Another advantage of concrete anchors is that it's quite easy to
calculate their strength. Assuming the anchor rod isn't the limiting
factor, just add up the weight of the concrete and the dirt on top of
it. That gives you the absolute minimum force it will take. (It will
probably be much more.) If that's greater than the combined strength of
the guy wires, you're good. (Assuming the guy wires are properly sized.)
Rohn even gives some figures for the strength of their recommended
anchor configurations, which are greater than the above.
I fully concur with the recommendation to rent or hire an excavator. I
dug mine by hand in 1989, and my back has never been the same. I've
spent more on Ibuprofen than the excavator would have cost.
73,
Scott K9MA
On 4/14/2020 11:12, Grant Saviers wrote:
I have to wonder if a permitting authority would allow these for
permanent structures without a soils test and engineering, and costs.
(Utilities run on different rules). Then a truck and hydraulic system
is needed to install them, more $$. All of this beyond even advanced
ham skills and technology.
A rental mini-excavator, some rebar ordered bent to spec, and a few
yards of concrete can be DIY. My (Rohn65) anchors are 2x4x6', full
rebar cages, buried 4' all DIY with some laborer help. One advantage
is the shank before backfull is available to be tar coated and 0.020"
gas pipe tape wrapped so there is no chance of corrosion failures.
(see TT posts of anchor shank failures).
My smaller prior R25 built to Rohn spec tower anchors and base were
all hand dug, rebar bent on site and Sakrete mixed in wheelbarrows
with friends and 807's..
Grant KZ1W
On 4/14/2020 04:02, Tyler Stewart via TowerTalk wrote:
It’s like anything else, if engineered and installed properly there
is nothing wrong with earth anchors. Lots are in use at big stations
for decades successfully. Improper concrete based anchors are just
as bad.
Ty K3MM
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On Tuesday, April 14, 2020, Rob
Atkinson <ranchorobbo@gmail.com> wrote:
I've never owned a tower but I would think the guy anchors need to be
set in a relatively deep hole that is filled with concrete. I don't
think I have ever seen a commercial tower that didn't have guy anchors
in concrete. I would not trust guying a tower by merely screwing any
kind of anchor into the ground. How tall is your tower? Maybe 60
feet of R25 is okay if you screw the helix deep, like 5 feet or more
but if you live anywhere with high winds, or soft soil, lots of rain,
or huge wind load like a TH7, I'd pour concrete. It's money spent up
front that saves on the replacement cost of a tower and antenna(s).
73
Rob
K5UJ
--
Scott K9MA
k9ma@sdellington.us
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