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JB1

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Reply with quote  #31 
Update International, false couple.....Googled it here.

http://updateinternational.com/Book/VibrationBook5h.htm
106Bones

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Reply with quote  #32 
I have no explanation for the lack of familiarity with False Couple or reason that more practitioners do not use Static - Couple Derivation. In the early 1980's few in  industry could field balance, those that could or were connected to OEM's were very busy. A slow week for me was 3 to 5, sometimes I did that many a day or more in plants that couldn't help themselves even with their educated Engineering staff. As a young man like many I had challenges with over hung rotors and off center center-hungs. It was something I had to address and learn my way out of it. I was fortunate to meet Ralph Buscarello who gave me insight into why what I was doing was not working, it went something like " Jim, you are completely wrong in your understanding and method" That stung but it was true, failing is its own confirmation of it. False Couple was the  reason my conventional 2-plane was often ineffective, Static-Couple Derivation was the corrective method. Along the way in a near 40 year career with service organizations of three OEM's I have likely balanced more than 3000 fan rotors in the field. Not always the new start up data collection units but the rotors with mods by less than attentive or experienced forces. Now that my 40 year apprenticeship is over I share what I know. I teach what I know and is proven beyond technical challenge. 

Its still fun when that 100 mil monster goes to 2 mils of tamed energy. Never boring except those long LOTO waits. 

106Bones
John from PA

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Reply with quote  #33 
Quote:
Originally Posted by 106Bones
I have no explanation for the lack of familiarity with False Couple or reason that more practitioners do not use Static - Couple Derivation. In the early 1980's few in  industry could field balance, those that could or were connected to OEM's were very busy. A slow week for me was 3 to 5, sometimes I did that many a day or more in plants that couldn't help themselves even with their educated Engineering staff. As a young man like many I had challenges with over hung rotors and off center center-hungs. It was something I had to address and learn my way out of it. I was fortunate to meet Ralph Buscarello who gave me insight into why what I was doing was not working, it went something like " Jim, you are completely wrong in your understanding and method" That stung but it was true, failing is its own confirmation of it. False Couple was the  reason my conventional 2-plane was often ineffective, Static-Couple Derivation was the corrective method. Along the way in a near 40 year career with service organizations of three OEM's I have likely balanced more than 3000 fan rotors in the field. Not always the new start up data collection units but the rotors with mods by less than attentive or experienced forces. Now that my 40 year apprenticeship is over I share what I know. I teach what I know and is proven beyond technical challenge. 

Its still fun when that 100 mil monster goes to 2 mils of tamed energy. Never boring except those long LOTO waits. 

106Bones


Static couple is likely something well known to many of us here, but just not known as “false couple”, nor honestly do I understand that choice of words.
106Bones

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Posts: 35
Reply with quote  #34 
John

  I think that if you will read or re read all my topic posts you will note I do not refer to Static-Couple and False Couple being the same thing, they are not. After being requested to elaborate I have plainly described the mechanism of False Couple, another poster was kind enough to post a link to update international where false couple has been their teaching topic known to me since 1982. 
 Static-Couple Derivation is a rotor balancing process I find and recommend as useful in scenarios that are false couple and benefit from a better faster more certain solution than conventional 2-plane.
  Again, please re read all my posts and look on that link and if you have any additional questions about definitions then, ask away.

 106Bones

OLi

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Reply with quote  #35 
I am always trying to be very pragmatic and in my world I find a very good result, the best when having a relatively long rotor like a Archimedes screw, cylinder etc. and it is sitting in a balancing machine so I can put weights anywhere even in places not on the drawing and I get the static/couple solution out of the machine, apply the static somewhere in the middle. Run again and apply the remaining couple in the ends, it is the best I can get, ever. On old refurbed overhung fans in the industry it get quick and dirty, a one plane as it has at some time in production been treated to the 2-plane and you rarely can access any more than 1 place for weights and it is normally good and quick. I do refuse to balance stainless steel hi temp fans with visible cracks longer than 10mm, there are limits. Exception are old ventilation fans with 2 wheels on 1 shaft then I start a 2-plane direct as that is more than 50% chance it is required. I am now having a set of difficult all plastic epoxy and molded fans and specific 1 design that is very narrow and run high speed and can "only be balanced 1-plane, static" mostly depending on the fan mounting as it even at stopped can be toggled left right on the shaft..... So I really don't care IRL if the dynamic i see are of any kind as long as it is of the kind I can measure and compensate for but that is only me. On the other hand I have only met 1 fan last 40 years I could not balance despite it fulfilled all requirements less that the 1xRPM vibration was not unbalance..... out of many hundreds or maybe closer to thousand(s) actually if I look back I can't count that many anyway ;-).


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106Bones

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Reply with quote  #36 
OLi

 You evidently are uniquely experienced and qualified. I agree with your pragmatic approach and have made it my practice to focus on what works by pragmatically removing what does not. Many struggle with overhung arrangements particularly in the field. It is a common complaint that parallels the original posters post. Like your reference about disregarding dynamic I often do as well because with overhungs because the dynamic couple symptoms are not true dynamic forces in the rotor but a reaction of static imbalance on the arrangement geometry.

106Bones
Alex

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Posts: 204
Reply with quote  #37 
With all respect I am surprised how much complication comes from a simple case. Overhung fan? Really? Is that so complicated? I have balanced many of them, never had any issues with a simple one plane balancing. Outer plane / Inner plane? It doesn't really matter. The last one I balanced on Sunday 9.6.2019. 1st peak from 8,5 mm/s to 0,5 mm/s. Did I do anything wrong? Will it break down? Relax and take it easy [smile]
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