MOVED>>union exploded and i walked away from it

Tell stories about your spud cannon adventures!

Postby luckythirteen13 » Sat May 29, 2004 10:18 pm

today my friend brian and i were out testing my hybrid. we wanted to take apart an old computer stand and could think of no easier way then to shoot batteries at it till it fell apart.:D we decided to use 4x mixes. one shot went fine so we tried again but with a leaner mix. this time the gun made 270psi and the union exploded. the pieces were not sharp and they didnt move very fast/far. i think i have proven now twice to you guys that a union exploding will not hurt you. we all remember my first hybrid right? the one that blew its union at 80psi. heres the link http://www.koolpages.com/potatohell/Hybrids.html pictures are at the bottom as always
luckythirteen13
 
Posts: 2449
Joined: Tue Sep 30, 2003 12:26 am
Location: USA
 

Postby plasticex009 » Sat May 29, 2004 11:34 pm

How far did the pieces fly and how far were you from the launcher?

I am starting to believe exploding pvc pieces will not cause serious shrapnel wounds at moderate/close distances unless the pvc pieces are propelled by some explosive compound that generates large amounts of gas (such as bp). From my experience with pvc fragments, they have little mass, high surface areas, and are not generally sharp. These traits don't make pvc a good shrapnel material because the shards slow down quickly when traveling through the air and will most likely impact an object with a blunt edge.

New methods for holing burst disks need to be developed.
plasticex009
 
Posts: 2865
Joined: Sat Aug 02, 2003 1:31 am
Location: USA
 

Postby chimera » Sun May 30, 2004 1:56 am

That’s too bad :(

It doesn’t sound like it will be that big a deal but good luck getting it back together.

plasticex009

I agree with what you’re saying but maybe it is the use of burst disks that need to be changed?

If you remember back to our conversation about using a longer barrel and a burst disk strong enough to hold back only the pressure of the "X"bar mix as apposed to the explosion of the mix. I still plan on testing the idea; it’s just the whole time issue. Hope fully once school is out my friend TheBigJC and I will have the time and money to do the testing. We have already built an extension for our barrel putting its length at a few inches shy of 20 feet. We just need to build a stand now....
chimera
 
Posts: 690
Joined: Sat Feb 28, 2004 9:11 pm
Location: USA
 

Postby Dextromethorphan » Sun May 30, 2004 12:26 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by plasticex009
[br]

I am starting to believe exploding pvc pieces will not cause serious shrapnel wounds at moderate/close distances unless the pvc pieces are propelled by some explosive compound that generates large amounts of gas (such as bp).
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
So, do you think a 20" piece of 4" sch40 wouldn't be too dangerous if it decided to give in on me?
Dextromethorphan
 
Posts: 1423
Joined: Wed Mar 03, 2004 10:32 pm
Location: USA
 

Sponsored

Sponsor
 
 

Postby luckythirteen13 » Sun May 30, 2004 7:22 pm

plasticex009, most of the pieces i found where directly below or just to the side of the gun. one piece did fly over the neighbors fence and 2 pieces landed about 15 feet behind the gun. my friend and i were standing about 10 feet behind and just to either side of the gun. i was thinking about shooting video that day but at the last minute decided not to. im kicking myself for making that decision. ill have to cut the union off and reglue a new one on. i dont know when though. if i try any more 4x mixes, it wont be with 3 burst discs, it will be most likey with 2 plastic discs and 10-15 layers of foil.
luckythirteen13
 
Posts: 2449
Joined: Tue Sep 30, 2003 12:26 am
Location: USA
 

Postby plasticex009 » Sun May 30, 2004 8:52 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Dextromethorphan</i>
<br><blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by plasticex009</i>
<br>

I am starting to believe exploding pvc pieces will not cause serious shrapnel wounds at moderate/close distances unless the pvc pieces are propelled by some explosive compound that generates large amounts of gas (such as bp).
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
So, do you think a 20" piece of 4" sch40 wouldn't be too dangerous if it decided to give in on me?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Are you planning on having this happen?

It depends on a lot of factors. What method of propulsion are you using, at what pressure does the launcher burst, how does it fragment (big or small chunks) [this will be somewhat dependent on temperature], are you hugging the chamber or just holding it, is the chamber located by your head (RPG style)?

<hr width="70%">
Chimera, I do think that idea would be a good alternative to increase launcher durability, but it will probably yeield less projectile energy.

The maximum speed of the propellent gas will also play a factor in barrel length. I wouldn't be surprised if you encounter a max velocity in your tests.

The hotter the gas, the faster the max flow speed. If one hybrid generates greater combustion temperatures than another, then count on it having higher projectile energies/velocities. I am thinking a launcher utilizing high pressure burst disks will generate higher combustion temperatures.
plasticex009
 
Posts: 2865
Joined: Sat Aug 02, 2003 1:31 am
Location: USA
 

Postby MJA » Tue Jul 20, 2004 11:27 pm

The 3" endcap on my pneumatic blew off one day. I had been using the launcher a ton of times to 125 psi a year earlier. This time however I was putting air in it and it suddenly exploded, the endcap blew into pieces leaving only a ring around the end of the pipe. The pieces were very small and were scattered all around, and when I looked at a plant that was about ten feet away, there was a piece of pvc shrapnel lodged in the plastic pot that the plant was in. Luckily no one was hurt.:? And for some reason I cant figure out, the male threaded adapter that connected the 1" sprinkler valve to the barrel also broke. This made it hard to get it out of the sprinkler valve in order to salvage it.
MJA
 
Posts: 86
Joined: Sun Sep 28, 2003 5:49 pm
Location: USA
 
 

Return to Stories

cron