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QEV's and PVC

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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QEV's and PVC

Unread postAuthor: Flying_Salt » Wed Jun 20, 2007 12:23 pm

For my entertainment this summer I am thinking I might build a qev marble gun that I won't spend a whole afternoon pumping up like my other one.
I can't afford metal pipe, nor do I have the tools or experience to solder it. So I was wondering if it would be ok on the pvc threads if I connected them to a qev or a safety valve. I know that unscrewing it is bad for the threads so I was just wondering about leaving it there.

Thanks,
Salty
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Unread postAuthor: noname » Wed Jun 20, 2007 12:39 pm

It'll be fine. Where'd you hear that unscrewing was bad for the threads?
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Unread postAuthor: hi » Wed Jun 20, 2007 12:51 pm

they are all npt threads so it would be fine.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

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Unread postAuthor: Flying_Salt » Wed Jun 20, 2007 12:57 pm

noname wrote:It'll be fine. Where'd you hear that unscrewing was bad for the threads?

Someone was saying how the metal chews up the pvc threads, I can't remember who or where it was.

Well, since it won't explode in my face, I'd say production chances are going up :D
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Unread postAuthor: Velocity » Wed Jun 20, 2007 1:08 pm

It was probably in the launcher failure log, where my piston valve failed because the metal bushing "bit" too tightly into the PVC female adapter.
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Unread postAuthor: Flying_Salt » Wed Jun 20, 2007 2:21 pm

Darnit I just ran into a problem. When I looked around McMaster for qev's I got these funky-looking solenoids, and when I looked at home depot's web site I got trash can storage.

Does anyone know a) where on McMaster (or preferably home depot or other local store) I can get a qev and B) what a good size is for a 3'' chamber and a 1/2'' barrel.
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Unread postAuthor: chartreusesnot » Wed Jun 20, 2007 2:25 pm

On the mcmaster QEV section, go to the top of the page, and you will see 3 or 4 different pages. Click the last one. This will bring you to the right qev section. the largest qev they have is 3/4 inch.

edit: the page is 941
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Unread postAuthor: noname » Wed Jun 20, 2007 2:32 pm

A 3/4" QEV is $20 on McMaster, part number 6646K23.
Be sure to bookmark that page. I've been there about 10 times and it still took me 10 minutes to find it.
You can also search Exhaust Control Valves, and then scroll down a ways.
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Unread postAuthor: hi » Wed Jun 20, 2007 2:34 pm

even if its a 1/2'' barrel, still get a 3/4'' QEV, ou will get slightly better proformance.
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Unread postAuthor: Flying_Salt » Thu Jun 21, 2007 6:41 pm

Ok, I was searching around while I was designing it to find out where it was filled from etc. and I realized that it was piloted and filled through the same hole. I don't have an air compressor so I came up with this idea; attach a tee to the qev and have a schraeder and a ball valve on the tee.

Image


EDIT: Another thing I was wondering was what size of pipe or coupling do I need for a ghetto breech on 1/2'' pipe? (I'm planning to O-ring it)
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Unread postAuthor: PVC Arsenal 17 » Thu Jun 21, 2007 7:14 pm

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Unread postAuthor: Acdcmonkey1991 » Thu Jun 21, 2007 7:22 pm

I actually used a brass bushing on one of my cannons, threaded into a plastic 1/2 in. elbow. i was looking at it a week after I had finished it, and the plastic elbow had cracked! Long story short, the bushing "killed the plastic threads on my gun.
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Unread postAuthor: Flying_Salt » Thu Jun 21, 2007 7:26 pm

Whoah...it's been under my nose this whole time. I hope you don't mind if I copy your valve setup.

I was also planning to make a barrel support tee thing, but I'm gonna keep my ghetto breech idea.
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Unread postAuthor: Velocity » Thu Jun 21, 2007 7:29 pm

Flying_Salt wrote:EDIT: Another thing I was wondering was what size of pipe or coupling do I need for a ghetto breech on 1/2'' pipe? (I'm planning to O-ring it)


1/2" coupling... Come on Salty, use that thing on your shoulders :lol: :D [/i]
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Unread postAuthor: PVC Arsenal 17 » Thu Jun 21, 2007 7:48 pm

Flying_Salt wrote:Whoah...it's been under my nose this whole time. I hope you don't mind if I copy your valve setup.

I was also planning to make a barrel support tee thing, but I'm gonna keep my ghetto breech idea.


Go for it. My breech idea really only works with .40 blowgun barrels because the quick disconnects fit right over them. Whatever you come up with, good luck!

rmich732 wrote:
Flying_Salt wrote:EDIT: Another thing I was wondering was what size of pipe or coupling do I need for a ghetto breech on 1/2'' pipe? (I'm planning to O-ring it)


1/2" coupling... Come on Salty, use that thing on your shoulders :lol: :D [/i]


hehe... it happens.

Check out this page: http://www.flexpvc.com/cart/agora.cgi?p ... VC-Couples

Somewhere on there are extra long couplings. They might work better if you decide to make a longer breech.
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