I didn't run in here and post a pic right away, because, well, it's pretty much run-of-the mill. Over and under. With a homemade piston valve, a modified sprinkler valve, and a blowgun as a pilot valve.
Second post:
Like I said, just a run of the mill, over-under. Nothing to write home about.
I will be adding a support between the end of the chamber, and the barrel.
Yes, the grey pipe on the back is plastic. It is from the sprinkler section.
Aside from the blowgun and the fill valve, there is only one metal part in there. That is a 1-1/4" metal nipple between the piston valve and the chamber.
I don't like having to use the metal, because of the possibility of causing stress cracks in the plastic, when tightening the joint.
But I am using what I have laying about, for these builds. I can't afford to go buy new fittings. And I don't remember ever seeing a 1-1/4" plastic nipple, anyway.
Third post: Refers to picture titled "third post"
Ok, this is a pic of the components of my piston.
It is simply a 3/4 cap. A 3/4 coupling. Some rubber. Some washers. And a screw.
Put together in the order you see them in the pic.
I hogged out the inside of the coupling, so I could slide it completely over the pipe. (Ignore the second coupling. LOL)
Fourth post: refers to picture titled "Fourth post"
Here is the completed piston and the pilot chamber it will be put into.
The bumper in the bottom of the chamber is a sandwich of two pieces of neoprene rubber from the plumbing section, with a piece of kneepad rubber between them.
Fifth post: Refers to picture titled "Fifth post a" and "Fifth post b"
Once the valve is put together, you can see how much travel there is.
I did it the way I did, so that when the piston throws open, the same neoprene that was sealing the barrel, now seals the pilot chamber.
This psiton works surprisingly well. Given that it is my very first attempt at one.
This forum is a great source of information. Thank you all.
Plus, I learned from Kludgeboy@kludgeboy.com, how important the condition of the barrel face is, if you want to get a good seal.
I laid sandpaper on the benchtop. And, while holing the piece of pipe upright, slowly sanded that face as flat as possible. Going through three grits of sandpaper.
The piston slaps open lightning fast !
And seals immediately, when it shuts.
Sixth post
Well, that pretty much completes the valve build.
All those extra fittings off to the left are there because the grey one actually holds the 1" pipe that is the base of the barrel. And the rest is added so I can exchange barrels via a 1-14" female adaptor.
Plus, the valve can be easily dismantled for service. I could have made it smaller, if I just glued everything together. But I wanted it modular, like it is, so I could dismantle it.
And the remaining picture is two 'loads' that I built for it, early this morning.
I don't have a video camera. Nor one of those fancy machines that tells you how fast a projectile is going. So there will be no 'damage reports' as far as that goes.
But I'll probably go out and test shoot these two loads, sometime tomorrow or the next day.
If I do, I'll get pics of the results.
So far I know that pill bottles don't go all that far, because they tumble every which way. D batteries go pretty straight, but a level shot starts falling off, at about 40 feet.
One D battery was in such bad shape, that it literally exploded in the barrel, and came out in pieces.
Seventh post: refer to picture titled "seventh post"
And now, today's build.
My second one, ever.
The piston valve is constructed using a 1/2" tee, a 3/4" female adaptor, a piece of wooden dowel, some metal repair tape, some rubber, a screw and some marine goo.
The gun is about the same size as, and handles about the same, as my 12ga pump shotgun does. Only a lot lighter. LOL
I still haven't glued anything together. That'll come tomorrow, after I test shoot the other one again.
The barrel support is just a piece of pipe, turned sideways. And a couple of nylon wire ties.
I don't think I am going to sprinkler valve this one. I am going to see how the piston responds to just having the blowgun as a pilot valve.
Before finishing the glue-up, I will add a couple of fittings on the end of the valve, so I can change barrels.
Once I have the kinks worked out of the piston valve, and have it all glued together, I think I'll make some darts for this thing out of milk jugs and nails.
In the end, this one may end up being a work in progress. I'll probably change a few things as I can afford them.
Like the trigger, for one. I may end up buying another of the other type of blowguns. Then build up around that. Possibly adding a stock, and other niceities.



