Thread: Propellor pattern

This is just an explanation of how a prop pattern is made before casting and machining. Most people who see it find it interesting.

http://industrialshapeandform.com/blog/blogs/index.php/how-a-marine-propeller-pattern-is-made

I apologize if it's not related enough to machining, but if you've ever machined the hub and key-way of a prop, then maybe this will give you some insight to what comes before your step.

The link seems to be broke . Can you repost it ?

Go to

http://industrialshapeandform.com/blog/blogs/index.php

Do a search for propeller. Then It should come up.

WOW , that is awesome , Really labor intensive . I allways wondered how they did that .
Thank You!

Why are "screws" as used in water not given "air foil" shapes!

It works for air!

Inquiring minds....
CalG

Well they are foiled, except they call them hydro-foil.

We also make struts which hold the prop in place, basically a barrel, that the shaft goes through, with one or two "legs" that attach to the hull with a mounting plate called a "foot"....I think I made that sound more complicated than it is

The legs of the strut definitely have a hydrofoil shape looking at the cross section.

Hopefully this link works now....

http://industrialshapeandform.com/bl...ller&submit=Go

Great read, thanks for sharing that.

It's not information that's easy to find. It's even hard to find print manuals for doing it anymore.

Ok, not to be too dense, but how exactly is the one blade mold used to make a 5-bladed or 3-bladed prop? I can dream up some unlikely scenarios but what I can imagine does not seem to make sense. It has to be trick ot get them all registered correctly and bedded into a foundary mold. Pray tell how it is done.

Denis, who seems to have bronze where his brains should be....

There is a hole in the top of the pattern.

They use that to line the prop up on an index plate.

The index plate has designations in degrees, different angles make 3,5, or any number of blades on a prop. 120 degrees makes 3 blades for example.

They use a starting position, mold one blade, on its drag face, move it according to the index plate and repeat until you are back to where you started in a circle.

The same starting position is used on the cope face and the whole thing is repeated using the index plate.

The two halves are closed together, metal is poured in and you have a prop.

Well then the machinists get a hold of it...then its a prop

Keep in mind this is the method we usually make patterns for, there are other methods...

Thanks,
The indexing of the mold is easy enough to see--now that you have explained it. But isn't there a somewhat complex surface on the drag that has to match the cope at the leading and trailing edge of each blade? What I am saying is that surface has to vary in height as you sweep through 120 degrees for a 3-blade prop. So how do you get the two surfaces that need to fit tightly together to actually do so? Is the "seam" of the casting at the leading and trailing edge fo the blades? I guess another photo or two of say a rough casting and or a drag might clearly answer the question I am *trying* to be clear about.
Denis--only 50 miles south of you in Bellingham.

That is awesome!

Do you have any picts of the foundry process? I'd love to see them!