Combustion Launcher Explosion

Post questions and info about combustion (flammable vapor) powered launchers here. This includes discussion about fuels, ratios, ignition systems and anything else relevant to launchers powered by igniting things like hairspray or propane.

Postby aturner » Wed Feb 28, 2007 10:41 am

mcook, the link you posted to an image on spudfiles does not work. No such image.
<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by mcook
[br]...The 6" screw caps are schedule 40. The manufacturer is Spears... If you go to there website, you can review the specs of all their pipe and fittings....Believe me, those caps are heavy<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
Yes, that type of cap is heavy. After a quick look at the spears website, I found that their 6" sch40 caps weigh 1.5 lbs for a female plug (FIPT) and 1.7 lbs for a male (MIPT) plug.

If, as you say, you were able to hurl these heavy endcaps across a street at high velocity, then I have no doubt they could easily crash through a window and a layer of drywall. Heavy plus fast often equals damage.

On the other hand, everyone (myself included) seems to agree with the part where you say...<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">There was a loose rag in the barrel opening. This would have been the path of least resistance.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

My final 2 questions:
1. what were the barrel dimensions?
2. How many times did you fire this launcher before the "accident"?

If your story is true and complete, then one explanation I could potentially accept would involve the barrel being too restrictive for the massive chamber volume of >61 liters. However, even if flow were choked by a small diameter barrel, this possibility still seems unlikely considering the pressure expected from combustion. I wonder if you could be leaving out some other key detail, like oxygen enrichment, launching before the solvent welds have fully cured, etc.
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Postby hi. » Wed Feb 28, 2007 7:36 pm

maybe he had a burst in it that didnt burst.... just a thought.
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Postby TurboSuper » Wed Feb 28, 2007 8:16 pm

This is a bit silly...we're essentially just guessing all the reasons why a combustion launcher would do that without any real evidence to tell if we're right or not.

If an endcap goes flying at that velocity, it probably didn't have much resistance, ergo, it wasn't screwed on right/too small.

The only reason to tell would be a pic of the cleanout. You'd see where the threads broke.
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Postby joannaardway » Thu Mar 01, 2007 4:49 am

We have to guess, because we have no images to look at.
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Postby aturner » Thu Mar 01, 2007 8:49 am

Turbo, this whole hobby is a bit "silly".

Most of the time we don't have any real evidence to tell if we're right or not. In the past, even when there have been pics of launcher failures, it is difficult to precisely nail down the cause. Sometimes we collectively figure it out....other times we don't.

So what?

The process is entertaining.

For some reason we all seem to like to talk about building devices that are capable of hurling objects, and maybe make a good "boom" or "thwumppf" in the process. In this case, we're just talking about an endcap(s) hurled by a 61L launcher.
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Postby Legendpilot » Tue Mar 06, 2007 6:42 pm

I can personally tell you that I had something similar happen to me.

<a href=>
This gun</a> was one of the few combustions I've made. I shot this particular gun maybe a half a dozen times at best without a hitch. One day we decided to make a little noise due to some type of festive occasion that was occurring. We perched the gun out the back sliding glass doors, loaded a wad of paper down the 2" barrel nice and tight, and filled the chamber with Oust. (I hadn't graduated to propane yet, but the Oust worked well) The clean out cap never did screw on very well, maybe a turn and a half, but I always wrenched it down with a strap wrench - until now. We anticipated the boom that was about to take place on <i>the other end</i>, when all of the sudden my hearing was gone, completely, it gradually returned throughout the next few minutes. My knee was in extreme pain as I was brought to ground, immediately. The clean out cap had flew off with such force I still have pain there today, and this happened in January.

I will edit in a pic of the carpet that was singed by the escaping gas asap. Just thought I'd share my story. -Lp
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Postby InvisibleAndThenSome » Wed Mar 07, 2007 12:27 pm

It's really strange that Sch40 and 80 pieces failed, no doubt. However, I've gotten hit with thread endcaps at great speed by my spud pistol, which is 2"x6" chamber and 1"x10" barrel. Hit me square in the stomach.

I think the morals of the story are
a) Screw your endcaps good and tight! (wow that sounds wrong :-P)
b) If you know your cannon has enough power, consider building sandbags or barriers.
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Postby frankrede » Thu Mar 08, 2007 12:01 am

I want a picture of this cannon postmortem.
So your in vegas? Which side of town? I live in summerlin, and I used to be over by Nellis AFB
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