Well.... I'm an idiot. I recently built a PVC air cannon with a a 4" air tank with 2 90 degree elbows and a 4'-2' reducer. I was shooting it a moth ago out in 15 degree Fahrenheit weather at no more than 75psi MAX. Today, while glueing some barrel attachments for a tennis ball barrel I ordered, I read on the side of the 4' pipe NOT FOR PRESSURE. I don't know if i got lucky or what, but some people seem CRAZY over not pressure rated PVC. Mind you now I'm not taking this thing over 60psi. I'm going to buy some of this fiberglass filament tape from staple http://www.staples.com/Staples-Fibergla ... uct_456927 and besides wrapping a couple layers of it around my air tank, will it be safe to still pressurize it to 60psi. It would be great if someone could give me the max pressure for the 4', sine it HAS to be able to hold pressure. Even though the pipepipe that clearly says on the side NOT FOR PRESSURE
You need to do some studying! Pine tree for a back stop? Who lives on the other side of that tree......Things that make you go hmmmm.
Posted: Mon Apr 08, 2013 7:07 pm
by millons70
The pine tree was just there to hold up the board :p. There are houses 500 feet behind.
I like to live life on the edge.
P.S. On a serious note, it was just packed snow that if it fails to obliterate on impact, it gets broken apart flying through the bush. But my tennis ball and golf ball barrel are suppose to arrive in 3 days and I will definitely be using a better backstop when shooting pop cans :p
Posted: Mon Apr 08, 2013 7:12 pm
by millons70
I appreciate that link! So I'm safe if i stay under 90 psi. I'm just confused on the required minimum burst pressure? That chart is for non pressure rated pipe correct? And does that go for my 4' fittings that i believe aren't pressure rated as well?
Posted: Mon Apr 08, 2013 7:15 pm
by Technician1002
The big problem with PVC is the failure mode. It shatters.
See the test cannon in my sig. It has some material discussions.
Posted: Mon Apr 08, 2013 7:57 pm
by millons70
That's what i'm worried about. Will the 4' shatter if i only fire at 60psi max? And will using fiberglass filament tape help aswell even if it does decide to explode on me?
Posted: Mon Apr 08, 2013 8:13 pm
by mattyzip77
It could shatter at 20 psi...Make a new cannon dude. Re use the 4 inch for a cheap o conbustion cannon or a barrel. Also not one of your fittings are pressure rated either... Is losing a eye or killing yourself worth it??? Start over from scratch!!!!
Posted: Mon Apr 08, 2013 8:15 pm
by millons70
well shit...... And wrapping 3-4 layers of fiberglass filament tape won't work?
Posted: Mon Apr 08, 2013 10:07 pm
by evanmcorleytv
millons70 wrote:well crap...... And wrapping 3-4 layers of fiberglass filament tape won't work?
NO. I've had parts explode on me before, it's VERY frightening, and sudden, and has a ton of potential to cause injuries.
Posted: Tue Apr 09, 2013 6:20 am
by millons70
Well looks like I need to make another cannon. And how far does this shrapnel explode?
Posted: Tue Apr 09, 2013 12:14 pm
by mattyzip77
Are you serious???? Does it really matter???? Just as far as a grenade!!! I would be more worried about those DWV elbows you are using. If you even look at those things the wrong way they break. :laughing3:
Posted: Tue Apr 09, 2013 5:51 pm
by millons70
I'll search myself too, but anyone have a design using 3 inch parts since my menards has pressure rated 3' with fittings I believe. I'm want one to have about the same size air tank if not larger, using about 10 feet of 3'.
Posted: Tue Apr 09, 2013 6:08 pm
by millons70
And any of the elbows that are raised near the connection aren't pressure rated? I read the wiki link, so are both my elbows non pressure rated? It doesn't seem to say if they're pressure rated on menards at http://www.menards.com/main/plumbing/ro ... c-9383.htm
I apologize for all these questions. I thought I knew what I was doing. I just don't want to make the same mistake again and waste even more money.