UK’s biggest warship suffers propeller shaft damage off south coast after setting sail for US

[Bouba]

I think that the amazing thing is that with only two days notice another aircraft carrier is ready to go in place of Prince of Wales...

 

[Fr J Hackett]

I think that the amazing thing is that with only two days notice another aircraft carrier is ready to go in place of Prince of Wales...

It would have been very embarrassing if it hadn't been.

 

[Bouba]

It would have been very embarrassing if it hadn't been.

In effect there are two fleet carriers operating simultaneously...it was never meant to be...so that shows the RN is on top of things

 

[Fr J Hackett]

In effect there are two fleet carriers operating simultaneously...it was never meant to be...so that shows the RN is on top of things

Yes usually a rock or some other underwater obstruction.

 

[Bouba]

Here’s an interesting article...it’s about a Nimitz class carrier, so nuclear power so it’s much bigger and much more powerful than either of the RN carriers.....but the torsional stress on the shafts must be universal
Tactical Action Officer on a US Navy aircraft carrier tells how long does it take to a Nimitz Class aircraft carrier to go to flank speed - The Aviation Geek Club

 

[capnsensible]

• HMS Queen Elizabeth sails from Naval Station Norfolk today - heading for New York @FutureAtlantic https://t.co/TQPIhjuWIG

For anyone interested....

 

[penfold]

Here’s an interesting article...it’s about a Nimitz class carrier, so nuclear power so it’s much bigger and much more powerful than either of the RN carriers.....but the torsional stress on the shafts must be universal
Tactical Action Officer on a US Navy aircraft carrier tells how long does it take to a Nimitz Class aircraft carrier to go to flank speed - The Aviation Geek Club

Don't know who did that article's maths, but a prop shaft will not pretzel itself and twist 1.5 times at full power.

 

[Bouba]

Don't know who did that article's maths, but a prop shaft will not pretzel itself and twist 1.5 times at full power.

The article says that it would be even greater if the engine power wasn’t limited

 

[burgundyben]

Don't know who did that article's maths, but a prop shaft will not pretzel itself and twist 1.5 times at full power.

Since every material has a modulus of elasticity and since in operation there are opposing torsional forces on the shaft it must twist.

Article says its 184ft long and twists 540 degress. 184/540=0.341 degress of twist per foot of shaft length.

Without loads of other data, particularly the prop details and shaft material, I couldnt say if thr 540 degrees is likely.

 

[Chiara’s slave]

Since every material has a modulus of elasticity and since in operation there are opposing torsional forces on the shaft it must twist.

Article says its 184ft long and twists 540 degress. 184/540=0.341 degress of twist per foot of shaft length.

Without loads of other data, particularly the prop details and shaft material, I couldnt say if thr 540 degrees is likely.

Have another look at that little sum? The twist seems rather high to me, I don’t think I’d like to be aboard when it’s twisted 54 degrees, let alone 540.

 

[Bouba]

Since every material has a modulus of elasticity and since in operation there are opposing torsional forces on the shaft it must twist.

Article says its 184ft long and twists 540 degress. 184/540=0.341 degress of twist per foot of shaft length.

Without loads of other data, particularly the prop details and shaft material, I couldnt say if thr 540 degrees is likely.

It’s nuclear powered....I would regard the power as unlimited....and the propeller is 30 tons....I would say the biggest problem is stopping it torsioning

 

[burgundyben]

Have another look at that little sum? The twist seems rather high to me, I don’t think I’d like to be aboard when it’s twisted 54 degrees, let alone 540.

You think my maths is wrong?

The acceptable amount of twist very depends on the details within the mechanical design, but 184ft is a lot of shaft.

 

[burgundyben]

It’s nuclear powered....I would regard the power as unlimited....and the propeller is 30 tons....I would say the biggest problem is stopping it torsioning

Regardles of engine power, the shaft twist will be a function of the prop design among other things.

Read Dave Gerr's prop book to understand.

 

[Chiara’s slave]

You think my maths is wrong?

The acceptable amount of twist very depends on the details within the mechanical design, but 184ft is a lot of shaft.

Your calc is upside down. It’s ange/length, not length/angle, to get distortion per foot. 3 degrees per foot is nuts. In fact, this 540 degree claim is much debated on the net. It’s not hard to find. When you do the sum right, you’ll realise that 540 degrees is beyond the elastic limit.

 

[Chiara’s slave]

Further to that, normal design criteria would say that around 0.3 degrees of twist per foot would be acceptable, so in spite of my nervousness, 54 degrees would be acceptable. Comfortable, even. Obviously, I’ve never been on a nuclear powered aircraft carrier with 180 ft prop shafts, I’m extrapolating from rather smaller scale stuff!

 

[Frogmogman]

When you do the sum right, you’ll realise that 540 degrees is beyond the elastic limit.

….or non-Hooky as my old mate rad Steve of material science at Uni would call it.

 

[Chiara’s slave]

….or non-Hooky as my old mate rad Steve of material science at Uni would call it.

Indeed. And as a resident of Freshwater, the man is dear to us.

 

[burgundyben]

Your calc is upside down. It’s ange/length, not length/angle, to get distortion per foot. 3 degrees per foot is nuts. In fact, this 540 degree claim is much debated on the net. It’s not hard to find. When you do the sum right, you’ll realise that 540 degrees is beyond the elastic limit.

Oh bum. Not had my first coffee yet.

 

[Chiara’s slave]

Oh bum. Not had my first coffee yet.

These things happen. Hopefully the designer of that shaft got their sums right first time, though doubtless they too were checked, and re checked.

 

[Spirit (of Glenans)]

It’s nuclear powered....I would regard the power as unlimited....and the propeller is 30 tons....I would say the biggest problem is stopping it torsioning

Relatively unlimited in duration perhaps, but limited by the physics of boiling water and the mechanical limitations of steam turbines I would expect.