SpudFiles

Figured I would get things out of the way IN THE TITLE. This was meant to be a little time-waster, with not much power, and a unique valve.

In that note, please don't tell me to upgrade to a piston valve, sprinkler valve, hammer valve, metal air chamber, CO₂ filling, etc.

This thing was cheap, complicated, and required a good bit of hand machining, and it's pretty weak. I fire around pens and marbles indoors at suitable targets.

How it works is a piece of 1/2" SCH-40 is plugged off at one end, and an o-ring is installed above the plug. Above the o-ring, the pipe is ported, and a 1" coupling is centered over the pipe with a modified bushing, with #6-32 stop screws at the end.

A bottle is modified by cutting the threads off the top, and inserted into the coupling, and the stop screws tightened in place. When the bottle is pulled back against the screws, the o-ring seals in the neck of the bottle, and air is pumped in. The bottle is then pushed forward, shoving the ported section of pipe into the bottle and allowing air to flow out the barrel.

Filling is accomplished by a piece of 1/4" hose passing from the front of the bushing and through the back of the 1/2" pipe plug, and epoxied into place. This restricts flow quite severely, but performance isn't that critical.

Construction is explained further in the captions below. Feel free to ask any questions, and bash at your own leisure.

... I think I like it if it works how I'm envisioning it, care to draw up a diagram?

interesting design.. I understand it now. Fun idea, sort of like a hammer valve in essence. my guess is performance would be limited by the small holes, and air may leak around the outside of the bottle.

Neat concept though, never thought of it before.

Simple diagram added to the original post.

I actually experimented with banging the bottle against the wall to use it like a hammer valve, but, being performance sucks anyway, the projectiles barely left the barrel when doing that.

Nothing in pneumatics is new

Made a valve like that on my first "cannon"

Seals were electrical tape wrapping and the barrel was a plastic tube with holes cut in the sides and the end closed with hot glue. Chamber was a steel broomhandle.

As I recall, the only thing stopping the barrel from being the projectile was a bit of string...

Still, it was good fun to make and provided entertainment firing pens into the air.

Aside from the clunky pump action nature of the valve it's very simple and easy to make, literally a manual poppet valve.

Yup, but I bet yours actually had higher performance, as it didn't have a piece of 1/4" OD hose blocking flow.

Pretty simple valve, though, like you said. Only time consuming part was cutting the o-ring groove.

Haha!
Great project!

I have made a similar valve once, but with the barrel running all the way through the back.
I figured I would not have to fight the pressure.

But friction certainly made it nearly impossible to open fast...and a lot of air leaked through the port..wich doubled as a breech..

So actually...yours IS more powerful!

Oh well..you can't win 'em all.

Nice thinking outside of the box!