Ok, I have been working on this sucker for a long time(probably about 2 months) and I finally got it to where I wanted it for the most part. I still have a small leak problem I need to take care of, but hopefully it wont be too much of a problem. My goal was to build a valve that allowed full 1.7"(1.68 acctually, but im rounding) flow for a golfball and I wanted to be able to build it in a 2" tee, which is much harder than it sounds. Also, there were no special machines such as lathes used when making these valves, only a saw, dremel, drill, and one of those grinding wheels, and all the parts were found at my local Ace hardware store. I went through 3 1/2 different versions of this thing and 2 piston designs until I finally got it working. I have noticed several people talking about valves similar to this lately so I figured I would share my experiences so people can have more to base their designs off of.
My first design was a piston in 2" pipe that blocked a hole in the side of the pipe leading to the barrel, and I was hoping releasing the pressure on one side would slide the piston sideways and open the hole. But when I released the air I could never get the piston to slide enough to allow full flow. It just opened partially and let out all the pressure through the small crack it made.
My second design was similar to my final (diagram below) but instead of the bushings and 1.5" pipe as the barrel entrance I tried to use slit 2" inside 2". and on this version I neglected to make sure the sealing surface was flat before glueing it into the tee. I couldn't get the thing to seal very well at all.
This is where the 1/2 version comes in. I kept the same tee, but I busted the slit 2" out with a screwdriver and air pressure. The air pressure was a bad idea, it sent a piston flying into the ceiling in the garage(pics below). Then I cut a shorter piece of slit 2" and reglued it in there, but this time I left about a quarter inch of 2" unsleaved on the inside of the tee. I was hoping I could use an o-ring to seal against the wall of the unslit 2". Well, this acctually worked and I managed to get a perfect seal after much testing and retesting. Well why did I build another version then? Well the way I finally got it to seal involved a loose o-ring and whenever I would fire the gun it would shoot the o-ring out at very high speeds (put 2" holes in a cardboard box and dented the ceiling) No matter what I tried to glue the o-ring to it would shoot off still.
That brings me to my final version, it was easier to make and should be easier to seal (still working on that
), and it uses my simple piston and opens all the way. I forgot to mention that on my previous versions that I had to build a complex version of the piston because the valve would only crack open sometimes and not fully open. Ill stop yakkin now and show you the valve [:p])
view of my simple and complex piston and my bumper which is a rubber 1.25" coupler
complex piston. basically the back end is built on a lamp bolt(hollow) and when the air pressure is dumped the back end slides back, compresses the spring, then unseals the front end from the barrel when it reaches the back of the bolt, and the compressed spring pulls back the front end away from the barrel once it is unsealed. I will see if performance is affected any with this one vs. the simple one once it warms up and i get around to doing some testing
I also had many many different ends for the pistons when tring different sealing methods, in these pictures they just have the classic rubber washer
and finally heres my blooper of shooting my pison into the cieling
If you have any questions let me know. And is anyone interested in seeing a video of it in action? I haven't shot projectiles(golfballs) with it yet, but when I do I will make a video if anyone wants to see it.