[TowerTalk] Leaning Tower of Challenge
Roger (K8RI) on TT
K8RI-on-TowerTalk at tm.net
Thu Mar 13 14:34:57 EDT 2014
On 3/13/2014 12:34 PM, Wilson wrote:
I'd planned on saying something earlier, but...
Referring to trees as anchors. Big trees work quite well with "screw in
anchors" (eye bolts) They do not move if relatively close to the ground
and remain at the same location even as the tree grows taller and
larger. 5 feet off the ground today will be 5 feet off the ground 20
years from now even if the tree doubles in height. Trees grow from the
top up, not the bottom. They grow out from the surface, not the center
(tree rings). In a few years they (if still growing) they usually
completely encase the anchor leaving a strange looking guy wire entering
the tree. Often the wire and anchor create a bole (I think that's the
name). However wire wrapped around the tree will eventually cut that
thin layer between the bark and core, killing the tree. This layer is
where most of the nutrients travel. It's how the little Emerald Ash
borer can kill such a big hardwood in a single season.
Another point: When a tree dies, it's a good idea to get the guys off it
right away. The root structure decays with no visible signs above the
surface. Depending on the tree and its size this may take many years, or
just a few. You have no real way of knowing how much strength is left.
I assume the guy wires are still attached to the tower?
> The base is fine, never meant to hold the tower up.
> I doubt the few pounds of ice on the wire were a factor. How were the winds? Was the maple swaying much?
> The tower is obviously strong enough to move the base, so just pull it with come a longs, as recommended.
> Pull slowly, a little each day, and verify that it’s moving with an inclinometer or plumb bob. Rate effects are significant re this sort of soil deformation!
> If you want to do a little math, get the max allowable bending moment from Rohn (if they will help) and you can easily calculate how hard to pull...just a little trig. Half the max is likely more than you need to get back up.
> Dig around the base a bit and soak it, if you want to make the pull a little easier.
It's easier to use a hydraulic drill to thoroughly soak the ground
around the base. drill down at least 3/4, if not all of the way to the
bottom of the base on 4 sides about 6" out. Once that deep in a hole,
let the water run "slowly for about 10 minutes. You can turn the soil
around the base into soup, just not under it.
> I’d say 30 yr on a cheap installation is pretty darn good! If you put a loop around the base of the stumps, so it can’t slip up, it’ll likely hold several more years. My 50HP tractor can’t begin to break off or uproot a 6” pine stump, until it rots nearly away.
A lot depends on the soil composition, wetness and PH.
Pines have their own preservative so they do tend to last longer. As the
one pine stump already pulled out of the ground, I'd be hesitant to
trust the other.
OTOH under normal conditions, a 50 foot tower isn't much load on the
guys. In the "old days" I guyed 40 and 50 footers with nothing more than
steel fence posts driven in at an angle, 90 degrees to the guy which was
wrapped around its base. The towers had a 5L 20 M KLM, 6L 15M KLM and 7L
Wilson 10 meter beam. (one antenna per tower) Open farm land with no
protection from the winds. They stood without a problem through several
strong storms and one major ice storm that took out over half a mile of
power line a quarter mile to the West of us. Lines were over 3" in
diameter. That's 1.5 to 2" of ice.
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