homemade cps system - simple pvc setup

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
tech23
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Post by tech23 » Wed Jun 29, 2005 9:30 pm

Hi, I have made an APH, and started wondering why very few people had made a homemade cps gun. I looked at al the sizes of pvc, and with a little sanding to 1 pvc piece, you can mak a good cps chamber. It is mounted on 1" pvc (but could easily be changed to 3/4") and the pvc extends into the chamber with a coupling on the end. You attach the balloons to the coupling and secure them (via clamp, tape, glue, whatever). Then you get some bushings and take the one you are using to increase the 1/2" pvc to something bigger, say 3/4" and sand the ridge (on the inside, it keeps the pipe from going all the way through) down to where it is even with the pipe. Then you slide the bushing onto the 1/2" pipe where you want the bottom of the pressure chamber to be, and add bushings or bell reducers/increasers to get the diameter of the pressure chamber. then you just add pipe to it and a cap, and you're set.


Here's a picture if you don't know what I mean.
("edge sanded" means the ridge is sanded down)
Image

So how do you good do you think this is?
(I've checked the sizes, it should work.)

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Post by SSCBen » Wed Jun 29, 2005 9:58 pm

I've made a simple balloon CPS homemade before - to sum up it's power in a word: bad. Balloons simply are silly to work with when you have something better - latex rubber tubing. And there's even a system superior to latex rubber tubing - constant air pressure!

Balloons aren't very hard to work with, but there simply are not the best you can use. You should have seal problems as the number of balloons increase, and I really would expect the chamber to blow off at higher pressure unless you have it on extremely securely.

The real reason that nobody makes a homemade CPS water gun is because I haven't made instructions on how to make one. I've made several simple ones that served mostly as experiments, and I could (and should) make a guide to those two homemades. ;)

And welcome to iSoaker.com!

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Post by isoaker » Thu Jun 30, 2005 7:18 am

And there's even a system superior to latex rubber tubing - constant air pressure

Me: I can't quite agree with you on that one. Constant air-pressure systems using either a pump or compressed gas cylinder to take up the slack just requires more necessities such as a stronger compressor pump or gas canisters that are not readily refillable by common household equipment. Sure, it is easier to use compressed gas to achieve greater pressures than the rubber-bladder based systems. However, there's still something nice about using a soaker that can be manually pressurized as opposed to needing external sources of pressure.

The real reason that nobody makes a homemade CPS water gun is because I haven't made instructions on how to make one.

...while you've helped bring building homemades more accessible, others have been building water launching devices before. I think it'd be good for anyone interested with the knowledge on building stuff to try their hands at making and writing up instructions on how to build a soaker: air-based, CPS-based, etc. 'tech23' seems to have some interesting ideas, but could use some work on some of the specfic details.

@ tech23: as Doom noted, balloons typically don't generate enough elastic pressure when stretched, even when layered many times over. Latex tubing or other more-elastic rubber tubing (i.e. some bike tire inner-tubing) may yield much better power, yielding better pressurization of water when stretched. Of course, the problem with using tubing is that you'll need to devise a system to close off the other end. As well, definitely ensure that your home-made CPS-chamber is housed in a protective sheath of plastic just in case of rupture.

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tech23
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Post by tech23 » Thu Jun 30, 2005 8:07 am

Of course, the problem with using tubing is that you'll need to devise a system to close off the other end. As well, definitely ensure that your home-made CPS-chamber is housed in a protective sheath of plastic just in case of rupture.


Well, you could still you the same technique of sanding the ridges to make a strong chamber for latex rubber tubing. You could also sand the ridge to add support to a gun, get a tee and sand the two holes in a line and then slip it onto a pipe, and you have a socket to add a pipe for structural stability. Here's a picture for the tubing system.
Image




Edited By tech23 on 1120137891

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Post by isoaker » Thu Jun 30, 2005 8:35 am

That looks more promising.. you'd definitely need to add in clamps to affix the tubing on the pipe at the bottom and closure at the top. As well, for added power, using 2-3 layers of latex tubing will give more elastic strength, thus more pressure on the water. With the design, I'd say you can turn it on its side so that the flow from the PC will go straight into the nozzle as opposed to having to turn 90 degrees. Straight flow -> less turblence/better lamination -> better stream performance.

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tech23
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Post by tech23 » Thu Jun 30, 2005 9:19 am

I've got some money, I think I'll make a gun like that. But I have one question, where can I get latex rubber tubing? I'll use that technique to strengthen it too. I just got to get a design.

EDIT: I drew a simple design. It looks real good, except for when the water exits the pc, it will have to contend with the tee going to the check valve. The flow is like this:

Code: Select all

   V- ball valve
 _ ,___0  <- Pc
       |       <-check valve
 -----'---    <-check valve
  ^pump shaft
The front pipe is structural support. No water can get in there. Here is the design. (click on the picture to enlarge it)[/color]



Edited By tech23 on 1120145127

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Post by Aquarius » Thu Jun 30, 2005 10:32 am

tech23 wrote:I've got some money, I think I'll make a gun like that. But I have one question, where can I get latex rubber tubing? I'll use that technique to strengthen it too. I just got to get a design.

My recommendation would be butyl tubing or bladders. It is far more durable than latex, otherwise known commonly as natural rubber. Bicycle tubes are usually butyl.

Readily available bladders are often too large, as they are found in soccerballs, basketballs, etc. A custom fabricator can make almost anything from any polymer--tubing, bladders, you name it. Bladders and tubes aren't that complex, so this isn't necessarily cost prohibitive.




Edited By Aquarius on 1120145725

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Post by SSCBen » Thu Jun 30, 2005 10:36 am

For all interested. please read my article on why I feel that
CAP homemade water guns
are superior to all other systems.

That design, tech23, definitely won't work correctly. The tubing expands not only in height, but in length as well. I'm afraid that the tubing will either scruntch up or push the other side out. I have a picture that demonstrates this very well. Please note that the tube previously was about one foot long - now it is over three!

I usually seal off one end with a bolt or tubing barb and endcap and then tightly attach a clamp, careful not to cut into the tubing.

I also am glad that people finally are mentioning my design practices! Please read this slightly dated article for more information tech23: http://techlog.sscentral.org/archive....gn.html

You can buy latex rubber tubing online at McMaster. Do a search to find it. AlsoTake a look at my completed constant pressure homemade water gun if you'd like to see a previously made one.

Good luck on your homemade water gun! :;):

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Post by tech23 » Thu Jun 30, 2005 10:57 am

For all interested. please read my article on why I feel that
CAP homemade water guns are superior to all other systems.

I didn't completely understand the article, could you draw a picture or diagram?

And if the tubing also expands lengthwise, how do the cylinder-shaped pressure chambers work in stock guns? I've never had one so I haven't be able to look at them.




Edited By tech23 on 1120147088

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Post by isoaker » Thu Jun 30, 2005 11:21 am

From Doom's article:
Constant air pressure systems have two main pressurized chambers: one for water and one for the pressurized air. Separate pressure chamber systems have one main pressurized chamber, the pressure chamber.

I don't understand that concept. If you are splitting water from air, the only way water will be pressurized if there is a movable divider like done in the Aqua-Master Pre-Charge system. Otherwise, the air won't be pressurizing the water if the chambers are separate.

The tubing expands not only in height, but in length as well. I'm afraid that the tubing will either scruntch up or push the other side out.

True, but that's only true if you allow one end to move. If you fix both ends like in tech23's design, it'll just expand outwards. There will be more strain around where the tubing is clamped, but it would not push out the top unless the top is poorly mounted or until all the space in the allowable expansion area is filled with water.

In the cylindrical CPS models, when the chamber is being filled, it does get extended until it hits the limit of the casing. At that point, once the tube hits maximum allowable length, it just expands sideways to fill the rest of the plastic sheath. tech23's design would be akin to just having a shorter tube for the CPS-chamber, but it'll just fill sooner. The main problem with tech23's design is that there will likely be some dead space in the tubing that'll hold a little non-pressurized water that'll make completely draining it difficult.

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Post by SSCBen » Thu Jun 30, 2005 1:31 pm

Apparently no one understands that one without a picture! Problem is I can't make anything myself. iSoaker, I need you to make a flash of the CAP design! :cool:
I don't understand that concept. If you are splitting water from air, the only way water will be pressurized if there is a movable divider like done in the Aqua-Master Pre-Charge system. Otherwise, the air won't be pressurizing the water if the chambers are separate.


If you read more of the article, you would see that the air is shot into the water chamber with a regulator. :)

True, but that's only true if you allow one end to move. If you fix both ends like in tech23's design, it'll just expand outwards. There will be more strain around where the tubing is clamped, but it would not push out the top unless the top is poorly mounted or until all the space in the allowable expansion area is filled with water.


No, I'm completely serious when I say that the tubing will push out one end. Tech23, built it like that and you'll see what I'm talking about. I've tried that sort of stuff myself - it pushes with quite a bit of force!

And if the tubing also expands lengthwise, how do the cylinder-shaped pressure chambers work in stock guns? I've never had one so I haven't be able to look at them.


http://www.sscentral.org/gallery/intern ... .php?pic=1

You can see what I mean - just seal off one end but leave it mobile so it can expand.

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Post by frankenbike » Thu Jun 30, 2005 1:49 pm

CAP systems are superior only because you have an excessively pressurized system with air charge to spare for the purposes of a soaker. But you could easily use that full charge to release a huge drenching in a few seconds, in which case it really isn't constant air pressure at all. Such systems could more properly go by the description, "air battery systems", in which you draw less than the full capacity over a period of time. The one I just described would be more like an "air capacitor system" in which you draw the full charge all at once.

The CAP systems essentially assume a vertical water reservoir in which the air above the reservoir is pressurized and exerts force on the water. It is metered through a regulator at a specific pressure. The air forces the water out of the reservoir and into a firing stream until there is no more water, and if you don't turn the valve off, it will just release air. It will also release just air if you turn the tank upside down.

The advantage a CPS system has over a CAP system which does not have a piston dividing the reservoir between water and air, is that the reservoir can be oriented any way that you want.

As far as I can tell, you can also hybridize a system in a variety of ways. You can have a CPS tube encased in an APC so as it expands it increases air pressure around it for extra boost. You can have a sealed APC around it that allows the air to escape as the CPS expands, and then you can open a valve to a CAP pressure tank to pressurize the CPS container so it will have pressure on it until it's emptied completely (but you have to make it so the CPS tube itself doesn't invert and go inside out from the pressure).

In the rubber CPS systems, the CPS is functionally equivalent to a piston and spring combination. By combining the concept with CAP, you can use a lighter gauge CPS tube that is easier to fill, then pressurize the chamber to drive the force of the water. By combining the concept with the APC (as appears to be the case in Tech23's drawing), you multiply the power (though it is hard to pump) in the initial burst (like a capacitor).

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Post by isoaker » Thu Jun 30, 2005 1:52 pm

You can see what I mean - just seal off one end but leave it mobile so it can expand.

That's the thing. Yes, the CPS chamber would like to expand length-wise if it can, but if you set a length and reinforce it properly, it isn't a necessity. CPS chambers expand length-wise since it is distributing the expansion in all the directions it can. By expanding lengthwise, it probably also yields better laminar flow since part of the water will be squeezed/pushed in the direction towards the opening/nozzle when the trigger-valve is opened. However, there is no physical need to allow expansion length-wise. The chamber will still pressurize, though perhaps not as well as if the far end were allowed to move. There is probably a lot of strain, as Doom notes, on the end cap that'll make it want to pop, but from a physical standpoint, it really shouldn't matter.

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Post by NiborDude » Thu Jun 30, 2005 2:03 pm

I understood the concept. It's like mixing two chemicals together to create what you want. What I'm interested in is how to get the air pressure to stay constant and not mix in with the water PC.
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Post by isoaker » Thu Jun 30, 2005 3:34 pm

What I'm interested in is how to get the air pressure to stay constant and not mix in with the water PC.

Actually, frankenbike did a pretty good job at explaining some possibilities in the last two paragraphs of his post.

To re-iterate, for air-pressure to be kept constant, you need a regulator and a higher-pressurized-gas source to take up the slack as water is pushed out the nozzle. To keep the air and water separate, you can either have a sliding piston (like what is done for the Aqua-Master Pre-charge system), an encapsulated inner CPS-type chamber (basically like an XPS, but open up the air side to the regulator), or even just a non-CPS-divider like a plastic bag to keep the air from mixing with the water side (though using a plastic bag isn't a good idea since it'll likely tear or deform after use or rupture during the filling process). The air pressure being kept constant would be controlled by some sort of regulator that allows the higher-pressure compressed gas/air to enter the air-chamber side if it detects any drop in pressure as water exits the other side of the firing chamber.

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Post by SSCBen » Thu Jun 30, 2005 4:05 pm

To clear up what may become a misconception, you do not need to keep the air and water separate in Constant air pressure. That is completely optional unless you want to allow your gun to be shot at all angles. Regular air pressure still works without a divider - this is no different in CAP except that the pressure drop is compensated for. :;):

Also, I extremely highly suggest against putting an "encapsulated inner CPS-type chamber" or anything similar in. That's going to be nothing but trouble down the road when the chamber bursts, and it's just plain wasted money with replacement involved. Believe me to, I've bought loads of latex rubber tubing and I would extremely highly suggest against putting extreme loads on it (part of why I am so pro-CAP). Especially with weaker parts such as a plastic bag!

Besides the point, having an inner CPS chamber is going to be a pain to fill because you'd either need to pump it or use a QFD-style filler. Let's keep it simple.

For those interested in using a divider of sorts, please read how MrPukeOnYourHead did it: http://www.sscentral.org/mpoyh/newsoakr.htm

A well lubed divider made with large O-rings should be just about the best you can do if you want to shoot at any angle. :cool:

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Post by isoaker » Thu Jun 30, 2005 4:30 pm

^ MrPukeOnYourHead's divider is pretty much how to home-make what is done in the Aqua-Master Pre-Charger System.

As for the weak plastic bag example, twas used simply for illustration purposes and definitely should NOT be used if high pressures are involved. Of course, if one opts to go for a really strong-type of waterproof fabric or work at lower pressures, the concept is the same.

The sliding piston is undoubtedly the better way to separate highly-pressurized air from the water side. CPS-chambers face the problem of getting overly compressed once all the water is out, the chamber will then need to hold back the pressurized air and may be stressed where the opening on the nozzle end is. This is onlya problem, of course, if you're using pressures beyond the strength of what the rubber can handle. All depends on how high you want to go.

The problem with using really high pressures is I can almost imagine water streams nearly vaporizing upon exiting the nozzle if the pressure difference between the atmosphere and the water is vastly different. If one doesn't divide water from the pressurized air, while it'll work, you'll also be undoubtedly dissolving more gas into the water, increasing the likelihood it'll froth or bubble upon exiting the nozzle.

In the end, it really depends on how high the air-pressure one is using. Of course, the rest of the soaker's assembly should be built to withstand the higher pressures as well (heavy PVC pipe and/or metal plus perhaps a safety cage around the highly pressurized areas in case of rupture).

However, this is starting to drift a little far from the original nature of this thread. Making a cps-homemade is most definitely possible.

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Post by tech23 » Thu Jun 30, 2005 6:23 pm

Well, regardless of what system you use, you aren't limited to pvc if you think about it. Take ridge sanding, for example. You can do that and position it anywhere along the pipe without cutting it. You can use it for support, or use it to create a second layer of pipe.
You can modify pvc. You aren't limited to what you see it the stores, because you can change it to suit your needs, which opens us up to new possibilities. All we have to do it create the system, the parts are there.
:soakon2:




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Post by SSCBen » Thu Jun 30, 2005 7:35 pm

The problem with using really high pressures is I can almost imagine water streams nearly vaporizing upon exiting the nozzle if the pressure difference between the atmosphere and the water is vastly different. If one doesn't divide water from the pressurized air, while it'll work, you'll also be undoubtedly dissolving more gas into the water, increasing the likelihood it'll froth or bubble upon exiting the nozzle.


I don't feel that will happen unless the pressure is extremely extremely high (over a couple thousand PSI). The water is essentially incompressible for our purposes - it would take a ridiculous amount of pressure to make that kind of difference.

I personally feel that there is a limit at about 150 PSI of what will be useful (and it still edges on the potentially dangerous). I'll bring up the example of Xray's 300+ PSI test - it shot a full gas grill tank of water out of a very small nozzle in less than a second, with massive recoil.

As always, I will recommend that people use all water guns with safety in mind. Fact is, my air compressor doesn't go higher than 150 PSI to begin with - and neighter does most other's.

Now... less talk and more building. :)

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Post by frankenbike » Thu Jun 30, 2005 7:47 pm

If anyone wanted to make an APC with a divider in it, I've seen what parts would be good to accomplish this. You can get plugs that go in the PVC/ABC tubing that are glued in to seal the tubing, and cut the end flange off, and that could be your piston. Only thing is, it increases the size of your APC and takes up volume that could be used for water storage.

OTOH, you could also use a much larger, horizontally mounted APC.

In yet another example of where a decent sized lathe would come in handy, you'd get the best results if you made two grooves in your plug/piston for o-rings, so you'd get a better seal.

Also, as with the CPS system, you don't get to use all of the water that is in the system. Once the piston is pushed all the way to the end of its stroke, the application of pressure stops. If you want to pump it up again, it would be useful to have a compression release to make it easy to fill up again.

As for maximum pressures that are useful for a water stream, it's pretty much higher than is safe with any kind of PVC or ABS pressure chamber. Your main problem isn't the pressure differential with the atmosphere, it's air resistance. A high power pressure washer operating at 3000 PSI with a zero degree nozzle can shoot a very hard 1/4 inch stream over 100 feet. High operating pressures will let you use larger nozzle openings to get even more distances.

But when you're running water out of the nozzle at 150mph, the air is definitely working to slow the water down. The bigger your nozzle, the more mass the water has and the farther it can go. I think the 1/4" zero degree power washers can't hit more than 100 feet, which you can achieve with a much lower pressure APC/CAP system running around 100 PSI. I think that puts a stream out at about 40mph, which is enough to be pretty painful if you're hit at close range.

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