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Destrutive testing

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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Destrutive testing

Unread postAuthor: Jeeperforlife » Fri Sep 19, 2008 10:37 am

I am done with the projects I had this summer and now i'm back. I have built a very secessful Hybrid with a 32 ounce CO2 paintball tank and a 1/2" union.

Any way back to the subject I was reading some old topics about the failing of Black iron pipe and fittings. I have a piece of 4 foot 1" sch 40 Seel pipe and was thinking of capping it off and loading it to 30X to see what worst case scenario would be. I have several acres to do this in and have a remote ingition system so I could do it safely. I even thought of drilling a 2" hole 5' in the ground to contain the energy.

Do you think it will burst and give any meaninful info? I was thinking of seeing how it splits and fractures. Or if it just blows off the end caps.
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Unread postAuthor: SpudFarm » Fri Sep 19, 2008 12:15 pm

go for it, might not burst the first times just so you know it.

also, try to get a DDT in there
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Unread postAuthor: Sticky_Tape » Fri Sep 19, 2008 2:57 pm

Just in case you didn't know spudfarm wan'ts you to put the sparkgap at the end of the pipe.
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You can tell how awesome a cannon is by the pressure used.
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Unread postAuthor: rp181 » Fri Sep 19, 2008 7:22 pm

i bet the threads will strip.
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Unread postAuthor: DYI » Fri Sep 19, 2008 7:44 pm

I wouldn't be at all surprised if it didn't burst. I have several SCH 40 pipes and fittings on my 30x hybrids (mind you, none as big as 1" diameter), and I've never had a failure in any of them. I know with relative certainty that one of these hybrids is reaching in excess 2500 psi due to the strength of the discs used.

You could try it, but I believe you might need higher mixes than 30x to get consistent failures in 1" SCH 40 steel.
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Unread postAuthor: brogdenlaxmiddie » Fri Sep 19, 2008 9:32 pm

One question- What are you going to do if it doesn't fail?!?!? Have a pipe with extreamly high pressure in it just sit there??? :shock:
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Unread postAuthor: Pilgrimman » Fri Sep 19, 2008 10:13 pm

Once the gas cools off, the pressure goes down.
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Unread postAuthor: Jeeperforlife » Fri Sep 19, 2008 11:17 pm

Sticky_Tape wrote:Just in case you didn't know spudfarm wan'ts you to put the sparkgap at the end of the pipe.


I was only planning a spark plug on one side.

I want to try 30X because I don't want to take my compresser past 500 psi. If I dont have any luck I have some 10 foot sticks of 3/4" with any luck I can get DDT with 10 ft of run up distance. :twisted:

I have the first one ready. It will be a little wile before I get to try.
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Unread postAuthor: Gippeto » Fri Sep 19, 2008 11:23 pm

I'm not sure which threads you were looking at, but what kind of pressures are you expecting?

According to this;

http://www.engineeringtoolbox.com/wroug ... _1123.html

1" sched 40 steel pipe should fail around 8000psi.

Do 30x mixes actually generate that much pressure?

Are you using adiabatic flame temps to calculate pressure rise?
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Unread postAuthor: Fnord » Sat Sep 20, 2008 10:34 am

What we really need are tests for 1.5" and 2" sch40 steel and fittings. Tests of 1" stuff are fine to have in the database, but almost everyone uses 1.5 or 2" steel pipe for mid-sized hybrids.
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Unread postAuthor: Jeeperforlife » Fri Sep 26, 2008 10:08 pm

well at 25X I did not get any damage. The caps did not even blow off. :?
I will regroup, plan better with different pipes and ways of achieving higher mixes
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Unread postAuthor: DYI » Fri Sep 26, 2008 10:23 pm

Well, 25x wouldn't produce anywhere near 8k psi. 80 or 90x seems a bit more realistic for the rupturing of 1" SCH 40 steel pipes.
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Unread postAuthor: Jeeperforlife » Fri Sep 26, 2008 10:28 pm

well I do have a oxygen bottle for my torch set. I guess I could run strait Mapp and oxygen.
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