Thanks to Greg Locock and Klyde for their posts in the original thread.
I have since made progress in my quest to understand the workings of the typical propeller/rotor dynamic balancer, but the original thread was closed, so I started a new thread.
I now have a desktop "rotor simulator" fabricated with a small variable speed AC motor, and an 8" flywheel to which I can attach trial weights at 10 degree increments. My simulator sounds much like Klydes' description of his.
Capturing scope-screens and Excel files from the accelerometer and Hall effect phase marker is now a snap.
The accelerometer signal is a beautiful, nearly noiseless sine wave. The phase markers are crisp and clean.
Initial data that I've captured, and rudimentary waveform analysis I've done, seems to indicate that the positive going velocity zero-crossing is different than the phase angle reported by the commercial instrument to which my simulator is attached.
The poccess I'm using is to generate an integral (velocity) curve of the acceleration waveform, via Sigview waveform analysis tools. The positive going zero-crossing of the velocity curve corresponds to 162 degrees from the zero degree phase marker.
The commercial instrument reports that phase angle at 320 degrees. A difference of a factor of 2. I'll test other samples at other imbalance to see if this holds true.
I've measured the phase lag "stack-up", due to electronics circuitry, of the commercial instrument between the input connector and the output of the anti-aliasing filter, and it appears to be precisely (and happily) 360 degrees. So electronics-induced phase lag error appears that it should not be a factor here.
The 90 degree shift due to critical speed that Klyde described in his post doesn't seem to apply here, although I do not yet know what the critical speed of my rotor simulator is.
I'd be happy to supply screen captures or Excel files if anyone cares to see them.
Can anyone offer some insight here?
I have since made progress in my quest to understand the workings of the typical propeller/rotor dynamic balancer, but the original thread was closed, so I started a new thread.
I now have a desktop "rotor simulator" fabricated with a small variable speed AC motor, and an 8" flywheel to which I can attach trial weights at 10 degree increments. My simulator sounds much like Klydes' description of his.
Capturing scope-screens and Excel files from the accelerometer and Hall effect phase marker is now a snap.
The accelerometer signal is a beautiful, nearly noiseless sine wave. The phase markers are crisp and clean.
Initial data that I've captured, and rudimentary waveform analysis I've done, seems to indicate that the positive going velocity zero-crossing is different than the phase angle reported by the commercial instrument to which my simulator is attached.
The poccess I'm using is to generate an integral (velocity) curve of the acceleration waveform, via Sigview waveform analysis tools. The positive going zero-crossing of the velocity curve corresponds to 162 degrees from the zero degree phase marker.
The commercial instrument reports that phase angle at 320 degrees. A difference of a factor of 2. I'll test other samples at other imbalance to see if this holds true.
I've measured the phase lag "stack-up", due to electronics circuitry, of the commercial instrument between the input connector and the output of the anti-aliasing filter, and it appears to be precisely (and happily) 360 degrees. So electronics-induced phase lag error appears that it should not be a factor here.
The 90 degree shift due to critical speed that Klyde described in his post doesn't seem to apply here, although I do not yet know what the critical speed of my rotor simulator is.
I'd be happy to supply screen captures or Excel files if anyone cares to see them.
Can anyone offer some insight here?
