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cant seal cannon, its like a cheese with holes :(

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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cant seal cannon, its like a cheese with holes :(

Unread postAuthor: Fizento » Fri May 21, 2010 7:47 pm

Hi guys!

Today i did this project with a friend of mine and we could get everything sealed at about 40psi (permanently pumping into the gun) there was the limit and you could hear air coming out to all the fittings :(

You all got so beautiful guns but at my gun nothing is can be sealed, do you get 100% pressure hold behind the piston if everything else is top? or do they leak a little ?

here are some pictures:
i used tape on the threads and bolted all together as much as i could, i also hotglued some fittings. but still if i use the pump and stop, the air floats away in just the same second.
ah and the blowgun is also leaking thought this stuff would go up to 200psi or so...

I would have so much ideas for my gun... but if the heart of it isnt working this all is just in my mind and wouldnt make sense to be done

I hope someone can help me...

total overview for now
http://img714.imageshack.us/i/dsc00245k.jpg/


just made that to get the blowgun installed have bigger plans for that :D
http://img29.imageshack.us/i/dsc00244mm.jpg/


right side is like no sealing...
http://img3.imageshack.us/i/dsc00243zj.jpg/


Last question does anybody know what pressure such drikingbottle can hold? On the first picture you can see its a SIGGI (dunno if someone knows this) drinking bottle

best greetz happy spudding

Fizento

PS: It is all 3/4"
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Unread postAuthor: Crna Legija » Fri May 21, 2010 8:04 pm

did you use PTFE all the seals, i put about 10 raps
hot glue wont seal crap. use epoxy instead

and i wouldn't trust those bottles at any more than 170, i don't think anyone has pressure tested them yet
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Unread postAuthor: Gun Freak » Fri May 21, 2010 8:07 pm

First off, try doing and image link to show the photos directly in the post.
Second, teflon tap isn't a sealant, it is a lubricant. You can thread it in then take the teflon off and it would still seal.
Third, we had a discussion a while back about those Sigg bottles, nobody ever tested one though, as -_- stated.
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Unread postAuthor: chinnerz » Fri May 21, 2010 10:25 pm

here are the pics
Image
Image
Image


Gun Freak wrote:Second, teflon tap isn't a sealant, it is a lubricant. You can thread it in then take the teflon off and it would still seal


I do not agree. Well i should say that my personal experiences do not agree with you. it does seal, but it does help to seal. And the more you use the more it helps. probably as it is physically adding something in between the threads.

Hot glue WILL NOT HELP AT ALL!!

I would suggest getting an angle grinder as cutting 1-2MM of the threads, and adding a gasket so that when you put it together it the two pieces squeeze the gasket forming a better seal.
if you cant find a gasket, and if your good with a knife, i would suggest trying to make one out of some thick (2-3mm thick) rubber sheeting.


.
Third, we had a discussion a while back about those Sigg bottles, nobody ever tested one though, as -_- stated.


i do not have the capabilities to do such a test, but maybe someone who does should give it a test
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Last edited by chinnerz on Sun May 23, 2010 4:29 am, edited 1 time in total.
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Unread postAuthor: Technician1002 » Sat May 22, 2010 12:06 am

The only thing I can suggest is to take each connection one at a time and seal each and leak check each. Simply hand screwing things together won't work. Are you using pipe wrenches? I did not see any sign of wrench marks.

After you get the simple normal plumbing leaks fixed you can concentrate on the more unusual connections such as the water bottle. It is not built like regular plumbing fittings.
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Unread postAuthor: MRR » Sat May 22, 2010 1:22 am

First off, teflon tape is no "lubricant", it is specifically designed to seal pipe threads. The trick is to wrap it into the opposite direction in which you screw on the next fitting.

http://en.wikipedia.org/wiki/Teflon_tape

...and yes there are several guns with aluminium drink bottles as chambers in the cannon section, you only have to search.

Beautiful gun from Spike33:
Image

Actually, I used one on my first pneumatic piston valve.
Image

It wasn't too bad for a first but when the bottle came loose at 120psi and hit my knee I moved on to more solid chambers.
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Unread postAuthor: Fizento » Sat May 22, 2010 6:28 am

i used the tape do wrap the threads and i used a pipe wrench everything is as tide as i could get it

I would suggest getting an angle grinder as cutting 1-2MM of the threads, and adding a gasket so that when you put it together it the two pieces squeeze the gasket forming a better seal.
if you cant find a gasket, and if your good with a knife, i would suggest trying to make one out of some thick (2-3mm thick) rubber sheeting.

Image


remove a little bit of the thread and get a gasket on this space? or did i get that wrong?


And i used the hotglue AND the tape but i think i need to take more tape to fit all together.

only 2 probs left my piston is also leaking i think the rubber in the piston isnt the right one
and my blowgun doesnt hold the pressure coming from the second T i installed it like it would be used normaly on a compressor not in the other direction cause i read that in the other direction there is only a spring that would hold the pressure.
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Unread postAuthor: cannon monkey » Sat May 22, 2010 7:50 am

let see if i can help.... for the blow gun get a reducing bushing from your 2nd tee to the size of the blow gun input then just use a nipple fitting.... more thread tape 5-9 times around is what i use...

not sure about your chamber ( drinking bottle ) as far as the gasket goes i think he means put it closer to the top of the threads ( thats what i did ) wait til he post back
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Unread postAuthor: Fizento » Sat May 22, 2010 4:29 pm

ok i got it sealed till now i tested 80 psi only got one prob when i want to remove the pump the qev reacts and the gun fires :D

perhaps i need to get a ball valve to secure the weap...
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Unread postAuthor: Gun Freak » Sat May 22, 2010 4:54 pm

Try puting a ball valve between the fill valve and the tee. Open the ball valve, fill it, close the ball valve, then disconnect the pump. This will prevent air loss when removing the pump head, so the gun will not fire.
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Unread postAuthor: Fizento » Sat May 22, 2010 5:21 pm

ah ok thats what i thought about thx
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