JDP's combustion cartridge prototype

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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JDP12
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Sun Feb 07, 2010 3:08 pm

Well going off of JSR's efforts I've decided to make my own prototype.

It's 4" of 1" PVC, I have to let it cure and then add electrodes.

If I am happy with it I will make it without the endcap and cast the end with epoxy so its one smooth cartridge.

as You can see, I've decided to just go with 1" bore, same as the cartridge for maximum power according to HGDT.

You can see what it predicts below. Testing will come soon.

Watch this space
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cartridge 2.jpg
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jackssmirkingrevenge
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Sun Feb 07, 2010 3:27 pm

Looks interesting, are you going to try and make it eject though? with barrel and cartridge diameter being equal I wouldn't be too optimistic about that.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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JDP12
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Sun Feb 07, 2010 3:56 pm

No plans for ejection atm, if this works im going to make a double barrel shotgun (sawn off of course).

Then a revolving shotgun,

both based off of borderlands guns of course.
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spudtyrrant
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Sun Feb 07, 2010 4:18 pm

JDP12 wrote: (sawn off of course).
i think you mean sawd :lol:
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jackssmirkingrevenge
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Sun Feb 07, 2010 4:32 pm

In that case you should have a workable project, cartridge power is irrelevant to its function. Good luck :)
i think you mean sawd
The correct English term is "sawn-off", but since when did you yanks care about correct English :roll:
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Ragnarok
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Sun Feb 07, 2010 5:03 pm

spudtyrrant wrote:i think you mean sawd :lol:
I think you might want an "e" in "Sawed".

And as Jack says, "Sawn-off" is entirely acceptable.
In the end, this forum is full of different variants of English - you have to expect different words for the same thing, or different meanings of the same word.
There are many cases where I have to overlook words that are considered perfectly acceptable in the US but which are highly offensive in the UK.
Does that thing kinda look like a big cat to you?
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Marffy
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Mon Feb 08, 2010 12:07 am

this would be awesome if it went in a huge side-by-side double barrel. i would think the layout would be good to.
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JDP12
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Mon Feb 08, 2010 1:00 am

Well have to see.. Im gone for 15 hours aday right now.. So i dont get a whole lot of time to work on my projects but im doing the best i can.

Tests will come soon with a 20" barrel
iknowmy3tables
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Mon Feb 08, 2010 10:03 am

wait but those HGDT results only 178fps on a small caliber spudgun, if your fine with that I wouldn't start working on auto ejection/loading until there's power to spare but the idea of a break open shotgun is sounding pretty apealing
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JDP12
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Mon Feb 08, 2010 12:54 pm

Yea, the velocity doesn't appeal to me too much.

Depending on how testing goes I may slap a 3/4" or 1/2" piece in there and try that.

178 fps is pretty weak i'll admit, i'm looking to at least equal a paintball gun in velocity and ft/lbs (10 approx).

So if i could get 280 fps and at least 10 ft lbs with a .5" or .75" barrel I would definitely go with that.

Tonight I'll be adding electrodes and gluing a coupler to a barrel so I can get a few tests going.


First up obviously is a double shot gun. Something with one of these suckers on it would be pretty damn sweet... homemade of course.

more information...

If I don't go with a borderlands style gun after a double shot....I'd prefer to do a revolver style gun as per borderlands, but If i don't....

This would be pretty sweet..

Image[/url]


Little update-- After fiddling with HGDT i found my barrel length is TOO long, which is a slight issue. fiddling revealed I could get 213 fps.

Also I have an idea for getting more power out of it, if I'm not interested in getting ejection/blowback...

Will be posted later

UDATE 2: decided to slap a 3/4" piece in there and make it that calibre as HGDT predicts approx 245 fps with a 10 gram projectile and only a slight difference away is 1" bore, plus by choking it a bit it may have more potential for blowbak if i ever go that route. i have mostly everything glued up, curing.

Pictures tomorrow

So we'll see...
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Sat Feb 13, 2010 3:39 pm

if you need a certain barrel length for aesthetics you can use a fake larger diameter barrel.

that's probably a good move to size the caliber down I can't imagine a efficient combustion made from a straight pipe where only 1/6th of the pipe is chamber. it should also be easier to make an integrated silencer because I imagine that there will probably be a part that you will put the cartridge into that will be made with 1.25" pvc and aesthetically it you can extend that 1.25" pvc to wrap the rest of the barrel in front of it and there should be enough plenty of space for a muffler between the inside of the 1.25" pvc and the outside of the 3/4" pvc, unless you want a silencer for some water-cooled machine gun look
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Sat Feb 13, 2010 3:40 pm

DELETED duplicate post: sorry I accidentally resubmitted when the page wasn't loading for a while so my reply above got sent twice
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JDP12
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Sat Feb 13, 2010 7:40 pm

Sorry for no updates ive been way too busy lately.

I do have it all epoxied up with 3/4" inch, but havent been able to test it. I will be sure to post results when i do
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jackssmirkingrevenge
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Sun Feb 14, 2010 2:14 pm

JDP12 wrote:Image
That's definitely a project on the drawing board :)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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JDP12
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Sun Feb 14, 2010 6:28 pm

Indeed......
Hope to be testing soon... Curse you school
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