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My first cannon ,, and allready havin' questions!

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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My first cannon ,, and allready havin' questions!

Unread postAuthor: freez » Fri Apr 25, 2008 1:14 am

hi, this is actualy my first air gun i am making ,,
but i got a question for youre guys i am strugglin' with
i know , i allready drilled a hole ,, but don't worry a bout that ,,
my qustion is ,, can you guys maybe give me some ideas how i can get air in to the aliminium bottle in a nice and good way ?
because i was tryin' to do this with a auto tire thing ,, but then i got to the conclution it aint a good way ,, can someone help me ?
maybe wit some pictures and all ,, i would be real happy :p

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sorry for my bad english ,, iam from belgium ^^

Grtz,
freez
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Unread postAuthor: starman » Fri Apr 25, 2008 1:30 am

Welcome to Spudfiles Freez!

The "auto tire thing" is called a schrader valve and you should be able to find one that can be used there. Now that you have a hole there, your best bet would be to tap it with 1/4" NTP threads to plug it, and install a schrader valve in it. This one was just displayed by someone else on the forum here, but it's an example of a schrader with 1/4" threads.

http://www.acehardware.com/product/inde ... rader&sr=1

You may have been better off to plumb a schrader up around the bottle side of the neck instead of puncturing that pristine tank.
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Unread postAuthor: Lentamentalisk » Fri Apr 25, 2008 1:49 am

Seeing your stainless steel water bottle makes me at least a little nervous/inspired. Has anyone actually tested those bottles to see what pressure they are good to? They could make really nice, compact chambers if they last to a high pressure...
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Unread postAuthor: THUNDERLORD » Fri Apr 25, 2008 2:09 am

@freez, Try a tire valve for a car from an auto shop. It will be threaded and put it through the hole with the rubber washer on each side and tighten the nut on the outside.

@Lentamentalisk, they had these stainless steel drinking flasks(the contoured kind) at a gas station nearby and they were so thick I was thinking they're useless as a flask because there so heavy then :idea:
I'm not really into combustions but it would be 007 to add a tube that maybe fits inside unscrews and screws back on for barrel. I was thinking someone could add a bbq type sparker for the trigger and maybe fuel it w/drops of 190 proof alcohol.
There are some that look like they could hold 400psi maybe and the top is threaded for the cap!!!
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Unread postAuthor: BigGrib » Fri Apr 25, 2008 3:27 am

freez welcome to spudfiles it's too bad you already drilled a hole in your tank for a schrader valve. if it was a pnuematic i would put a "T" in between the tank and ball valve and put a fitting for either a quick coupler or a 1/4 NPT fitting to schrader valve deal. however since you already drilled a hole i would reccomend drilling it out bigger and putting a threaded scrader fitting in it. a couple questions though. what size is the opening of the tank when you take the valve off just curious cause a schrader valve is what about 3/4 inch in diameter and may not fit into the tank. forgot the other question
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Yea, that's definitely going to get you at least a tazer.

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Unread postAuthor: freez » Fri Apr 25, 2008 5:15 am

BigGrib wrote:freez welcome to spudfiles it's too bad you already drilled a hole in your tank for a schrader valve. if it was a pnuematic i would put a "T" in between the tank and ball valve and put a fitting for either a quick coupler or a 1/4 NPT fitting to schrader valve deal. however since you already drilled a hole i would reccomend drilling it out bigger and putting a threaded scrader fitting in it. a couple questions though. what size is the opening of the tank when you take the valve off just curious cause a schrader valve is what about 3/4 inch in diameter and may not fit into the tank. forgot the other question

jup its a 3/4 inch one ,, and it fits even better than perfect :)

thx for the help i'll let ya'll know when i fire the first shots :p

edit; i found a valve but it was really expensive like 10$ :O
drilled the hole a bit bigger ,, and gluwd it all together with a 2 componont lime,,airtight indeed :D,,can someone maybe help me with finding a better/cheaper system on getting air presure in to something ? because the valve is a bit to expensive,, ( maybe with some pictures of the material ) ,, maybe planning on making a new cannon with pvc pipes that are used for under ground constructions :),,but because i am really new to this ,, help will come in handy,,
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Unread postAuthor: jimmy101 » Fri Apr 25, 2008 2:44 pm

Freez... welcome to the forum.

How good are you at math and physics? Do you know how to calculate how much force there is on the valve you have installed in the bottom of the bottle? Do you trust the valve, epoxy (lime?) and bottle to withstand that much force?

It is always a good idea to calculate the forces on parts, especially when you are using parts for something completely different than what they were designed for.

So, you said the hole is now 3/4". What is your target operating pressure and how much force will there be on the 3/4" connection?

Can you apply that much force with your hands? If you do, can you rip the fitting out of the bottle? What about twice the calculated force (which would be a reasonable safety margin)?

Do you feel confident that if you dropped the charged chamber and it landed on the fitting that it is strong enough to not snap off?
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