Jim Lux wrote in
:

....
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.

The vertical elements of a tower framework should take their load in line
with the element. They are slender elements which are tied in by bracing
to prevent buckling.

It seems to me that in a typical construction where the end of that
vertical element in each section is not free to hinge, that twisting of
the section deforms the vertical element and would assist buckling if the
downwards force in the element is very large... as it is on very large
structures.

(If you read the USCG manual on towers, they are obsessed with ensuring
that not only is the tower vertical, but that each vertical element is
vertical (ie twist within specified limits.)

I wonder about the benefit in shorter structures, but can see that
dynamic forces caused by rotator brakes trying to instantly stop a
rotating beam might be better accommodated by the pier pin base.

For hints on amateur applications of towers, look at these pics:

(note the extension of the winch handle)

http://www.users.bigpond.com/vk3bjm/...s/image016.jpg

and the counterweight in more detail:
http://www.users.bigpond.com/vk3bjm/...s/image018.jpg

Owen