Thanks Bill. What I am worried about is buckling where the flange
is cut away and bent over near the center. At a compressive stress
level of 55,000  psi buckling cannot be too far away. The 1/4 square
key stock will serve to stiffen the flange.

As far as yielding at the rubber bushing ends IMHO that is not very
important. A bit of yielding out there won't hurt a thing.
Hard to predict that anyway because all the load is fed into
the beam through the rubber bushings. There is a 1/2 inch thick
2.25  inch by 2.25 inch alloy plate out there that can be screwed or
riveted to the bottom of the beam if necessary.

What method did you use to apply the rubber bushing loads?

Paul Lamar

Buckling <<<

       If you look at any of the pictures, you might notice that the side
flanges are deflecting outward rather severely at the ends. I suspect that
the sides of the beam will thus "unfold", then the beam web (base) will
fold upward at the ends, rather than buckling at the center. The two bolt
spacers in the center region add a lot of lateral stiffness, and act to
suppress buckling at the center.

       The stress alone does not really predict buckling. It is the
slenderness ratio, modulus, and the stress combined.

       Unless I run the buckling simulation, this is all conjecture of
course.

Rubber washers <<<

       I simply drew up a thick washer, attached two of them to the beam,
then defined the material properties.

       Bill Dube'

OK Bill I see.  No problem. I think the thick aluminum plates
we already have out there will reduce the stress concentrations.

Paul Lamar