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PVC and copper

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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PVC and copper

Unread postAuthor: airman » Tue Dec 02, 2008 6:23 pm

I'm trying to build my first airgun and I'm having a hard time finding the right material in canadian hardware stores. I finally managed to find PVC at Home Depot but still, not a big choice. I think I'll be getting everything at Fastenal.

My first question is how to make a ½" copper barrel stick to PVC if I only want to go through a PVC 3" capped pipe acting as my air chamber and be really air tight and pressure resistant. I mean the copper barrel would stick out an inch or two in front of the PVC air chamber.

The air supply would come out of the PVC chamber from the other end of the copper tubing screwed to the PVC cap.

The ½" tubing would then be connected to a ½" QEV (¾" threaded QEVs seem impossible to find!) and then connected to the ½" barrel, and finally get back through the air chamber and get out at the other end. I really hope you can picture what I mean.

This design is to build a more compact gun. By integrating the barrel inside the air chamber, I still can have a fairly long barrel without having and overall long airgun.

Any suggestion would be appreciated.

Question number 2: is there an advantage in using CPVC over PVC?

Thank you
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Unread postAuthor: rp181 » Tue Dec 02, 2008 6:41 pm

Normal PVC is fine for this application. CPVC is better for Higher temperatures and industrial applications. It has flame retardant properties, and chemical resistance.

As for the copper, look for these types of things:

http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100159268&N=10000003+90051+528105
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Unread postAuthor: airman » Tue Dec 02, 2008 6:44 pm

Thanks for the CPVC/PVC comparison but I don't want a link for the copper. I need an answer because I know a lot of you here joined copper to PVC. What did you use? Epoxy?

And your link doesn't show anything else than a blank Home Depot page.

Any of you ever tried: http://www.homedepot.com/webapp/wcs/sto ... ogId=10053

Is it good with air?
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Unread postAuthor: Eddbot » Tue Dec 02, 2008 6:52 pm

click the link, it's for a copper to pvc adapter, although, i don't think it'll work for a coaxial

epoxy would work fine, you could search around for a special adapter, but epoxy seems to be the easy route
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Unread postAuthor: pocket » Tue Dec 02, 2008 7:11 pm

epoxy could work but there are also fittings that go on the copper via solder and then on the male end there are threads then all you have to do is find the fitting that fits the threads looks like this
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Unread postAuthor: TurboSuper » Tue Dec 02, 2008 9:05 pm

I see some fully threaded copper pipe at Canadian Tire sometimes, get some of that and a reducer bushing.

Another option would be a long, threaded galvanized steel/copper nipple and a pair of threaded adaptors at either end.
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Unread postAuthor: airman » Tue Dec 02, 2008 10:19 pm

Just to make sure we all understand each other, I'm talking about a ½" barrel going through the whole 3" air chamber and getting out the front and rear ends. I will drill a hole in each cap so the barrel can go through. The drawing isn't exactly what I meant... The pipes won't be threaded.

Pocket, what is the material used for your fitting?
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Unread postAuthor: airman » Wed Dec 03, 2008 11:13 am

It's so damn hard to find a QEV in this world!!! :x Why the hell?!?

I only managed to find one ½" threaded aluminum QEV at Fastenal in Quebec and it's not in stock! Hope I'll be able to screw it to copper or brass fittings... Even when searching Google, you only find QEVs in China! Is it a prohibited item? Are they anticipating that people will use those valves to create weapons of mass destruction? It has to be an anti-terrorist law passed by Bush!!! :x :wink:


And please, some questions remain unanswered...

Thank you very much


Sorry, MrCrowley...
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Unread postAuthor: jackssmirkingrevenge » Wed Dec 03, 2008 12:02 pm

This one seems to be in stock ;)

As to joining dissimilar materials, you can have a browse through this epoxy casting how-to.

edit: shameful spelling of "dissimilar" :oops:
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Last edited by jackssmirkingrevenge on Wed Dec 03, 2008 3:23 pm, edited 1 time in total.
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Unread postAuthor: airman » Wed Dec 03, 2008 12:07 pm

It's exactly the one I was talking about. It says "in stock" but the store still has to order it and it will take 2 to 3 days... I know I just called... :wink:

Thank you for the procedure. It will be quite handy. :)
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Unread postAuthor: jackssmirkingrevenge » Wed Dec 03, 2008 3:28 pm

Mastery of the epoxy technique will allow you to create effective launchers at low cost, using very little standard parts:

Image

The disadvantage of the technique however is that aside from being very unforgiving, the resultant launchers usually can't be serviced, so it is probably best used in conjunction with standard store bought parts.
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