SpudFiles

ok so i'm making my golfball cannon after i found a supply shop near my house that sells SDR 21 (20 feet for 10 bucks ).my chamber is 3inch dwv pvc. BUT.. it's gonna have pressure rated fittings that are almost glued directly together.so it's almost a double layered chamber. in this order... end cap, coupling, coupling, bushing. kinda like PCGUY's mad-caddy's chamber. is that ok?

I would think that would work, but you would have to make sure the fittings are up against each other, which requires lots of annoying measurements which usually come out wrong anyway. I would just go to home depot or someplace and get a 2' section of nsfpw 3"

It would be nice if you gave a better description of the gun; pneumatic or combustion?

Mad-Caddy is a pneumatic. It is not a good idea to use non-pressure rated PVC for the chamber of a pneumatic. Even if your fittings are "almost glued directly together" you stll have the problem of the longitudinal load.

Don't waste your time trying to use the piece of DWV, which is only worth a buck or two anyway. Get rated pipe.

ok i also forgot to post this but i came back from lowes and discovered that the bell reducers are dwv. and so are the bushings!!!!!! so what do i use?

Find yourself some pressure rated pipe. Have a good look through the yellow pages for a pipe supplier. They should have all the pressure rated pipe and fittings you'll need. If all else fails you can always order online through http://www.mcmaster.com or http://www.savko.com.

If you're making a combustion launcher, you should be fine. Many people have used DWV (and still do) for combustions. However, if you're planning to make a pneumatic, you should scrap both the DWV pipe and fittings (or save them for a combustion) because pressurizing that stuff is very unsafe. Don't skimp out to save a couple bucks - you could end up hurting yourself or worse.

The ONLY things that I would ever use DWV in a air cannon would be couplings and reducer bushings. When you do this you layer over things and it will hold up, but that is only if it is a last ditch effort.

Many users on Spudfiles who are not allowed to order over the internet have found a Fastenal location near them. I myself have found them to be very reliable, and they have a wide variety of fittings. Sadly, they carry no SDR-21.