"Jim Lux" wrote in message
...
Rick (W-A-one-R-K-T) wrote:
On Mon, 01 Oct 2007 13:38:14 +0000, John Passaneau wrote:


I've seen profesonal towers put up that way, sorta. They had a single pin
that a hole in the flat tower base set over.


Hmmm... Now that you mention it, I recall that the base plate had what
looked like a capped tube rising from its center. Maybe that tube goes
down over a pin of some kind that was embedded in the concrete.

I'll have to ask him about that.


that would be what's known as a "pier pin" base, and, as noted, it greatly
reduces the torsional load on the tower. Whether the force causing the
tower to fail is torsional, I'm not sure. Guyed towers fail by buckling
from the compressional force exerted by the guys. Obviously, putting
another force on the tower in addition to the compressive force is going
to increase the load on at least some member of the tower, and if failure
of that member causes enough asymmetry to get the buckle going, then it is
an issue.


Interesting and long discussion of Pier Pin vs Embedded Base at QTH.COM
http://www.qth.com/ka9fox/pier_pin_vs_embedded_base.txt

The Shadow who has never owned a tower but has ARRL Honor Roll -- brag
brag. Verticals do work