Rick (W-A-one-R-K-T) wrote:
I went to visit a ham acquaintance of mine today. He is putting up a
100-foot tower with a large HF beam on top, guyed in three places.

He is not fastening the base plate of the tower to the concrete base in
any way... the tower just rests on the top of the concrete base, and the
three sets of guys hold it in place.

He explained that the main failure mode for towers is due to twisting in
high winds with high-wind-load antennas, so by not fastening the base
plate in any way and just letting it rest on the concrete, he allows it to
rotate a few degrees if needed (by sliding on the concrete) and lessens or
prevents rotational stress on the tower.

With the weight of the tower and the downward force of the guys aiding
the friction on the base, and the guys' resistance to the tower twisting
I doubt not fastening the base has any appreciable effect, but as you
said (farther down), WDIK?

Even so, It's very doubtful the friction will be the same over the whole
base-concrete interface, such that on a windy day his tower might just
walk off the concrete or at least far enough out from under the rest of
the tower that the force from the guys becomes unbalanced enough that it
pulls itself down, but as has been said, WDIK?

I understand what he is saying but this is the first time in 45 years as
a ham that I've ever heard of a tower being erected in this way.

Is this a common way to install a tower, and does it make sense?

If it's common it's a well kept secret.

Sure does seem to me like bolting the tower base plate down to the
concrete has a lot more upside than downside, but WDIK?

Exactly, what do we know? If he's able to get a licensed, professional
engineer (who would know) to sign off on it I'd come within a radius of
1.5 times the tower height, otherwise I'd keep my distance.

This method sounds very dangerous. I could see putting some kind of
bearing or at least a recess so the base doesn't slide out from under
the rest of the tower but just plunking it down without any method of
keeping it on the concrete, yikes!


Reminds me of a day back in the 1970's when a bunch of us were working on
a 120-foot tower, guyed in three places, that held our repeater antenna.
Due to events the details of which I have long since forgotten, all three
of the guys on one leg became disconnected so that there was absolutely NO
guying support on that side. One of the team was about 80 feet up the
tower at the time. The tower curved over like a banana but stayed up, and
we were able to re-install the guys before the tower came crashing down
taking our friend with it. He did have to change his pants, though. :-\

Pretty easy to imagine what would have happened if the tower base hadn't
been fastened down...

Death, destruction, litigation... you should advise Mr. Baseless to
have a licensed engineer look over his installation, especially if
there's any insurance companies involved in any way.

But yeah, WDIK?
W8LNA