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Oi, long time no post!

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Oi, long time no post!

Unread postAuthor: jaythedogg » Sun Sep 20, 2009 8:10 pm

Well guys, I am back (like any of you know me anyway) after a long computer break.... Now I am in College for Manual Machining & Renewable Energy Technologies.

Forget the second half for website purposes (unless you can help me design a solar powered, wind dynamo charged spud gun lol) & let's focus on the machining half.

Being too broke to buy the proper size machining, I was sitting in "Math for machining" Thursday & asked my teacher (also the machining instructor) if I could come in on my own time & make chambers for coaxial air cannons, or combustion guns...

He said "No, but the shop is open from 7:30am to 4pm Monday through Friday if you wanted to make a few hydraulic cylinders & valves for personal use."

Yea, badass, covers his but while telling me to rock on. :)

So because we haven't & won't cover pressure systems, what would be a good thickness of chamber wall for a LARGE combustion cannon?

I can make a chamber up to 5" outer diameter, & thread the ends for easier disconnect. So if I was using metered propane as a fuel, what would my wall thickness be safe at?

I am debating between steel & aluminum for a chamber, steel would be safest, but HEAVY, I could probably get away with a 1/2" steel wall for the chamber, but aluminum, what, about an inch to be safe?

If I can get this figured out, I will share the rest of the plan, I think you guys might like this one.

Thanks.
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Unread postAuthor: theBOOM » Sun Sep 20, 2009 8:30 pm

For a regular combustion you wont need a 1 inch wall for sure! If pressure rated sch 40 pvc has been used im sure you could use less than 1/4 steel OR aluminum and still be WAAAAYYY over the safety limit :P

If you are going to build this I would say go for a handheld hybrid maybe 5x to be on the safe side? ... I'd look into moonbogg's cannons as he has worked with aluminum combustion guns alot and he know's what he is doing.. his cannons include the cobra venom and the cobra stinger ( I think that's what they are called)
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Unread postAuthor: Technician1002 » Sun Sep 20, 2009 9:32 pm

I'm not sure of the wall thickness, but a regular propane tank will handle 1X combustion just fine and should handle a 5 X with no problems. They have a 240 PSI working pressure and a minimum burst pressure of 4X that for DOT certification. They are not very thick or heavy in smaller sizes.

Forget the second half for website purposes (unless you can help me design a solar powered, wind dynamo charged spud gun lol) & let's focus on the machining half.


How patient are you? I probably could assist you on that one. Friday night I had a 100% solar power cooked dinner. The beverage was solar cooled with ice provided by solar power. Using the power source to power a tater tosser won't take much modification.
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Last edited by Technician1002 on Mon Sep 21, 2009 1:44 am, edited 1 time in total.
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Unread postAuthor: Moonbogg » Sun Sep 20, 2009 11:26 pm

Don't fool yourself into thinking that any certain wall thickness is safe. Radial surfaces hold tons more pressure than flat ones, so any flat surfaces must be taken into careful account with your build. Make a sketch of your design idea and show us if you would like more specific feedback.
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Re: Oi, long time no post!

Unread postAuthor: jackssmirkingrevenge » Mon Sep 21, 2009 1:12 am

jaythedogg wrote:Now I am in College for Manual Machining & Renewable Energy Technologies.


Pah!

That could be translated as the School of Virile Manliness & Hairdressing.

Bloody liberal wishy-washy socialist nword-loving red left-wing homosexual commie greens infecting the education system *sigh*

But yes, good on you :)
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Unread postAuthor: Gippeto » Mon Sep 21, 2009 1:28 am

Jay, machining a 5" chamber from even thick walled tube would be a total waste of time and material. For a basic 1x combustion, all you would need is exhaust pipe. Max chamber pressure will be ~100psi.

5" steel pipe with a .035" wall and low grade (35000psi tensile) will have a burst pressure of ~500psi.

But then, I've never seen exhaust pipe that thin. :wink:

Large bore, piston valves on the other hand...would not be a waste of time and material. :twisted:

Just my .02 :)
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Unread postAuthor: Technician1002 » Mon Sep 21, 2009 1:46 am

Gippeto wrote:Large bore, piston valves on the other hand...would not be a waste of time and material. :twisted:

Just my .02 :)


High pressure 5 inch piston valve.. I like the way you think. :twisted:
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