Water Cannons [formerly Launchers] - A New Class of Weaponry!

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
DX
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Post by DX » Thu Aug 03, 2006 5:00 pm

The 6 inch at Home Depot is pressure rated [I haven't seen drain/non-rated pipes, since I memorized where the pressure rated is]. I don't know the internal diameter, since I've never bothered to check.

I have never exceeded 110 PSI, mainly because it is difficult to get that high via bike pump. And especially with 4" PVC. My multi-shot nerf homemade takes 100 pumps to reach 70 PSI. Then again, the 4" air chamber is several feet long.
marauder wrote:You have to explain things in terms that kids will understand, like videogames^ That's how I got Sam to stop using piston pumpers

Drenchenator
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Post by Drenchenator » Thu Aug 03, 2006 7:01 pm

If the pipe you saw is schedule 40, chances are it likely is the correct diameter.

I would worry if the pressure rating is significantly lower, but if it is as high as 180 PSI, I wouldn't worry too much. Just don't take the water gun out in the extreme heat and there should be no problems. Be sure to pressurize it in the heat if you choose to so there isn't any increase in pressure due to an increase in the heat. The ratings are conservative to begin with and as long as you don't play it stupid there shouldn't be any problems.

I always do a little research before buying pipe now, because I've noticed that between brands and different times of the year, there can be big changes in pressure rating and price. The 4 inch PVC used in Supercannon II was bought online at McMaster-Carr before I found any locally, being rated at 220 PSI at 73.4 degrees. They don't have the same product any longer - the pressure rating dropped dramatically. The 4 inch PVC in SuperCAP was bought locally and was cheaper. Same pressure rating as Supercannon II. It actually seems that McMaster-Carr cleared out their good schedule 40 pressure rated pipe.

Tommorow I'm hoping to try a 100 PSI test shot with 5% glycerin just to see what I can get with better lamination. I bought a gallon of the stuff last year and it still has not been used (what a waste of money!). The more efficient your system, the less effect glycerin would have. Since my system is essentially as efficient as it will get, I'm wondering how much of an effect glycerin will still have on the stream. I do know it will prevent the stream from breaking up at the end of the shot due to air resistance. Since I don't use one of the experimental nozzles that will protect the stream from air resistance, I am interested in seeing the improvement.




Edited By Lt. Col. Drench on 1154649775
The Drenchenator, also known as Lt. Col. Drench

SSCBen
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Post by SSCBen » Thu Aug 03, 2006 7:04 pm

That post above was me. I didn't notice Drenchenator was logged in. I'm surprised this was the first time that happened.



Edited By Ben_ on 1154649886

SilentGuy
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Post by SilentGuy » Thu Aug 03, 2006 8:42 pm

I actually didn't notice that this thread had grown so much--but it's pretty good reading. And regarding the above two posts, I was about to say...

A lot of this is assuming that larger ID means more force is transferred--and although that makes sense according to the logic you used in the unregulated CAP article at SSC, I still want to voice my doubts. Perhaps a direct comparison of water cannons identical except for PC size is necessary...

Not to sound so pessimistic or anything, though--I'm just as excited about more power as everybody else is. :angry:

DX
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Post by DX » Thu Aug 03, 2006 9:37 pm

Just wondering, how could 2 water cannons be identical except for pc size? The pc is like the whole cannon. Your only constants would be the ball valve and nozzle. :p
marauder wrote:You have to explain things in terms that kids will understand, like videogames^ That's how I got Sam to stop using piston pumpers

Drenchenator
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Post by Drenchenator » Thu Aug 03, 2006 10:09 pm

A lot of this is assuming that larger ID means more force is transferred

A larger internal diameter means a larger area. Pressure is simply the force applied per unit of area. In fact, one look at the common units should justify this completely (pounds per square inch). So, to find the sum (total) force applied to an area, you just multiple the area by pressure (from P=F/A, F=PA). It's actually quite simple to understand really.

By the way, this is the real Drenchenator (hopefully that will not happen again).
The Drenchenator, also known as Lt. Col. Drench

SilentGuy
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Post by SilentGuy » Fri Aug 04, 2006 4:29 pm

Sorry, I meant PC length as the same, although the width would be different--though it might also be neat to try a narrow but long PC vs. a wide but short PC.

I understood the original logic, but nobody has come up with a solution to the conundrum I was talking about. That is, you pump a soaker with the PC vertical for less surface area and less resistance, and then you fire it with the PC horizontal for more area and more force. You can't get energy out of nothing.

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Post by SSCBen » Fri Aug 04, 2006 5:59 pm

The work would be the same with each angle. I don't see how that's a problem really. No energy magically appears because the shot is shortened with greater force after the rotation. The work done is the same. I'd ask at some physics forum if you'd want a more specific answer.

SilentGuy
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Post by SilentGuy » Fri Aug 04, 2006 8:56 pm

It makes sense, but I can't physically explain it--asking at a physics forum might help, so thanks for the offer.

Compare this to a car. You could drive from point A to point B at 50 MPH, or you could drive at 20 MPH. Yes, you are doing the same amount of work because you're moving the same object the same distance, but it takes a different amount of energy.

Of course, if it does work, that would be great. I suppose it would be like the "step-up" feature of the standard APH, and you could accomplish wonders with it--similar to using a smaller pump. However, a smaller pump would really be pumping a smaller amount of water, while the PC would be filled at a fast rate this way.

That's not to pull this thread off topic too much--it's just a concern I've had with the surface area and force argument. I'm actually waiting for somebody to find the solution to my "conundrum" and prove me wrong...

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Post by SSCBen » Sat Aug 05, 2006 7:02 am

Compare this to a car. You could drive from point A to point B at 50 MPH, or you could drive at 20 MPH. Yes, you are doing the same amount of work because you're moving the same object the same distance, but it takes a different amount of energy.


Work is a measurement of energy expended in physics. So total energy would be the same if the work was the same. :goofy:

SilentGuy
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Post by SilentGuy » Sat Aug 05, 2006 11:26 am

I must have been deluded then...that's the consequence of jumping to conclusions. Thanks for informing me of my error.

But I still believe there is a different amount of work/energy...

Anyway, I suppose I'm just being picky. Common sense and the logic you've used provide almost complete evidence that greater surface area provides greater force, so I won't criticize that theory anymore. I'll just try something a bit more constructive--that is, the design of the PC that I was talking about.

A bit off topic, but how is the unregulated CAP project going? Is it worth it to do that instead of to build a CPH due to greater force? ???

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Post by SSCBen » Sat Aug 05, 2006 12:07 pm

The unregulated CAP idea simply was an idea. There's no way anyone could construct that without a machine shop or rapid prototyping equipment. It simply would be easier and cheaper for us to use regular regulated air pressure or rubber tubing. My main hope was that it might be a CPS alternative for Buzz Bee Toys, but I think for even them construction would be an issue.

I'll also admit that I posted it as one of those "I thought of it first!" claims. :D

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