wee_niall
Member
wow, that does sound cheap! not sure when i'll next be through in weegie land though (last time i was there was last april going through the Forth & Clyde!) but i'll bear that in mind.
worn propeller shaft at cutless bearing
- Thread starter wee_niall
- Start date
david_bagshaw
Well-known member
Dont get it turned down and sprayed, as it does fail. we had it in the 70s.
Lastly does the coupling have the same taper, so you can turn the shaft?
If not have new shaft made with equal tapers each end along with a new coupling, then you will get a double life from each shaft, in the future
Last thought is there room to have another coupling fitted between the existing one and stern tube, then you can get the intermediate bit made in steel, and the length to do the double taper on the existing shaft, along with it being shorter for replacement in the future.
Lastly does the coupling have the same taper, so you can turn the shaft?
If not have new shaft made with equal tapers each end along with a new coupling, then you will get a double life from each shaft, in the future
Last thought is there room to have another coupling fitted between the existing one and stern tube, then you can get the intermediate bit made in steel, and the length to do the double taper on the existing shaft, along with it being shorter for replacement in the future.
wully1
Well-known member
Mine w as made in Buckie or Banff by a fishing boat engineering company whos name I can't remember, cost about £80.
Jcorstorphine
Well-known member
Not a bad idea but I’m quite keen to keep things fairly standard and not get into having to get custom things made up. There’s also the problem that the worn bit hasn’t worn even so would need more than polishing and the rest of shaft aft of the bearing would need reduced. I’ve asked the engineers for a quote to reduce the diameter of the last foot so hopefully it will be nice and cheap
Know what you mean by keeping it standard BUT! If you buy a standard 7/8" bearing its OD will be 1 3/8" but the 1" bearing fitted at present will be 1 1/2" so you will need to get a nonstandard made up, hence suggesting a composite bearing rather than a rubber one.
These are the dimensions from Norris, other may differ.
wee_niall
Member
Shaft isn't tapered at the gearbox end - just plain with a key. Not planning on metal spraying now (too expensive), just reducing diameter to 7/8"
I think i've probably had a quote from the place in Buckie (http://www.falpropellers.co.uk/) - they were a wee bit cheaper but still 200+
I thought that as well initially when i looked at the Norris website but other suppliers have 7/8 shaft bearings with an OD of 1 1/2 so it still looks like a good option to me
Old Troll
New member
prop shaft
Actually I was seeking a good quality prop shaft and not bothered about the cost. I got a certificate of quality with the shaft. Another point of interest was that the company can supply very tough shafts which I was reluctant to buy in case my machine shop man could not work the material. Small diametres shafts can be got that retain the strength of the heavier diametres.
Actually I was seeking a good quality prop shaft and not bothered about the cost. I got a certificate of quality with the shaft. Another point of interest was that the company can supply very tough shafts which I was reluctant to buy in case my machine shop man could not work the material. Small diametres shafts can be got that retain the strength of the heavier diametres.
HunterWanderer
Member
Not a bad idea but I’m quite keen to keep things fairly standard and not get into having to get custom things made up. There’s also the problem that the worn bit hasn’t worn even so would need more than polishing and the rest of shaft aft of the bearing would need reduced. I’ve asked the engineers for a quote to reduce the diameter of the last foot so hopefully it will be nice and cheap
I can only think the prop and shaft assembly is out of balance to cause uneven wear like this. Is the shaft straight? If not the machine shop should be able to straighten it for you. Even new shafts are often not straight especially after machining.
wee_niall
Member
It's uneven lengthways rather than being oval or anything like that (if that makes sense?) - i think it's just the way the cutless bearing has worn meaning that the wear is slightly more at the very aft end of the bearing.
Tranona
Well-known member
Suspect misalignment might also have caused the uneven wear. Make sure it is all aligned correctly when you get it back together.
wee_niall
Member
my cunning plan has hit a snag - it looks like the cutless bearing is actually a stuart all rubber type so getting an undersized replacement is going to be even more difficult that i thought! Along with spilling a 750ml can of danboline in the engine compartment it's not been a good day
Jcorstorphine
Well-known member
Stuart Bearing
I replaced the Stuart Bearing in my boat last winter. In my case it was a straight swop for a T Norris aftermarket bearing as my shaft was OK. As you say, the original Stuart bearing is an all rubber type with no brass or phenolic shell.
I have just checked my notes and the Norris website and the replacement for the 1" is 1 7/8" od or 47.6 mm in new money.
The actual bearing Norris supply has a normal rubber insert but the phenolic shell is about three time the normal wall thickness making up for the very thick walled Stuart rubber bearing.
So the problem is that you have a bronze stern housing with a 1 7/8" bore but the nearest 7/8" cutless bearing is either
1 3/8" or 1 1/2" OD so you need to make up a difference of 3/16" or 1/4" on the radius (I think)
1st alternative:- remove the Bronze Stern housing and get a machine shop to fit a bronze sleeve which will need to be shrunk in. Then you can use a standard off the shelf cutless bearing.
2nd Alternative:- Get the machine shop to produce a sleeve which they shrink onto your new 7/8" cutless bearing which you then fit as normal.
3rd alternative:- This is the cheapest option but is fraught with potential problems but is based on a repair (non boaty) I have done in the past to increase the diameter of very high power electrical feedthroughs. You take your undersized cutless bearing (relative to the bronze housing) and very carefully wind on a number of layers of fibreglass woven roven wetted out with resin and make up the diameter in excess of the required diameter. You then need to machine down the new OD to the ID of the bronze housing. You will need access to a lathe and will require to machine a steel mandrill to be a tight fit in the cutless bearing such that it can be mounted on centres in a lathe. You just might get away with a piece of doweling but a bit iffy.
4th Alternative:- As mentioned in previous post talked to Neil Y of this forum and get him to machine you a solid composite shell bearing.
5th Alternative:- Buy a new shaft and a new Stuart aftermarket bearing. (sorry but that could be the cheapest option in the long run )
my cunning plan has hit a snag - it looks like the cutless bearing is actually a stuart all rubber type so getting an undersized replacement is going to be even more difficult that i thought! Along with spilling a 750ml can of danboline in the engine compartment it's not been a good day
I replaced the Stuart Bearing in my boat last winter. In my case it was a straight swop for a T Norris aftermarket bearing as my shaft was OK. As you say, the original Stuart bearing is an all rubber type with no brass or phenolic shell.
I have just checked my notes and the Norris website and the replacement for the 1" is 1 7/8" od or 47.6 mm in new money.
The actual bearing Norris supply has a normal rubber insert but the phenolic shell is about three time the normal wall thickness making up for the very thick walled Stuart rubber bearing.
So the problem is that you have a bronze stern housing with a 1 7/8" bore but the nearest 7/8" cutless bearing is either
1 3/8" or 1 1/2" OD so you need to make up a difference of 3/16" or 1/4" on the radius (I think)
1st alternative:- remove the Bronze Stern housing and get a machine shop to fit a bronze sleeve which will need to be shrunk in. Then you can use a standard off the shelf cutless bearing.
2nd Alternative:- Get the machine shop to produce a sleeve which they shrink onto your new 7/8" cutless bearing which you then fit as normal.
3rd alternative:- This is the cheapest option but is fraught with potential problems but is based on a repair (non boaty) I have done in the past to increase the diameter of very high power electrical feedthroughs. You take your undersized cutless bearing (relative to the bronze housing) and very carefully wind on a number of layers of fibreglass woven roven wetted out with resin and make up the diameter in excess of the required diameter. You then need to machine down the new OD to the ID of the bronze housing. You will need access to a lathe and will require to machine a steel mandrill to be a tight fit in the cutless bearing such that it can be mounted on centres in a lathe. You just might get away with a piece of doweling but a bit iffy.
4th Alternative:- As mentioned in previous post talked to Neil Y of this forum and get him to machine you a solid composite shell bearing.
5th Alternative:- Buy a new shaft and a new Stuart aftermarket bearing. (sorry but that could be the cheapest option in the long run
)wee_niall
Member
it does look like the 5th option might be the best - although the other (still expensive) option is to replace the bearing housing but that seems like even more work! I'm going to scout out Neil_Y to see how much a custom composite bearing would be (just need to get the dimensions).
Out of interest, how are the stuart bearings held in the housing? Are they just squashed in? The old one is impressively smooth and looks to be as old as the boat
Out of interest, how are the stuart bearings held in the housing? Are they just squashed in? The old one is impressively smooth and looks to be as old as the boat
Jcorstorphine
Well-known member
it does look like the 5th option might be the best - although the other (still expensive) option is to replace the bearing housing but that seems like even more work! I'm going to scout out Neil_Y to see how much a custom composite bearing would be (just need to get the dimensions).
Out of interest, how are the stuart bearings held in the housing? Are they just squashed in? The old one is impressively smooth and looks to be as old as the boat
When I removed the old Stuart bearing insert, there was no sign of any adhesive or fixing screw so I suspect that it was shrunk / frozen in Liquid Nitrogen and pressed in.
However when I fitted the Norris aftermarket bearing insert, I glued it in with epoxy and a small screw into the thick phenolic shell through the bronze bush. You will find that you need to sand down the shell slightly as I have fitted two and they were both a bit oversized.
Tranona
Well-known member
I had my Stuart housing sleeved to take a standard cutless. Press fit with a grubscrew for security. You need to shorten the cutless to 3 5/8" from the standard 4". I also had the inboard housing machined to take the white metal out and replace with a length of cutless, and the outer diameter reduced to take a Volvo seal. Much better arrangement as it gets rid of the need for grease in the stern tube.
wee_niall
Member
well Neil_Y has come up trumps and can supply a suitable bearing for sensible money and the machine shop are going to hopefully reduce the shaft on monday once i get it to them. Just need to double check the sizes of the bearing housing and i'm good to go.
Did you just cut through the old rubber bearing and pull it out? I tried (briefly) to remove the housing as i figured it would be easier to replace it off the boat but i think i'll maybe leave well alone.....knowing my luck at the moment i'd end up shearing the stern tube!
I'll need to take some before and after pics as well just for posterity
Did you just cut through the old rubber bearing and pull it out? I tried (briefly) to remove the housing as i figured it would be easier to replace it off the boat but i think i'll maybe leave well alone.....knowing my luck at the moment i'd end up shearing the stern tube!
I'll need to take some before and after pics as well just for posterity
Tranona
Well-known member
Unscrew it. Might need a bit of effort to shift it with Stilsons, but once you break the seal of crud it will unscrew easily. You can then press the old bearing out from the front end. If you mess up the locking screws you can get replacements from www.seaware.co.uk they are bronze woodscrews, 20*3. Countersunk on mine but some I have seen are coachscrews.
wee_niall
Member
Thanks Tranona - i'll have another bash at unscrewing it, hopefully nothing goes "ping"!
Your other modifications to the stern gland sound really good and have got me wondering about that part of the setup.....might have to leave it as it is this year as my fit out budget is stretched to breaking point already
Your other modifications to the stern gland sound really good and have got me wondering about that part of the setup.....might have to leave it as it is this year as my fit out budget is stretched to breaking point already
wee_niall
Member
finally managed to get back down to the boat and get the housing off - stilsons are amazing
My only concern now is that is does seem to be a bit corroded - i'm kinda assuming though that a wee bit of pitting/chipping is ok?
My only concern now is that is does seem to be a bit corroded - i'm kinda assuming though that a wee bit of pitting/chipping is ok?
wee_niall
Member
here's some pretty pictures of the worn shaft and the bearing housing
vyv_cox
Well-known member
Yes, that's worn. Based on your other thread showing the inner end it would appear that you have a grease packed stern tube with a bearing at each end. Seems to have been under-greased. I think you may have to bite the bullet and order a new shaft, as replacing everything needed to change it to 7/8" may well prove more expensive.