K8CC and perhaps others have written on earth screw anchors in the NCJ dating
back probably ten years or so. I personally have used earth anchors on my
small, 45 foot Rohn 25G tower. 60" x 6" screw in this case.
There exists a wealth of information on using screw anchors for larger
applications, but
not in the ham literature. I researched this a bit when planning my larger
tower and talked with some companies that install earth anchors for towers
and for other applications such as foundation supports (serious anchors used
to shore up failing foundations). These guys knew exactly what I wanted and
were able to provide specifications right away. For about $300 a pop they
can provide and install an anchor with sufficient capacity to handle a
several hundred foot tower. These are obviously not the 4" to 6" screw in
anchors that most hams think about!! The installation tool is hydraulic and
attaches to a Bobcat type tractor.
For more information do a web search for the AB Chance Company. They offer
many different earth screw products. If your area has one of the popular
annual home improvement shows take a stroll around and look for concrete and
foundation type people. Odds are one of them will have a bunch of info on
earth screw technologies and they are usually bored stiff at these shows and
will talk to you forever.
FWIW, in the end I went with concrete but if I had not been able to get a
concrete truck close enough to do a reasonable shuttle I would not have
hesitated to use the industrial earth anchors installed by a proper vendor.
Cheers,
Mark
KI7WX/4
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