On Fri, 31 Jul 2009 13:39:44 -0700, "Bill Noble"
wrote:

if you have a scope, and a strobe, and the speaker "accelerometer", then why
not just "do it right" - make a paint mark on the wheel as an "index", synch
the strobe to the rotational speed and synch the scope and see where the
peak is WRT your accelerometer location and then just add weight at the one
place where it is most effective?

Things are not as simple as they may appear. There will be phase lag
in the accelerometer (speaker with reference mass). In addition, the
grinder on compliant mount is very probably operating well above
resonance (as Jon noted) so the acceleration vector will very probably
lag the location of the imbalance.

Jim's method combines quadrature resolution of the error vector with
trial -and- careful observation to make phase ambiguity irrelevant. No
reference marker sensor needed, don't even need an o'scope.

Brilliant!

"Don Foreman" wrote in message
...
On Fri, 31 Jul 2009 13:39:44 -0700, "Bill Noble"
wrote:

if you have a scope, and a strobe, and the speaker "accelerometer", then
why
not just "do it right" - make a paint mark on the wheel as an "index",
synch
the strobe to the rotational speed and synch the scope and see where the
peak is WRT your accelerometer location and then just add weight at the
one
place where it is most effective?

Things are not as simple as they may appear. There will be phase lag
in the accelerometer (speaker with reference mass). In addition, the
grinder on compliant mount is very probably operating well above
resonance (as Jon noted) so the acceleration vector will very probably
lag the location of the imbalance.

Jim's method combines quadrature resolution of the error vector with
trial -and- careful observation to make phase ambiguity irrelevant. No
reference marker sensor needed, don't even need an o'scope.

Brilliant!

actually, I have sitting right in front of me a very old device called a
"Davey Vibrometer" that is an entirely mechanical (well, it uses electrical
power to light a light bulb) solution to this problem - it is basically a
very sensitive "dial" indicator with a mirror and a beam of light.

(if you can't resist having this, make me an offer I can't refuse - I don't
actually collect tools, but this thing is cool and works) - you can find me
via my web site, wbnoble.com

I believe it was used for exactly this purpose (balancing), but I have never
found anything to confirm that 100%