Flexible coupling query

[surekandoo]

On my last visit to the boat, a maintenance inspection revealed that a stud had come loose and dropped out of the engine side half of the flexible coupling on the prop shaft. I had to dismantle the whole coupling to replace the stud which is now (hopefully) fixed in place with Loctite.

The coupling consists of a tri-lobe engine flange into which are fixed three studs, a rubber doughnut with three holes with steel sleeves which correspond to the three studs, a sliding three lobe boss which clamps onto the prop shaft and engages with the rubber doughnut, a "saucer shaped" loose flange which has three holes in corresponding to the studs, finally three nyloc nuts to hold the assembly together.

What I would like to know is should there be any "free" space inthe coupling, i.e. a small gap between the flanges and the rubber coupling to allow for any angular misalignment or should the whole thing be done up tight?

 

[rob2]

Your coupling sounds rather like a Vetus Bullflex, which is said to be OK for up to 2 deg of misalignment. I'd take a look at their website to confirm and then check out the manual, but I can't see that leaving slack would do anything but allow chafe.

Rob.

P.S.Ideally, you should use new self-locking nuts to prevent them falling off again!

P.P.S. The manual gives torque settings for all the fasteners.

 

[ean_p]

just as an aside to the op , you should try to minimise mis-alignment as much as possible really as the 'error acceptance' quoted by fleible coupling makers is what the coupling will accept, not what is good for your gearbox etc.

 

[rob2]

Yes, even if it does turn out to be a Bullflex, or similar, do try to get the alignment as close as possible. I would hazard that if it looks good by eye you don't need to faff about with feeler gauges, though. When as central as possible, the joint will then happily cope with the engine bouncing around on its mounts in all directions.

Rob.

 

[surekandoo]

Thanks for this every one.

Perhaps I should have said that as far as I know it's a proprietory Vire coupling, the latest type I believe, before Vire engines became obsolete. The engine was profeesionally fitted new to the boat with engine in 1984 by Fairways Marine in Maldon who are unfortunately no longer in existance.

I've also contacted the Vire "expert" but he's baffled me with science & I'm no further on.

Engine & drive did run beautifully last weekend so perhaps all is OK.

 

[rob2]

Interesting! I have a Sole mini-14 supplied by Fairway 1986/7 with a Vire shaft seal, fed from a reservoir like a remote master cylinder (cap says "Vire"). I can't say that I've taken any particular notice of the flexible coupling, but I guess it'll be the same as yours. It's quite probable that all these "Vire" fittings are actually common parts branded as Vire, so spares may be available from other sources, I hope!

Rob.

 

[Tugw]

Any flexible coupling should have the nuts/bolts tightened to the correct value.There should be no "gap" in the various components.If there is then the distance between shaft ends(gearbox to propshaft) is too great or the coupling is not installed correctly.

 

[surekandoo]

Any flexible coupling should have the nuts/bolts tightened to the correct value.There should be no "gap" in the various components.If there is then the distance between shaft ends(gearbox to propshaft) is too great or the coupling is not installed correctly.

That sounds like the answer I was looking for, and is the way the coupling was left after reinserting the stud. Thanks.

 

[Steven Miller]

There should be no gap between the faces and it is very worth your while faffing around with feeler gauges as any misalignment will cause wear to the stern gear and damage to the gearbox in the long run, the coupling is there to cope with rubber mounts on the engine not to allow misalignment.

 

[eagleswing]

is there a proprietary vire gearside adaptor?

depending on what your engine is, vire may likely have fitted a proprietary gearside adapter to mate the coupler to the engine. those gearside bolts should not be backing out or coming loose. i'd pull all of the gear-side bolts and check them all for proper torque if one has already backed out the others may not be far behind. if you ran a while before discovering the missing bolt, who knows what effect that had on the renewable parts of the coupler...and if you can't get parts for it how soon will it be before the whole vire thing selfdestructs, possibly wrecking your engine gear box ?? i might thorw the money into replacing the old coupler with a new CENTA $ or VETUS $$ or AQUADRIVE $$$.

. both VETUS and CENTA have manuals available on the internet with install directions for their couplers, the vire can't be much different... on the modern couplers, to remove the whole coupler, you remove the mounting bolts then there are different jackbolt empty holes into which you thread proper size jackbolts, which press on the coupler and back it out prop-side for easy removal.

PS- don't ever glue in the coupler's shaft side bolts, they will be a bear to remove if you need to pull the propshaft and/or replace the cutless bearing.