doug748
Well-Known Member
...and Norris deserve a boot wedged up their stern tube for selling a two quid item for that price.
Refitting the prop - dumb question
- Thread starter Stemar
- Start date
...and Norris deserve a boot wedged up their stern tube for selling a two quid item for that price.
Heckler
Well-Known Member
...and Norris deserve a boot wedged up their stern tube for selling a two quid item for that price.
I was looking for one a few months ago and saw that, my thoughts were along that line! I bought a Vetus one for about a fiver and thought that was too dear!
Stemar
Well-Known Member
Nope, won't be buying it from Norris. Even think Vetus are taking the piss at a fiver, but maybe I'm forgetting the It's Marine Quality, Sir surcharge
boatmike
Well-Known Member
You appear to have a problem if the prop came off the taper easily and is only being stopped from rotating by the key. Take the key out and lap the prop to the taper using fine valve grinding paste. Then clean it thoroughly with white spirit and try it on the shaft again. It should "wring" up tight by hand on the taper. Then replace the key making sure it is not holding the prop off the taper. If the split pin hole does not line up and its through drilled rather than castellated then the easiest solution is to get a thicker washer and reduce its thickness until tight. Conversely reduce the nut as others have suggested. A belt sander will do a good job of this if you have the skill to use it.
davidmh
Well-Known Member
I agree with boatmike. I find the best way to get the pin through the hole is file the top of the nut down, leave the mating surface alone, that way you do not need to worry too much about squareness of the filing. Try using various thicknesses of washer and get the best combination so you only need to take the minimum off the top of the nut.
David MH
David MH
RichardS
N/A
I don't understand.
How does filing anything off the none friction side of the nut help the nut turn a little bit further?
Richard
penberth3
Well-Known Member
I don't understand.
How does filing anything off the none friction side of the nut help the nut turn a little bit further?
Richard
Also confused me. I can only guess he thinks the split pin is going behind a plain nut, rather than through the slot in a castellated nut.
RichardS
N/A
I don't think it's even a castellated nut as that could be tightened at bit more. I think it's just a nut with a hole drilled across it.
Richard
PetiteFleur
Well-Known Member
Yes - I can remember doing that as an exercise when I started my apprenticeship - what a useless exercise, filing a 4" long hexagon bar into a rectangle...
Stemar
Well-Known Member
I recall a friend grumbling about an exercise like that as an apprentice at Rolls Royce. I don't know if he ever used that skill, but it didn't seem to do him any harm, as he was seconded to Lockheed in the USA for a joint project and ended up working for them for the last half of his career.
As for filing the back of the nut, I think those suggesting it are thinking of an arrangement like this
Mine is a nut about 35mm long, drilled through each flat about 10mm from one end. I couldn't find a pic.
The prop isn't binding on the key, it's firmly on the taper, so I don't think there's any problem there, it's just that the hole in the shaft lines up roughly with a corner of the nut when everything is tight. From the comments, I can see three possibilities, listed in order of preference: a thinner SS washer, with or without the existing one, a plastic washer that will squish up to align the holes, between the existing washer and the prop, or some delicate work with a belt sander on the nut.
Drilling the shaft isn't a serious option as getting it out is an engine out job, and trying to drill it in place, lying on my back under the boat feels like a recipe for a drill bit broken off inside the hole and jamming everything.
Thanks all!
As for filing the back of the nut, I think those suggesting it are thinking of an arrangement like this
Mine is a nut about 35mm long, drilled through each flat about 10mm from one end. I couldn't find a pic.
The prop isn't binding on the key, it's firmly on the taper, so I don't think there's any problem there, it's just that the hole in the shaft lines up roughly with a corner of the nut when everything is tight. From the comments, I can see three possibilities, listed in order of preference: a thinner SS washer, with or without the existing one, a plastic washer that will squish up to align the holes, between the existing washer and the prop, or some delicate work with a belt sander on the nut.
Drilling the shaft isn't a serious option as getting it out is an engine out job, and trying to drill it in place, lying on my back under the boat feels like a recipe for a drill bit broken off inside the hole and jamming everything.
Thanks all!
lw395
Well-Known Member
Thin wave washers make good shims.
If the nut is reversible, you could drill the other end to give alternative hole options?
If you can work out what shim you need, one of the many spring or lock washer flavours might do it?
The traditional method of course is to try drilling a new hole through the shaft, break the drill and tell yourself 'that won't move!'.
If the nut is reversible, you could drill the other end to give alternative hole options?
If you can work out what shim you need, one of the many spring or lock washer flavours might do it?
The traditional method of course is to try drilling a new hole through the shaft, break the drill and tell yourself 'that won't move!'.
rogerthebodger
Well-Known Member
To find out the thickness of a washer you can measure the thread pitch and measure the angle between the nut hole and the shaft hole when he nut i tight.
Then packing washer thickness = thread pitch * hole angles difference / 360.
Then you can search for a washer that thickness.
Then packing washer thickness = thread pitch * hole angles difference / 360.
Then you can search for a washer that thickness.
KREW2
Well-Known Member
OP hasn't yet confirmed that it is not being prevented from tightening on the taper by the key.
Put the prop on the shaft with the key in place. Shine a torch from the back of the prop, and see if you can see light between the key and the prop.
If not the key needs filing down
Put the prop on the shaft with the key in place. Shine a torch from the back of the prop, and see if you can see light between the key and the prop.
If not the key needs filing down
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I reckon he's just a pussy and needs to tighten it properly.
RichardS
N/A
Stemar
Well-Known Member
I'll plead guilty to pussy - I don't have a lot of strength since sepsis and open heart surgery a couple of years ago, but I've got the nut as tight as I can get it using a 10" wrench and it needs to go another 1/12 of a turn, something over 0.1mm of thread pitch.
I've either got to expand the bronze prop on the taper, compress the SS taper or stretch a roughly 15mm diameter SS rod by maybe 1% over the length available to stretch; in practice, I'd expect a bit of all three. I'm no engineer, so the calculations are beyond me - what sort of torque are we looking at to do that?
RichardS
N/A
If you have a torque wrench I would certainly try it and see what torque you are up to at the moment. I wouldn't go beyond 100 Nm but an M15 SS thread and nut would be fine even beyond that. However, I would use a shim/washer if I had to go beyond 100 Nm but that's just my personal preference.
Richard
Heckler
Well-Known Member
Even more Gosh! when you realise that at the time the poster of this advice was advocating it when in reality the prop could have been riding on the key!
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Poignard
Well-Known Member
I like your new avatar but I never realised Boris was quite so tall.
Wikepedia must be wrong because it has him as only 5'9".
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rogerthebodger
Well-Known Member
If you put some grease on the thread and nut /prop face you will be able to tighten the nut a little more without extra torque.
Just remember some of the tightening torque will be taken up by the friction in the thread and nut/prop faces.