of the
failures are braces on the outside of the tower, not on the inside and are
all on one side. When I was up there, I thought my heart was going to stop.
There were four broken braces in a row up the tower on one ten foot section
and the tower section had a bulge. Fortunately I had some of the G8A
stronger braces to fix the problem. The tower is 140 ft with a 2el 80 mtr
beam and a 4el 40mtr. Probably way over loaded at 35 sq ft. wnd area.
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