Without the details of the design, I can only speculate.  On one occasion I had worked on a gearbox at a jet engine test facility that had a high speed pinion supported on rolling element bearings.  The pinion had to pass through a critical speed in its normal use.  In spite of my balancing efforts the vibration was extremely high and the service required the gearbox to start/stop several times daily.  I had the machine disassembled and slightly opened the bearing bore and added a groove with o-ring.  This provided sufficient damping to enable passage through the critical.  The application was somewhat similar to what is called a squeeze film damper.

This was a case where a gear sales person fancied himself a consultant on gear design.  Ultimately the gearbox was replaced by a unit with fluid film bearings that was designed/manufactured by a reputable gear manufacturer.  But several years of service were obtained with the original gearbox. 

Dear John,

Thank you for your info. Anyhow, recently i have a problem in bearing looseness and wear at BPFO from this motor at NDE side, then we have a series of investigation including vibration analysis and come to replace the bearing. We are successfully replace the bearing but not the o-ring, since then during machine startup we experience a high vibration and spectrum shows bearing looseness, then we came to the replace the o-ring then the vibration went down. 

It so happen that i am curious for the function of this o-ring and i cant find any. 

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HACKATHON in association with IMC-2019

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