CPS water guns

[hydroblast]

As a few of you are discovering I like to make challenging projects, preferrably that actually work. I've had my share of dissappointments in regards to watergun development. But I will never quit. The rewards are worth it.
I tried to develop a CPS water gun. (Continous Pressure System).
I was well along and had some great initial results, but then the laws of physics reared its ugly head. I found that the rubber bladder ages or loses its "snap" quite quickly. Think of the bladder as rapidly aging surgical tubing used in sling shots. Well we all know that the tubing wears out with use, so it should'nt be any surprise to anyone that the CPS bladder also wears out, but far more quickly than I expected.
This is a note to others who can hopefully learn from my experiance.

If your looking for a high performance watergun, my advice is to chose a large capacity, (4inch), pvc tube backed or driven with air,(driving water of course). I believe Ben spoke of the physics of this type of design in one of his forum entries.
I designed a backpack model based on the advantages of a large capacity air/water drive system and was blown away with the performance. I found that I could shoot a 1/4inch stream steady "on" for 2 mins. The max. range was 50-55 ft. In addition all you had to do was fill it by hose... no pumping. You rely on the municiple water pressure to pressurize your unit.

Anyway, your comments are welcome.

Thanks Hydroblast

[Silence]

The air probably isn't pressurized, unless you threaded or screwed the PC case onto the water gun to create a seal. Glue obviously isn't a good method as it would prevent access to and maintenance of the bladder. And if the air is pressurized, that means you won't get constant pressure.

That's impressive range for a hose-pressurized system. I live on a hill, meaning I can't really obtain high pressures just from a hose.

Ben's Beast got about 60 feet of range though. Maybe, if your hose can provide sufficient pressure, you could add bicycle inner tubing to increase the range.

Did you get that range before or after the rubber lost strength? I don't have experience here, but I'm guessing the rubber is abnormally strong out of the box, just like balloons are. It might settle into a certain pressure now.

I do know that rubber bladders do lose quite a bit of strength if they're allowed to expand to great dimensions. But part of the bonus of using a homemade is being able to replace the bladder.

Anyway, congrats on building a CPH! I'd love to see some pictures.

[hydroblast]

Hey Silent Guy
Thanks for the reply.
The backpack water gun I'm referring to is a "loop,(square), of 4 inch sch.40 pvc. At the top I placed a schader valve and a pressure gauge. At the bottom I placed a one way valve with a hose connection and an outlet point.
I pre-pressurized the unit with 10-15psi of air, then filled the water gun with all the municiple pressure there was, 60psi.
This gave the performance I mentioned. When you hear air instead of water you stop immediatly and go refill.
No pumping all day long, just soaking people. Its great! You can check it out on myaircannons.com or youtube.com under twoleafs or backpack water gun.
As far as the cps water gun goes, I could send you a picture of the 4 inch shell with the 1/2 inch pipe on top. I pulled the bladder out. I used the same braided line to the 1/2inch pipe as you can see in the backpack water gun.

Thanks Hydroblast

[Silence]

Oh, two different guns...sorry. Thanks for clearing up the confusion.

Neat video...that is a lot of shot time. And the dropoff isn't noticeable at all. Looks pretty cool!

[Ben]

The rubber thinning happens whenever the rubber stretches. It's unavoidable for the most part, but Larami did do a little trick to extend the life of CPS bladders. There is a reason their CPS water guns have lasted so long. They limit how much the bladder can expand with a smaller diameter tube. The bladder does not expand fully. This reduces the tear on the bladder.

Would I suggest that method? If the reduction in power doesn't bother you, I would suggest it. It should be noted however that reducing the amount the bladder can expand reduces the pressure it creates.

I don't bother reducing the expansion because I have a lot of the tubing myself and the thinning never had too significant of an effect of the power of my water guns due to something else I had done. I have noticed that if you layer tubes, the outer one provides much of the power and it is not stretching anywhere near as much as it could, reducing it's tear. The inner one might stretch fully, but the loss of power is reduced due to the

There is a forum with a little bit of information on the subject: http://www.rubber-tubing-worldwide.com/forum/

Sadly, this forum has not been updated in several months and the guy who runs it doesn't answer my emails.

I apologize if my writing is not very clear. I am very lightheaded at the moment and likely will remain that way until tomorrow. If another explanation is needed, I can make it another day.