On Fri, 31 Jul 2009 20:35:43 +0200, Robert Roland
wrote:

On Fri, 31 Jul 2009 15:05:13 +0100, wrote:

the job can be done with an oscilloscope and an
old 2" computer loudspeaker

That's brilliant, Jim.

How about adding some sort of synchronization signal? Paint a white
dot on the cup and use a photo transistor connected to the scope's
other channel to get a reference to make it much easier to figure out
where to add weight.


I have played with that sort of system but it gets complicated.
For the comparatively small balance improvement needed for a twin
wheel grinder the stark simplicity of the speaker plus 'scope is
all that is needed.


Is a grinder fast enough to use self-balancing similar to what they do
in CD-ROM drives? I think it's simply some sort of drum with loose
steel balls inside.

I'm pretty sure that would work but I've never tried it.I think
the system is a bit like my cup but with the edge of the cup rim
turned in to retain a partly filled complement of balls. Wen run
up to speed the balls space themselves out into a pattern that
cancels the unbalance.

Jim