CentaFlex Torsional Couplings

2011 December 12
by Chris Brown
Centa Toursional Coupling

Centa Coupling Disassembled Exposing Roller Elements

Tis the Season for working on torsional couplings.  This particular unit came out of a 75′ Sunseeker with a ZF V-drive and Cardan shaft configuration.  Similar to the last post on Vulkan Couplers, this unit is attached to the flywheel and designed to take the various torsional loads that are transferred between the drive-line and engine.

The Captain had a concern with vibration on one engine and an alert engineer noticed the movement right at the Cardan shaft u-joint.  The u-joint was fine; the movement was from the play in the center bearing and outer “roller” elements of a Centa CF-RV coupling.Once the Centa coupling was removed and disassembled it was clear that the center bearing was damaged and the roller elements were worn.  The urethane roller elements (hockey pucks) disperse the torque loads by gradually compressing as the inner assembly torques in the housing (see picture).How can this failure occur?  With many of our projects we are able to make a determination as to the root cause of a failure.  Just replacing a bearing and sending the customer on their way is not enough.  We checked the cardan shaft alignment (engine to remote ZF) and it was good.   Apparently this engine had been rebuilt some time ago and an engine alignment took place at a later time.  We can only speculate that the initial engine rebuild mechanic left the engine out of alignment and the bearing was damaged from u-joint loading.  Once damaged it gradually wore the roller elements and continued to wear the inner bearing.After sea-trial the customer was happy.  We made his short turn-around schedule which made the “boss” (owner) happy, to keep on schedule and use the boat.We are very familiar with most CentaFlex Torsional couplings systems.  Please give us a call if you notice some play in the Cardan shaft bearing area.

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