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My First Two Cannons

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: williamfeldmann » Tue Oct 16, 2007 11:46 am

I absolutely agree with BC.

DWV is fine for certain things. It makes excellent silencers and bipods and stuff. The problem is not necessarily that people don't know any better, its that they go to the HD or Lowes and buy the 3 and 4 inch fttings that are displayed right next to all the pressure rated fittings.

The second cannon shows a good bit of design and evolution from the first. But none of us learns without first making mistakes. Chalk this up as a lesson learned.

I can't wait to see some pics of it rebuilt and working at true potential.
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Unread postAuthor: dapallox1 » Tue Oct 16, 2007 1:45 pm

Thank you all for the suggestions and complements. I am aware of the usage of DWV to be very unsafe. And I had no idea that the elbows were DWV. I have a few questions though. How can I tell the difference from a DWV elbow and PVC? Also, on my next (safer) cannon, I want to use a quicker release valve. Which is better, a piston valve, or diaphram valve? And, how could I get the glue off of Lauren to remove the chamber?
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Unread postAuthor: williamfeldmann » Tue Oct 16, 2007 3:02 pm

PVC cement doesn't dissolve very well. Your best bet is going to be cutting it off. The end cap is okay from what I can see, so just cut at the bell fitting and replace it.

If you pick up any pvc fitting, somewhere on it will be lettering. Part of that lettering indicates size, brand, etc. and another part will say something like NSF-DWV or NSF-PW. DWV = drain waste and vent PW = potable(drinking) water. PW is pressure rated solid core pipe. Everything you use that is plastic should say pw, including any pipe. Even if it has a pressure rating on it, look for pw. Just because something has "sch XX" on it does not mean pressure rated.

As for speed of release, you will not notice much difference between a piston and diaphram. Both are fast and can be built to the same size. If you really want power and speed, burst disk is the way to go. They have the full, unrestricted flow of a ball valve, so no twists and turns, and they burst faster either of the sealers can open.
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Unread postAuthor: DYI » Tue Oct 16, 2007 4:47 pm

PW has nothing to do with pressure rating, but most PW plastic pipe is pressure rated. The only surefire way to tell if plastic pipe is pressure rated is if a rating is printed on it.

It seems to be a common misconception that DWV and PVC are different things. PVC is a material, while DWV is an NSF rating meaning Drain Waste Vent. Some DWV rated pipe is also pressure rated, but as far as PVC goes, all DWV PVC fittings are non pressure rated, hence the usage of the three letter "DWV", as opposed to the three word "non pressure rated".
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Unread postAuthor: dapallox1 » Tue Oct 16, 2007 5:36 pm

okay, I see the difference between non-DWV and DWV. Thanks, but how the hell am I going to get this sprinkler valve off now? I can get the barrel side off, but not the chamber side, it is glued in there. There isn't a spot i can cut it because then i wouldn't be able to connect anything there.... what now?

EDIT: I think if i cut it right before the one inch male-threaded adapter, that it will fit snuggly into a 1.5" tube.
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Unread postAuthor: thespeedycicada » Tue Oct 16, 2007 5:44 pm

well not to be mean but the first one looks (and probaly is if you take it to 100 psi) like a badly made ghetto pipe bomb.The second one just is an overly complicated pipe bomb do reaserch before you build a gun those two are very unsafe.well if you need to rebuild the cannon completly take off the sprinkler valve and rebuild with pressure rated pipe.
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Unread postAuthor: dapallox1 » Tue Oct 16, 2007 5:58 pm

thespeedycicada wrote:well not to be mean but the first one looks (and probably is if you take it to 100 psi) like a badly made ghetto pipe bomb.The second one just is an overly complicated pipe bomb do research before you build a gun those two are very unsafe.well if you need to rebuild the cannon completely take off the sprinkler valve and rebuild with pressure rated pipe.


The first one is completely fine, the tape on it makes it look 'ghetto.' I only put it on there because i was bored, and around the valve because it was holding a piece of plastic in place so that the fill valve wasn't accidentally pushed in do to it being stood up that way. And it can also go to 120 psi safely. The second one, i have been told plenty of times now, i need to replace the elbows. Well, I'm not going to replace anything on it. I'm just going to build a whole new one, and use this for a different project. I am going to salvage the sprinkler valve though.
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Unread postAuthor: sandman » Tue Oct 16, 2007 6:01 pm

and you said it was glued so you have two options
1. cut off the pipe and dremel out the inside where the pipe is until you can insert another pipe
2. cut off the pipe and dremel the outside until it fits inside some size fitting like a coupler
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Unread postAuthor: Fnord » Tue Oct 16, 2007 6:04 pm

Does the second one have a pressure rating on the barrel? Don't scrap the pipe if it does. I'd also save the capped half of the chamber if it is rated.
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Unread postAuthor: dapallox1 » Tue Oct 16, 2007 7:43 pm

Everything is rated but the elbows
Do these ratings apply for connection pipe too? http://www.northernpipe.com/NPP_PVC_Hom ... _vent.html
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Unread postAuthor: DYI » Wed Oct 17, 2007 4:39 pm

You bought the pipe from that site? Most DWV PVC, and all DWV PVC at hardware stores is not pressure rated. That site specifically says that their PVC is "dual marked".
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Unread postAuthor: dapallox1 » Wed Oct 17, 2007 4:50 pm

bob-a-lu wrote:will somebody please go ahead and close this? its stupid all the replys are about the parts being dwv, and that he needs to scrap it hey if he doesn't listen to us who cares thats his problem. so somebody just please lock this up. :!:


Hey, watch it... I am going to listen, if you would read what i wrote, i said that i am going to scrap it and build a new one with that valve... so chill out and think before you speak. As to you DYI, I didn't buy the pipe from there, i was just wondering if those ratings were for all DWV pipe, thank you for clearing that up.
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Unread postAuthor: thespeedycicada » Wed Oct 17, 2007 6:08 pm

ohh sorry if you took that first part of my post seriously i was kidding i realized it was pressure rated without dwv.But i dont think its "safe" to take pvc to 120 psi but im very cautious with pvc after my horrible hybrid accident.Bob-a-lu please be quiet dapallox may be a newbie but dont bash him because youre a a$$hole/bully who picks on people all the time because they are new you're post was stupid,didnt do anything for dapollox or this topic,and was un-called for.
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Unread postAuthor: dapallox1 » Sat Oct 20, 2007 5:01 pm

It's cool, now that I re-read that, I don't see why I got mad about it. Oh well. Well, I went back to Home Depot and bought pieces for my 2" piston valve and I have it all put together. It won't be until monday that I get to test it all out though. But I was very cautious on picking out pressure rated parts! :D
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Unread postAuthor: BC Pneumatics » Sat Oct 20, 2007 7:24 pm

That's good to hear. Hopefully others will see this topic and build safely from the start. :)
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