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Metal barrel sealing tee design

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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Metal barrel sealing tee design

Unread postAuthor: )DEMON( » Thu Jul 13, 2006 8:08 am

Those of you that have used metal fittings and stuff befor help me out.
I want to build a small powerfull piston cannon with my fire extinguisher for the chamber. I want it to be all metal sort of like Brians sawn off( http://www.spudfiles.com/forums/viewtopic.php?t=1342& ). I am not that good with pistons and only have one working piston cannon ( http://spudshot.com/Forum/viewtopic.php?t=35 ) Can you guys help me with the design. I want it to be cheap and simple. I will use this fire extinguisher for the chamber, not the top just the cylinder ( http://www.spudfiles.com/forums/viewtopic.php?t=2428& )
I want to design it compact.

I did some research on spudtech and came to the conclustion that a barrel sealing tee would be the right thing but I don't what pieces I would have to use to make it metal. http://forums.spudtech.com/topic.asp?TO ... hichpage=1
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Last edited by )DEMON( on Sat Aug 05, 2006 1:40 am, edited 2 times in total.
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Unread postAuthor: Brian the brain » Thu Jul 13, 2006 4:20 pm

Okay so get an elbow from the tank up to the T.
I needed to extend the Tee towards the excaust valve to get it to slide and seal properly.And to not get it "drop"into the bottom section of the Tee..Go fairly large on the fittings (1.5" ) because the piston will slide inside the extension wich has a smaller diameter than the Tee.( the galvanised fittings I have are bigger inside than at the threads so I can't get a piston in there).If you can,dremel out the welding seam.
Get a compression fitting to connect the barrel to the Tee and grind out the ridge that keeps it from sliding through all the way.You can use a spring to get the piston to seal better.I got one that pushes directly at the ball in the ballvalve.It does'nt matter because the ballvalve never opens fully.My ballvalve has two connections to the sides of it for the shrader and a gauge.Not shown in the picture..

(edit; I read the thread on the bottle, the gauge is perfect but you need a schrader behind the piston!!You probably can't fill it from the chamber side)I'll go look for my camera right now and put up some pics of the inside of the sawn-off.
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fire-idea.JPG
something like this??
fire-idea.JPG (10.82 KiB) Viewed 2653 times
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: )DEMON( » Fri Jul 14, 2006 4:54 am

Thanks, I have the idea now. I should be able to make it with no problems but I will have to see what parts I can get. That is how I want the fire extinguisher to go but the threads might be too small, in that case I would have to get an adapter. Instead of an elbow going to the tee I will put another tee so the pressure gauge can go there as well. Thanks for the help Brain.
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Unread postAuthor: Brian the brain » Sat Jul 15, 2006 3:33 am

You're welcome. :D Good luck on the adapter.That would be the only hard thing if the bottle has unusual threads.
The rest should be easy.
Remember the fill valve should be behind the piston!

The T valve allows you to build some kind of breech loader.At your request; I'll post some new pics in my sawn off thread today.
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: )DEMON( » Sat Jul 15, 2006 4:24 am

I have started constuction on my valve and have some pics. I am not sure if the piston is too long, how long is your one? I have done all I can do so far until I can go to the hardware store and get more fittings. So what do you think of it?

The fire extinguisher has irregular threads so I will have to wait until I get my welder.
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Attachments
mp1.jpg
This is the inside of my valve so far.
mp2.jpg
This is the piston and home-made spring.
mp3.jpg
This is the piston housing and exhaust, I am using a one way valve for the exhaust. This means I can make a hammer to trigger the one way valve.
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Unread postAuthor: Brian the brain » Sat Jul 15, 2006 5:58 pm

The inside shot of the valve looks okay,
but the piston and it's housing are too long.Big pilot volume :cry:
Get those compression fittings as close to one another as possible.
I didn't see a shrader...are you filling from the back??
I have my doubts on the excaust valve aswell..either the hammer valve won't open because of too much pressure, or, if the surface that opens(?) is small enough to be opened against the pressure, the flow will be too little.

are my english skills deteriorating or what?? Didn't know how else to explain it.

I'm not trying to be negative, I just wanna help you out
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: )DEMON( » Sat Jul 15, 2006 6:10 pm

Ok, I will shorten the piston and housing,thanks. The fill valve and stuff will be behind the piston of course but like I said, I haven't got all the parts yet. The exhuast valve works well, I have used it befor ( it has much greater flow rates than a blowgun). I know you are helping me and I appreciate it greatly. I also am thinking of using a female quick dissconect instead of a schardar.

Sorry, you might not be able to see the gun for a while because I am entering it in the spudgun build off. :D
The gun should be rated to a few hundred psi and I plan to make it double barrel (jump up and down with exitement)

I LOVE SHOTGUNS!
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Unread postAuthor: Benny » Sat Jul 15, 2006 6:38 pm

He used the one-way-exaust-valve idea on his piston cannon.
http://spudshot.com/Forum/viewtopic.php?t=35
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Join the spudshot forum!!!!!

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Unread postAuthor: Brian the brain » Sat Jul 15, 2006 6:51 pm

Well if you love shotguns ( like me!) check out my latest version.
I included some pics of the insides just for you. :P
As you will see the piston is relatively long to keep it from tumbling
inside it's housing.The housing is now as short as possible.

Double barrel huh? :shock: You got my interest Will they fire seperately??
I see great things happening :D
A few hundred psi is right.#00 to be exact cause I see copper.
By the way; At 300 psi you don't need a reservoir the size of a fire extinguisher.
That would free you from irregular threads.
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: )DEMON( » Sun Jul 16, 2006 4:31 am

Thanks Benny.

I don't think I will be able to fire the barrels separately because it will only have one chamber.I also want to run it off co2 and I plan to do a few thinks never seen befor 8) I also want to get those metal bbs .177 cal and make special rounds for the shot gun. I will most likely make it breech barrels because the pump action design is too troublesome.
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Unread postAuthor: Brian the brain » Sun Jul 16, 2006 5:05 am

try and get the lead bb's :D
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Can't ask for a better compliment!!
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Unread postAuthor: )DEMON( » Sun Jul 16, 2006 5:15 am

I have seen copper and steel ones but I will just get some lead shot from a hunting store.
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Unread postAuthor: )DEMON( » Sun Jul 16, 2006 7:08 am

I did what you said and shortened the piston housing, I also put 20mm pvc inside it for a really snug fit. I am happy with this,everything lines up.
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Unread postAuthor: Brian the brain » Mon Jul 17, 2006 5:47 pm

looks better now don't it! :D The piece of pvc should give the piston a smooth ride!

Just a question
What diamiter barrel are you using? Isn't it too close to the piston diameter? The piston should always be bigger you know. :roll:

If that's okay then you have the right material to build a super fast valve.
I wish I had those fittings over here man!! :D
I think you could ( take a good look at it before you even try) take a piece off the barrel, so it doesn't go into the Tee as far as it does and just extend the 20 mm pvc further into the Tee.That way you might even mount the excaust valve directly onto the connector coming out of the Tee.
Shorten the piston some more and shorten the spring.If you can get that to fit it would actuate incredibly fast.Maybe try it with some leftover pieces of pipe first.Don't cut the barrel until you know if you can fit all the parts in.
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Attachments
demon valve.jpg
look closely at the picture.THe barrel port is shortened.The piston should be guided in 20 mm pvc, further into the Tee.It should be visible from this side.
demon valve 2.jpg
This picture should explain.Just do as I did with the picture.If it doesn't work you can always put it back together like it was.
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Unread postAuthor: )DEMON( » Tue Jul 18, 2006 8:30 am

I will do some more designing. The 20mm pvc only fits in the larger copper pipe but maybe I can just put an adaptor on the fitting that has the larger copper pipe in. The piston is the same size as the barrel, is that a bad thing?

I can move the barrel forward without cutting any peice off, it is not fully crimped on. I will post more later.

CHANGES!

I shortend down the piston and got rid of the copper piston housing when I found out that the fitting was holding the 20mm pvc. I am going to place a tee on it with a female quick disconnect coming out the bottom and the pilot valve on the other side of the piston. I moved the barrel forward a very small amount.
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new-internal-piston-photo.jpg
Here is a pic of the internals.
back-of-piston.jpg
Back of the piston.
back-of-piston.jpg (17 KiB) Viewed 2497 times
piston.jpg
super small piston.
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