Torsional Beam Fill: EG vs Concrete

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The stand for my new mill is almost done and if I'm preparing the stand for my new lathe (PM-1130V).

I'm going to torsional beam route and have acquired just about ev everything including the beam, a 3/16 4x10x60" rectangular steel tube.

Many have stopped there but I want to go further and fill the tube (after welding in pipe penetrators for the mounting bolts to run through).

So EG or a non shrink grout and why? Money isn't an issue as I already have a gal of epoxy (nothing special) and grout is cheap (also already have plenty of additives like plastisizer).

I cant remember the numbers of the rough math I did but they shouldn't differ too much in weight. I guess a big decider would be what compliments the rather thin 3/16" wall tubing.
 
I would probably reserve the epoxy granite for complicated shapes with thin sections, and just go with the grout slurry pour for this one. It would be cheaper, easier, and would probably produce less in the way of voids and occlusions. I haven't done either, but that's what my gut tells me. Occam's razor, etc.
 
I agree with pontiac428, I used regular cement to fill metal speaker stands, it added significant weight and dampening. Since it was contained within the metal frame (similar to what you are proposing) I did not see the need for more complex dampening options. I have also heard of people filling the base of machine stands in a similar fashion to add mass/dampening to the base. The PM-1130 is a light lathe overall, so benefit may be minimal when added to a torsion beam, but may reduce vibrations and noise transmitted into the beam.
 
What is EG? Epoxy/Gravel? This is the route I would go. Not because I think it would be any better than grout for this application but it would be a good way to gain experience with this mixture for future projects.

I assume with grout you would just dump it in then vibrate as much of the air out as possible? It seems like it would be much harder to eliminate air with the epoxy gravel mix... something I would want to learn about on an easy project like you are proposing. Just mixing the epoxy and gravel to make a somewhat homogeneous mix sounds like a challenge... best done with an easy project first.
 
I guess the consensus leans toward cement. Something else I didn't think about is it will be much faster/easier to accomplish as well.

Like mksj said, it is a relatively light machine and the EG would be better suited to fill voids in the underside of the bed if I think it would benefit in the future.
 
+ 1 for grout. Be sure to leave the ends exposed so it can dry throughly.
 
I have to ask, is this for strength or dampening?

If dampening the dry sand is way better than grout or cement. The sand does a great job of adding heft, and reducing vibration.
If looking for more strength, both grout and concrete offer that. I would think concrete might be better by a small margin, but both are difficult to get fully loaded without a rod to compress and knock out the voids. You can probably fill them after cutting and before welding. That way you get are assured a good packing.
 
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