I have seen a number of HBX & HDBX series towers with rotor plates torn
just as K7LXC described, but far worse than that...I have seen a couple
that had rivit failures...once while a friend was climbing down his
tower, and two rivets let go at the same time, dropping him to the point
where his safety belt paid for itself. It was only a short drop...but he
skinned his shins pretty badly...and he swears that it felt like the
entire tower was coming down. At one time I saw a TH-6, a Hy-gain
"shorty forty", a 6 meter 5 or 6 element yagi, and assorted 2 meter
antennas on that tower all at the same time. I don't know what the
practical limits of that series of tower really are, but when we took his
down, it was clear that the torsional stress on the tower was destroying
the rivets, and several of the braces were tearing at the legs, and a
number of the rivets at the mid points of the braces were gone. There is
no doubt in my mind that his tower was seriously abused by the loads he
put on it. By the way, that fellow now has a Trylon tower. Last I heard
it had beau coup antennas on it, but it showed no signs of yielding.
I had an HDBX-48 for about 15 years...heck of a tower for the money. For
about one year I had a 3 element Cush-Craft 10 meter yagi, and followed
that with a 2 element tri-band quad for several more years. Then I moved
to my present QTH...and when I moved the tower I noticed that the rotor
plate was failing. I had a local machine shop fabricate plates from 1/4"
steel, which was, of course, gross overkill...but it sure did the job,
and was darn cheap. I just took the original plates to them and had my
new ones within about an hour. Cost about $12 (but that was more than 20
years ago.) At my new QTH I had a TH-3 followed by a TH-6, and I also
added two 8' straight sections at the bottom for 64'. The TH-6 was
within inches of the top of the tower, but I had a long mast, with a G-6
mounted at about 75'. The tower never failed, but was not severely
tested by weather in all those years. Rust finally got to the point that
I decided to replace it with a 100' free-standing Pi-Rod that can handle
more load than I have yet dreamed of putting on it.
By the way, I heard one horror story about a fellow that decided to have
his HBX series tower cleaned and re-galvanized. He took it to a plating
shop, where they dipped in an acid bath to clean it before galvanizing
it, and they pulled out lots of pieces...the acid ate away all the
aluminum rivets, and just left the individual channels. I cannot confirm
that this actually happened, perhaps it falls into the category of an
American Folk Tale...but I still shuddered when I heard it.
Well...this turned out longer than I intended, but once those memories
are triggered, it can be hard to shut me up.
Very 73,
David Bunte - K9FN
129 Ivy Hill Drive
West Lafayette, IN 47906
dpbunte@juno.com or
dpbunte@wbaa.purdue.edu
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