Thinking about a hinge like this (end view): ____(O)____ where "___"
is the plate, "( )" is the barrel, and "O" is the hinge pin. It would
be bolted through the plates to the surface below. The barrel sits
"on top" of the plates. Hope that makes sense.

It's in tension and/or compression (some torsion also), so obviously
the hinge pin needs to have a lot of shear strength. Clevis pins are
designed for this application, so it's a matter of doing the sums and
selecting a properly-sized one from the catalog.

But the *barrels* of the hinge are a weak point. A plain rolled
piano-type hinge would obviously just pull apart if the barrels aren't
connected back to the plate. What's the best way to prevent this?

Weld the barrels back to the plate so they are closed and can't pull
open? Makes sense - but how sure can you be of the tensile strength
of that weld? Build a test article and test it to destruction?

Or perhaps you could make the hinge by folding a strap around the
clevis pin, and back over itself. Then you have a double-thick plate
- extra weight. And tension would tend to pull the barrel out of
round and make the clevis want to center between the straps:
=====O==== rather than "on top": ____(O)____. Also, you'd have a
sharp reflex bend - potential crack site - where the barrel comes down
around the pin and then flattens out as the top layer of the two-layer
plate: __(

Ideas? I know somebody has to have already solved this. btw - assume
that the issues of properly bolting the hinge to the material below,
and properly heat -treating the assembly, have been solved. We're
just looking at the mechanics of the hinge barrel, unless I'm missing
something.

(Rich, yes, you know why I'm asking... ;-) )

Corrie "alllllways thinkin'..." B.