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combustion competition

Built a combustion cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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combustion competition

Unread postAuthor: xXunderXcoverXx » Thu Feb 14, 2008 10:20 pm

So at the beginning of the year I posted something about the combustion competition. and Hear it is.

Chamber:
42"x4"
120,000 volt taser
2 spark gaps
Chamber Fan
Metered Mapp or Propane (mapp)

Barrel:
15' (feet)x 2"
beech load

Its a pretty basic gun, fun to so off.
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Unread postAuthor: rp181 » Thu Feb 14, 2008 10:25 pm

15' barrel? O.o

what kind of damage?
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Unread postAuthor: mega_swordman » Thu Feb 14, 2008 11:21 pm

The barrel looks like ABS, so be prepared for numerous observations of the sort. Your cannon looks nice otherwise.

Also, what competition do you speak of?
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Unread postAuthor: bigbob12345 » Thu Feb 14, 2008 11:28 pm

That is rather large which means it is in line with the first law of spudding "The Bigger The Better" :
You did a nice job with it.
It isnt very clean looking but neighther are any of my guns.
I bet it is really powerful a video would be nice.

Edit:I just realized how strangely I put together my post
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Unread postAuthor: xXunderXcoverXx » Fri Feb 15, 2008 12:06 am

Thank you all, Never shot it at anything, Parents concern, the competition was a challenge from my Girlfriend to see who could build a potato gun that shot further.

Yes i won. she showed up on launch day with a 1:1 3foot barrel 3 inch chamber and propane. (never shot) her dad wanted to put oxygen on it after the propane because he thought that it wasn't getting enough air. yes pure. I told him it would be a fatal mistake and after he saw my gun took my advise.

I know my gun is not very clean but its functional and got the job done. It shot a Russel Baker potato an estimated 350 *yards*

Next upgrade:
Disk burst
a very simple hybrid design
shorter chamber and barrel to make it more functional.
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Unread postAuthor: OuchProgramme » Fri Feb 15, 2008 12:08 am

bigbob12345 wrote:That is rather large which means it is in line with the first law of spudding "The Bigger The Better"


Not quite...

DDT may just end it all
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Unread postAuthor: xXunderXcoverXx » Fri Feb 15, 2008 12:14 am

The first shot she admitted defeat. so after winning I didn't care if the gun broke cause I'll have time to fix it. so I lubed another potato with vegetable oil shoved it it and strapped the mapp gas bottle to it. The whole gun all 19 feet of it kicked back probably 2-3 feet. it was so beautiful. tears filled my eyes as I stood up and watched it fly. not quite but close.


ps. and her dad owns the local hardware store. LULZ
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Unread postAuthor: Novacastrian » Fri Feb 15, 2008 12:49 am

Her dad owns a local hardware store but he wanted to inject oxy into a spudgun? (I hope i never happen to wander into his shop and ask for advice)
I am impressed by the fact that you had a "shoot off" with your girl, she must be a very nice specimen.
:P
I wish my girl loved my Cannons/Cannon more... :roll:

BTW-Your avatar is lacking clarity, i know that you are undercover and all but it makes me question the amount i have had to drink after seeing it. :)
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Unread postAuthor: Davidvaini » Fri Feb 15, 2008 1:04 am

Off topic:
xXunderXcoverXx, do you pronounce the x in your name like ecks or like a Z?

On topic:
Looks good and now all you two need to get into is airsoft :D
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Unread postAuthor: bigbob12345 » Fri Feb 15, 2008 9:40 am

xXunderXcoverXx wrote:Next upgrade:
a very simple hybrid design


Never use this in a hybrid design it will explode.
If you want to make a hybrid get some metal it is the only thing that you are safe using. Of course people generally exept Sch80pvc but if you do that I wouldn't recomend taking it above 2x because pvc hybrids have blown up before and will blow again.

OuchProgramme wrote:Not quite...

DDT may just end it all


I dont think it is possible with a combustion.
It may be with fuels like hydrogen and acyteline(exuse my horrific spelling)but I dont think it has ever happened before.
If you mean in hybrids then yes DDT is a concern and "The bigger the Better" does not always apply.
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Unread postAuthor: xXunderXcoverXx » Sat Feb 16, 2008 9:27 pm

The "X"'s are just deviders

When I make it a hybrid I wouldnt take it about 2x or mabye 3x

yes I know my avitar is messed.

I dont quite know what DDT is. Can anyone explain?

yes my GF is amazing and sometimes I think her dad is quite using his brain.

Thanks
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Unread postAuthor: Novacastrian » Sat Feb 16, 2008 9:33 pm

DDT would have the effect of making you very unhappy if you were near the cannon when it happened.
It is basically when a hybrid turns into a bomb, however to my knowledge no-one has managed to induce it in a launcher. It is thought to happen when the flame front burns too quick, in turn pressurising the remaining fuel and causing it to detonate.
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Unread postAuthor: MrCrowley » Sat Feb 16, 2008 9:34 pm

Never make this into a hybrid full stop. It's ABS, not even pressure rated and you seem to have a clean out cap on the back.

An advanced combustion, slightly smaller then this, made from DWV ABS failed because of the threaded fittings put too much stress on the pipe and cracked it.

And it was made by one of Spudfiles most experienced spudders.


Please don't take this past what it is now, it will fail.


Deflagration to Detonation Transition. In other words, if it happens, you will be seriously hurt. It's when the flame front goes supersonic.
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Unread postAuthor: DYI » Sat Feb 16, 2008 10:56 pm

With a perfect mix, you'd need a 4" chamber at least 35' long to achieve DDT without fans/HE ignition/Schelkin spirals, so you probably don't have to worry about that.

I believe you could make a 2x DWV SCH 40 solid wall ABS hybrid, the problem is that it would be too unsafe to use without standing behind a shield. Also, the cleanout cap would blow out on the first shot. I know from personal experience, and my hearing still isn't quite what it was before. The personal experience I refer to happened when I did something like what your gf's dad wanted her to do, except I use oxy/MAPP pressurised to 6psi. Atmospheric pressure oxy/propane guns can be done safely with ABS, because when it does fail, it won't shrapnel unless you've tapped holes into its walls like Spudblaster did.

Congrats on winning the contest, and on having a gf that's into your hobby. The best most of us can hope for is tolerance.
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