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Question about fittings....

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Question about fittings....

Unread postAuthor: Scuds20 » Tue Apr 10, 2007 10:16 pm

So I decided to build a SpudGun today... Just looking for a little help here.

I know you're supposed to use sch.40, and I was able to find that for the chamber and barrel... My question is, none of the fittings, end caps, bushings, etc, were marked as sch.40, just DWV (I think, some 3 letter random acronym.) Should this present a problem or am I going to be ok?

Second question, the directions I found called for a chamber (3" x 12" long) and a barrel (1.5" x 51" long) with a breech loading/interchangable barrel system. This sound about right, or should I change some stuff up?

Thanks a lot for tolerating my noob-ness.

Edit: All PVC...
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Last edited by Scuds20 on Tue Apr 10, 2007 10:30 pm, edited 1 time in total.

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Unread postAuthor: keep_it_real » Tue Apr 10, 2007 10:21 pm

Some people use DWV but I would find fittings that say NSF-PW. They are pressure rated and just safer. The dimensions sound fine...
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Unread postAuthor: skinner » Tue Apr 10, 2007 10:29 pm

Well, first off, DWV stands for Drain-waste-vent, so that gives you an idea of what its intended for, you could use it, but it would be highly unsafe and it would be recommended that you try and get some Sch 40 fittings, try mcmaster, they should have all you need.

As for the second question, I read somewhere that a good ratio to have on a pneumatic gun was around 1:1 (correct me if Im wrong) so in order to have that ratio, you would need to make your barrel 24" long.

But, dont just go by my words, get some imput from other members.

Cheers.
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Unread postAuthor: hi » Tue Apr 10, 2007 10:30 pm

with that size, dwv is ok if it just a combustion, but make sure it sch40 dwv. they make some that is smaller. just compare it with that wall thickness of the pipe. you might want to go around it a couple times with duct tape, but thats just me, it will probbaly be fine the way that is right now.
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Unread postAuthor: boilingleadbath » Wed Apr 11, 2007 6:41 pm

Duct tape doesn't really do anything, other than providing a bit of protection from UV irradiation.

Anyways, I don't really recommend DWV fittings... although people normally get away with using them.
In case you decide to be lazy with your health, I'll mention that fittings tend to fail by becoming unglued, launching themselves inline with the pipe's direction. Ya wanna guess where you don't want to be standing when that happens?

That is, don't stand behind DWV fittings while they are holding pressure.
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Unread postAuthor: Bubba05 » Sat Apr 14, 2007 8:17 am

Dont use DVW fittings they fracture and people get hurt. I got a mate thats still digging PVC outa his arm!

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Unread postAuthor: lukemc » Sat Apr 14, 2007 9:22 am

ok since this is in the combustion section and its a first cannon i guessing your just going to be using spray deoderant power and in that case DWV if fine


As for the second question, I read somewhere that a good ratio to have on a pneumatic gun was around 1:1 (correct me if Im wrong) so in order to have that ratio, you would need to make your barrel 24" long


well one this isnt a pneumatic so i dosent realy matter but pneumatics generaly work well with a ratio bigger than 1:1 like a 3or 4:1 is not uncommon
however a 1:1 is good for combustions
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Unread postAuthor: WOW!! » Sat Apr 14, 2007 11:38 am

DWV can mean Sch40, Sch80 Sch20 etc. All that means is that the pipe and fittings allowed to be used in drain,waste and vents systems for homes and other buildings. They are approved by code. But you can use them, but I really wouldnt recommend it.

You should be able to find Sch40 end caps because they are cheaper to make then the Sch20 ones. And on Burnt Lake on there tests they said the .8:1 was the best performance one and they used 1.5:1 on most of there other launchers.

Good luck to ya.
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