On Fri, 31 Jul 2009 09:15:55 -0500, Ignoramus21205
wrote:

Jim, this was very interesting, but I have a question.

It would seem to me that the amount of vibration in a grinder, would
depend on two things:

1) Eccentricity of wheels
2) Mass of the grinder (or the grinder and its pedestal)

In other words, if the grinder has a thick enough shaft, and is
rigidly attached to something heavy, that act by itself would dampen
vibration.

i


The vibration we are trying to minimise arises when the centre
of mass of a rotating disk is not coincident with the axis of
rotation.

It is the mass distribution not the shape that matters. The
ONLY reason that a rotating eccentric disk generates vibration is
because the weight distribution is wrong. The actual shape and
the eccentricity have nothing to do with it.

The mass distribution error can be considered as perfect
wheel with a single error mass attached at a known radius. The
rotating force generated by this error mass tries to move the
mass of the grinder plus pedestal. The grinder mass plus anything
it is rigidly attached to acts reduce the amount by which the
grinder body moves.

Things get a bit more complicated if you have a wide wheel
and there are axial variations in mass distribution. However the
same arguments apply - the heavier the grinder in relation to
it's unbalanced wheel the smaller the observed vibration.

Jim