Expansion Chamber Qs

[Lentamentalisk]

I am planning to make a vortex gun (of sorts, somewhat plays off the vortex cap idea, but also not) and I want to run it off of unregulated CO₂ canisters, but at a more decent pressure, such as 100psi or less. I read about you guys using expansion chambers to lower the pressure, and I was wondering what sort of calculations are done to figure out how big it has to be. You dont need to do all the calculations for me, I just want to know what they are so that I can do it all my self and adjust it to my likings.

Also I had several ideas that i had on my BBMG that I though I might as well share to see what you guys think.
First, make an expansion chamber with multiple parts, connected via ball valves, so that you can adjust the operating pressure by opening and closing valves.
My next idea was to make a very low flow very high pressure pump, and just refill old CO₂ cartridges, to save tons of money. This should work, though I am not entirely sure how the valve works on the canisters.

[Hubb]

Assuming your are talking about the 12g CO2 cartriges, check this out. It's not exact, but it will get you in the ball park.

I don't really understand your first idea. Please explain. As far as the pump goes, it would work on larger CO2 tanks, but I don't know how it would work on the 12g ones.

[Lentamentalisk]

I don't really understand your first idea. Please explain.

just an adjustable sized expansion chamber. Adjustable size, with a given number of moles of gas means adjustable pressure.

I do seem to have misunderstood the idea of the expansion chamber though. I though it was just a chamber that the air flows through when you press the trigger in order to lessen the pressure and up the volume, however from what you pointed me too it seems like it is just a chamber that you dump your CO₂ cartridge into, like the reservoir of a compressor. Which is the case?

[jackssmirkingrevenge]

My next idea was to make a very low flow very high pressure pump, and just refill old CO₂ cartridges, to save tons of money. This should work, though I am not entirely sure how the valve works on the canisters.

There's no valve in CO2 capsules, there's sealed at the factory and pierced by whatever you use them with. Brocock sells refillable cartridges for use with a scissor pump, the same used to refill the Brocock air cartridges.

Here's a link about converting 12 gram cartridges to a refillable configuration.

[Hubb]

An expansion chamber is a unit that you dump the CO2 into that allows it to expand from a gas to a liquid, making it more stable.

[jackssmirkingrevenge]

An expansion chamber is a unit that you dump the CO2 into that allows it to expand from a gas to a liquid, making it more stable.

..because gasses are more compressed than liquids...

[Lentamentalisk]

damn that is complicated... is there anything easier? I can go with larger tanks, and dont really have any need for it to hold that much pressure, I just want some compact storage.

[Lentamentalisk]

Ok, so i decided to forgo the entire refilling CO₂ cartridge thing, and just go for a highly compressed chamber of something like 1" copper pipe, that i take up to 1000-2000psi (assuming my joints and all are strong enough)


click on it to see it correctly

[Sticky_Tape]

I thought that soldered joints can olny hold 400psi ?!

[POLAND_SPUD]

is there an in-built regulator in CO2 tire inflators ?

[Lentamentalisk]

is there an in-built regulator in CO2 tire inflators ?

lol, we have been over this soooooo many times in so many threads. No there is not, they just have too little flow and too little CO₂ to pop the tire. They just slowly dump out unregulated CO₂.

[judgment_arms]

There’s nothing complicated about an expansion chamber, think of like this: we all know that a 12gm cylinder will only fill a chamber to a certain psi, the max being about 700psi, right? Well the expansion chamber is basically a chamber that is just the right size for the Co2 to only fill it to a certain psi, in this case at least.

Actual expansion chambers merely give the Co2 a chance to go completely from a liquid to a gas.

Judging by you choices in avatars, is it safe to assume that you’re a Firefly fan?

[Lentamentalisk]

Ok, I had a fair misunderstanding on expansion chambers. I though that they were something that as the high pressure low volume air flew through, it expanded into low pressure high volume air.
Now what I am gleaning off you guys is that it is a static chamber that you fill up once from a canister that just expands the gas, rather than being an "on demand" expander type of thing.

@Judge: yes

[judgment_arms]

Sounds like you've got it.


I haven’t gotten up the money to buy/rent Serenity yet, is it as good as the TV series was?

[THUNDERLORD]

This may be a stupid idea,or not but could you maybe use one empty large c02 tank for the expansion chamber and one full one to refill it to a safe pressure then close a valve between some how? I am thiking about similar designs. thanks

btw, That looks like a nice design for your bbmg Lentamentalisk and also @jsr, thanks for adding the link to refilling c02 cartriges.