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Soda bottle or PVC?

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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Unread postAuthor: Ragnarok » Mon Oct 13, 2008 9:27 am

elad311 wrote:But, normally, PVC explodes at 100 psi... right?

No, not at all. The pressures at which things fail depend on so many factors, material, shape, construction - there is no generalisation for these things.

1" PVC, assuming it's rated, should handle 150 psi.
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Unread postAuthor: starman » Mon Oct 13, 2008 9:42 am

elad311 wrote:Well, I still don't know what to use, I think, or to use
the 1.75L plastic bottle, or to use a 40cm 1" PVC PIPE (as a chamber)

And, should I use 3/4" valve and barrel, Or 1/2" valve and barrel?


Forget about using a soda bottle for your chamber!! You've come here for advice and Rag is gently trying to push you away from an irresponsible chamber choice to a responsible one.

Properly cement the PVC and use pressure rated parts and you'll be good to go.
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Unread postAuthor: elad311 » Mon Oct 13, 2008 9:49 am

Thank you, but, my pump isn't so good, It doesn't have
a pressure gauge, should I put one in my spud gun?
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Unread postAuthor: FishBoy » Mon Oct 13, 2008 9:51 am

i would suggest you read this- http://www.spudfiles.com/spud_wiki/index.php/Identifying_Pressure_Rated_PVC

edit- yes, you definitely should put one on your gun
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Unread postAuthor: starman » Mon Oct 13, 2008 10:07 am

elad311 wrote:Thank you, but, my pump isn't so good, It doesn't have
a pressure gauge, should I put one in my spud gun?


To repeat Fishboy, yes, pressure gage is a requirement. As much as knowing how much pressure you're putting in, knowing you have a charged chamber or not is an extremely valuable safety feature.

BTW, load you're projectile first, before charging your chamber.
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Unread postAuthor: elad311 » Mon Oct 13, 2008 10:34 am

These are my plans for the gun:
(I'm gonna take it up to 100 psi, I hope it won't explode!)

Tell me if it looks good!
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Unread postAuthor: Ragnarok » Mon Oct 13, 2008 10:43 am

That will work, although a better valve choice would be a 3/4" sprinkler valve if you can find it - even an electrically operated one, although not ideal*, will provide a lot heap power than a ball valve, but not be hugely more complex to set up.

Eventually you'll be grateful you did, it'll be more worth keeping.

*In an ideal world, you'd mod it for blowgun operation, but not everyone wants to do that.
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Unread postAuthor: elad311 » Mon Oct 13, 2008 10:45 am

Ragnarok wrote:That will work, although a better valve choice would be a 3/4" sprinkler valve if you can find it - even an electrically operated one, although not ideal*, will provide a lot heap power than a ball valve, but not be hugely more complex to set up.

Eventually you'll be grateful you did, it'll be more worth keeping.

*In an ideal world, you'd mod it for blowgun operation, but not everyone wants to do that.


Thank you, I hope I'll find a 3/4" sprinkler!
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Unread postAuthor: starman » Mon Oct 13, 2008 10:52 am

It won't explode.

This should work fine. You could get by with 35 cm of tank if you wanted. That would still give you a 2:1 c:b ratio and would be plenty for marble shooting.

Also, the pressure gage on the end is not recommended. One of the first things you'll want to do is stand the gun up on its butt....goodbye gage. You could build a tee configuration with your schrader and include your gage there...just cap off the back.
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Unread postAuthor: elad311 » Mon Oct 13, 2008 10:58 am

starman wrote:Also, the pressure gage on the end is not recommended. One of the first things you'll want to do is stand gun up on its butt....goodbye gage. You could build a tee configuration with your schrader and include your gage there...just cap off the back.


so, Should I screw a regular cap in the end, and put the gauge near the schrader?
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Unread postAuthor: ckman » Tue Oct 14, 2008 12:22 am

use pvc looks cleaner and I think it is less likely to blow up and I think it is also eaiser to put the shrader valve in :wink:
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Unread postAuthor: ckman » Tue Oct 14, 2008 12:23 am

use pvc looks cleaner and I think it is less likely to blow up and I think it is also eaiser to put the shrader valve in :wink: and no if you put pressure rated pvc it shouldn't blow up but it might at like 170-200 maybe
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Unread postAuthor: starman » Tue Oct 14, 2008 1:09 am

elad311 wrote:
starman wrote:Also, the pressure gage on the end is not recommended. One of the first things you'll want to do is stand gun up on its butt....goodbye gage. You could build a tee configuration with your schrader and include your gage there...just cap off the back.


so, Should I screw a regular cap in the end, and put the gauge near the schrader?


Or just a cemented cap. Tap one 1/4" NPT hole where you show the schrader and install a tee through 2 layers of PVC. On one connection of the tee install the schrader, the other install the pressure gage.
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Unread postAuthor: Hydra » Tue Oct 14, 2008 4:01 am

If you want, you can make that T come out more with a little bit of pipe to make a small stock.
Make it so the end of the chamber looks like a w. The schrader and gauge are both pointing forwards (on the side of the T) and the long, bottom part of the T has nothing on it (except some end caps) so you can use it as a stock.
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Unread postAuthor: elad311 » Tue Oct 14, 2008 4:26 am

can you draw it for me?
I didn't understand..
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