Ultimate Low-Cost Piston Gun!

[Molerat]

Today, while sitting in the floor of Home Depot I had an epiphany. I was trying to figure out a way of making a low cost piston gun that was powerful, simple, and anyone can build. While searching Spudfiles, I found FoxxLord's (he gets credit for piston!!!!) 3" barrel sealing piston valve tutorial. I was amazed at the low cost and simple design of the valve. I love his idea, but its fatal flaw lies within the method of it's chamber. In a barrel sealing valve setup, the barrel goes back into the chamber, meaning the gun must be very large to have a significant chamber. My method involves putting a tee between the barrel and piston valve. In doing so, my design allows you to branch off of the bottom and have a huge 4" chamber. When you dump air from behind the piston, the piston gets forced backwards against a spring or bumper, etc. When the piston goes back, the barrel gets opened up to the full brunt of a massive amount of high pressure air.
Needless to say, this idea would be quite powerful, and could be made for no more than $60.
Here is a drawing of the idea. I would appreciate feedback.

<img src="http://www.spudfiles.com/uploader/uploadFiles/ultimate.jpg">

[Velocity]

Is that not just a regular barrel sealing tee valve? By moving the barrel portion up past the center of the tee, I believe that you are losing flow...

[Molerat]

Flow may be important, but it isn't as important as volume or pressure, and that is what this design is implementing. It is merely an easier means of increasing the volume of the typical Low Volume of a barrel sealer. Hell, If I get enough feedback about flow, it wouldn't be much of a problem to put the piston in front of the tee as a solution. Thanks!

[joannaardway]

You have to have the piston IN the tee.
And flow is essential - at least equivalent to volume or pressure - if not more so.

And that's a regular barrel sealer anyway - it's nothing new. Identical to however many hundreds of them I've seen before.

[Molerat]

Aw, oh well. I've never seen one like this. How would I go about putting it in the tee?

[Freefall]

In simplest terms, it's a standard coaxial with a chamber extension. I like the configuration, but from a technical point it's nothing new.

[hi.]

If you do make it, add several feet to the barrel. Another thing i would do is turn the elbow 180 degrees and use it as a stock and have the exaust on the side.

[Suppresive Fire]

It is nothing more than the child of a coaxial and a barrel sealing tee.

[Molerat]

Yeah, I understand that now, and have changed my idea to a regular coaxial. I've already nearly completed the piston, so I'm mostly done. Regular coaxials are more efficient in the flow, anyway.

[InvisibleAndThenSome]

You should consider making a threaded joint between the Tee and the section of pipe that goes into the chamber (I'm not talking about interchangeable barrels, the blue part that looks like a 4 to 3 in reducing coupling) That way, if you have issues with your sealing surface, you can just replace the inner pipe rather than rebuild the entire valve.

I built this very design and had to go through 3 rebuilds after tons of trial and error R&D. Also, it is quite possible to leave the pipe short enough that you don't have the 180 degree airflow. For 4" Tee or Wye junctions, a 3" coupler lathed down fits perfectly and can move freely between the inside of the junction and the 4" pipe behind it.