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Need a tank

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Need a tank

Unread postAuthor: canadian » Wed Jan 31, 2007 9:53 pm

well, im in the process of building a golf ball cannon, and need some thoughts on what i should do.

i and constructing the entire cannon from steel. im not gonna change my mind now.

i got a barrel the fits a golf ball nicely, now i need a air chamber. i would rather not construct this part myself. i would rather use something prebuilt, such as a fire extinguisher.

i also don't know how long the barrel should be. the length of pipe i have is 5.5feet long. but i could cut it down.

any thoughts or opinions are welcome, and dot say its gonna be heavy, because i already know that.
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Unread postAuthor: MrCrowley » Wed Jan 31, 2007 10:43 pm

Ok,If your using a fire extinguisher I would recomend say a 9kg one,nice and big, Only problem is you cant get Fire Extinguisher threads. They're a funny size, My fire extinguisher mod will work but it will put too much strain on the joint so thats out of the question, leaving the FE's(fire ex) valve on will restict flow and it will be pointless. So your left with getting it welded which shouldn't be a problem for you. Other tanks you can use are big Co2 tanks used for welding or propane tanks(medium size ones not the ones found at petrol stations :P )

Search GGDT in google go to the website and download it, Enter your parameters and fiddle around with the barrel length until you find the maximum velocity. Your probably going to be stuck on some of the parameters so look on his site, he explains them all. What are you using for a valve?
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Unread postAuthor: canadian » Thu Feb 01, 2007 1:57 am

well, whatever i use, i am definitely not going to mess around with threads. im just going to weld it.

also, any thoughts on the piston valve would be appreciated
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Unread postAuthor: MrCrowley » Thu Feb 01, 2007 2:57 am

Metal, Barrel Sealing....

this should help you:
http://forums.spudtech.com/topic.asp?TO ... hichpage=1
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Unread postAuthor: shud_b_rite » Thu Feb 01, 2007 4:09 am

Hi im new here

when I bought a fire extinguisher and I knew that I wouldnt be able to find the right threads for it so I bought an extinguisher that had a black hose on the end of it which was used for aiming the dry powder.

Simply cut the black hose to the desired length (making sure that you dont cut the part that is attatched to the fire extinguisher) and simply buy an air fitting with a barb that is a suitable size for the hose and use a hose clamp to secure it.

This is what I have done and it works good at 100psi. Just go to your local hardware shop and you should be able to pick up some kind of fitting that will fit into the hose. I used a brass 1/4 inch air compressor male connector.

I have found this to be the easiest way to build a cannon, all you need is a knife, screw driver, a meter or 2 of hose that is suitable for holding high pressures, a selection of fittings and a fire extinguisher. The valve built into the fire extinguisher is all that is needed for firing as it is quick. A cannon can be made in about 15 mins using this method.

I have just joined this forum today and this is my first post. I am just waiting for some parts to arrive in the mail and then I will showcase my gun on this website.
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Unread postAuthor: MrCrowley » Thu Feb 01, 2007 4:13 am

I know what you mean, but you still have to use the fire extinguishers valve which is in basic terms sh*t. Sh*t flow and everything else. Try my mod: http://www.spudfiles.com/forums/viewtopic.php?t=5296&
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Unread postAuthor: shud_b_rite » Thu Feb 01, 2007 4:26 am

Well actually I have found that the valve on my fire extinguisher works very good. Once you have got all of the powder out of the fire extinguisher it has good air flow and is very easy to press unlike a 90 degree ball valve.

Maybe its just my fire extinguisher or I have very low expectations. If you want real fast (am I mean really fast) air flow then I would suggest a CO2 fire extinguisher, but they are to expensive and would require very well built attachments built by people that really know and are experienced in what they are doing (unlike me).
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Unread postAuthor: MrCrowley » Thu Feb 01, 2007 5:13 am

shud_b_rite wrote:Well actually I have found that the valve on my fire extinguisher works very good. Once you have got all of the powder out of the fire extinguisher it has good air flow and is very easy to press unlike a 90 degree ball valve.

Maybe its just my fire extinguisher or I have very low expectations. If you want real fast (am I mean really fast) air flow then I would suggest a CO2 fire extinguisher, but they are to expensive and would require very well built attachments built by people that really know and are experienced in what they are doing (unlike me).


Ah, Well there's your problem. If you switched to a sprinkler valve you would be suprised with the performance increase. Or a piston valve....
Ball valves are paintfully slow. I would pick a Fire exitinguisher valve over a ball valve as well.
Incase you havn't seen it this is my <A HREF="http://www.spudfiles.com/forums/viewtopic.php?p=56422&#56422">Dual Fire Exintguisher Paintball Rifle<a>
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Unread postAuthor: canadian » Thu Feb 01, 2007 9:17 pm

alright, ive got some more thoughts and questions.

my original plan was to build a breech loading gun, but now the more i think of it, i think i should build it as a coaxial with diaphragm.


so my questions are, can i build a diaphragm valve from rubber from an inner tube? i think the pressure would maybe pop it though in the barrel, so would it work if i bolted a steel plate to the middle of it to give the part that contacts the barrel some rigidity?


i'll draw up a picture of what i mean.
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Unread postAuthor: canadian » Thu Feb 01, 2007 10:18 pm

Image

Yellow=steel
Red=rubber
Green=hardware (nuts, bolts, washers, ect)


there are 2 valves at the bottom (drawn as ball valves, but i will use an air gun) one is to fill, and one is the release.

tell me what you think..

(click the image to make it larger)

i would have a small hole in the diaphragm to fill the main tank.
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