For those who were interested in how it turned out (not that I'm sure
the story is over):

I had some help from a contractor friend. He ground off the welds at the
ends of the hinge plate and we were able to nudge the tower back into place;
however, the pieces of the pin would not move after much hammering. We
unbolted the hinge plate (which was remarkably easy considering the age of
the bolts--why doesn't modern galvanized hardware hold up like that?) and
took it back to his shop where he heated it with a big oxy/acetylene torch.
The two pieces of pin eventually yielded to the heat and more hammering.
Unfortunately, the pin appears to be a non-standard size between 5/8" and
3/4" (maybe a little more than 11/16"). A machine shop was able to turn down
some 3/4" stainless rod, but it may be a bit too small and it isn't clear what
stress it can take.

We brought the torch back to the tower, but after hours of heating, hammering,
and oiling the piece of the pin in the central tube would not move. My friend
was going to get a welder to cut off the tube and attach a new one but (and
I wasn't actually there when this happened) he instead had the idea to slice
off the ends of the tube and pin. This allowed the pin to come out. I cleaned
out the carbonized lubricant as best I could, applied liberal grease, and put
everything back together with the new pin. But now I'm a little worried about
trying to tilt the tower:

-The central tube took a *lot* of abuse from the repeated heating and
hammering. There are little beads of metal all over it which I assume
is re-melted zinc galvanization. It is probably bent a bit as well.

-Because the central tube is now about 3/8" shorter than it was, a lot of
the pin is exposed and the forces are no longer as close to shear.

-Because the pin isn't quite as big as the old one and the tower isn't
perfectly balanced one side of the hinge plate is down about 1/8" making
the tower a bit off plumb. The bottom of the tower is pressing against
one side of the bottom bracket where it used to be centered.

-I have no idea how strong the new pin is.

So, everything is fine for now as the stress on the hinge is minimal when
the tower is up. But I'd like to get somebody to look at it before I try
to tilt and expose the hinge to a few thousand pounds of force...

Dan Lanciani
ddl@danlan.*com