[TheForge] Off-topic: Anyone have experience with dynamic balancing, vibration sensing & vib-synched stroboscopes, and/or critical disk and/or rotor speeds?

[Bruce Freeman]

I'm working on a mechanism that involves a high-speed rotor, and I'm
to the point where I really need to dynamically balance the thing.
I've run it at about 1740 RPM and maybe as high as twice that.  (I
haven't measured the pulleys.)  I get more vibration than I want, but
it's not flying apart or anything scary.  (I'm aiming for an arbitrary
10kRPM.)

So, I've spent the day reading up on dynamic balancing and have
learned a fair amount, but nothing I can put to immediate use.  I have
learned that above the (first) critical speed (i.e., the speed
equivalent to the fundamental vibration frequency of the rotor), the
vibrational behavior changes and it is possible to automatically
balance the device.  There are patented mechanisms that utilize this
phenomenon.  However, I have no idea whether I have yet approached the
critical speed for this rotor, and trying to calculate that speed
(which is possible, in principle) would be rather difficult due to the
odd construction of the rotor.  Furthermore, I'm not at all sure I
want to take it up to the critical speed without first dynamically
balancing it.

The best alternative I've come across so far is to utilize some sort
of sensor that will register vibrational period and amplitude and,
preferably, trigger a stroboscope so that one can visualize where the
excess weight is on the rotor.  Unfortunately, I'm quite unclear about
what sort of sensor this requires.  I actually have a stroboscope, and
can easily "stop" the motion of the rotor with it, but it is triggered
by time, not by an external sensor, and correlating the flash to the
vibration is beyond my abilities for the nonce.

Furthermore, I read that in dynamic balancing, it may be necessary to
have a support structure with "soft" bearings.

As anyone knowledgeable in the field can tell, I'm in over my head
here.  I would appreciate any pointers, assistance, words of wisdom,
URL's or whatever that you can provide.

-- 
Bruce
NJ

The total lack of evidence is the surest sign that the conspiracy is working.