short of bolting it to the concrete floor, any ideas on how to
stabilize the base?
How 'bout bolting it to a piece of plywood, large enough so there’s
room to hold that board down to the floor with sandbags.
Or use a bit more plywood to make a low flat box onto which the lap
can be bolted. before covering over the top, fill it with concrete.
You don’t need to bolt it to the floor, in order to have it bolted to
a hundred pounds of concrete (or just loose rock filling the box
would probably do it too.)
I’m kind of thinking of the trick some people have used to secure
their Kerr centrifugal casting machines. The one where one scrounged
up an old oil drum, puts casters on the bottom so it will roll
around, fill it half way with concrete wo it weights a whole lot, cap
the concrete with plywood or something to which you an bolt the
machine, and it’s secured, while the upper part of the drum gives you
a shield for the machine… Even when the arm isn’t balanced at all
properly, done right this can still be totally rock solid. Sheer
mass holding it in place. You don’t need the shield, and could have
it lower down, but the basic idea is the same.