Brazing new gear teeth on a sailboat propeller.

[Eddyde]

Hi All,
A friend of mine is restoring a 42' sailboat the "Anna" he bought in Portsmouth RI over a year ago. I helped him sail her to Kingston, NY last August, which was quite an adventure....
The other day, he found some of the gear teeth on the propeller blades to be worn (sailboat propellers fold flat when not in use to reduce drag), stripped and asked if I could repair them. I feel confident I can do the machining, but have some questions and problems to work out before I get started.
1. I am not 100% sure of the material. My research so far found, Nickel-Bronze-Aluminum is a common alloy used in such propellers and has a more yellow "Brassy" color, than the more common Bronzes, so that is my best guess. Is there any way to test it?
2. I have no experience brazing Bronze. Is it possible to simply build up the teeth by laying down beads of filler, or do I have to braze on individual teeth?
3. What is the best way to determine the pitch & pressure angle of the existing teeth?
4. Another approach would be to machine out all the teeth and braze in a semicircular piece of material and then machine the new teeth, Or braze on semicircular pieces of gear rack with pre-machined teeth. Another option to that approach would be to cut the sections out of an existing gear, if one could be found with the correct diameter, and braze them in place. Both those approaches eliminate me having to exactly match the existing gear-tooth geometry so I am starting to think they may be the best option but I am open to suggestions?

Has anyone here done anything like this before?

Thanks in advance for your input and advice,

Eddy

 

[mickri]

Contact Minneys in Newport Beach, CA. They have hundreds of used propellers for sale. The rational for the geared folding propellers is so one blade of the propeller does not flop down when the propeller is horizontal. This can only happen at very low speeds when there is insufficient water flow to keep the blades folded. Sailors that are anal about this mark the propeller shaft so they can orient the blades to be vertical when under sail.

 

[C-Bag]

That particular project I’d be silly enough to try if was in my lap. I’m comfortable with brazing and with my last big project of fixing the screw wheel on my antique press and using oven to prep and let the temp down slow I had success. The fact it’s a straight gear is also encouraging. But the final piece is I think I could cut the teeth with my Atlas shaper. This not to say it would be easy and there’s a lot that would show I’m in over my head, but it looks like an interesting challenge but a total time sink fer sure.

 

[Nutfarmer]

I would be concerned with the liability of the repair.

 

[woodchucker]

It doesn't look like a hard repair. I'll be watching this to see how it goes. I'm thinking just build up the area with silicone bronze.. face off the flat areas top and bottom...
Then go cut teeth..

 

[dirty tools]

TIG welding would be a better method

 

[rwm]

TIG welding would be a better method

Good idea. I am assuming you mean build up the material and re-cut the teeth? What exact filler rod would you select?

 

[Eddyde]

Contact Minneys in Newport Beach, CA. They have hundreds of used propellers for sale.

He is going to buy a new propeller. His plans are to eventually sail overseas, so wants to fix this one for a back up.

 

[woodchucker]

TIG welding would be a better method

why? what does it do that a braze won't in this case?

 

[C-Bag]

TIG welding would be a better method

I would like to hear how it would be better than OA. And what that process would look like. I have machined some OA brazing and found it to be exceptionally pocket free. But it takes good equipment like cerrowool, a good oven and lots of attention to detail. I'm just contemplating getting a tig machine and getting into that whole world and the idea of brazing with tig is very new to me.