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Aluminium, is it safe?

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Aluminium, is it safe?

Unread postAuthor: MaxuS the 2nd » Sun May 25, 2008 6:05 am

Hey guys,

I just need an opinion on whether Aluminium would be ok for a Hybrid chamber. The walls of the chamber will be atleast 3mm thick. It's seamless and considering I'm making it myself from a length of 1.25" thick Aluminium Bar, it won't have any stress points.
Will I die a bloody death if I were to use this?
I was planning on using up to an 8x mix.
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Re: Aluminium, is it safe?

Unread postAuthor: Necrosis » Sun May 25, 2008 7:00 am

MaxuS the 2nd wrote:Will I die a bloody death if I were to use this?


I see what you did there. :P

And yes, if it's a normal 1060 alloy, you most likely will die a bloody death on an 8x mix.

Atleast, if you are using a 3mm thick wall..
I let my program calculate the factor of safety for 1kilo psi, and it was 0.5.. wich means certain death. And I think 8x would produce 1 kilo psi, right?

(I think I've read it somewhere but i can not confirm this)
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Unread postAuthor: MaxuS the 2nd » Sun May 25, 2008 7:17 am

It's a 6082 Alloy, but God knows what that means.

:lol: I thought I'd incorporate the Necrosis joke into it.
8x should produce around 1kpsi.
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Unread postAuthor: Necrosis » Sun May 25, 2008 7:22 am

MaxuS the 2nd wrote:It's a 6082 Alloy, but God knows what that means.

:lol: I thought I'd incorporate the Necrosis joke into it.
8x should produce around 1kpsi.


In the case of 6082 you may or may not die. it has a factor of safety that is 1.

With a wall thickness of 5 mm the Factor of safety is about 2.

Wich still might fail if any ddt occurs.
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Unread postAuthor: MaxuS the 2nd » Sun May 25, 2008 8:10 am

Hmm, I think that I will probably give it 6mm walls just to be safe and use it up to 7x or perhaps 6x. it is unlikely that DDT will occur because the chamber is only 5cm long.
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Unread postAuthor: SpudFarm » Sun May 25, 2008 10:00 am

i am going to put it like Larda said it to me.

think of a soda bottle. 100 psi no problem then you think of this: do you think your chamber is ten times as strong as a bottle? :D
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Unread postAuthor: MaxuS the 2nd » Sun May 25, 2008 10:06 am

I like it. The answer is yes, yes indeed.
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Unread postAuthor: SpudFarm » Sun May 25, 2008 10:12 am

there you go
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Unread postAuthor: Larda » Sun May 25, 2008 12:18 pm

I downloaded this data-sheet for 6082: Link
I don't know which tempers but if its a bar-stock its normally T4,T5 or T6.
Lets say its T4 because it have the lowest Tensile Strength, 205 MPa.

S = Tensile Strength:205MPa=29700Psi
OD = Pipe OD= 1,25"
T = Wall thickness=0,118"

Burst pressure= (2*S*T)/(OD-2*T)

(2*29700*0,118)/(1,25-2*0,118)
=
6912~6900PSI

So if my calculations are right the burst pressure would be 6900Psi and gives you a safety factor of almost 7.
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Unread postAuthor: MaxuS the 2nd » Sun May 25, 2008 12:28 pm

Wow, so it would be perfectly safe at a 8x aslong as the other components held.
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Unread postAuthor: D_Hall » Sun May 25, 2008 12:46 pm

Another nice feature of aluminum....

....When it ruptures it tends to not fragment. You'll see a split, obviously, but the chamber will most likely be in one place. Kinda like ABS just splits.
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Unread postAuthor: DYI » Sun May 25, 2008 1:56 pm

What formula does your program use, Necrosis? Because that number's a hell of a long way off.

So yeah, the 3mm walled chamber made of T4 6082 should have a reasonably good safety factor up to 10 or 12x.
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Unread postAuthor: MaxuS the 2nd » Sun May 25, 2008 2:33 pm

Wow, much better than I thought it would be.
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Unread postAuthor: Necrosis » Sun May 25, 2008 3:00 pm

DYI wrote:What formula does your program use, Necrosis? Because that number's a hell of a long way off.

So yeah, the 3mm walled chamber made of T4 6082 should have a reasonably good safety factor up to 10 or 12x.


Cosmosworks. Hmm. I think it uses a different scale... i looked at the stress log and it didnt bulge out or anything.. i think it's the factor when elastic deformation occurs actually. I must edit this setting some day.
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Aluminum alloys

Unread postAuthor: kenbo0422 » Thu Oct 16, 2008 8:50 pm

You may not believe this but I have about a half ton of T6 6061 aluminum that I got from scrapped machines at work. Most is about 3/4 to 1 1/2 inches thick. My question, is 6061 good for a chamber? Say up to 4x mix, what would the wall thickness be recommended to be?
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