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Iron max pressure?

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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Iron max pressure?

Unread postAuthor: b1galez » Sat Feb 10, 2007 11:31 am

I am making full metal hybrid with iron pipes. I did made some combustion ones time ago... and now i think it's time for the hybrid! :P
However, i'm asking how much pressure can carry a metal chamber 2" x 10" (3mm thickness or more where there're joints)... anybody know it?
I'll post photos as fast as i can to let you see it! ^^
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Attachments
preview.jpg
This is just a preview of my hybrid: i need other joints and i've modified some parts of the project to ensure safety... and i think i'll add a safety valve that opens at 50 bar, maybe controlled by a ball valve to close it when i wanna make an experiment with the remote ignition.
preview2.JPG
This is my project finished (i have only to replace the lighter starter with something else)
Last edited by b1galez on Mon Feb 12, 2007 4:24 pm, edited 2 times in total.

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Unread postAuthor: ammosmoke » Sat Feb 10, 2007 12:17 pm

OK, either use the spudwiki, and if its not there google it.

We are not google.
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Unread postAuthor: b1galez » Sat Feb 10, 2007 12:43 pm

ammosmoke wrote:OK, either use the spudwiki, and if its not there google it.

We are not google.

Yes, i tried and i found nothing. And on the pipes there's nothing written...
However, the spudwiki lacks about iron and any metal made guns... so...
About google, i found on wikipedia the general resistance of iron... but i don't think it's the same for pipes; however, this is a community with my common interests and i thought somebody was glad to help me... and once finished i could have shared my project with you (for example writing something about the iron made guns...)
Sorry about it.
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Unread postAuthor: Recruit » Sat Feb 10, 2007 1:23 pm

Umm what type of iron wrought, cast, tempered, the list goes on.
Without knowing pipe diameter inside and outside; pipe thickness; exact type of iron we cant tell you much.

Edit though 9if you what dig a six foot deep hole put a seal section of pipe in there connected to your compressor. About 1foot from the ground wedge boards in the side of the hole and fill the hole up to the top standing 10 feet away behind a barricade of some sort. Pump it with your compressor (having a pressasure gauge visible) till it blows.

Note you might want to where hear protection. THIS IS VERY I REPEAT VERY DAGEROUS do this at your on risk and no I am not exagerating the protective blockers
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Last edited by Recruit on Sat Feb 10, 2007 1:28 pm, edited 1 time in total.
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Unread postAuthor: Brian the brain » Sat Feb 10, 2007 1:26 pm

Iron will be fine for a hybrid.
Normal iron fittings have a working pressure of 25 bar.
The burst pressure is much much higher.
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Unread postAuthor: b1galez » Sat Feb 10, 2007 7:54 pm

Oh, thank everyone for the answers! :D
So... the pipe diameter is 2"; its thickness is 3mm... so the external is 2.12".
About the type... i really don't know, i bought it in an hardware store and it the same kind of iron used for my house's pipes... however, the blow test is beyond my possibilities cause i don't have a similar compressor (and as you said, i think it's too much dangerous!).
My question was about a general type of iron, just to have an idea... and brian said that a normal working pressure is 25 bar... so i think i can try a 4x mix for example, right? (I've read somewhere that 4x mix produces 18-20 bar... so i think it would be fine!)
About my project... i took a photo with the digital camera, but i can't find the usb cable in this disordered room... but when i'll find it, i'll be glad to send some photos! :D
About the project... all has start with one idea: making a backpackable hybrid potato gun. So barrel is detachable (obviously) and divisible in many parts, like the fuel meter part.
The chamber can be easily replaced with another one (for future upgrades!) and the barrel is modular, so i can put a silencer (to be made) on it, just screwing it at the top! ^^
About the ignition, i think i'll try with a camera flash (cause here in italy the stun gun is illegal and is really more cheap) powering a spark plug (an automotive one).
Thank everyone for the answers... and if it will works, i'll write something on the wiki as promised ;)
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Unread postAuthor: b1galez » Sun Feb 11, 2007 8:30 am

For everyone is making a full metal hybrid: 2" iron pipe with 3mm thickness working pressure is generally 50 bar, i've just found it on a datasheet.
So i could try to use a 4x-5x mixture, like prometer hx says. But i'm not sure a 5x mixture (with ddt) will cause only 50 bar... however, my cannon isn't ready yet and i have other things to make, just wanna to tell you about it.
See you!
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Unread postAuthor: Recruit » Sun Feb 11, 2007 9:37 am

Ok sorry I forgot about standard iron piping :oops: :oops: . I would love to see a metal hybrid.
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Unread postAuthor: boilingleadbath » Sun Feb 11, 2007 1:00 pm

The run-up distance for fairly complex hydrocarbons (read: larger than, say, methane) isn't all that dependent appon initial pressure (not that even H2 is that dramatic), and the semi-closed nature of a hybrid's chamber should tend to keep the flame-front velocity slower.

...that is, DDT isn't any more likely with high mixes than with low mixes.
(ok, it's a bit more likely - but really, unless you have a 10' long by 2" diameter chamber, you are safe.)
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Unread postAuthor: b1galez » Sun Feb 11, 2007 1:58 pm

Mmhh thank you boiling for reassuring me ^^
However, i've just downloaded the image from the camera... here it is ^^
I made some modification to this project, so something isn't where you see it now, i'll update it when i have new joints.
The barrel is jointed cause i can detach and screw it to fit into my backpack ^^
Hope you like it! :D
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Unread postAuthor: squeaks » Sun Feb 11, 2007 9:16 pm

wait, where's the union/cam-lock to hold the burst disk. Maybe I'm just blind and I can't see it.
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Unread postAuthor: b1galez » Mon Feb 12, 2007 6:30 am

If i can find a cheap sprinkler valve, i'll use it where fits the barrel, otherwise, i'll put a burst disk at the same place (after the curve, before the barrel).
I bought the unions, so now there's only the hole for the spark plug to be made... and this afternoon should be complete (except for sprinkler valve... however, i wanna make some tests without much pressure, so the potato shouldn't get out the barrel before the ignition).
I'll take a photo this evening to show it ^^
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Unread postAuthor: frankrede » Mon Feb 12, 2007 7:49 am

Why a sprinkler valve?
Your diaphragm might melt.
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Unread postAuthor: b1galez » Mon Feb 12, 2007 3:33 pm

Uhm... i don't know... but i bother to add a burst disk anytime i gotta shot a potato! -.-''
Isn't there another solution to the burst disk?
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Unread postAuthor: b1galez » Mon Feb 12, 2007 3:49 pm

Oh, sorry... i've just read the thread "valve setup in hybrid" and now i know that sprinkler valve holds 150 psi max... so the only way is the burst disk :(
Sorry for the ignorance :)
Anyway other solutions are accepted ^^ (obviously they should be compatible with my project!)
See ya! :D
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