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My first cannons, trouble with punisher valves

Unread postPosted: Mon Feb 13, 2006 1:30 pm
Author: JustinMeisse
Hi, I'm new here. I made these two cannons this week, the large one was more of a learning experience, hence the lack of handles. The smaller one is my attempt at a nerf cannon.

My number 1 problem is the screw on caps, they leak like crazy, I tried sealing the larger one with Loctite Plastic Epoxy but it didn't seem to help. What is a good epoxy and method to sealing these things?

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Unread postPosted: Mon Feb 13, 2006 2:23 pm
Author: saladtossser
cue DWV patrol
using cleanouts are a bad idea. you can solvent weld them on permenatly if you want

Unread postPosted: Mon Feb 13, 2006 2:45 pm
Author: JustinMeisse
what can I substitute a cleanout plug with for the punisher valve? Could I just put an end cap on the back and then cut a 1" long section of pipe, reduce it so it fits snug, and place it in the endcap to create a ledge for the diaphragm?

The smaller gun isn't going to use large amounts of air pressure, I want it to be a nerf gun. I stuck a dart in the end and one pump of the foot pump shot it out with considerable force.

Unread postPosted: Mon Feb 13, 2006 3:41 pm
Author: spudshot
oh my.... ABS + DWV + high pressure = accident waiting to happen.

re build these with proper NSF-PW marked fittings only. cleanouts have failed on just combustions, pneumatics will make em pop quick

Unread postPosted: Mon Feb 13, 2006 5:13 pm
Author: JustinMeisse
Here's my plans for a modified punisher valve that removes the cleanout from the equation while also providing a triple layer of PVC to tap through.

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Let me know what you think.

I have one other question, does the schrader valve have to be placed behind the diaphragm for this to work? I was thinking of placing it on the opposite end of the chamber so I can attach one of those small bicycle shock pumps to it without using any hose.

Unread postPosted: Mon Feb 13, 2006 5:52 pm
Author: boilingleadbath
Filling behind the piston/diaphram isn't strictly neccecary... but if you don't, you'll have to use a spring to get it to seal initialy.

And although I'm not sure those are ABS couplings, they should be replaced if they are - mixed plastics don't bond very well.

Unread postPosted: Mon Feb 13, 2006 6:12 pm
Author: JustinMeisse
A spring eh, interesting. I'll be mounting the schrader near the back after all, I did a test fitting and it's easier to have the pump handle facing away anyway. I'll make sure everything is ABS when I purchase more supplies, neither cannon works and are using dwv parts so I'm going to cut them up for their pipe.

I just noticed something, all my pipe has squares on it that say "NSF-dwv" as well as "NSF-pw", so what is it? dwv or pw, or does that just mean it will work in either pw or dwv environments?

Unread postPosted: Mon Feb 13, 2006 9:33 pm
Author: CS
[quote"JustinMeisse"]I just noticed something, all my pipe has squares on it that say "NSF-dwv" as well as "NSF-pw", so what is it? dwv or pw, or does that just mean it will work in either pw or dwv environments? [/quote]

Can you say G-o-o-g-l-e? Sorry if that seems rude, but this is the perfect question for a search engine.

Dont use ABS because almost always it celluar core (google if you dont know what that is). Next time just dont use threads rather just use a PVC cap. If you felt so inclined to as teflon tape the hole threads of the cannon that would work.

Unread postPosted: Tue Feb 14, 2006 4:12 pm
Author: boilingleadbath
Yeah, I checked... 45 seconds with google scored me answear - a preliminary search is always nice.
And yeah, if both are there, it means it has been verified for both applications.

Unread postPosted: Tue Feb 14, 2006 5:38 pm
Author: JustinMeisse
Thanks for the help, I never really thought pneumatics would be more powerful than combustion. I'm really bummed out that the t-section I used on my small gun is DWV, it has a really nice grip to it.

I'm going to experiment with different valve designs this week and see if I can get a new gun ready this weekend.