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combustion check valve help

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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combustion check valve help

Unread postAuthor: singularity » Thu Nov 22, 2007 1:32 pm

this should be the last bit of information i need to finish my new combustion mortar. in a previous thread i asked how i would vent my chamber, some of you recommended a bed inflater. well i tried it, at 40psi reverse pressure the check valve failed... so i need to make/buy a new one that can wistand combustion. are there any ghetto check valves that i could make do i have no choice but to buy a big PVC one?
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Re: combustion check valve help

Unread postAuthor: frankrede » Thu Nov 22, 2007 2:30 pm

singularity wrote:this should be the last bit of information i need to finish my new combustion mortar. in a previous thread i asked how i would vent my chamber, some of you recommended a bed inflater. well i tried it, at 40psi reverse pressure the check valve failed... so i need to make/buy a new one that can wistand combustion. are there any ghetto check valves that i could make do i have no choice but to buy a big PVC one?
Or buy a big brass check valve
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Unread postAuthor: hi » Thu Nov 22, 2007 2:40 pm

what do you need the check valve for anyway? between the barrel and chamber or between the vent and chamber?
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

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Unread postAuthor: singularity » Thu Nov 22, 2007 3:18 pm

between the vent and the chamber, there is no clean out on my particular design so i had to build a vent port into it
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Unread postAuthor: hi » Thu Nov 22, 2007 4:02 pm

why not just use a ball valve?
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

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Unread postAuthor: singularity » Thu Nov 22, 2007 4:29 pm

becuase the hole firing process needs to be automated (or else i will consider the project a failure)

ok i just had a really out there idea, so bear with me. a PVC check valve would cost a good deal of money and be rather bulky which would take away from the mortar look. i happen to be in possession of 5 semi working airsoft AEG gearboxes, could i use them to vent the chamber? it would most likely require the use of two small check valves (one on the nozzle the other on the cylinder) but do you think it would work?

for all of you who have never seen a AEG gearbox it uses a motor to pull back a spring loaded piston then the gear runs out of teeth and the piston it forced forward very quickly creating a burst of air which would propel the bb. you can think of it as a very small air compressor which runs off batteries.
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Unread postAuthor: psycix » Thu Nov 22, 2007 4:55 pm

Maybe create a ghetto check valve with the use of flaps coverting holes.
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Unread postAuthor: Hubb » Thu Nov 22, 2007 6:16 pm

I posted a thread the other day. It may help.

http://www.spudfiles.com/forums/viewtopic,p,135570.html#135570
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Unread postAuthor: mopherman » Fri Nov 23, 2007 5:39 pm

Why not build one? just build a spring loaded ball check valve like this.
Image
hope this helps.
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Unread postAuthor: mark.f » Fri Nov 23, 2007 6:17 pm

Take a look at this page from Burnt Latke.

http://www.burntlatke.com/25cb-testday.html

They have a pretty good vent check system that might be of some use to you. There may be a way to contain it inside a bushing or some such so that the pressure, (although negligable), from the inflater can push the plug back.
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Unread postAuthor: meatballs » Sun Dec 02, 2007 10:35 pm

I know you've already considered this singularity, but im curious to think what other people think - do you guys think the fan from the bottom of an rc hovercraft, the one that lifts it off the ground, that forces air under the craft by sentrifugal force, do you guys think that has enough flow to vent the chamber in a few seconds?
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Unread postAuthor: windshrike » Sun Dec 02, 2007 11:05 pm

Depends. Cheap RC hovecraft or the top-of-the-line $500-for-just-the-body models that I've wanted ever since I was a lad?
I'm guessing the cheap ones and it's a maybe, upping the voltage and/or current should help it a lot.

And, meatballs, what do you mean by 'a few seconds'? 1-5, 5-10, etc......

@singularity: Go with mopherman's design, or just buy one.

EDIT: There are fairly large PVC check valves near the water pumps in Home Depot or Lowes.
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Unread postAuthor: singularity » Mon Dec 03, 2007 4:34 pm

the problem with mophermans design it it would require something like compressed air to open it. i think the only choice i will have is going with compressed air if i want to keep it small. i suppose if could get a decent sized metal chamber pump it to 300-ish psi then reg it down to like 30psi it would last a while. that way i could use a small brass check valve and eliminate the need for DWV parts (would have been used with the fan idea)
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be sure to check out my <a href="http://www.spudfiles.com/forums/ak-style-airsoft-vortex-gun-t10959.html">AK Styled Vortex Gun</a> and my <a href="http://www.spudfiles.com/forums/at-4-t9627.html">AT-4 Rocket</a>

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