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Curmudgeon

Propshaft turning at idle

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1 hour ago, Mike Hurley said:

All motorcycles i have owned will turn the back wheel when placed on a centre stand with gearbox in neutral and engine idling, just drag in the gearbox.

Does a motorcycle have a stern gland greaser? 

  • Haha 1

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1 hour ago, Murflynn said:

just be grateful you were not the chief engineer on HMS Queen Elizabeth during her trials when the thrust block on one of her 2 propshafts started to disintegrate.  (last night on C4).

All caused by a lobster pot caught on a prop. It was a lucky accident though, uncovered a faulty prop seal which caused an imbalance which revealed a faulty thrust block design calculation. Fascinating I thought. 

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8 minutes ago, nb Innisfree said:

All caused by a lobster pot caught on a prop. It was a lucky accident though, uncovered a faulty prop seal which caused an imbalance which revealed a faulty thrust block design calculation. Fascinating I thought. 

 

I agree. Fascinating.

I shudder to think what would have happened if they'd got the stern line caught in the blade... 

  • Haha 1

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10 hours ago, Nightwatch said:

Does a motorcycle have a stern gland greaser? 

They can certainly make the stern gland pucker a bit, sometimes flutter and occasionally let go altogether! :o

  • Haha 2

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On 22/04/2018 at 22:52, Dr Bob said:

Same engine and gear box. Mine does the same but not noticed the boat moving forwards.

^^ + 1

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16 hours ago, Dr Bob said:

Stop press: Mine doesn't go round when it's hot. 

Emojii free zone.

So this seems to  point oil viscosity then, Which would tie in with previous answers and also confirm that it's not a real problem.

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10 minutes ago, reg said:

So this seems to  point oil viscosity then, Which would tie in with previous answers and also confirm that it's not a real problem.

That's what I thought. Maybe I need to change the oil?

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My PRM280, does but only occasionally. Its a good sign that the shaft and gearbox are in alignment. The PRM 160 does too, its the constant mesh gear clusters in hydraulic boxes stirring the oil up. Shame we can't do a tow start.

Its also why if someone falls in you turn the engine off, not just into neutral.

  • Greenie 2

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10 minutes ago, Boater Sam said:

Its also why if someone falls in you turn the engine off, not just into neutral

That's something I've never thought about I suppose there may be just enough momentum in the blade to cause a nasty hit to the head. Always something new to learn

Edited by reg

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Its also why if someone falls in you turn the engine off, not just into neutral.

 

Not only that, you could become tangled with clothes in the prop and held under.

Edited by Boater Sam
corrections

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16 minutes ago, Boater Sam said:

 

Its also why if someone falls in you turn the engine off, not just into neutral.

Good thought. Never had the problem before so not thought about it. Have a greenie!

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3 hours ago, Dr Bob said:

That's what I thought. Maybe I need to change the oil?

Try a thinner oil when you change it, choose your viscosity, makers specify any quality engine oil. 

  • Greenie 1

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On a cold morning my shaft turns slowly. PRM150 box with clean, correct grade oil. A good reminder to put on a warm coat :)

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My Beta43 and PRM 150 spins about 1 rev per 2 seconds. Certainly wouldn't move the boat. My old Barrus Shire 40 with a PRM 150 did the same.

Edited by Alway Swilby

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13 minutes ago, Mike the Boilerman said:

 

And the propshaft on your boat??? :giggles:

Even slower:cheers:

  • Haha 1

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On 23/04/2018 at 08:38, Murflynn said:

just be grateful you were not the chief engineer on HMS Queen Elizabeth during her trials when the thrust block on one of her 2 propshafts started to disintegrate.  (last night on C4).

More on this on the recent BBC documentary. 38:30 here:  https://www.bbc.co.uk/iplayer/episode/b0b11bb1/britains-biggest-warship-series-1-2-in-at-the-deep-end 

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On 25/04/2018 at 09:47, Slim said:

On a cold morning my shaft turns slowly. PRM150 box with clean, correct grade oil. A good reminder to put on a warm coat :)

Bragging o complaining? ;)
Our PRM 150 does likewise, the previous technodrive on same engine didn't. You sure knew when the techno engaged gear though!

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Hydraulic boxes contain all constant mesh gears which will transmit some torque to the output shaft via the oil in the box, the colder/thicker it is the more torque will be generated.

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1 hour ago, Boater Sam said:

Hydraulic boxes contain all constant mesh gears which will transmit some torque to the output shaft via the oil in the box, the colder/thicker it is the more torque will be generated.

But mode4rn mechanical boxes also use constant mesh gears. I think its the wet multi-plate clutches on things like the PRMs that allow oil drag and shaft turning.

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On ‎22‎/‎04‎/‎2018 at 20:53, Curmudgeon said:

I am new to owning a narrowboat and to engines in general so apologies if this seems a silly question. When my engine is running and the gearbox is in neutral if I lift the engine hatch you can see the propshaft turning very slowly / lazily. Any movement of the controller forward or back clearly engages the gears in the appropriate direction and the movement increases accordingly. Should the propshaft be completely still in neutral? Or do they just sometimes have some movement in them?

Any advice much appreciated.

 I would suggest disconnecting the morse cable from the lever at the gear box, with engine stopped,your engine control lever on dash board in neutral, push the lever back and forward, find the neutral position, now the important bit ,attempt to put the morse cable back on, if it does not line up with the hole in the lever,then adjust the cable to suit exact line up, there usually  is extra adjustment at the other end of the cable at the control lever on dashboard, call me on 07759 421998 if more info required, Alan, (marine engineer rtd)

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