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Aluminum Joints

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: D_Hall » Mon Nov 16, 2009 11:57 pm

SpudBlaster15 wrote:but it's easy enough to regain the strength by having the entire structure post-weld annealed and then artificially age hardened.

In my world, the words "easy enough" generally imply something that can be done at home. Heat treatment of aluminum? I can have it done at the office, but beyond that I wouldn't have the first clue where to go around here to have that done. Certainly not my garage. In other words, I don't think the words "easy enough" apply here.
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Unread postAuthor: D_Hall » Tue Nov 17, 2009 12:04 am

kjjohn wrote:It says that once it is molded and hardens it is fully machinable and has a tensile strength of 4000psi. Would it be possibly to make a mold and create a whole cannon out of this, or would it not be able to withstand high pressures? I don't exactly know enough about material strength to know if that 4000psi of tensile strength will convert to 4000psi of pressure in a chamber.


No, 4000 psi tensile strength will NOT yield 4000 psi pressure in a chamber. Well, it could, but as with all things it depends. But let me put it this way... 6061 T6 aluminum has a tensile strength on the order of 40,000 psi. In other words, your epoxy has 1/10th the strength of a pretty standard aluminum product.
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Unread postAuthor: spudtyrrant » Tue Nov 17, 2009 12:33 am

brazing may work, IDK if it would be hot enough to "de-temper" the aluminum tho
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Unread postAuthor: kjjohn » Tue Nov 17, 2009 7:32 pm

Another question, i aluminum bought from websites like onlinemetals heat treated or anodized? If not, will it cause a substantial loss in strength, and will it rust? I will also be using pure oxygen in the chamber, so I am assuming that this will contribute to the oxidation. I know how to anodize aluminum myself, but it requires large amounts of H2S04, and that gets very expensive. Anodizing also thickens the walls, so the piston may not fit afterward.
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Unread postAuthor: Moonbogg » Tue Nov 17, 2009 11:00 pm

kjjohn wrote:Another question, i aluminum bought from websites like onlinemetals heat treated or anodized? If not, will it cause a substantial loss in strength, and will it rust? I will also be using pure oxygen in the chamber, so I am assuming that this will contribute to the oxidation. I know how to anodize aluminum myself, but it requires large amounts of H2S04, and that gets very expensive. Anodizing also thickens the walls, so the piston may not fit afterward.


If they sell anodized aluminum its likely only small tubing. I have not seen it there myself. They sell several different types of aluminum at onlinemetals and similar stores. The most common type and cheapest is 6061-T6. The "T6" part refers to the heat treating of the aluminum. So yes, it is heat treated. 6061-T6 is what I use for my cannons and it is what spudtech used for their SP9004 cannon. There are stronger types of aluminum, but they get expensive and are not really worth it. So as long as what you buy sais "6061-T6" you are good to go as far as the aluminum being the right material.
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