Gearbox to propshaft alignment advice

[skenn_ie]

This is also posted in the calssic boats forum:
Hi, Can anyone advise me on the best procedure for aligning Engine/gearbox assembly with the propshaft. I am replacing Portisham's complete propulsion system with 2, 250HP engines with attached Twindisk MG507A's. Engine cradle will rest on original gearbox rails, engines -0.5 degrees from ship's datum(keel). Cradle has been made with the angles incorporated, so, theoretically, the top of the cradle should be horizontal, with underside resting on old rails, and centreline aligned laterally and vertically, with shaft.
I am also looking for dimensions of Twindisk's 11 1/2" "rubber block" coupling. I can send a sketch by email to anyone who can advise on this.

Thanks
Shane

 

[omega2]

Not sure what you mean by the "rubber block " but if you use R&D couplings you should have no bother. The method of alignment is described on the box. See www.clementsmarine.co.uk for supply.

 

[aquatom]

I think the (rubber block) coupling you are talking may be a R&D coupling. Have a look at www.randdmarine.com

hope this helps

 

[skenn_ie]

Twindisc couplings

Re: Alignment, it is the engine and gearbox will already be bolted together, then I need to align that unit with the propshaft.
Re: Coupling, actually, no. It's the ones with outward and reverse spider, with rubber bobbins on the spider. It is the outer ring with internal prongs that I need to fabricate.

Thanks

 

[NorthUp]

Marine & Industrial Transmissions will possible have the part you require-
http://www.mitgroup.co.uk/

 

[omega2]

Re: Alignment, it is the engine and gearbox will already be bolted together, then I need to align that unit with the propshaft.
Re: Coupling, actually, no. It's the ones with outward and reverse spider, with rubber bobbins on the spider. It is the outer ring with internat prongs that I need to fabricate.

Thanks

SEE THE SIX HOLES IN THE REAR COUPLING? these are the ones that the R&D coupling bolt to and then to the prop shaft coupling that should also have six holes, if your prop shaft does not have six holes then get one from Clements, the lining up is done by shifting the engine gearbox unit, by altering the engine bearers. for up/down and sideways. until the rounded head of the R&D has the same clearance at 12,3,6,9 o'clock, checked with a 20thou feeler gauge.

 

[Tranona]

Re: Alignment, it is the engine and gearbox will already be bolted together, then I need to align that unit with the propshaft.
Re: Coupling, actually, no. It's the ones with outward and reverse spider, with rubber bobbins on the spider. It is the outer ring with internat prongs that I need to fabricate.

Thanks

Looking at your picture, the coupling seems to be the damper between the engine flywheel and the gearbox. This would be a Twin Disc part so best to contact them or their agents as already suggested.

As to lining up the gearbox output with the shaft coupling, this is straightforward provided the beds are correctly installed to line up vertically and horizontally. Fine adjustment is carried out by adjusting the studs on the flexible mounts if that is what you are using or shims under the feet if it is solidly mounted.

 

[skenn_ie]

OK, so it is as simple as equalising the (small) gap between the flanges. I had wondered if there were any particular techniques used, but apparently not. The propshaft flange is bigger than the gearbox one, so I'll need an adapter, and possibly a short spacer to clear the gearbox oil pump.
I spent days getting 2 bevel drives working smoothly on the steering system, then was given a (manual)hydraulic pump and ram to use !. Far lighter, and almost zero backlash.
On the damper/coupling, I will ask MIT. Thanks to all who responded.

SEE THE SIX HOLES IN THE REAR COUPLING? these are the ones that the R&D coupling bolt to and then to the prop shaft coupling that should also have six holes, if your prop shaft does not have six holes then get one from Clements, the lining up is done by shifting the engine gearbox unit, by altering the engine bearers. for up/down and sideways. until the rounded head of the R&D has the same clearance at 12,3,6,9 o'clock, checked with a 20thou feeler gauge.