At long last, the concrete is in the ground for my 110' Rohn 55 tower! Whew,
that was a lot of work. And a lot of concrete -- 8 yards. I went with 4d
anchor specs, which doubles the hole size. Even then, we had some problems
digging "small" holes with an excavator and ran into some ledge and big
boulders. Took a lot of concrete to fix that. Some photos and more details
are posted on my website, www.wc1m.com, under Big Tower Project.
Here's the "But...". The base is level. All the anchors are at 45 degrees
and the equalizer plates are level. Two of the anchors are pointing at the
pier pin exactly on the compass heading I had planned. But somehow one guy
anchor is off about five degrees or so in azimuth, so it doesn't point
directly at the pier pin. In fact, it points several feet to one side of it.
I'm pretty sure we had it right before the pour. It's possible the rod
shifted during the pour, but I checked it several times and thought it was
aimed OK. The last time I checked it there was so much concrete in the hole
I didn't think the rod could move anymore. One possibility is that the
weight of the bucket loader we used to shuttle concrete to the holes
slightly shifted the ground around the anchor, moving the whole section of
earth and the anchor rod with it (the bucket loader was positioned between
the rod and tower, fairly close to the rod.) Maybe the shift happened after
I checked the rod, when he dumped the last load of concrete. At any rate, I
didn't discover the angle error until the concrete had set enough to prevent
For those of you wondering why the groove in the side of the hole didn't
hold the rod in place, this anchor is uphill from the base. Consequently,
the rod extends further above the surface than it would on level ground, and
only a very shallow groove was needed to set the angle. Besides, if I'm
right about the effect of the bucket loader, a deeper groove wouldn't have
helped. BTW, the uphill rod in question is not the one shown on my website.
That one is OK. I'll post pictures of the rod in question tomorrow if I get
So, my question is... will 5-10 degrees of error in azimuth cause problems?
There's at least a yard and a half of concrete in that 6'x3'x4' hole, maybe
more. I don't think the slab is going anywhere. Seems to me the anchor rod
might bend a little. But the GAC3455 rods are very beefy. Even if it bent a
little, I can't imagine it would be weakened enough to break. I'm using
1/2"x12" eye-jaw turnbuckles. Could they be bent or damaged by the angle
error? Is this a problem, or am I just worrying over nothing? Seems to me
there's not a heck of lot I can do about it at this point!
73, Dick WC1M
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