Shaft coupling

[Guest]

I have recentlybought a Colvic Watson 26' with Thorneycroft 108 4 cyl diesel and PRM 101 gearbox. I have no experience yet of it afloat. I currently have the engine out for overhaul. The coupling is pretty rigid and I'm thinking of fitting a more flexible coupling, but not as costly as an Aquadrive. I'm fitting new rubber mounts - any recomendations on a reasonably priced, fairly flexible coupling that can take thrust and allow a little vibration damping and shaft/engine alignment tolerance? I belive some also offer some protection from serious prop groundng etc?

 

[Guest]

Granted Aquadrives are expensive. I had one fitted when I changed the engine on my last boat and thought it well worth the money. I can't help feeling that cost cutting in the propulsion region could end up VERY costly if not fatal if the gear failed in the wrong circumstances.

Regards,

Peter
http://www.mistressofmourne.com

 

[scottie]

do you have a flexible stern gland?
if you have then you must leave the coupling solid
R + D do a "plastic" coupling which works well abd is supposed to be fail safe

 

[VMALLOWS]

Thankyou for confirming what engineering logic has always told me.....you can't just put a flexible coupling (eg the R+D type) in a typical yacht installation between the gearbox and the (flexible) stern gland. Unfortunately certain vendors, including some representatives at boat shows, have been unable to grasp this point.

If you want a flexible coupling there must be something to take the thrust load off the propeller shaft. The Halyard (aquadrive) certainly does this, but unfortunately is too bulky to fit in many modern yachts.

Perhaps its easier just to align the engine/sterngear accurately?

 

[scottie]

Re:r&d Shaft coupling

I think that in many cases the R+D is stiff enough to be used against the rule

it more from a stabalising point that you must leave one rigid element in the set up

 

[Avocet]

Re:r&d Shaft coupling

Centaflex do something similar - it's still pretty expensive though. I made myself one out of two Centaflex rubber elements and a bearing in a housing that could take thrust and radial load from the RS catalogue. I guess it cost about £150 in the end.