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Chamber Venting with compressed air.

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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Chamber Venting with compressed air.

Unread postAuthor: Davidvaini » Mon Jul 20, 2009 3:55 pm

Now in my local area pretty much any cannon is allowed regardless of its power as long as its not a combustion.

But I am an "Ideas" person and Idk if anyone has done, thought of, or attempted to do this idea..


My idea is instead of using a computer case fan to vent out the chamber, why not use compressed air flowing through a nozzle of some sort? Use the flow of that to vent the chamber/mix, etc... It could also vent faster and allow quicker semi auto shots, perhaps even could be used in a full auto combustion.

just throwing out ideas, it may be a stupid one, but then again it may not be.
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Last edited by Davidvaini on Fri Aug 21, 2009 2:02 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Mon Jul 20, 2009 4:01 pm

Chamber Venting with CO<sub>2<sub>


Bit of a flawed concept considering how many fire extinguishers work?

If you do have a bottled supply of compressed air, you'd likely use it for a pneumatic as opposed to venting a combustion.
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Unread postAuthor: kjjohn » Mon Jul 20, 2009 4:08 pm

that's an interesting idea. you would have to make sure the compressed air was distributed evenly throughout the chamber, but it might work. For enhanced combustion, you could even inject a certain amount of oxygen into the chamber like an internal combustion engine if you had a strong enough chamber.
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Unread postAuthor: Davidvaini » Mon Jul 20, 2009 4:09 pm

As far as compressed air goes...
yes, but some people are combustion crazy,I just want to introduce a possible way that would increase the speed of venting a chamber and therefore increase ROF slightly...

Idk I know there are people out there that only make combustions, and perfer them over pneumatics.

I myself am a pneumatic guy.
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Re: Chamber Venting with co2, compressed air.

Unread postAuthor: Ragnarok » Mon Jul 20, 2009 4:15 pm

Actually Jack, the CO2 fire extinguishers work through cooling the fire (decompressing CO2 at those rates results in solid CO2 in the exhaust) below the temperature at which it can still burn, not by suffocating it.

However, your point is still valid. You need to vent with an oxidiser, not a combustion product.

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Subject to that caveat, the idea is however workable. With HPA, this actually the core of my (unlikely to make it off the ground) full auto hybrid plans.
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Unread postAuthor: starman » Mon Jul 20, 2009 4:30 pm

Been there, done that. That's what I have used the male quick connect/inline check valve on Trip Thunder for... although only from an air compressor, not from an HPA tank. Venting with CO2 is a non-starter...the venting gas must provide O2 for the next firing.

I think the concept is solid and would be the only way to reasonably and cheaply pursue relatively rapid fire capability in a combustion. You may still want a fan in there for mix and turbulence.
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Unread postAuthor: Davidvaini » Mon Jul 20, 2009 4:37 pm

hazzah my idea isnt soooo dumb!

in fact it sounds good.
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Unread postAuthor: psycix » Tue Jul 21, 2009 7:58 am

You could look into an automatic piston hybrid which doesn't vent, where you simply inject fuel into the combustion products, and top it off with compressed air. You are leaving the combustion products (which are at atmospheric pressure after the shot, or even a vacuum due to cooling) simply inside.
So you can cycle as follows: inject fuel, inject air (or oxygen!), fire, inject both again, fire again, and so on.
The amount of fuel will have to be calibrated to the amount of oxygen you inject every shot, thus the first shot will have an overdose of oxygen due to the air already inside not being combustion products, but that doesn't matter much.

It is what I would do when would build a hybrid Gatling gun. Which I could build in a few years... :roll:
Oh what a wonderful continuous thundering sound would it make...
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Unread postAuthor: Hubb » Tue Jul 21, 2009 8:13 am

starman wrote:I think the concept is solid and would be the only way to reasonably and cheaply pursue relatively rapid fire capability in a combustion.
I still think that a carburetor system is the way to go on that idea.....actually, I'm kinda tired of talking about it. I think I might have to venture into it a bit when I finally decide to finish my combustion.

As far as venting with a compressed air, definitely doable. That's how I vented on my hybrid (when it was in tact). Made the process much faster than using a bike pump or compressor.
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Unread postAuthor: chenslee » Tue Jul 21, 2009 1:18 pm

I use a torch head as a carburetor. It injects fuel and draws outside air in at the same time.

It NEVER misfires. EVER. Even after 50+ consecutive shots it ignites every time. Even without a spark strip. Even without a fan. It also only takes about 3 seconds to re-fuel with a single valve.

Eventually I'm going to do a write up called "How NOT to build a propane meter".
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Unread postAuthor: spudamine » Tue Jul 21, 2009 3:33 pm

yep, I also vent my hybrid with a blast of premixed fuel and air, not the most efficient, or safest way to do it but it works well enough and it's the simpest solution if you want to go automatic.
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Re: Chamber Venting with co2, compressed air.

Unread postAuthor: Technician1002 » Tue Jul 21, 2009 5:51 pm

Ragnarok wrote:Actually Jack, the CO2 fire extinguishers work through cooling the fire (decompressing CO2 at those rates results in solid CO2 in the exhaust) below the temperature at which it can still burn, not by suffocating it.

However, your point is still valid. You need to vent with an oxidiser, not a combustion product.

~~~~~

Subject to that caveat, the idea is however workable. With HPA, this actually the core of my (unlikely to make it off the ground) full auto hybrid plans.


Sorry to pick on your reply.. But have you tried to cool a fire with liquid Oxygen lately?

[youtube]http://www.youtube.com/watch?v=UjPxDOEdsX8[/youtube]

CO2 cools, but also displaces Oxygen. It works by cutting Oxygen and then cooling to prevent re-ignition by lowering the temperature below the auto ignition point. CO2 does not have enough cooling to extinguish a large fire by cooling alone.

Found a better video. A lit match is dropped into very cold liquid Oxygen. Wait for it.. :D The extreme cold should put the match out.
[youtube]http://www.youtube.com/watch?v=iKIi8KLLvbA[/youtube]
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Re: Chamber Venting with co2, compressed air.

Unread postAuthor: Ragnarok » Tue Jul 21, 2009 6:56 pm

Technician1002 wrote:Sorry to pick on your reply.. But have you tried to cool a fire with liquid Oxygen lately?

You're just deliberately misinterpreting what I said here. I was talking about CO2 extinguishers specifically.
Of course if you use a such a horrifically concentrated oxidiser as liquid oxygen, then it'll just make things worse. A total idiot could tell you that.

I assumed this forum was devoid of people whose intelligence wasn't even capable of making the meagre rank of total idiot, so the fact I needed to specify that pouring liquid oxygen onto a fire was unwise completely slipped my mind.

Do I also need to tell you that feeding body parts into wood chippers is also a bad idea? What about standing on railway tracks? And where's the stance on drinking poison?

Will I have to append an exhaustive disclaimer to the end of every post just in case anyone with no common sense should happen to take one thing I've said as an endorsement of something quite different?
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Unread postAuthor: Technician1002 » Tue Jul 21, 2009 7:01 pm

I come from a world where they have to print on laser pointers, do not stare into beam, and on hot coffee, caution contents may be hot. :D You may know not to put out a fire with liquid Oxygen.

I would hope everyone who has access to liquid Oxygen knows better, but it seems not everyone who drinks hot coffee knows the contents may be hot. Don't take the lid off in your lap while driving.
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Unread postAuthor: Ragnarok » Tue Jul 21, 2009 7:22 pm

Coffee may be hot is a disclaimer, an attempt to protect themselves against people not taking responsibility for their own accidents or clumsiness.

I doubt there are many people who are unaware coffee can be hot. There are however a lot of people looking for a quick buck.
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