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a few Q's

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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a few Q's

Unread postAuthor: crsaz » Fri Apr 06, 2007 9:12 pm

okay since my combustion blew up I am thinking of building a pneumatic

1. if I use sch 80 chambers can I use sch 40 caps and will it be safe up to 100-125 psi?

2. I want to make it with a piston valve(barrel sealing) will I be able to make it in a 4 inch tee, if so will it be able to go up to 100-125 psi, if not will I be able to use a 3 inch tee upto that pressure?

3. if I use sch 80 for the chambers will sch 40 fittings be safe up to 100-125 psi?
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Unread postAuthor: Velocity » Fri Apr 06, 2007 9:15 pm

1) Depending upon your solvent welding skills, you would be able to bring a pneumatic up to 100 PSI and beyond just by using SCH 40 PVC. However, I would go with the SCH 80 chambers and SCH 40 caps, just to be safe.

2) Once again, it all depends on your skills. If you suck at solvent welding, then probably not. But if you are pretty good, you should be able to create a safe 4" piston valve that can handle 100 PSI.

3) ...umm...
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Unread postAuthor: hi » Fri Apr 06, 2007 9:26 pm

if you do suck at solvent welding, the do the very best you can the use some epoxy, then it should be safe. The answer to all your questions is yes.
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Unread postAuthor: benstern » Fri Apr 06, 2007 9:28 pm

Your combustion should not have blew up if you made it correctly, which I doubt you did. SCH80 is used for hybrids and pneumatics going over 300 psi, which means you don't need it.
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Unread postAuthor: crsaz » Fri Apr 06, 2007 10:01 pm

I built the combustion correctly it was cell core. the side blew out, the fittings were un effected

one more question
If I use all sch 80 pipes and fitting could I bring this gun up to 200+ psi?

If I can get ahold of some helium I want to try to get a lead or copper (golf ball) to or past the speed of sound :lol:
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Unread postAuthor: pyromaniac » Sat Apr 07, 2007 9:19 am

Yes you can take it up to 200 psi with sch 80. But i take my sch 40 nsf-pw gun all the way to 110. So for the 100-125 you don't need sch 80.
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Unread postAuthor: mopherman » Sat Apr 07, 2007 9:25 am

same here. save your money and use sch40. just dont get crazy and blow up.
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Unread postAuthor: imablackskater » Sat Apr 07, 2007 9:29 am

wow. listen most pvc should have a bunch of words on the side somewhere it will tell you how much psi it can take so subtract 50 from the given number and you should have the max you will be safe and with sch 40 you can go to 200 psi or even higher i took mine to 300 once. So dont worry about taking it to 125 but worry about your piston making skills.
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Unread postAuthor: crsaz » Sat Apr 07, 2007 10:30 am

you took 4 inch sch 40 to 200 psi? if so someone was looking out for u that day :angel11:
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Unread postAuthor: boilingleadbath » Sat Apr 07, 2007 11:03 am

Eh, no.
4" sch 40 PVC is rated to 220 psi, so the fact that it didn't blow up is not the least bit surprising.

That said, pressure rated sch 40 is fine for reasonable pressures in pneumatics, like what you plan on using.
The cell-core stuff... well, you know.

However, if you feel the extra safety margin of the sch 80 is needed, go for it.
It certainly won't be less safe.
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Unread postAuthor: crsaz » Sat Apr 07, 2007 11:12 am

4 inch sch 40 is rated to 110 psi
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Unread postAuthor: crsaz » Sun Apr 08, 2007 6:36 pm

I just got my air supply for this cannon even though I won't be building this cannon for a few months I just had to buy this, 20 pound bulk co2 tank and it was only $30 I can't really make out the entire stamp but the year is 99 they said it was in the garage when they moved in its empty right now but I'll get it filled soon

I have one more question

how much more speed could I get out of this gun with dual chamber sealing pistons rather than a barrel sealing piston in a 4 inch tee?

would it be possible to make vales like the supah at home(not as good ) but same principle and same size

sorry one more question,

will a modded srpinkler vave used to accuate a barrel sealing piston make it ans faster than say a half inch ball valve
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Unread postAuthor: cdheller » Mon Apr 09, 2007 4:55 pm

crsaz said
""I just got my air supply for this cannon even though I won't be building this cannon for a few months I just had to buy this, 20 pound bulk co2 tank and it was only $30 I can't really make out the entire stamp but the year is 99 they said it was in the garage when they moved in its empty right now but I'll get it filled soon""


Houston we have a problem

tanks have to be tested and re certified every 5-10 years .(10-20 dollers)
I'm not saying your tank is unsafe, but I dont think they will refill a out of date tank.

your milage may vary though
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Unread postAuthor: n00b » Mon Apr 09, 2007 8:02 pm

The main issue with dual piston valves is the added complexity of building and simultaneously firing two valves. As for muzzle velocity increases, as long as your valve building is up to par, a single 3 inch ported valve will have a higher flow coefficient (and thus produce higher muzzle velocities) than dual 2 inch ported valves, if GGDT is any indication. The other major limiter to airflow in a cannon is barrel diameter, but GGDT indicated that 2 inch and up shouldn't run into flow issues.

-n00b

(This is my first SpudFiles post, but I lurked on Spudtech for about a year, in case you were wondering)
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Unread postAuthor: crsaz » Mon Apr 09, 2007 9:20 pm

if the tank needs an inspection then I'll have it done.

I just found out the best news any spud gunner could ever hear

almost unlimited free pipe 8) 8) 8)

well my dads company does some work for a major pvc and other pipe manufaturer, maybe you heard of the manufacturer "cresline"

what does that mean for me? you ask

well it means free sch 80 pipe up to 8 inches
their sch 80 8" pipe is rated 250 psi


hmm maybe this connon will penetrate the sound barrier if I can get ahold of some helium. won't be dificult thanks to my connections with air gas.

I could possibly make the piston in a 6" tee :lol:


hmm ggdt says 1113 fps with this gun charged wsith 200psi of helium
thats with a 50 gram projectile an a six foot barrel and 1318fps with a 10 footer but I think thats extremly optomistic
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