Metal barrel sealing tee design

[MrCrowley]

if i ever make a copper cannon which i will after my first pneumatic due to be finished end of august,i will base the design on this one if you don't mind 8)

[)DEMON(]

I got all the things to make a new piston housing(and jelly beans). My exhaust valve is a brass one way valve, I could post a pic of it it you like. I got it from a local irrigation store. My new compression fittings are copper, do they also need teflon tape?

*Go ahead, this is a great design.

[Brian the brain]

Yep. tighten first, unscrew and teflon over the ( now compressed) ring.Make sure to "" merge"the pipe to the ring with the teflon.

If you use a reducer "ring", tape it up too.


This gun should be in the competition!!!

[)DEMON(]

You must be crazy, I have not even completed 1/3 of the work I am going to do on this gun.

My piston housing is nice and sealed but the metal fittings always seem to have a leak, I put loads of teflon tape on them! I will just have to apply massive amounts of tape then try again.

I have decided a double barrel will be too hard to make with what I have got but a special barrel which is designed to fire shotgun like cartiges will take its place. I am planning to use a paintball cylinder as a portable fill source. From what I have gathered the set up must go: tank>paintball inline regulator>ball valve>pipe>chamber(back of piston). I am sure this will work but do you know of any ulternitives for the regulator?

I realized today that where I glued the chamber and valve together is a little off center, which causes the barrel to be a little un-paralell to the chamber. I will just buy some new fittings(hehe).

Another question I have been thinking is how to make a barrel sealing/normal piston valve automatic. This would be great for a SMG. If I take the chamber and attatch it to the piston valve directly (so it is perpendicular to the barrel) I could make a cannon to closely resemble the world war 2 STEN SMG. Thats why it would be nice to make an automatic piston.

[Brian the brain]

THe reg has no substitute.It's an absolute must.

If you can set the flow of the Co2 tank low enough, so it doesn't interfere(sp?) with the pilot-excaust, it should be semi auto.
May I suggest you unscrew that tiny pressure gauge from you extinguisher, and use that on you gun?
Should make it look even cooler.

The compression fittings have to be tightened very hard.Clamp the fitting into a vice and use a long wrench to get leveridge.
They should seal properly then.

I'm very impressed by this build!
I'm looking forward to seeing more.

[)DEMON(]

I have completely fixed all the leaks but I can't fire it off at more than 50psi because I can't push the one way valve open. A hammer is the next thing to get. Thanks for the idea of using the small pressure gauge, I will use that.

I have been thinking of a few semi auto ideas but I haven't figured out how to refil after every shot but I have to trigger, bolt and return set up planned. I will keep it simple for now. When I said regulator I ment if there was any other regulators I could use other than the paintball one, I is quite pricey. I know nothing about co2 regulators.

Now with the piston, I am not sure it has to be bigger than the barrel. I just has to have a big surface area. So if you made a piston similar to the one I am using but with and irregular surface that should be enough to open sufficiently. With that you could make small pistols and other goodies.

What do you think I should call it? How about the BULLDOG, project BULLDOG.

[Velocity]

You could call it "Brian the Brain's sawnoff replica". We already have about 5 of those

Just kidding... maybe project Bulldog... what do you have left to do?

[)DEMON(]

Well, I wouldn't want to give away details befor the contest now would I?

I have lots more work to do on this, if you read all the pages then you will find out.

[Brian the brain]

I use a soda stream regulator.I like the look of a paintballtank and PB reg better but hey.
And you shouldn't call it a replica.
It has evolved beyond that.It's different( I won't say it's better yet!!).Too bad you can't open the pilot valve that easy.
It will need a REALLY heavy hammer from what I can tell.

[)DEMON(]

I have some heavy tension springs to use in the hammer design, it will be all steel but I am not sure if it will work or not.
The worst thing that can happen is I have to change the pilot valve.

*Preformance issues.

Ok, I got rid of the one way valve because you needed too much force to open it. It works fine for sprinkler valves but not as main exhaust valves. The only other think I can think of is a ball valve but when I was testing it I found that you need to open it very quickly to get the piston to work.

I came to a conclusion that the more space after your piston, the bigger and faster exhaust valve you need. Therefor I need to get the least space possible behind my piston. I will have to see what happens if I put the ball valve directly after the piston housing but then I will have to put the filling tee and another ball valve after that.

Using a ball valve to fire it off is very loud. I suggest using a spring loaded design for ball valve. Example: with your hammer design, instead of the hammer having a point of rotation on a skrew it can be connected to the ball valve handle (handle removed, connected on the actual threads). Then a trigger like that of yours will lock the 'hammer' when it is cocked. When you pull the trigger the ball valve will be shot open.

What is your opinion?

[WOW!!]

Sweet gun, that thing is awsome. If you still have problems with the leaks get some liquid sealer(not really a liquid more like a paste), I use it and it seals really good and it costs about the same as 2 rolls of teflon or you could use the gas pipe sealer(yellow tape)that stuff is a bit thicker.

[Brian the brain]

If you use a spring you should be able to fill from the chamber side.
I used a ballvalve that has 2 extra 1/4" ports.
That was very expensive.A little spring would solve your problem.

I did the same thing.Screw on the schrader part, fill, close valve, and remove the schrader( in a pipe with endcap)

[WOW!!]

You could use a femlale quick connect, and then have a male one with the shrader on it and do it that way.

[)DEMON(]

I am using a spring so I could try filling from the chamber side. I would like to sort out the valve problem first.I have a question:
If your exhaust valve is too big or your piston is not a perfect seal then could the majority of the air get exhausted befor it exits the barrel?

Another question:
Could the power of the gun be limited if a lot of the air is used to push the piston back?

I want my cannon to be very powerfull but I find if I dont open the valve fast enough the piston dosn't work like it should. Mabey my piston is too short or the housing is too long and the piston is travelling further back than needed.
What should I do?

[WOW!!]

As long as the piston has a good seal all the way around it should make it go back, if it does not the piston wont move and all the air will go away. That is what happened on mine. The best thing to do is just try it.If it does not work you could put some tape on it a little at a time untill it works, and when it gets a good seal put some heavey grease in the houseing so that it will slide easyer.