"Ted Edwards" wrote in message
...
Ed Huntress wrote:

Because the tubes could be of larger diameter and *also* have thicker
walls,
for the same weight -- thus producing a higher value "r."

I picked 2" as an example but the same comparison applies to any OD
until the walls become so thin that other factors become involved.

In fact, that's how the Bobsy was designed, with aluminum tube space
frames,
back in the '60s.

That doesn't neccessarily make it right.

Correct me if I'm wrong, Ted (and this is stuff I'm 'way rusty about), but
the larger diameter tube made possible by lower density of aluminum will
have a higher value for the radius of gyration than will a steel tube of the
same weight, and of smaller diameter.

Correct?

Ed Huntress