Super Soaker Central forums

Jonas · 10-16-2006, 03:25 PM

Something I've come up with when thinking of a constant pressure water gun. Haven't seen an idea like this anywhere so I decided to share it.

Principal:

A fully saturated steam is in a state in which no more liquid can evaporate. into the gas. Steam and liquid find an equilibrium, in which as much say water turns into steam than steam turns into water. The interensting part is that if we squeeze or expand this steam-liquid mixture the pressure stays constant. If you decrease the volume steam will turn into liquid. Increase it and some more liquid evaporates. But p stays constant. I haven't fount a V/p phase diagram on the internet like the 1 in my physics book. The straight line is ss.

The pressure of this system, in which no more liquid can evaporate is determined by the liquid's propeties and temperature. This means that water shot from an "saturated steam" pressure chamber will have exactly throughout the shot as long as there's enough steam inside.

Water is in this state when the temperature is 212 degrees. You do not want to shoot anyone with that and besides it would be impossible to keep the temperature steady. But there are better steams out there: aerosols.

Concept:

basically a sspc water gun would work like pumping water into a spraypaint can, then spraying it out. The water and aerosol would be separated with a piston or balloon, of course so that you don't have to add more. There are a lot of gases to choose from and with p/T tables it wouldn't be that hard to find one which has a good pressure range. Perhaps green gas or red gas, like used in airsoft guns.

benefits:
- Structurally very simple, because you don't need any pressure valves and air tanks for constant pressure.
- a lot lighter, and more compact.

problems:
- the pressure dependant on temperature. If your cannon heats up in the sun it could pop. When selecting a gas you need to take this into account
- how are you going to get enough of that stuff into the pc? You'd probably need to pump it in.
- when you shoot the mixture cools down slightly reducing pressure, and when you pump the mixture warms up increasing the pressure you have to fight against when pumping. This leads to reduced efficiency

note: saturated steam is probably not the official term, just something directly translated from what I have lectures in.

Ben · 10-16-2006, 04:15 PM

Welcome to Super Soaker Central!

Very interesting idea. I don't suppose it is very practical however unless you have access to aerosols and can afford or carry pipe that can take the temperature. Steel pipe is heavy to the point where it will make your water gun weigh twice as much as it normally would.

I think it would be worth a try however if you do have access to such materials.

joannaardway · 10-16-2006, 05:41 PM

Aerosols use Propane, Butane and other nasties.

Propane usually liquifies at 90 psi, which would mean that you got a constant 90 psi.

It might make for a very good principle if adapted to fit the PCg chamber with the moving piston, but using flammable gasses is highly dangerous.

If you could find a safe gas to do it with, it would be an excellent idea, but using LPG is a definate no-no.

I can't immediately think of a gas that would work, but that's not to say that one doesn't exist.

Silence · 10-16-2006, 06:50 PM

Neat idea, and while perhaps impractical, it does have potential. Welcome to the forums!

Perhaps brass pipe could be used instead? It might be a good bit lighter, although I can't say for sure.

Jonas · 10-17-2006, 07:57 AM

Propane shouldn't be that dangerous if you keep it inside a piston with very little air. Famous last words perhaps? At 90 psi it is a bit too high but I think there are some cfcs with more manageable pressure, though they too are flamable.

Evening the temperature would be tricky. Fail at that and the gun is totally non-constant pressure. Placing the brass or steel CPg inside a pvc pipe water tank would help, but then the initially simple design turns into something complicated and heavy.

Flashflood · 10-17-2006, 05:57 PM

Hey Jonas you show comes on and a little bit. I'm not putting down the show, I love it, you probably love it too. I could talk about the 303rd forever but I'd rather comment on how you are just as smart as your alter ego that comes on tonight in about two hours. It's ironic, no, rather funny, that you are just as smart as The Jonas but yet your'e not. I wonder if there is any correlation. My Tennis coach say, "If you look like a tennis player you'll play like a tennis player" I found that this also relates to water gun battles. When I look like a soldier I act like one. For instance, you usually don't put on a mask and not act like the one that you are impersonating, but you act like the person you impersonate. It's a mental box in a since, you have to think out of the box to not impersonate the person you are imerpersonating. This is my Theory.

Silence · 10-17-2006, 06:20 PM

@ Jonas: True, but the potential for explosion is always there. It's up to the operators' priorities as to safety vs. potential performance. But it's nothing like the danger of a flamethrower.

@ Flashflood: Slightly off topic...

Flashflood · 10-17-2006, 06:35 PM

With my clues, I wonder if anyone would know what show I am talking about. It is The Unit which comes on in an hour and 20 minuets.

Silence · 10-17-2006, 07:20 PM

Yeah, but that wasn't really the topic of discussion. I'm not really into TV, but perhaps somebody else would know. An interesting theory, though.

Ben · 10-17-2006, 07:37 PM

If you want to discuss your favorite TV show, do it in another topic. This thread is for a new CPS idea... not a completely off-topic TV show. I bet that Jonas here doesn't even have any idea about what you're talking about either.

cantab · 06-16-2008, 12:22 PM

Quote:

Originally Posted by Jonas

I think there are some cfcs with more manageable pressure, though they too are flamable.

CFCs, also known as halons, are NOT at all flammable - indeed, they're used in fire extinguishers!

They are, however, tightly regulated, owing to their ability to destroy the ozone layer, that reduces the amount of skin-cancer-causing ultraviolet radiation reaching the Earth's surface. That's why aerosol spray cans now use propane or butane. I would not recommend you power a water gun with CFCs - it might be illegal if the gas gets vented, and it would also seem inadvisable, when water warfare is best practiced in the sunshine, to make a gun that makes going out in the sun unsafe. (OK it would take a zillion like it to make any noticable difference)

/environmental rant

Silence · 06-16-2008, 03:36 PM

I agree. I wouldn't use CFCs or HCFCs on principle, and also because the "it's an insignificant amount" attitude doesn't work when everybody's saying it.

There are some grayish (in ethics, not color) substitutes that are used in dusters and the like. HFC-134 (I think) is used in airsoft and is known to have lower vapor pressure than propane, which has lower vapor pressure than carbon dioxide.

joannaardway also mentioned propane's vapor pressure is around 90 PSI. A chart I looked at said it varies from 110 to 150 PSI as temperature varies from 70 to 90 degrees Fahrenheit. 90 PSI is probably not very common in the summer, depending on where you live.

This is an old thread, but that doesn't really matter.

10-16-2006, 03:25 PM	#1
Jonas Junior member Join Date: Oct 2006 Posts: 4 UserID: 894	Constant pressure concept: aerosols Something I've come up with when thinking of a constant pressure water gun. Haven't seen an idea like this anywhere so I decided to share it. Principal: A fully saturated steam is in a state in which no more liquid can evaporate. into the gas. Steam and liquid find an equilibrium, in which as much say water turns into steam than steam turns into water. The interensting part is that if we squeeze or expand this steam-liquid mixture the pressure stays constant. If you decrease the volume steam will turn into liquid. Increase it and some more liquid evaporates. But p stays constant. I haven't fount a V/p phase diagram on the internet like the 1 in my physics book. The straight line is ss. The pressure of this system, in which no more liquid can evaporate is determined by the liquid's propeties and temperature. This means that water shot from an "saturated steam" pressure chamber will have exactly throughout the shot as long as there's enough steam inside. Water is in this state when the temperature is 212 degrees. You do not want to shoot anyone with that and besides it would be impossible to keep the temperature steady. But there are better steams out there: aerosols. Concept: basically a sspc water gun would work like pumping water into a spraypaint can, then spraying it out. The water and aerosol would be separated with a piston or balloon, of course so that you don't have to add more. There are a lot of gases to choose from and with p/T tables it wouldn't be that hard to find one which has a good pressure range. Perhaps green gas or red gas, like used in airsoft guns. benefits: - Structurally very simple, because you don't need any pressure valves and air tanks for constant pressure. - a lot lighter, and more compact. problems: - the pressure dependant on temperature. If your cannon heats up in the sun it could pop. When selecting a gas you need to take this into account - how are you going to get enough of that stuff into the pc? You'd probably need to pump it in. - when you shoot the mixture cools down slightly reducing pressure, and when you pump the mixture warms up increasing the pressure you have to fight against when pumping. This leads to reduced efficiency note: saturated steam is probably not the official term, just something directly translated from what I have lectures in.

10-16-2006, 04:15 PM	#2
Ben Founder Join Date: Mar 2003 Location: Maryland Posts: 5,974 UserID: 1	Welcome to Super Soaker Central! Very interesting idea. I don't suppose it is very practical however unless you have access to aerosols and can afford or carry pipe that can take the temperature. Steel pipe is heavy to the point where it will make your water gun weigh twice as much as it normally would. I think it would be worth a try however if you do have access to such materials. __________________ email: ben at sscentral dot org / Forum rules Read this page before emailing me. Do not send me a PM or email with a water gun question if someone else could answer the question. Post at the forums. You will get a response from me along with others' views or ideas. Do not send me a PM or email about reading a certain post unless it's been a few days since you've posted. I try to read every post. Last edited by Ben : 10-16-2006 at 04:23 PM.

10-16-2006, 05:41 PM	#3
joannaardway Do not adjust your TV set Join Date: Feb 2006 Location: SW Hertfordshire, England Posts: 875 UserID: 549	Aerosols use Propane, Butane and other nasties. Propane usually liquifies at 90 psi, which would mean that you got a constant 90 psi. It might make for a very good principle if adapted to fit the PCg chamber with the moving piston, but using flammable gasses is highly dangerous. If you could find a safe gas to do it with, it would be an excellent idea, but using LPG is a definate no-no. I can't immediately think of a gas that would work, but that's not to say that one doesn't exist. __________________ "Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore "So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

10-16-2006, 06:50 PM	#4
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,246 UserID: 576	Neat idea, and while perhaps impractical, it does have potential. Welcome to the forums! Perhaps brass pipe could be used instead? It might be a good bit lighter, although I can't say for sure. __________________ Forum Rules

10-17-2006, 06:20 PM	#7
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,246 UserID: 576	@ Jonas: True, but the potential for explosion is always there. It's up to the operators' priorities as to safety vs. potential performance. But it's nothing like the danger of a flamethrower. @ Flashflood: Slightly off topic... __________________ Forum Rules

10-17-2006, 07:57 AM	#5
Jonas Junior member Join Date: Oct 2006 Posts: 4 UserID: 894	Propane shouldn't be that dangerous if you keep it inside a piston with very little air. Famous last words perhaps? At 90 psi it is a bit too high but I think there are some cfcs with more manageable pressure, though they too are flamable. Evening the temperature would be tricky. Fail at that and the gun is totally non-constant pressure. Placing the brass or steel CPg inside a pvc pipe water tank would help, but then the initially simple design turns into something complicated and heavy.

10-17-2006, 05:57 PM	#6
Flashflood Junior member Join Date: Apr 2006 Posts: 13 UserID: 580	Hey Jonas you show comes on and a little bit. I'm not putting down the show, I love it, you probably love it too. I could talk about the 303rd forever but I'd rather comment on how you are just as smart as your alter ego that comes on tonight in about two hours. It's ironic, no, rather funny, that you are just as smart as The Jonas but yet your'e not. I wonder if there is any correlation. My Tennis coach say, "If you look like a tennis player you'll play like a tennis player" I found that this also relates to water gun battles. When I look like a soldier I act like one. For instance, you usually don't put on a mask and not act like the one that you are impersonating, but you act like the person you impersonate. It's a mental box in a since, you have to think out of the box to not impersonate the person you are imerpersonating. This is my Theory.

10-17-2006, 06:35 PM	#8
Flashflood Junior member Join Date: Apr 2006 Posts: 13 UserID: 580	With my clues, I wonder if anyone would know what show I am talking about. It is The Unit which comes on in an hour and 20 minuets.

10-17-2006, 07:20 PM	#9
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,246 UserID: 576	Yeah, but that wasn't really the topic of discussion. I'm not really into TV, but perhaps somebody else would know. An interesting theory, though. __________________ Forum Rules

10-17-2006, 07:37 PM	#10
Ben Founder Join Date: Mar 2003 Location: Maryland Posts: 5,974 UserID: 1	If you want to discuss your favorite TV show, do it in another topic. This thread is for a new CPS idea... not a completely off-topic TV show. I bet that Jonas here doesn't even have any idea about what you're talking about either. __________________ email: ben at sscentral dot org / Forum rules Read this page before emailing me. Do not send me a PM or email with a water gun question if someone else could answer the question. Post at the forums. You will get a response from me along with others' views or ideas. Do not send me a PM or email about reading a certain post unless it's been a few days since you've posted. I try to read every post.

06-16-2008, 03:36 PM	#12
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,246 UserID: 576	Re: Constant pressure concept: aerosols I agree. I wouldn't use CFCs or HCFCs on principle, and also because the "it's an insignificant amount" attitude doesn't work when everybody's saying it. There are some grayish (in ethics, not color) substitutes that are used in dusters and the like. HFC-134 (I think) is used in airsoft and is known to have lower vapor pressure than propane, which has lower vapor pressure than carbon dioxide. joannaardway also mentioned propane's vapor pressure is around 90 PSI. A chart I looked at said it varies from 110 to 150 PSI as temperature varies from 70 to 90 degrees Fahrenheit. 90 PSI is probably not very common in the summer, depending on where you live. This is an old thread, but that doesn't really matter. __________________ Forum Rules

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