Build A Net Gun

Step 5 Assemble And Test Valve and Pressure Chamber

Once your pressure chamber has cured for 24 hours, and your trigger valve has cured long enough for the epoxy to reach full strength, you are ready to assemble and test the trigger valve and pressure chamber.

Supplies
Assembled pressure chamber from step 3
Assembled trigger valve from step 4
PVC pipe joint compound (pipe dope) such as this
Source of pressurized air
Wrench or channel lock pliers
optional 5 gallon bucket filled with water

Assembly

• Thread your trigger valve onto the pressure chamber for a test fit. The arrows on the side of the valve point in the direction of the airflow, they should be pointing away from the pressure chamber. The goal is to get the blow gun situated vertically in front of the pistol grip to act as a trigger. Use the channel lock pliers or adjustable wrench to get the trigger valve as tight as possible. If the sprinkler valve bottoms out before the blow gun trigger is vertical, you can file off small amounts of plastic from the end of the threaded street elbow until it fits perfect.
• Fill the chamber to 80 psi. Aim in a safe direction and briskly pull the trigger, you should get a loud POP and feel a bit of recoil. Here is a great troubleshooting guide if your valve does anything other than go bang.
• Once you have a successful test, remove the trigger valve. Apply the pipe joint compound to the street elbow threads and tighten down the valve once more.
• Optional: perform a leak test. Pressurize your chamber to 80 psi. Fill a 5 gallon bucket with water and dip the assembly, look for any bubbles. Tighten and add pipe joint compound to areas with leaks. If the PVC joints are leaking on the pressure chamber, you can apply a vacuum and suck super glue into the voids.

Comments

[Dnorton]

Here is where it is leaking. It is passing the diaphragm and out the valve outlet but I cleaned it as well like the troubleshooting guide said and it made no difference. Is there anything else it could be?

[Dnorton]

Oops wrong image but the inner ring that the diaphragm seals is where it is leaking.

[crispyjones]

The metal tube/guide rod in the center is connected to the nipple in the middle of the outlet port, lower left pic indicated with the pencil. Make sure this is sealed, you may have a small imperfection in the epoxy that is allowing air to escape. This seems like the most likely culprit. A second thing I notice, and maybe you took it out for the picture, is you are missing a plastic ring. The white ring in the upper right pic (yours may be black) fits underneath the diaphragm. The upper left pic is a taken apart view in order of reassembly left to right, it shows the ring installed. Make sure you have the valve oriented correctly relative to the pressure chamber. The arrows point to the outlet and away from the pressure chamber and towards the launcher section. Let me know how you make out.

[kingcole816]

My valve is leaking air through the outlet and won't hold any pressure. My first inclination was that the diaphragm was defective, but i replaced it and I'm still having the same issue. My valve doesn't have the bleed hole in the outlet port, so I'm wondering if that could be creating the pressure issue. It still has the open notch that is connected to the bleed hole, but the hole itself isn't there. It's the model you recommended, but I'm working with it years after you wrote the article so they may have redesigned. Hopefully you still check this forum because I *really* want to finish this thing

[crispyjones]

Make certain that the valve is oriented in the correct direction, the arrows on the inlet and outlet ports should be pointing away from the pressure chamber. I am assuming the valve still has the metal tube going through the center of the diaphragm. This tube has to go somewhere, blow in it, if air comes out the "notch" than you need to plug wherever it is escaping. If it seems like the air is going in the pressure chamber, then you absolutely have the valve on backwards. It might be easier to simply drizzle epoxy into the metal tube directly, you just have to be careful to clean the outside surface of the tube so the diaphragm can slide freely. Good luck.

[Kantor]

Do you think that you would be able to make a video on how to make the trigger setup?

[fenderoneoone]

im worried about how the air is going to get to the net firing device, when i blow into the green valve in the correct direction and pull the trigger the air just comes out the bottom of the air gun trigger device... dont want to carry on untill i know what the problem is

[crispyjones]

I don't think blowing in the valve is a valid test. You need enough pressure to overcome the internal spring, I don't think anyone could do that with their lungs.

[Dnorton]

I haven't had time to work on it today but last night i cleaned the valve again and it pressures up to 80 psi now when it used to not make it past 40 but it is still leaking with both diaphragms the one with the larger equalization hole and the normal sized one so I think it might be the epoxy I will have to check that tomorrow.

[Dnorton]

I just did my pressure test on Thursday and the valve is leaking around the inner perimeter. It will get up to 40 psi and fire off cleanly but it will not pressure up past that. I read the troubleshooting guide and enlarged the equalization hole in the diaphragm and there was no change. I replaced the diaphragm in case it was torn and there was no change. So this Saturday I filled the pressure chamber with a little water in the front and and with water sealing the valve instead of air it went up to 80 psi. But I cannot get the orbit valve to seal with air pressure. Was this a problem for anyone else or did I do something wrong? I did epoxy the bleed holes on the valve.

[crispyjones]

I think I can help, but I am not clear on what you mean by the "inner perimeter." Here are couple guesses. If it is leaking around the threads of the jar top, you probably just need to tighten the ring some more. This easier said than done, I have some enormous channel lock pliers I use, an oil filter wrench might work, and smearing a little pipe dope should help as well. If it is leaking past the diaphragm, you will get a slow leak out of the valve outlet. This can be caused by debris (usually bits of PVC) on the sealing surface of the valve and diaphragm, clean both surfaces thoroughly and it should clear up. If I didn't guess right. Please let me know exactly what make/model valve you used and where it is leaking (dunk it in water while you are pressurizing it).

[geek27]

Hello, I am currently fabricating my very own net gun, but I have run into a problem that I was hoping you might have an answer to. First of all, I have completed both the pressure chamber and the trigger valve assembly. However, I have noticed that the threads of the 1" Slip/MPT Street Elbow on the end of the pressure chamber does not thread all the way into the sprinkler valve. After threading it about 3/4 of the way, it becomes tight and is impossible to screw in the rest of the way. In a dry fit test, it leaks air at low pressures (around 20-30 PSI). I have not applied the pipe joint compound yet, but I am concerned that if I do, the pressure chamber might still leak. I am wondering whether I should construct a new pressure chamber with a 1" Slip/MPT Street elbow that threads all the way into the sprinkler valve, or if I should apply the pipe joint compound and thread the sprinkler valve in 3/4 of the way. Finally, when I do decide to apply the pipe joint compound, would it be okay if I put teflon tape on the 1" Slip/MPT elbow before applying the pipe joint compound, or would the teflon tape prevent the two threaded parts from adhering? Thank you, help would be much appreciated!

[crispyjones]

I would put on the pipe joint compound, it will help seal it and act as a lubricant, hopefully allowing you to thread it farther in.

[crispyjones]

Sorry, didn't answer your whole question. You can use Teflon tape and pipe joint compound together. The only time I did this was when I had a threaded elbow that bottomed out in the sprinkler valve, as you are having the opposite problem, it might be overkill. Additionally, pipe joint compound is not an adhesive, you can still disassemble the threaded joint after applying, it will just be a little messy. I would start with pipe joint compound then leak test, if you still have leaks, try pipe joint compound and teflon tape together.

[geek27]

Ah, thank you, that answers my question. I'll try that and see if it works. I noticed that putting Teflon tape of the 1" Slip/MPT elbow produced a nice seal at pressures around 40-50 PSI, so I will try the pipe joint compound and see if it leaks, after which I might try the Teflon tape/pipe joint compound combination. Thanks for the help!

[geek27]

I finally got the air compressor, and I have found that even at 100 PSI, Teflon tape covered in pipe joint compound seems to do the trick, and I cannot spot any leaks. Just to make it more leak proof, I will probably apply JB-Weld to the spot where the exposed threads meet the sprinkler valve, covering any potential small leaks. It's coming along well so far, and all I have left to do is make the net (waiting for shipment). Here's a picture of how it's coming along. The name you see there was a joke sent to friends, it says The McSlumdog-Cruelty-Horse-Killing Special

[geek27]

Whoops, sorry for the double-post, picture didn't attach, hit the wrong button. Here it is:

[crispyjones]

Looks great, thanks for posting the pic. If you don't have any leaks I would stay away from the JB-Weld, once you use it everything will be permanent. Sounds like you haven't built the net yet, check the comments for some helpful hints and encouragement from SkipperOf and tk4717.