I use 16 feet of 6", 1/4 inch wall steel pipe braced with heavy I-Beam and
channel.
The pipe goes all the way through about 2.4 yards of rerodded concrete and
has cross pieces of rerod welded across the bottom end.. I think each
anchor weighs about 17,000#
The old, 90' tower used 4" steel pipe set in the ground about 5 fee with
about 8 bags (640#) of concrete pored around them. In roughly 15 years the
tops of those guy anchors moved about two feet toward the tower. They
should have been "back guyed" to prevent that. The current ones have the
front braces and sheer mass and size of the concrete to hold them.
I don't have any photos up showing the old guy anchors, but I think I will
see if can I find some
to put up as a comparrison between the old and new.
With any elevated guy anchor there are several things to take into
consideration. Guy tension, how springy the I-beam, bending moment, mass,
soil composition, depth of the anchor and size of the mass holding the
anchor.
Under tension the anchor will want to tip toward the tower so it points to
the top, or even slightly below. The soil would have to be pretty loose to
allow that, but they will move some.
You can also run into resonances with the mass of the guy line, tension,
depth of the catenary, and tower wind load all coupled to the I-beam, or
pipe.
With the 4" pipe set in concrete and poured full of concrete. The guy line
was 1/4" EHS with a very noticeable catenary. I could climb up the tower and
put my weight out onto the guy line and spring that 4" diameter pole full of
concrete nearly 3 inches.
I used a shorter one to hold a c-band satellite dish, but not for long. It
was so flexible the thing would resonate in a 15 MPH wind to the point it'd
swing off the satellites. It had a low frequency resonance that would swing
and bob the dish both up and down as well as side to side by about 10
inches.
So, there are a lot of "what ifs" in there, but under normal conditions, I'd
think the I beam you describe would work. Just don't put a full size 4L on
40 up there. <:-))
Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
>I have been on this reflector for several months.
>Aside from the occasional sidetrack, it is pretty darn knowledgeable.
Having said that...I was >wondering if anyone has had experience with using
I-beams to anchor their guy-wires? I have >a Rohn 25 G up 60 feet. It has
the two, called for guy positions, one at 28 feet and the other >at 55 feet.
Would a 10 foot , W-6 X12 X10 foot handle the load? I would cement it in
the >ground 3 or 4 feet. The company says that this I - beam would weigh 120
pounds. Twelve >pounds per 1 foot of I-beam. I have never dealt with this
before as I usually run my guy-wires >to the ground. This is an unusual
situation because I have been graciously permitted by a >neighbor to place
two on his property. An attempt at using 10 foot schedule 80 galvanized
>water pipe got me no where, I now seek help using the I-beams so I can get
6 or 7 feet >above ground to allow grass mowing. I'd appreciate your
considerations.
>Regards
73
Conrad
WB3DQD
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and ask for Sherman, W2FLA.
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