Bullflex coupling alignment

[Awie Fourie]

How to check Bullflex shaft coupling alignment with boat in the water?

Cummins 450hp with Twin Disc gearbox

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[Tony Athens]

Monkey Motion Gear to propshaft flexible couplings

Awie,

My experience with these type of complex “engine to prop shaft” flexible coupling systems is limited but have seen and worked with a few over the years… None of them solved anything as to making things better compared to a more conventional engine / transmission packages mounted with properly designed isolators systems.. Of course the sellers, of these say different, but 30+ yrs of field experience work with 100’s of installations has shown me something different. Ever seen these systems in vessels that make ocean crossings or on vessels that run 2000-4000 hours per year for decades? That may help you understand my position of them.

As to proper alignment with a system that is inherently not accurate (+/- .001″ per inch of diameter which is an accepted minimum standard for gear to prop shaft flange alignment) as to its own concentricity, it’s basically impossible unless its removed and the prop shaft is slid fwd to the gear flange. For sure that cannot be done in this case, so the alternative it to have a rigid concentric cylinder long enough & fully machined in all planes and axis to +/- .001 and use that as a alignment jig.

Curious– What does the manufacturer or supplier tell you to do? VETUS maybe ??

Are you sure you are not hearing “gear rattle” because of the failing torsional coupling?

Wish I could offer more..

Tony

[Author]

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