Vamoose
Well-Known Member
Re: 2 Bladed Folding Props & PSS Dripless Shaft Seal
Gearbox Shaft Coupling
PSS Shaft Seal In Situ
Gearbox Shaft Coupling
PSS Shaft Seal In Situ
2 Bladed Folding Props & PSS Dripless Shaft Seal
- Thread starter Vamoose
- Start date
Tranona
Well-Known Member
Yes, I hope we get something from the oiriginal post, but without labouring the point, the problem has probably arisen because the original stuffing box was replaced with something that is more flexible. My best advice would be to to go back to that. The Volvo seal has from memory about 80-100mm bearing surface on the shaft right up to the point where it attaches to the tube, so it is obvious that just like a stuffing box it provides some support for the shaft. I fail to see how it can wear any more if the shaft is lined up correctly. In my view using this seal is this situation is no different from a stuffing box except that it is drip free.
I also know about the ways of overcoming the problem of centering the shaft, but that would not be necessary if the designers did a "proper job" and put a bearing on the inboard end in the first place! The reason they don't is because the stuffing box gives just enough support. But, of course we are now going round in circles.
For well designed sterngear that avoids most of these problems see the Vetus catalogue pages 156/7!
I also know about the ways of overcoming the problem of centering the shaft, but that would not be necessary if the designers did a "proper job" and put a bearing on the inboard end in the first place! The reason they don't is because the stuffing box gives just enough support. But, of course we are now going round in circles.
For well designed sterngear that avoids most of these problems see the Vetus catalogue pages 156/7!
Vamoose
Well-Known Member
Thank you all for your contributions there is lots there to get my teeth in to. I will of course update you all with the outcome.
However I have decided to take it a step at a time. Step 1 is to get the Alignment checked by a professional and then see if it helps. The Engine mounts were new last year so they should be OK.
If that does not work I may be faced with either replacing the PSS Seal or maybe installing a flexible coupling .. But we will decide on that later.
Thanks again for all your contributions
Alan
PS
Click below to see pic of the old shaft seal
Old Seal Arrangement
However I have decided to take it a step at a time. Step 1 is to get the Alignment checked by a professional and then see if it helps. The Engine mounts were new last year so they should be OK.
If that does not work I may be faced with either replacing the PSS Seal or maybe installing a flexible coupling .. But we will decide on that later.
Thanks again for all your contributions
Alan
PS
Click below to see pic of the old shaft seal
Old Seal Arrangement
Tranona
Well-Known Member
Very useful to have the piccy. This type of arrangement does provide some support for the shaft because you have the gland packing around the shaft and the flexible connector is stiff but does allow some movement. Note that you have a water feed from the engine - have you kept this? Also the end of the tube is a bronze casting which you may find has enough "meat" to machine to take a length of cutless. This will give positive support and ensure that the shaft runs true. However, if you do go that route you will need a flexible coupling to take up engine movement. If the shaft is knocking against the bronze it sounds far worse than it actually is!
Hope this helps
Hope this helps
Tranona
Well-Known Member
Just seen your other piccys which answers the question on the water feed
scottie
Well-Known Member
Re: 2 Bladed Folding Props & PSS Dripless Shaft Seal
Dont add a flexible coupling it wiil make it worse
check the flex mounts and the rear mounting brackets if the early bent metal type can fail and should be replaced with the cast type
Dont add a flexible coupling it wiil make it worse
check the flex mounts and the rear mounting brackets if the early bent metal type can fail and should be replaced with the cast type
webcraft
Well-Known Member
[ QUOTE ]
The design of stern gear that does not have a inboard bearing relies in part on the conventional stuffing box for shaft support. Remove that and the shaft can move as described and hit the tube - even if it is aligned properly.
[/ QUOTE ]
With all due respect, I think you are talking nonsense here. I replaced our stuffing box (Vega 27) with a Volvo seal and fitted a new Beta with centaflex coupling. The stern tube is approx. 1.75" and the shaft is 1".
I paid an alleged marine engineer to align the engine and the new Volvo seal leaked. Pulling it back I discovered that the shaft was almost touching the side of the stern tube, and would almost certainly have hit it under some load conditions.
I realigned the stern tube using a cone drilled for the shaft diameter then cut in half (easy enough to get made up in wood or metal by someone with a workshop and somewhat more effective than the roll of insulating tape mentioned above)
With the shaft now central in the tube the engine could be lined up and voila - no problems whatsoever in 550 hours running with a 2-blade varifold prop. Aligning the shaft with the stern tube is every bit as important as aligning the engine with the shaft, and is the first step.
Perhaps people do not take the trouble (simple enough using the split cone described above) to centralise the shaft properly . . . in which case problems are inevitable. The idea that the stuffing box (or any other form of seal) should in any way act as a bearing is absurd.
The use of a centaflex coupling also makes shaft alignment very easy using the 'clunk but not clunk-click' method (no point in messing about with feeler gauges if using one of these) and of course it helps dampen any vibration.
- W
The design of stern gear that does not have a inboard bearing relies in part on the conventional stuffing box for shaft support. Remove that and the shaft can move as described and hit the tube - even if it is aligned properly.
[/ QUOTE ]
With all due respect, I think you are talking nonsense here. I replaced our stuffing box (Vega 27) with a Volvo seal and fitted a new Beta with centaflex coupling. The stern tube is approx. 1.75" and the shaft is 1".
I paid an alleged marine engineer to align the engine and the new Volvo seal leaked. Pulling it back I discovered that the shaft was almost touching the side of the stern tube, and would almost certainly have hit it under some load conditions.
I realigned the stern tube using a cone drilled for the shaft diameter then cut in half (easy enough to get made up in wood or metal by someone with a workshop and somewhat more effective than the roll of insulating tape mentioned above)
With the shaft now central in the tube the engine could be lined up and voila - no problems whatsoever in 550 hours running with a 2-blade varifold prop. Aligning the shaft with the stern tube is every bit as important as aligning the engine with the shaft, and is the first step.
Perhaps people do not take the trouble (simple enough using the split cone described above) to centralise the shaft properly . . . in which case problems are inevitable. The idea that the stuffing box (or any other form of seal) should in any way act as a bearing is absurd.
The use of a centaflex coupling also makes shaft alignment very easy using the 'clunk but not clunk-click' method (no point in messing about with feeler gauges if using one of these) and of course it helps dampen any vibration.
- W
Tranona
Well-Known Member
Don't blame poor workmanship on the seal. Getting it so far out of line is incompetence. As I said in an earlier post, if the outer diameter of the tube is concentric with the internal diameter, then the Volvo seal automatically centres the shaft because it in turn is concentric with the shaft. If you read what I say carefully, I do not suggest it is a bearing in the same way that a cutless is, just that it provides support to keep the shaft centred in the tube, in the same way that a stuffing box does. If the engine and shaft are aligned properly then there is no need for it to bear any radial load - it just acts as a seal. From what I have seen the bellows on a face seal are too flexible to provide this support, and indeed have no radial support of the shaft at all. Your method of centring is OK if you have room to line it all up and then slide the seal down the shaft, but not all installations have this luxury.
Anyway the proof of the pudding for me is that my Volvo seal has neither worn nor leaked in over 10 years, part of which was before I put the additional bearing in because I wanted to fit a Bullflex to isolate the engine as far as possible from the shaft, which is now effectively rigid with a bearing at either end of a metre long shaft. A "proper job" in my view, but not possible/suitable in all installations.
Anyway the proof of the pudding for me is that my Volvo seal has neither worn nor leaked in over 10 years, part of which was before I put the additional bearing in because I wanted to fit a Bullflex to isolate the engine as far as possible from the shaft, which is now effectively rigid with a bearing at either end of a metre long shaft. A "proper job" in my view, but not possible/suitable in all installations.
30boat
N/A
Re: 2 Bladed Folding Props & PSS Dripless Shaft Seal
An Aquadrive coupling would entirely solve the problem unlike a standard flexible coupling.
An Aquadrive coupling would entirely solve the problem unlike a standard flexible coupling.
fastjedi
Well-Known Member
Most hunter boats with 1GM10s and Volvo PSS have this 'issue' to some extent. In cold weather and / or when the engine is cold there might be the faintest hit as gears are engauged and the prop starts turning. It is most evident in warm weather / when the engine has been running for 20 mins or so as the stern gland / engine mounts soften.
New engine mounts, cutless bearings, flex couplings and hours of engine alignment do not overcome the issue. A brand new stern gland does appear to offer better support for a while. I was told not to worry about it as it is almost inevitable with the above setup and does no harm (except to your pride when approaching a mooring within earshot of others)
At tickover try applying a little pressure to the prop shaft with your hand .... close to the stern tube: Up, down, left, right. If it's engine alignment it may well stop when you push in one of the directions.
If all else fails speed the slow run up /forums/images/graemlins/wink.gif
New engine mounts, cutless bearings, flex couplings and hours of engine alignment do not overcome the issue. A brand new stern gland does appear to offer better support for a while. I was told not to worry about it as it is almost inevitable with the above setup and does no harm (except to your pride when approaching a mooring within earshot of others)
At tickover try applying a little pressure to the prop shaft with your hand .... close to the stern tube: Up, down, left, right. If it's engine alignment it may well stop when you push in one of the directions.
If all else fails speed the slow run up /forums/images/graemlins/wink.gif
webcraft
Well-Known Member
[ QUOTE ]
Don't blame poor workmanship on the seal. Getting it so far out of line is incompetenc
[/ QUOTE ] erm . . . I think that was what I was hinting at when I said an alleged marine engineer . The seal is a great piece of kit.
[ QUOTE ]
I do not suggest it is a bearing in the same way that a cutless is, just that it provides support to keep the shaft centred in the tube, in the same way that a stuffing box does. If the engine and shaft are aligned properly then there is no need for it to bear any radial load - it just acts as a seal.
[/ QUOTE ] No, sorry, you've lost me. It either is just a seal or it provides support - you seem to be sitting on the fence here. The function of the Volvo seal is purely to seal ( the clue is in the name). It does not in any way support the shaft or keep it central in the tube. My propshaft is rigid and supported by the stern bearing at one end and the gearbox at the other - does yours somehow sag in the middle?
No-one has commented on the use of a made to measure split cone to centre the shaft in the tube - for some reason they seem to prefer wodging it up with any old junk they find lying around. Why not take a little more time and get it right?
- W
Don't blame poor workmanship on the seal. Getting it so far out of line is incompetenc
[/ QUOTE ] erm . . . I think that was what I was hinting at when I said an alleged marine engineer . The seal is a great piece of kit.
[ QUOTE ]
I do not suggest it is a bearing in the same way that a cutless is, just that it provides support to keep the shaft centred in the tube, in the same way that a stuffing box does. If the engine and shaft are aligned properly then there is no need for it to bear any radial load - it just acts as a seal.
[/ QUOTE ] No, sorry, you've lost me. It either is just a seal or it provides support - you seem to be sitting on the fence here. The function of the Volvo seal is purely to seal ( the clue is in the name). It does not in any way support the shaft or keep it central in the tube. My propshaft is rigid and supported by the stern bearing at one end and the gearbox at the other - does yours somehow sag in the middle?
No-one has commented on the use of a made to measure split cone to centre the shaft in the tube - for some reason they seem to prefer wodging it up with any old junk they find lying around. Why not take a little more time and get it right?
- W
john_morris_uk
Well-Known Member
[ QUOTE ]
________________________________
Quote
I had to remove the Volvo seal, because it had worn into an oval and leaked like a tap.
______________________________________
Was this caused by a 2 bladed prop being out of balance ?
[/ QUOTE ]No - we had a three bladed fixed at the time and it was perfectly balanced. There were a couple of broken engine mounts that probably didn't help, and may easily have caused the problem. As you can imagine the boat was in a bit of a state when we took her over.
Reading through the various replies, I still stick with my original thought. Volvo seals are good, but to claim that they are the 'PREFERRED OPTION' is overstating their efficacy.
Choose a shaft seal that will suit the situation. Personally, we have never had a problem with our PSS seals, and I could claim that therefore the PSS is the Rolls Royce. I don't claim that, and try to have a more balanced approach. (Perhaps I have a chip on both shoulders to make me completely balanced?)
On our own boat, the engine mounts have been replaced and we now have an Aquadrive shaft coupler which takes all the wobble out of the arrangement, and we have a super quiet boat when under power as a result.
________________________________
Quote
I had to remove the Volvo seal, because it had worn into an oval and leaked like a tap.
______________________________________
Was this caused by a 2 bladed prop being out of balance ?
[/ QUOTE ]No - we had a three bladed fixed at the time and it was perfectly balanced. There were a couple of broken engine mounts that probably didn't help, and may easily have caused the problem. As you can imagine the boat was in a bit of a state when we took her over.
Reading through the various replies, I still stick with my original thought. Volvo seals are good, but to claim that they are the 'PREFERRED OPTION' is overstating their efficacy.
Choose a shaft seal that will suit the situation. Personally, we have never had a problem with our PSS seals, and I could claim that therefore the PSS is the Rolls Royce. I don't claim that, and try to have a more balanced approach. (Perhaps I have a chip on both shoulders to make me completely balanced?)
On our own boat, the engine mounts have been replaced and we now have an Aquadrive shaft coupler which takes all the wobble out of the arrangement, and we have a super quiet boat when under power as a result.
doug748
Well-Known Member
Has anyone managed to trace the original query from the gent with the Spring 25? We could give him a PM. I really can't work this search jobbie.....
doug748
Well-Known Member
Found it. The members name was "springjupiter" and when last heard of (14th March ish) he intended to replace his PSS with the old stuffing box. Might be worth a PM to see if it helped matters
Vamoose
Well-Known Member
Thank you for taking the trouble to find that I will take a look and try and get in touch. Then report back
Thanks again
Thanks again
Tranona
Well-Known Member
Rather late response as I have been away. However, as I pointed out in an earlier post the Volvo seal has a fluted rubber bearing behind the lip seals - about 80mm long from memory on a 25mm/1inch size. This is water lubricated in the same way as a cutless and actually very similar to the old Stuart Turner rubber shaft bearings. In this sense they act like a cutless in completely surrounding the shaft over much the same length as a cutless. The difference is that the whole rubber moulding is designed to absorb some movement unlike a cutless which has a rigid outside casing fitted into a rigid tube. It is on this basis that the "seal" provides support. As it is water lubricated there is no wear on either the shaft or the bearing unless, like yours it was connected at an angle to the gearbox coupling and wore oval.
Just for information, the Tides seal and the new Radice development of the Volvo design use a similar "bearing". Just because the name of a product conveys one meaning does not mean that its design does not perform other functions. And of course it keeps it central in the tube if the conditions I stated are there - ie the outer diameter of the tube is concentric with the inner diameter. Of course the shaft can also be moved away from the centre if it is connected to a gearbox coupling that is not lined up correctly with the shaft as seems to have happened in your case with the inevitable result that the seal wore oval.
So the correct procedure is to put the seal/ (bearing) onto the shaft and locate on the tube. Then line up the gearbox coupling using the usual methods (feeler gauges and all) to be exactly square with the prop coupling and it can only be correctly in line. No need for spring balances, special half cones etc.
I have also referred to the Vetus design of sterngear. Note that their inboard fitting has both a bearing and lip seal, both positively water lubricated. Even then they would recommend an additional bearing on a 25mm shaft if the the length between bearings was more than about 1.4m. Have a look at many boats with a P bracket and measure the distance between the gearbox coupling and the P bracket. Then you will understand why, when you remove the support provided by the conventional stuffing box (or a Volvo) the shaft can move enough to hit the tube sides. Effectively you only have one support - the cutless in the P bracket. The whole length of the shaft moves in line with the engine on its mounts.
The issue about which design is more effective as a seal is a different debate, and I am less happy with the idea of a face seal as any movement of either face in relation to the other leads to the possibility of a catastrophic leak, whereas a radial seal, whether lip seal or packing will fail progressively and sends a signal through drips.
Just for information, the Tides seal and the new Radice development of the Volvo design use a similar "bearing". Just because the name of a product conveys one meaning does not mean that its design does not perform other functions. And of course it keeps it central in the tube if the conditions I stated are there - ie the outer diameter of the tube is concentric with the inner diameter. Of course the shaft can also be moved away from the centre if it is connected to a gearbox coupling that is not lined up correctly with the shaft as seems to have happened in your case with the inevitable result that the seal wore oval.
So the correct procedure is to put the seal/ (bearing) onto the shaft and locate on the tube. Then line up the gearbox coupling using the usual methods (feeler gauges and all) to be exactly square with the prop coupling and it can only be correctly in line. No need for spring balances, special half cones etc.
I have also referred to the Vetus design of sterngear. Note that their inboard fitting has both a bearing and lip seal, both positively water lubricated. Even then they would recommend an additional bearing on a 25mm shaft if the the length between bearings was more than about 1.4m. Have a look at many boats with a P bracket and measure the distance between the gearbox coupling and the P bracket. Then you will understand why, when you remove the support provided by the conventional stuffing box (or a Volvo) the shaft can move enough to hit the tube sides. Effectively you only have one support - the cutless in the P bracket. The whole length of the shaft moves in line with the engine on its mounts.
The issue about which design is more effective as a seal is a different debate, and I am less happy with the idea of a face seal as any movement of either face in relation to the other leads to the possibility of a catastrophic leak, whereas a radial seal, whether lip seal or packing will fail progressively and sends a signal through drips.
webcraft
Well-Known Member
[ QUOTE ]
So the correct procedure is to put the seal/ (bearing) onto the shaft and locate on the tube. Then line up the gearbox coupling using the usual methods (feeler gauges and all) to be exactly square with the prop coupling and it can only be correctly in line.
[/ QUOTE ] I don't understand how you say this. I hope you are not a 'marine engineer'.
What is to stop the engine and propshaft being perfectly lined up but the propshaft not being central in the stern tube? The shaft seal is NOT designed to centralise the shaft when it is only supported at the other (cutless bearing) end as it is far too flexible. As far as I can see failing to ensure the shaft is central in the stern tube before aligning the engine to it is a mugs game and can lead to exactly the sort of problems that if I remember correctly started this thread.
You did not read my response correctly. My shaft seal did not wear oval - it leaked for all of five minutes after a know-all had 'aligned' my engine using exactly the method you describe, which resulted in teh shaft being misaligned in the stern tube. I then redid the alignment myself, starting with centralising the shaft in the stern tube before lining up the gearbox coupling.
I also suggest you look up the definition of the word 'bearing' - I think you will find that it is a component that separates moving parts and takes a load. Now go and ask Volvo if they designed their shaft seal to take a load.
However, as you have told me I am speaking nonsense I will give up on this thread. In fact, I think I will give up on YBW . . . previously most of the unpleasantness was confined to the Lounge, but far too many threads both here and on Scuttlebutt now feature contributions from opinionated people who appear to be somewhat lacking in social skills and / or common sense.
- W
So the correct procedure is to put the seal/ (bearing) onto the shaft and locate on the tube. Then line up the gearbox coupling using the usual methods (feeler gauges and all) to be exactly square with the prop coupling and it can only be correctly in line.
[/ QUOTE ] I don't understand how you say this. I hope you are not a 'marine engineer'.
What is to stop the engine and propshaft being perfectly lined up but the propshaft not being central in the stern tube? The shaft seal is NOT designed to centralise the shaft when it is only supported at the other (cutless bearing) end as it is far too flexible. As far as I can see failing to ensure the shaft is central in the stern tube before aligning the engine to it is a mugs game and can lead to exactly the sort of problems that if I remember correctly started this thread.
You did not read my response correctly. My shaft seal did not wear oval - it leaked for all of five minutes after a know-all had 'aligned' my engine using exactly the method you describe, which resulted in teh shaft being misaligned in the stern tube. I then redid the alignment myself, starting with centralising the shaft in the stern tube before lining up the gearbox coupling.
I also suggest you look up the definition of the word 'bearing' - I think you will find that it is a component that separates moving parts and takes a load. Now go and ask Volvo if they designed their shaft seal to take a load.
However, as you have told me I am speaking nonsense I will give up on this thread. In fact, I think I will give up on YBW . . . previously most of the unpleasantness was confined to the Lounge, but far too many threads both here and on Scuttlebutt now feature contributions from opinionated people who appear to be somewhat lacking in social skills and / or common sense.
- W