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5 gallon gun

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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5 gallon gun

Unread postAuthor: sharpshooter » Sat Mar 31, 2007 9:02 am

We get bottled water delivered every... idk how long...3 weeks? any how, i have been eyeing them up to use as a chamber. They pretty much have the ideal shape: built in handle, reduced down to roughly 2" dia, short and wide=faster combustion, massive volume (atleast..... portable....), cheap (i think like $12 if they do not get returned), and light weight.

The thing I was wondering is if they could hold the pressure from a combustion? Or is this something that I'm gonna have to try and test myself? :idea:
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Unread postAuthor: CannonBall » Sat Mar 31, 2007 9:45 am

I dont think it would hold..
the plastic will melt overtime..
You can build a chamber just as big from abs or pvc.

Patrick
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Unread postAuthor: Los Frijoles » Sat Mar 31, 2007 9:47 am

Cannonball: If he waited a few minutes between shots, the PVC would not melt. Also, it would be very expensive to build a chamber that big from PVC or ABS.

If you can build a pneumatic from a coke bottle, you should be able to build a combustion from a water bottle. How thick are the walls on the bottle?
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Unread postAuthor: CannonBall » Sat Mar 31, 2007 10:21 am

Yes Los Frijoles you are right if he waited it wouldnt melt BUT we all want to shoot fast 8) waiting ain't fun.
I would build one from pvc or abs if your wallet reaches.

That my opinion
Patrick
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Unread postAuthor: sharpshooter » Sat Mar 31, 2007 11:47 am

Making a gun of that size out of PVC is out of the question. Just way to expensive to build somthing that, while more powerful, wont serve much more purpose than my current big gun (never posted it... just to lazy... but yea... 99" of 3" PVC barrel and 40" of 4"PVC Chamber).

But, if this can be done cheaply, then im all for it.

The sides are probably about 3/32 to 1/8 thick. I cant measure with my calipers down on the actual walls of the bottle, and the neck is not straight (i mean like theres different grooves for water bottle holders etc.) and seems to be slightly thinner. Because of this, i cannot get a good reading.

I would also assume that this thing would not be shot multiple times very quickly. Its just going to take more time to ventilate a chamber with only one opening. So heat hopfully will not be an issue.

I think i may put a 4" barrel on this... just because its somthing that I have not done before, and will open up some new ammo. The only problem is that it would require either living with poor flow due to a 2" opening out of the bottle, or trying to cut a bigger hole and all the difficulties assciated with attaching the barrel... I dont know ..... It will all work its way out eventually. aka... ill prolly end up with the 2"... :?
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Unread postAuthor: benstern » Sat Mar 31, 2007 12:25 pm

They are not made to hold pressure like a coke bottle. They would shatter over time. Also, A bigger chamber does not mean faster combustion.
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Unread postAuthor: Insomniac » Sat Mar 31, 2007 8:46 pm

They can hold pressure, take a look at this.
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Unread postAuthor: subterranean » Sat Mar 31, 2007 9:18 pm

insomniac thats right ive seen that site before. If you read it ,sharpshooter, i think it mentions pressure, but i know on mythbusters they did a water rocket myth and did pressure tests on this type of bottle. Their results showed they will burst at a presure exeeding 90 psi. For a combustion cannon they should work, but they are more rigid than a regular soda bottle and will tend to weaken over time. I tryd to make a water rocket with one of these last summer. I heated(with a hair dryer) half a coke bottle coated in exopy on it, over the opening, in oreder to shrink fit the bottle, to attach it to my launcher. You may try using this method to convert the opening of the bottle to a threaded coke bottle to easily attach a barrel to it, this will obviously constrict flow significantly.
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