Propellor welding

[Drains]

Okeydoke, I've asked about this problem in "another place", but no harm in tapping the great minds here...

Large (1m dia) nickel/ally/bronze boat prop, with crack right the way through one side of the boss.

Can it be repaired, and if so, how?

 

[snowcat]

Maybe posible to tig but depends on how pure the original casting was, Id tend to say its scrap, but without seeing it I dont know, the re machineing could be a problem thats a hell of a lump to swing...I dont think vertical borers machine tapers do they? Ehh not much help really Il see what "the other site" had to say.

 

[Reprobate]

I'd bin it. Far too risky. Apart from potential balance and cavitation problems, failure of the prop could cause a nasty leak should it fly off through your hull.

 

[rusty69bus]

no chance of...boring out the center to take an inset and weld both the outer faces (like a top hat shape pushed though)?

 

[shenion]

Aluminum alloy?

I would be tempted to use one of the new Al brazing rods.

The rods I have came with a video. Had small prop (12") that was missing 3" off one blade. They laid a bead on the edge and worked out. Then ground smooth. Could not even see the "weld" after it was balanced and polished.

The rods take practice, but filling cracks is easy. I'm tempted to try using it with TIG as oxide contamination would be less of an issue.

 

[Drains]

Aluminum alloy?

No, Nickel Aluminium Bronze.... so less than 10% Aluminium., no idea how much nickel, lots of copper and tin.

Nevertheless, the more interesting repair techniques for props, the better.

 

[snowcat]

Me mate wants a pic captain, He's done some tug boat props, Soo wants to see how far gone the beasty is.

 

[Cappy]

Watch Humphrey Bogart in 'The African Queen', I think he fire-welded a blade back on

Re:tug props, both of tugs I was on had cast iron props. As the jobs they did quite often resulted in damage to the propellor blades through wire or bottom contact so a cast prop was thought to be a lot 'cheaper' to replace that a very expensive bronze one.

 

[DIY Welding]

Prop

Can be welded without much problem
You can stick weld it utp 34n is the ideal electrode, pre heat to 200c and slow cool @50 c per hour, you could also tig weld it with the a320 tig filler, used to supply a firm in hull that did this work all the time

 

[shenion]

No, Nickel Aluminium Bronze.... so less than 10% Aluminium., no idea how much nickel, lots of copper and tin.

Nevertheless, the more interesting repair techniques for props, the better.

The Al rods work for most non-ferrous alloys.

 

[Hitch]

Its a lumpy piece, so the crack is pretty deep then?

You will be able to find wire very similar to the material if you look/ask around.
Marine engineering specialist are probably a good bet, same stuff is pretty widely used in marine/offsure enviroments.
Aufhaser, or something like that is one maker.

 

[Drains]

Some great info lads, top stuff. I'll see if I can get pics over the weekend.

BTW, three prop repairers have said "scrap". But from what I can gather, the only reason is "the risk", in other words they won't put their name to a repair, which is reasonable considering this is a heavy workboat which has to operate in all weathers, and as you'll understand a prop falling off might be a bit of an issue....

However, it may make a handy spare. (the one that was spare is now on the boat).

Hitch, the crack goes right through one side of the boss. Like I say, i'll put up pics later.
For weld type - it's got to be stick or pulsed mig, I reckon.

 

[Reprobate]

Your prop will probably be made of this-
Naval Brass: A brass made with 60% copper 40% zinc with 1% tin added for extra corrosion resistance.
Still wouldn't bother though for anything other than a learning project.

 

[Drains]

Your prop will probably be made of this-
Naval Brass: A brass made with 60% copper 40% zinc with 1% tin added for extra corrosion resistance.
Still wouldn't bother though for anything other than a learning project.

It isn't naval brass.
It's nickel aluminium bronze, as stated above.
A learning project? Its a 6000 pound propellor!!!!

 

[irondarren]

instant metal? super glue 3? Mig brazing? wonder about mig brazing but its a bit to expensive and important to have a gamble with

 

[Welderpaul]

Sorry mate - i'd say scrap. Imagine that little blighter coming out of the water at you.

 

[Drains]

Sorry mate - i'd say scrap. Imagine that little blighter coming out of the water at you.

That's not the issue. It's losing the prop in the middle of a storm, just near some nasty reef, that's the problem.

But lets face it, this was a perfectly good prop, that cracked on the boss, and nobody knew for years.

So in the great scheme of risk assessments, how much greater is the risk for a prop that's been repaired to a good WPS?

TBH, until somebody gives me a good reason to give up on this, I won't. Mind you, it's not my prop, so the owner of the boat may well forget about it. Me, I also have more important fish to fry, but I do like a challenge!

 

[Welderpaul]

oooo 6K for a new one. oouch

 

[Drains]

oooo 6K for a new one. oouch

See?

6K is a guess. It was about £1800 in 1986.

 

[Bigjoe]

Is this the boat that was in when i was at the yard Si? the big bugger with the 8 cylinder gardener diesel?

I was thinking about the prop the other day as i saw a program about a shipyard in the us.

I cant really offer any expertise in the matter but im thinking pre-heated tig with controlled cooldown would be the most appropriate method,but i could be talking utter ****e as normal

Bigjoe