11 replies to this topic

[DTReaper]

Ok so while I was making my last gun I was thinking of ways to fix and improve my pnuematic gun that I have and broke twice. I origanally repaired it for a leaking schrader valve (I tried to epoxy one in ther and it didnt work so well). After this repair for some reason I replaced one of the pieces of white PVC with a piece of conduit PVC and this worked for awhile but after I dropped the gun alittle I tried pumping it up and once I hit 140 psi (a pressure I reached severl times without fail) the piece with the conduit PVC shot out of the airtank and that piece hit a fence resulting in severe damage to all parts except for the airtank seen here

Now with this busted ass gun I decided that if it was broken like this I should make it better and I came up with a pnuematically actuated piston valve. I have several drawings here is a hand drawn one with no markings

and here is one made in paint with markings

Now if you have any particular questions about these just ask and I will try to answer them. Also as a side note for the drawings the neoprene washers most likely can be replaced by several o-rings. Now I have most of the parts I need for this gun but I still need a few last parts before I can finish these include a schrader valve and 2, 1 and 1/4 inch neoprene washers (if I decide to go that way). Also I could change the ballvalve in the valve for one of those blowgun things. Here is a picture of all the parts I currently have

I hope to start this project fairly soon but I don't know when I can but I will try to update from time to time.
But for now and questions comments or suggestions

-DTR

[bjack]

I don't understand what the ball valve on the top of the gun is for.

[DTReaper]

Ok essetially you first fill up the crader valve that is seen on the back of the valve. This closes off the barrel with a neoprene washer with the pressure from that side. Then you fill up the main tank to a psi that is slightly lower than the valve side of the gun. Now the gun is primed to fire it you simply use the ball valve to release all the air in the valve side. The pressure from the main tank will soon be higher than the pressure on the other side of the valve and this will force the piston back away from the barrel and release the seal on it allowing the air from the main tank to escape through the barrel and forces the dart out. I hope this clears up the confusion on how a piston valve works. Also the only reason the ballvalve was on top was so it could all be shown at the same time but it will be on the side of the gun when I build it.

-DTR

Edited by DTReaper, 21 July 2007 - 09:28 PM.

[bjack]

Oh, I've actually made a gun using this concept. It fired great, but for some reason the piston wouldn't always retract when it was supposed to, which resulted in a loss of pressure and thus a loss of range. I could never figure out the problem.

[DTReaper]

This is my first update so I got together most of the gun I have half the airtank finished and the rest isnt all that hard. I also need to aquire another schrader valve. Then I need to finish the exahust system, as of right now I can easily do a a ball valve exhaust but I am going to try to get a blow gun exhaust as it will work much better. I also have the parts for this bit but it will take a bit more effort to get it done. Hopefully I can get this done soon. Here are some pictures of it here its all together

and here it is with the matianece part opened and out and with the pieces that still need to be attached

So thats as far as I have gotten it any questions comments or suggestions will be taken

-DTR

[General Cole]

What do you mean by blowgun valve? Check Valve?

[n-Lord]

This is a great project im actually working on a piston valved homeade myself (Even with the... metric PVC sizes) and i have found that most piston valve homades have a small equilizing hole in the piston it self so as you pump the gun pressure builds up behing the piston or neoprene washer and some leaks directly into the tank and as you pump the pressure on both sides pretty much equilizes regardless your idea is brilliant i hope it gets finished soon oh and if anything is not quite clear in my explaination dont hesitate to ask

Regards

N

Edited by n-Lord, 25 July 2007 - 12:57 AM.

[DTReaper]

General Cole, on Jul 25 2007, 01:18 AM, said:

What do you mean by blowgun valve? Check Valve?

Well a blowgun is just the thing that people use in shops to focus pressurized air but the reason I want to use one is because it instantaniously opens and can exhaust the air behind the valve far faster than a ballvalve. So really it is the same thing just a little better than a ball valve. It pretty self explanitory but here is a picture of a blowgun http://www.homedepot...uctId=100073836 . So any more questions feel free to ask.

-DTR

[Sanityjr]

WARNING the bottom tee looks like a DWV part and could not be pressure rated! If it is, you might want to replace it before it is too late!

[General Cole]

Oh, thanks. I have one or two of those lying around from my compressors. I never thought about using them like that.

[Recruit]

DTReaper Warning Warning!! Do me a favor please stop right now. Ok listen several of your peices look like DWV, You should never use DWV Ever for a gun that while use more then 20 psi. Why I will tell you why DWV is not rated for preassure and checked for flaws as well. Thus it tends to be a lot weaker then properly rated pipe.
Also Bash time what are you think putting 140 psi in that gun after you drop it. Dont you know when you drop pvc its structualy integrety is compromised. Making prone to just blow apart, and you where very lucky with that other one. Know why, I will tell you pvc tends to frag when it blows (as in blow into many smaller peices with sharp edges).

So for your own safety please read up more on what you are doing.

http://www.spudfiles...title=Main_Page Link just for you

Also that piston is poorly designed. Over on spudfiles they have lots of piston valve designs and other stuff to, just dont post that gun unless you want every one to mega time bash you.

Edited by Recruit, 26 July 2007 - 03:23 AM.

[DTReaper]

I finally decided to finish this gun despite your warnings. It performs amazingly compared to all the previous generations of this gun. So all that really need to be done was fit the last endcap and the ball valve (exhaust valve) to the gun. So While I was at finishing those I also redesigned the piston to be lighter and far more durable. I went from a CPVC pipe and end cap piston to a bolt, nuts, washers, and neoprene. So here is a picture of it all taken apart

and here is the redesigned piston next to the old one.

as you can see I also decided to add a spring behiend the piston to make it more efficent so it automatically resteats itself once all the air in the primary tank is gone. It also means I don't need as much air behiend in the piston tank.
And here it is all together

All together I am extremely happy with the gun. It exhausts all the air in the primary tank really fast. A ball valve takes far longer to open then this valve. So this increases the initial velocity of the gun by leaps and bounds because it needs less barrel length to get the best air speed.
So questions comments critisism (besides the aformentioned issues)?

-DTR

edit: the ranges are spectacular, it has about a 12 inch barrel and it is getting over 100 feet flat with mega stephans. Also the ranges for angled are about 250 feet at least. once I get the right size barrel for this gun it will be hitting better ranges these are just the preliminary ranges.

Edited by DTReaper, 23 November 2007 - 11:12 AM.