Modding a "jar-top" sprinkler valve

Gun Freak · Mon May 31, 2010 7:48 pm

My buddy came over today for me to help him make his first cannon. It is a dual chamber, each with ball valves, for two shots. Valve is a 1" orbit sprinkler valve, but it is jar-top. I forgot to tell him to get the other kind, but I went ahead and tried to modify it anyway. I opened it up and saw the guide rail, and remember that I saw somewhere that when modding a jar-top you take that out. Out it went. I took out the solenoid, plugged it with epoxy putty. Drilled a 1/4" hole next to the center, JB welded a close nipple with 1/4" BV pilot. Is there something I did wrong here? Are these things even able to be modified?

Hubb · Mon May 31, 2010 8:16 pm

Yes there is. The rod should have stayed. Jartops are just as modifiable as the regular ones, and the same rules apply. You see,the guide rod acts not only as a guide, but it allows the pilot area to equalize (the air flows around the rod). Basically, what you've done, is made the equalization hole too big.

Gun Freak · Mon May 31, 2010 8:20 pm

Dammit, gotta go dig though the trash. That's what I was afraid of too, making the hole too big. Have I done everything else right?

Hubb · Mon May 31, 2010 10:01 pm

Yeah, everything else seems right. If you don't find the rod (or you do and can't get it back on), then try filling the hole with epoxy, then poke a tiny pinhole in the diaphragm. It won't be a permanent fix (eventually, the hole will weaken and expand) but it will get you by until you can replace it.

Gun Freak · Tue Jun 01, 2010 7:55 pm

Yeah that was an idea I had, I was thinking to JB weld the hole ion the center then poke a hole, but I think jsut using a nail would be better. Thanks for your help, as always.

Hubb · Tue Jun 01, 2010 10:03 pm

but I think just using a nail would be better

I'm assuming you're talking about replacing the guide rod? A nail is a good idea if you can find the right size. You may be able to find a finishing nail of the appropriate size, just make sure you polish it up really good because they may be coated or similar with imperfections.

If you have the time and patients, a better choice for the guide rod replacement may be to use a drill bit...

Gun Freak · Wed Jun 02, 2010 6:28 pm

What do you mean use a drill bit? If a standard nail won't fit in it then I can grind down a larger one to size and sand it smooth.

Hubb · Wed Jun 02, 2010 7:03 pm

If you grind down a larger nail, you are almost certain the have uneven spots on it. By using a drill bit, you can get precision much easier than trying to do it yourself.

Find one that is the right size and cut off the shank and epoxy it into the lid.

Gun Freak · Wed Jun 02, 2010 8:32 pm

Ok well I ended up using a nail, chopping the head off and then putting it in my drill and spinning it in some sandpaper to make it more even. Not perfect, but it works. I tested the valve on an old PVC tank and it shot good.

Hubb · Wed Jun 02, 2010 8:56 pm

Good to hear. I'm glad you got it working right (which reminds me that I do know what I'm talking about

). JK. When's it going on a launcher?

Gun Freak · Wed Jun 02, 2010 9:20 pm

Just got it functioning for now, I'll probably take the top back off and maybe put some vaseline on the nail to make it slide better, good idea or bad? It's gonna go on my buddy's dual chamber cannon tomorrow actually, so I'll probably post it. The two chambers are separated with ball valves and it has a bolt action breech loader for quick shooting.

1,000 POSTS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
W00T!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
:wav:
AND THE INSANELY OVER-CELEBRATING SMILEY FACE WAVE TO GO WITH IT!!!!!!!!!!!!!!!!!!! haha

Hubb · Wed Jun 02, 2010 9:29 pm

Use caution with Vaseline. It is a petroleum based lubricant and may (or may not) damage the diaphragm. If possible, use a water based lube, such as KY Jelly or similar.

And congratulations on your 1000 posts and may all your smileys be that exited from now on.

Gun Freak · Thu Jun 03, 2010 9:05 pm

I have some white lithium grease, how about that? The problem I am having is that it has to be filled from the pilot side in order to equilize fast enough. Even when I fill it VERY slowly from the chamber side it still pushed on the diaphragm and it opens, so I am going to sand down the nail some more and lube it, and if that doesn't work, I will have to sacrifice flow for function and add a stronger spring to it. I see you changed your title again, BTW