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8x pvc failure

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8x pvc failure

Unread postAuthor: pat123 » Thu Aug 13, 2009 7:14 pm

I was planning on entering the contest, but I had a little problem with my gun.

It is 1.5"sch80 pvc sleeved in 2" sch 80 pvc. everything had at least two layers of sch 80 pvc.

Me and Drex fired it seven times before it blew. one 2x, one 4x, two 5.5x, and three 8x. On the first 8x shot it put a 10" 19 oz nail through 4 pieces of 3/4" plywood. We expected a max chamber psi of about 900psi so we made a bomb shelter out of cinder blocks just in case.

The good news is that the remote ignition and the bomb shelter worked perfectly.

The video is processing on youtube so I will get that up soon.

[youtube]http://www.youtube.com/watch?v=Ku_M93bzu0o[/youtube][/youtube]
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Unread postAuthor: Hotwired » Thu Aug 13, 2009 7:23 pm

As I said before, not big on the PVC rule.

Still at least you were prepared for the consequences of pushing it, nasty shrapnel it put out there.
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Unread postAuthor: theBOOM » Thu Aug 13, 2009 7:25 pm

How much damage did the shrapnel cause? was it like massive dammage? also... wow 8x thats alot and that seems like a pretty long,thin chamber.. might've been ddt??
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Unread postAuthor: pat123 » Thu Aug 13, 2009 7:32 pm

The chamber was only 2' long so i doubt it was ddt.
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Unread postAuthor: theBOOM » Thu Aug 13, 2009 7:57 pm

and what was the diam? 1 ?
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Unread postAuthor: jonnyboy » Thu Aug 13, 2009 8:35 pm

theBOOM wrote:and what was the diam? 1 ?


One what monkey? fan? milimeter?

It is 1.5"sch80 pvc sleeved in 2" sch 80 pvc. everything had at least two layers of sch 80 pvc.


How about reading the whole post before asking questions.

Build it again.bigger.faster.stronger :)
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mobile chernobyl wrote:I can shoot a Canuter Valve off my '82 Chevy Ram F150 AT LEAST 3/4 Mile with 'ma cannon made of soup cans duct taped together, then I just squirt some bacardi 151 in the chamber and hold up my cigarrete lighta and WHOOSH! That thing flies at least 3/4 mile
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Unread postAuthor: Technician1002 » Thu Aug 13, 2009 8:58 pm

After seeing the copper barrel with a big blister, I wouldn't be surprised if it was some kind of wave front. Air is not safe, but high pressure combustion provides uneven forces. It's much like hitting it with a hammer.

Wow.. Thanks for sharing the video and photos. Good call on safety first. How far did shards fly?

From the orange stain, this may have been a used pipe with rust stains. That may have had some contributing factor.
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Unread postAuthor: pat123 » Thu Aug 13, 2009 9:04 pm

It wasn't copper. it was burnt pvc.
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Unread postAuthor: KineticAmbitions » Thu Aug 13, 2009 9:05 pm

What you're seeing here is less likely to be DDT than it is the result of pushing an unsafe building material past its limits. It is well established that PVC is brittle and, being a plastic, has a very low tensile strength compared to that of even mild steel alloys.

Consider the case of a very large block of ice with a small HE charge placed in the middle. Even if you make a cubic metre block of ice, chances are that it will still be cracked by the charge. If you repeat it several times, you could have an absolutely huge block of ice which will still crack apart and crumble away eventually. This seems to be what your PVC is doing, as there's no way that you exceeded the tensile failure pressure with an 8x mix.

I can see this happening on high pressure PVC barrels too - even if you're building a pneumatic for this contest, something similar may happen if you run at sufficiently high pressure. As Tech said, it's like the copper barrel with the bulge.
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Unread postAuthor: Technician1002 » Thu Aug 13, 2009 9:21 pm

pat123 wrote:It wasn't copper. it was burnt pvc.


Sorry I wasn't clear.. There was another cannon that had a barrel blow out a goose bump on the side..

However thanks for clearing up the burnt PVC. I thought that was rust from used pipe.

Does anyone have a quick link to the copper barrel with the goose egg? I have not found it in a quick search.

Maybe you should post the pics in this thread..
http://www.spudfiles.com/forums/it-just-went-boom-t18265.html
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Unread postAuthor: twizi » Thu Aug 13, 2009 9:36 pm

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Unread postAuthor: King_TaTer » Thu Aug 13, 2009 9:37 pm

This is a shame. Although I'm glad this happened to responsible people who realized the danger of this contest and took the necessary safety precautions. This could have been catastrophe if someone was careless enough to stand next to it. I wouldn't be surprised if someone got seriously injured because of this contest

"Oh what's thirty more psi?"

"How about we bump it up to 5 or 6x!"

"We only got through 5 boards! Let's add more air!"

Those are just simple and exaggerated examples but you get the point. In my opinion, the penetration contest encourages people to push themselves beyond their comfort zone and to act in the absence of common sense. It's basically a gamble. Money vs. Safety.

This is in no offense to you Pat, I'm just trying to make a point about the contest as a whole. Oh, and I like your idea about the double walled SCH 80, It's pretty neat. It's too bad she blew up. :(
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Unread postAuthor: twizi » Thu Aug 13, 2009 9:43 pm

maybe u should dip the gun in epoxy so it super strong st ronger then steal
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Unread postAuthor: MrCrowley » Thu Aug 13, 2009 11:07 pm

twizi wrote:maybe u should dip the gun in epoxy so it super strong st ronger then steal

What happened to my *facepalmheaddeskcombo* animation? I could use it right about now. :roll:

Maybe you should learn how to spell and only talk about things you know about. Dipping a cannon in epoxy wont make it stronger than 'steal'. :roll:
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Unread postAuthor: Moonbogg » Fri Aug 14, 2009 12:20 am

Damn it man. That really threw some shrapnel. When PVC goes, BOY does it like to go. Hopefully this serves as a warning to others. Glad you guys aren't retarded and remote fired it with a barrier. This only adds to the crap we hear in articles from whining parents about how spud guns are nothing more than pipe bombs with potatoes stuck in them.
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