Self-ejecting propellor shaft coupling

Cliveshep

Cliveshep

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I've got a problem with my propellor shaft coupling I need to solve without purchasing a new coupling which I cannot afford.

I picked up a braided rope around the prop a couple of years ago, which forced the shaft progressively out of the coupling over the next 200 miles home as it wound ever tighter. A lift-out at a boat-yard allowed cutting the rope away by which time it was like an iron bar around the shaft behind the prop. Ever since then I have had problems in keeping the shaft in the coupling.

The pic shows the coupling and a sketch the principle, basically it just clamps in, except periodically mine doesn't and in reverse the shaft is ejected from the coupling. It cannot be lost totally as the rudder prevents that but naturally all drive is lost.

That can make for interesting manouvers at times!

Does anyone either have or know for sure where a spanner to fit the notches in the threaded ring can be obtained, and does the team think that the addition of Loctite between shaft and the coupling "fingers" would assist in keeping it clamped into coupling

Propshaftcoupling.jpg


Propshaftcouplingsketch.jpg
 
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What you need is a C spanner.

Measure the diameter of the nut and try a decent tool suppliers or Goggle .
 
Maybe something like this would do, you would need to check the size of the lugs in the nut.

I am trying to picture what you mean by 'fingers'......I am assuming that they are acting like a collet setup?
If this is correct, I am wondering whether these fingers have been smoothed down when the shaft was pulled out, and may also be slightly tapered now?
I would suggest trying to get some replacement fingers, or, failing that, maybe try and get a local engineering shop to cut some shallow slots across them using a 90 deg cutter - where they grip the shaft, preferably at an angle (diamond cut).
A more drastic solution might be to get the end of the shaft 'knurled'.

I don't think that using loctite would be a suitable solution.........it might work, but you might never be able to get it apart again!
 
Yes exactly. These couplings need to be done up really tightly relying on collet action to grip the shaft. Whacking it with a punch and a glaswegan screwdriver wont do it up tight enough. You will need to stop the shaft turning when doing it up too. I find that putting the engine in gear alone is not enough. A C spanner with a gert big pipe over the handle will do it up OK but you will need to oppose the force with an equally big lever or you will just turn the engine over or do your gearbox a mischief.
 
It's an unusual looking coupling. Any idea who made it? I'd consider drilling through and fitting a spring cotter through the coupling and shaft, but not without knowing how the coupling goes together.
 
Interestingly it appears to show that a woodruff should not be used and it should be drilled and pinned across the inner coupling and through the shaft........
I wonder if the OP's is the same type as this or possibly an earlier one?
 
I wonder if the OP's is the same type as this or possibly an earlier one?
Click to expand...
Or fitted by someone who did not read the instructions.

We had a question on here a couple of years or more ago about them, but I think that may have been about how to get one off! I have a vague idea that may not have been pinned so advice to knock the pin out was not helpful!


Topcat47's suggestion looks a pretty valid one.
 
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It's strange that the image in your first link shows the collet with a woodruff slot........so perhaps the collet is able to spin in the housing.
On this basis I would suggest at least cross drilling and pinning, reassemble without the woodruff and tighten to the suggested torque.
 
Maybe the previous damage has worn the fingers and increased the internal diameter while leaving the tightening nut and collet partially seized in their old positions?

If you don't fancy cross drilling until all else fails:

How about disassembling, cleaning and drying all the components, roughing up the surface of the prop shaft with the edge of a triangular file, reassembling (making sure there is NO lube on the shaft and inside of the fingers, and sufficient lubrication on the taper/collet and threads to allow smooth tightening with the correct C spanner and length of tube?
 
VicS - that looks like the beast. Everyone else who reccomended a C spanner I've looked at those and the price is exhorbitant for an out-of-work bloke. However, you've all given me the germ of an idea which is to nip back down to the boat, knock off the nut and collar and roughen up the prop shaft as best I can, probably with a centre punch and hammer to get a rough surface for grip. The only way to extract the shaft is to get the boat lifted, remove rudder and stock, and draw the shaft out the back. I can't afford that until I get another job and the likelihood of that this year is slim. I'll bring the nut back home and re-dress the notches in my workshop and get someone to flame-cut a 24" long x 1/2" thick steel blank C spanner I can dress and finish at home.

I didn't realise it needed so much ft/lbs torque to do it up, that bit was a shock and I'm now not surprised it spits out the shaft in reverse.

For what it's worth and as belt and braces, I'll lube the taper as Vic's link shows as that makes a lot of sense, but I'll also put Loctite on the shaft as well. It is just too much like inviting a crash-into-something-disaster-with-no-propulsion scenario to take chances with it again. Many thanks guys, any one else got any input and I'll still be glad to hear it.
 
Cliveshep said:
I've got a problem with my propellor shaft coupling I need to solve without purchasing a new coupling which I cannot afford.

I picked up a braided rope around the prop a couple of years ago, which forced the shaft progressively out of the coupling over the next 200 miles home as it wound ever tighter. A lift-out at a boat-yard allowed cutting the rope away by which time it was like an iron bar around the shaft behind the prop. Ever since then I have had problems in keeping the shaft in the coupling.

The pic shows the coupling and a sketch the principle, basically it just clamps in, except periodically mine doesn't and in reverse the shaft is ejected from the coupling. It cannot be lost totally as the rudder prevents that but naturally all drive is lost.

That can make for interesting manouvers at times!

Does anyone either have or know for sure where a spanner to fit the notches in the threaded ring can be obtained, and does the team think that the addition of Loctite between shaft and the coupling "fingers" would assist in keeping it clamped into coupling

Propshaftcoupling.jpg


Propshaftcouplingsketch.jpg
Click to expand...
Clive
hang on, lets talk about basic engineering, thumblethumb fixes wont work here! Centre popping knurling etc NEVER work in the long term. Loctite wont hack it either. Get your C spanner, take it all apart, inspect for damage caused by the rope making the shaft slip. Weigh up if the C nut is going to tighten it all up before it bottoms or what ever. IF it all looks manageable then clean and re assemble, basically you have a jacobs chuck similar to a power drill chuck there, tighten the C nut and it forces the fingers to grip the shaft. If it is worn and I was going to do a permanent BODGE I would weigh up drilling through the whole lot and fit a roll pin.
Stu
 
SkipperStu - you're right of course, I'm currently mailing all and sundry for the proper C spanner and a new nut but I'm all for any belt and braces job as well, it's just such a pain to go drifting off helplessly with the engine and gearbox spinning freely whilst I bump into everything!
 
This may be a long shot, and I will bow to anyone's superior ignorance on this, get an engineer to 'jump up' the shaft, not sure if it can be done on stainless. Basically I think it involves dropping the shaft on its end so it 'swells' slightly.
 
Fisherman, good idea but read what I said earlier, it has to be sorted in-ship and not by involving a crane-lift-out/slipping and shaft/rudder removal. Reason is cash, I've been out of work (Construction Management - need I say more?) for nearly a year and money is tight. Your way is ideal, pull the boat out, strip out the lot. I suspect the outboard bearing could do with replacing and the prop fettled and balanced but those ideals are not available until I get back into work and that might not be until next Spring the way the markets are NOT moving.

All I want to do as a stop gap is figure out how to keep the shaft firmly stuck in the coupling until things ease up financially. The boat needs lifting next year anyway as it is in sore need of some TLC and then I might get the chance when it is slipped to pull out shaft and rudder and replace cutlass bearing, do prop, sort anti-foul plus some rubbing strake remedials. It is proposed to dry-dock next Spring for a few weeks at a friend's covered slip down the tideway but this little effort is to keep her going for now.

What a garage friend disparagingly calls a "kerbside overhaul" rather than a complete repair!

By the way, those who query the woodruff key shown to be omitted in favour of the pinning of shaft to coupling as the latest Vetus manual, the shaft is believed to be original, I'm guessing that this particular problem was encountered by Vetus in the past which resulted in the omission of the woodruff key in favour of pinning. However, the coupling is milled with a woodruff keyway, the shaft is stainless and the key is bronze.
 
Cliveshep said:
Fisherman, good idea but read what I said earlier, it has to be sorted in-ship and not by involving a crane-lift-out/slipping and shaft/rudder removal. Reason is cash, I've been out of work (Construction Management - need I say more?) for nearly a year and money is tight. Your way is ideal, pull the boat out, strip out the lot. I suspect the outboard bearing could do with replacing and the prop fettled and balanced but those ideals are not available until I get back into work and that might not be until next Spring the way the markets are NOT moving.

All I want to do as a stop gap is figure out how to keep the shaft firmly stuck in the coupling until things ease up financially. The boat needs lifting next year anyway as it is in sore need of some TLC and then I might get the chance when it is slipped to pull out shaft and rudder and replace cutlass bearing, do prop, sort anti-foul plus some rubbing strake remedials. It is proposed to dry-dock next Spring for a few weeks at a friend's covered slip down the tideway but this little effort is to keep her going for now.

What a garage friend disparagingly calls a "kerbside overhaul" rather than a complete repair!

By the way, those who query the woodruff key shown to be omitted in favour of the pinning of shaft to coupling as the latest Vetus manual, the shaft is believed to be original, I'm guessing that this particular problem was encountered by Vetus in the past which resulted in the omission of the woodruff key in favour of pinning. However, the coupling is milled with a woodruff keyway, the shaft is stainless and the key is bronze.
Click to expand...
Clive
you have just said that there is a bronze key?? Is the key intact? if so there is something not right here!
Stu
 
skipper_stu said:
Clive
you have just said that there is a bronze key?? Is the key intact? if so there is something not right here!
Stu
Click to expand...

It sounds as though what is happening is that the shaft is moving back far enough to allow the key to come clear of the keyway (and allow the prop to contact the rudder.)

As a temporary measure (bodge, before someone else says it), can you clamp something round the shaft between the coupling and whatever seal you have so as to limit how far back the shaft can travel? That should let you keep the key in the keyway and maintain some drive. Be careful, though, that whatever you put on can't damage the seal.
 
Cliveshep said:
All I want to do as a stop gap is figure out how to keep the shaft firmly stuck in the coupling ...
Click to expand...

I think you have had your answer:

217 lbs ft torque to do that nut up!

If you can't run to a 'C' spanner - and probably even if you could - grit your teeth and lean as hard as you can on a BIG (24-36") stilson. Not elegant, but if Needs Must...

Andy

(Bent a cheap 3/4" breaker bar putting 250 ft lbs on a camper van hub nut)
 
Be carefull

Ok here is my two cents worth, I work as a millwright on ski lifts and we use this kind of nut a fair bit we call it a ring wrench you should be able to find them at a reasonable price somewhere locally. 217 foot lbs is 217lbs 1 foot from the center of the shaft if you apply 70lbs or so 3 feet from the center of the shaft you have your 217lbs give or take. The point is that it is a taper and too much force you will split the sliding taper, this is also a dry torque so if there is any lubrication on the threads you will be in danger of applying too much torque resulting in a split taper or stripped threads. I would clean up the shaft as best you can do not knurl it or any other hokey hammer stuff. Assemble making sure there is no lubrication around and torque to the recommended amount at this point there needs to be some clearance between the fingers( at the small end) if not then the taper has bottomed out, probably because too much material was lost when the shaft spun during the original incident. See how you go with that if it still spins then you might be able to get away with a sleeve to take up some of the clearance you have. also check all the gaps between the fingers to be sure that loose material is not blocking the taper from closing up.

Good Luck
 
Gotcha. Are the fingers touching together before getting a good squeeze on the shaft? If so you could angle grind the edges. Drill and roll pin otherwise.
 
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