I put up Rohn towers the way the book says to: using a pier pin.
Construct your foundation, place your rebar, pour your concrete. Then,
when it starts to set up, stick the pier pin into the center of the block
and let the concrete cure. A few days later, you can place your Rohn
base plate on the pier pin with one tower section and then place
temporary guys. Stacking of subsequent sections can follow, followed by
the removal of the temporary guys.
IMHO, many people misuse the "short concrete base" section on guyed
towers. I believe it was intended for use on self-supporting Rohn
towers, up to the limit shown in the book. If you use a pier pin, not
only do you not have to worry about having the bottom section plumb, you
also achieve the following benefits:
1) You don't have to worry about water in the tower legs, as it will
naturally pour down the legs and out the weep holes in the base plate;
2) You are in essence putting a bit of a shock absorber on the base of
the tower, the tower can turn a bit from side to side to absorb torque in
high winds, resulting in less stress on the bottom section(s) of tower;
3) You don't have to worry about how the tower "short base section" will
interfere with the steel rebar in the tower base (you DO put rebar into
the concrete, don't you?).
The purpose of the base on a guyed tower is two-fold: to keep
the tower from sinking under the dead weight of not only the tower but
also the pressure of the guy wires, and to keep the base from kicking
out. A pier pin/base plate somehow seems easier to deal with than
worrying about making a base section plumb. The only drawback is the
requirement of having to put temporary guys on the first tower section
when the tower is being erected or dismantled.
Many ways to skin a cat, but that is how the Rohn drawings say to erect a
guyed tower.
73, Jim N6IG
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