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stern tube packing


jenevers

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8 minutes ago, jenevers said:

Who removes old packing before repacking the stern tube and why? I was told that the Royal Navy didn't.

Me. Royal Navy are lazy and cost of sorting a worn shaft through old hardened packing doesn't matter, us tax payers pay.

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Me - encore...

 

Methinks its a matter of scale and more importantly - design.

 

When you're at sea and in a hurry - there's no time to fiddle about with extracting a lenth of 9mm rope, thus the Grey Funnel Line do something different...

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HM's  War canoes don't have stern gland packing. 

 

Ships' boats used to, but these days most ships boat is a RIB with out drive and no stern gland at all.  Daresay the larger ones have a Captain's or Admiral's barge and these will be displacement craft with stern glands.  I'd bet if they are fitted with packed glands that the packing is removed and renewed to a schedule.  

 

All very much after my time now though.

N

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14 minutes ago, jenevers said:

Does the old packing really go hard if it’s constantly pressurized with grease?

But it is not, any pressure in the grease soon leaks away then the shaft can polish the packing surface. That makes it go hard. the grease is for the bearing, not the packing although some may get into the packing.

Edited by Tony Brooks
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I, once again, repacked our stern gland, I have to confess that I don’t remove the old stuff. Anyway, three or more weeks later the greaser seems to be non operative. The gland occasionally drips, a few turns on the nuts and it stops. I think the nuts vibrate loose. Turn the ‘T’ on the greaser and it feels solid. Had the tubes off at each end in case of a blockage. No blockage.

 

Could being a norty boy have caught up with me?

 

How do you remove old packing? I’m guessing a very long screw, screw into the old stuff and pull out somehow.

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And there is the possibility that slithers of old packing might break off and get pushed down between the shaft and bearing, jambing the shaft.  I've had to free the shafts on two boats that had done this, one the owner forced the boat along, busted the drive plate and burnt out the gearbox clutch plates.  I just sharpen up the end of a bit of 1/8'' welding rod and bend a little half hook on it to dig in and hook the bits out.  A screw should work too, but scrape around in there with a thin screwdriver or something afterwards to make sure it's all out.

Edited by bizzard
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It is amazing how packing can wear a shaft. Picked up a 12' x 1.5" shaft at Beaulieu boat jumble a few years back compete with taper and keyways for a tenner, (not for a narrowboat so v. long) it was worn by the packing but I took a chance and luckily all the worn bits missed my stern gear. Also picked up a damn great anchor and a heap of chain and was on my knees by the time I carried it back to the car.

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Strangely enough, on my set up, the plate that is held in place by the 2 bolts to squeeze the packing, has  moved towards the packing (ie.astern) and a gap has developed away from the locked nuts as if it’s been sucked into the stern tube. 

Edited by jenevers
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11 hours ago, bizzard said:

And there is the possibility that slithers of old packing might break off and get pushed down between the shaft and bearing, jambing the shaft.  I've had to free the shafts on two boats that had done this, one the owner forced the boat along, busted the drive plate and burnt out the gearbox clutch plates.  I just sharpen up the end of a bit of 1/8'' welding rod and bend a little half hook on it to dig in and hook the bits out.  A screw should work too, but scrape around in there with a thin screwdriver or something afterwards to make sure it's all out.

I helped a friend with his very old 60 ton barge and we ended up pushing seven (7!) rings of packing into the stuffing box. The shaft was maybe 60mm diameter, so pretty big, but 7 rings seemed excessive. Anyone know if it’s normal on a big prop shaft?

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5 minutes ago, jenevers said:

Certainly looks very dry. I’m surprised.

The replacement rope seems to have much more grease impregnated in it.  At the moment my stern gland is hardly accepting/using any grease at all. One drip a minute, and working fine. I have checked that the pipe is not blocked. Maybe it needs another enema.

https://scholargypsy.org.uk/2019/01/23/enema-and-walkway/ 

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Can i ask...

 

 My packing has never been replaced in the decade i have had the boat and probably not since she was built in 04. All is working perfectly...plenty of adjustment, not dripping more than it should, not dry, grease coming through, not hot, shaft turns by hand...  is there any merit in replacing the packing material? My feelings are no, if it aint broke etc which is why i have left it, but does it wear out... Any thoughts? Thanks

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5 minutes ago, Paringa said:

Can i ask...

 

 My packing has never been replaced in the decade i have had the boat and probably not since she was built in 04. All is working perfectly...plenty of adjustment, not dripping more than it should, not dry, grease coming through, not hot, shaft turns by hand...  is there any merit in replacing the packing material? My feelings are no, if it aint broke etc which is why i have left it, but does it wear out... Any thoughts? Thanks

I normally change mine every 5-8 years, largely when I run out of adjustment and the dripping gets a bit much.  The latest packing is excellent, I've not tightened it up for a year and i suspect it will last for a long time.  So I would have a lot of sympathy for your "if it ain't broke" point.  I sometimes have a similar thought when I change my fuel filters,  which are invariably  pristine. But they are so cheap, and the consequences of a problem more serious, that I continue to change all three every year!  

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8 minutes ago, Paringa said:

Can i ask...

 

 My packing has never been replaced in the decade i have had the boat and probably not since she was built in 04. All is working perfectly...plenty of adjustment, not dripping more than it should, not dry, grease coming through, not hot, shaft turns by hand...  is there any merit in replacing the packing material? My feelings are no, if it aint broke etc which is why i have left it, but does it wear out... Any thoughts? Thanks

 

If it leaks, it's 'worn out'

If it doesn't leak, it's not 'worn out'.

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13 minutes ago, Paringa said:

Can i ask...

 

 My packing has never been replaced in the decade i have had the boat and probably not since she was built in 04. All is working perfectly...plenty of adjustment, not dripping more than it should, not dry, grease coming through, not hot, shaft turns by hand...  is there any merit in replacing the packing material? My feelings are no, if it aint broke etc which is why i have left it, but does it wear out... Any thoughts? Thanks

I would not change it. I suspect that you either have a solidly mounted engine or something like an Aquadrive that allows for radial misalignment plus a thrust bearing. FWIW On  a 30 year old boat I adjusted it once in 20 odd years and I suspect it had the original packing in it.

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13 hours ago, Nightwatch said:

I, once again, repacked our stern gland, I have to confess that I don’t remove the old stuff. Anyway, three or more weeks later the greaser seems to be non operative. The gland occasionally drips, a few turns on the nuts and it stops. I think the nuts vibrate loose. Turn the ‘T’ on the greaser and it feels solid. Had the tubes off at each end in case of a blockage. No blockage.

 

Could being a norty boy have caught up with me?

 

How do you remove old packing? I’m guessing a very long screw, screw into the old stuff and pull out somehow.

I rather think you might have been. I replaced my tube, shaft and and stuffing gland (the gland may have been overkill) 12 months ago. This was after a protracted period of time experiencing exactly the same symptoms as you.  Any  number of experts, real and imaginary, had pushed , pulled, wiggled both ends of the shaft and declared "no significant wear". In the previous 12 months I must have changed the packing 6-8 times following best practice. When I finally pulled the shaft it was worn from 1.5" down to 1.25".   

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