[rowbare]

Most people I have read consider that the epoxy and aggregate for damping purpose alone are not critical as the purpose is to refract and reflect and hence diffuse vibration inducing impulses.I would expect little damping from tube filling though as the metals will carry most loads and so there vibrational characteristics will dominate.CI considered to have good damping properties.More damping probably best achieved by adding to more metal, to add stiffness and mass.
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You are neglecting that the whole system contributes to damping, not only the load bearing members. Taking your assertion to an absurd conclusion, an EG filled metal wind chime would make the same sound as the original. But it doesn't. Once you have met your stiffness and strength goals, adding more of the same metal is a diminishing returns proposition. You might have to add so much material that the machine can't be moved any more.

This is a good if somewhat lengthy read: http://www.mech.utah.edu/~bamberg/re...e%20Design.pdf

I agree with everything else you said though. Since you mentioned Taig, a bit of trivia: the Taig lathe bed extrusion is concrete filled...

bob