dslittle
Well-known member
You know that you’ve been around too long when you see the circle turning for the third/fourth time with another ‘new’ idea from some young bright thing (destined for higher ranks!!!)
UK’s biggest warship suffers propeller shaft damage off south coast after setting sail for US
- Thread starter Aeolus
- Start date
You know that you’ve been around too long when you see the circle turning for the third/fourth time with another ‘new’ idea from some young bright thing (destined for higher ranks!!!)
capnsensible
Well-known member
So, the speculators can relax. Or 'stand easy'. 
HMS Prince of Wales to be dry-docked while HMS Queen Elizabeth takes on some of her tasking | Navy Lookout
HMS Prince of Wales to be dry-docked while HMS Queen Elizabeth takes on some of her tasking | Navy Lookout
Chiara’s slave
Well-known member
Situation normal then. The press love to knock the Navy. So much so that I’m reluctant to disclose my previous occupation. No doubt folks can draw their own conclusions.So, the speculators can relax. Or 'stand easy'.
HMS Prince of Wales to be dry-docked while HMS Queen Elizabeth takes on some of her tasking | Navy Lookout
Poignard
Well-known member
.So, the speculators can relax. Or 'stand easy'.
HMS Prince of Wales to be dry-docked while HMS Queen Elizabeth takes on some of her tasking | Navy Lookout
Rosyth instead of New York!
Jolly Jack will be thrilled.
Kukri
Well-known member
Right: we have been told something.
The issue concerns an SKF coupling. SKF couplings are secured and released using grease.
A reporter may have been told that there was “insufficient grease pressure” and assumed that the “pressure” wasn’t the important word.
SKF used to insist on their people being present to witness the coupling push up…
Now we can speculate on what is meant by an “external coupling”.
The issue concerns an SKF coupling. SKF couplings are secured and released using grease.
A reporter may have been told that there was “insufficient grease pressure” and assumed that the “pressure” wasn’t the important word.
SKF used to insist on their people being present to witness the coupling push up…
Now we can speculate on what is meant by an “external coupling”.
Attachments
capnsensible
Well-known member
You are gonna love the irony here.
I've been down the marina doing engine runs on a couple of yachts.
One of them, a Beneteau 331 with a yanmar engine has a problem. When running in ahead, there is some vibration and a load of black smoke and unburnt fuel from the exhaust. All indications are that......there is probably something wrapped around the prop or shift! Gonna have to snorkel for a look....
Won't need a dry dock tho.
.ean_p
Well-known member
As a general rule such couplings are fitted using hydraulic pressure the release of which makes for a friction 'grip' on the shaft through which the 'drive' operates. Perhaps due to machining tolerances being out of spec or poor installation practice the friction grip has been overcome. If the shaft has slipped and scored the shaft then it will be some serious remedial work.
Kukri
Well-known member
Thanks ean_p.
Here’s some speculation:
Those outboard shafts are very long…
I will now guess that because the outboard shafts are so long, with not one but two “P” brackets, there has to be a coupling in the shaft, outboard of the stern seal, in order to be able to get the shafts out during docking, in which case you would want to have the coupling in a benign environment in which case you would think about shrouding the shafts at least as far as the first “P” bracket …
I think this might be a recipe for disaster… I think of the Blue Funnel “Super P” class ships which had deep tanks for palm oil etc. In the drive for maritime perfection the deep tanks, which of course had steam heating coils, had cofferdams. Which would have been great if there had been room to get into the space and paint it… but there was six inches…
Second picture is from the Daily Mail and could be wrong but it looks like the shaft is shrouded
Here’s some speculation:
Those outboard shafts are very long…
I will now guess that because the outboard shafts are so long, with not one but two “P” brackets, there has to be a coupling in the shaft, outboard of the stern seal, in order to be able to get the shafts out during docking, in which case you would want to have the coupling in a benign environment in which case you would think about shrouding the shafts at least as far as the first “P” bracket …
I think this might be a recipe for disaster… I think of the Blue Funnel “Super P” class ships which had deep tanks for palm oil etc. In the drive for maritime perfection the deep tanks, which of course had steam heating coils, had cofferdams. Which would have been great if there had been room to get into the space and paint it… but there was six inches…
Second picture is from the Daily Mail and could be wrong but it looks like the shaft is shrouded
Kukri
Well-known member
I foretell a line of worried men stood on the wall of Rosyth Dock no.1 and peering into the dock as the water is pumped dry…
penfold
Well-known member
It's in the DM, we can discard it as the product of a fever dream. A failed muff coupling is pretty unusual.
SaltIre
Well-known member
Did you not foretell earlier than she wouldn't make it past the bridges?
Kukri
Well-known member
My second picture is from Harmsworths’ Völkischer Beobachter, but Captain Sensible’s source for his report is much more credible:
HMS Prince of Wales to be dry-docked while HMS Queen Elizabeth takes on some of her tasking | Navy Lookout
So it does look like a failed coupling - I have heard of such a thing happening with a coupling inboard of the stern gland on one of OCL’s twin screw ships - the screw didn’t fall out, luckily, and some highly motivated engineers got the brake on and secured the shaft - so it’s not completely impossible, but it does raise questions about the accuracy of the machining and the fitting of the coupling.
Kukri
Well-known member
Did you not foretell earlier than she wouldn't make it past the bridges?
I foretold that she would need low water on a Spring tide to do that.
Bilgediver
Well-known member
Modern ships of an oil lubricated tail shaft. This means there is a face to face seal between the prop and stern tube as well as another similar seal in the machinery space. The out one has a guard so should be protected. Not sure that a fishing line would do much harm but a mooring line especially a wire spring could do a lot of harm if the shaft was turned before the wire was clear of the water.
The shaft bearing is lubricated by a header tank fixed above sea level and this might have emptied if a seal failed. Mind you normally a low level alarm is fitted.
jamie N
Well-known member
200 litres an hour leak?
FFS, I'd have been overjoyed with that if it'd been my carvel Folkboat after a winter ashore!
W
's
FFS, I'd have been overjoyed with that if it'd been my carvel Folkboat after a winter ashore!
W
's
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Chiara’s slave
Well-known member
That does sound quite modest for a 72000 ton ship. That's about 5 tons a day. I'd be surprised if the pumps on an aircraft carrier couldn't cope with 5 tons a minute.
Bilgediver
Well-known member
I wonder if it is a yard problem with the fitting of the sleeve couplings. Did they go a Full astern and the shaft slipped out
I believe a problem with the other carrier was that undersized and or insufficient bolts used on the main shaft thrust bearings. These sheared while the BBC were filming and the results shown to millions but not commented on. What we saw was the thrust load taken up by something mounted on the shaft in the engine space. This failed miserably in a cloud of sparks. I believe we also saw the thrust bearing displaced forwards. I was not impressed by those on watch. One would thing that an engineer or surveyor might have spotted the wee bolts!. In a later program we were shown the basic mod where the thrust bearings were now held in place with addition structure welded fore and aft to take the thrust to the hull and relieve the bolts. I was amazed these had not been spotted and removed from the program.
This appears to have been a drawing error.
Bilgediver
Well-known member
Maybe we should send a copy to Rosyth ?
Yes it is important to pump those well oiled taper components together. Suppose now they may check the others on both vessels.https://www.skf.com/binaries/pub12/...372---Couplings-brochure(4)_tcm_12-463858.pdf
Give here some of your buddies tugs and if she gets here by the 8th she might make it.
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Bilgediver
Well-known member
I take it that there is an SKF coupling somewhere between the P bracket and hull entry point. . Wonder if they have to draw all the shafting aft if the stern seal is at the end of a tube to the P bracket which the earlier sketch suggests. ? Maybe the prop fell off and that is what they were looking for
Kukri
Well-known member
I take it that there is an SKF coupling somewhere between the P bracket and hull entry point. . Wonder if they have to draw all the shafting aft if the stern seal is at the end of a tube to the P bracket which the earlier sketch suggests. ? Maybe the prop fell off and that is what they were looking for
That’s what I am thinking, too. It makes sense.
The only reason that I can think of for giving the afterbody the form that it has, is fuel efficiency.