Bob May wrote:

snipped

Since the machine is sitting on its 4 feet and the concrete isn't flat
enough to keep all 4 feet exactly on the concrete, an unleveled machine will
indeed be stressed in some way.

Not to disagree with you, because you are certainly correct in any
general practical sense, but:

It was only a few years ago I learned that you can get the legs of a
four legged stool to all contact an uneven floor and eliminate all
wobble simply by rotating the stool around it's central axis. You'll
find the spot where all four legs are touching within a quarter of a turn.

This works with considerable amounts of waviness of the floor, providing
of course there are no step discontinuities.

The proof of why this works isn't very intuitive, but with a little
thought you'll understand why it must be so.

I've found this trick works pretty well with rectangular four legged
tables too.

If you don't believe it, try it yourself.

Jeff



--

Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone
to blame it on."