Engineering Challenge

Threads about how water guns work and other miscellaneous water gun technology threads.
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adronl
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Engineering Challenge

Post by adronl » Tue May 12, 2009 8:22 am

The Engineering Challenge is for Everyone

Post a design of your best for a homemade Air, Cps, or Pre-Charge gun whatever

More details coming

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SSCBen
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Re: Engineering Challenge

Post by SSCBen » Tue May 12, 2009 8:27 pm

This isn't my best idea, but it's a wacky one I'll try out in a few weeks when I have time. While I am busy (and need to get working on a 30 page paper), I want to post this before I forget to again.

The basic idea is to use a hydraulic ram pump to generate a high pressure cyclic flow. Turbulence will probably have to be reduced with straws but that's acceptable. Adjusting the period and other parameters will result in streams of different lengths. The Plateau-Rayleigh instability suggests range will increase as long as the stream is shorter than pi times it's diameter, so we design for a stream of that length.

Maybe I should make a drawing for those who don't understand the concepts involved as they do deviate greatly from typical water guns. That'll have to wait for a few weeks.

Obviously, this water gun will need to be calibrated to work as desired, but if it does work I think it would be very interesting. Would it be practical? Maybe, but I doubt it.

Edit: The waste outlet would lead back to the water reservoir in my conception. What likely will be the practical problem with this design is the amount of energy lost due to the waste outlet. I believe this can be minimized.
Last edited by SSCBen on Wed May 13, 2009 2:45 am, edited 1 time in total.

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adronl
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Re: Engineering Challenge

Post by adronl » Wed May 13, 2009 1:23 am

You the man I would like to see it happen. Is the most expensive component going to be the hydraulic ram?

Are you going to use a pneumatic cylinder?

Sounds pretty complicated but pretty serious :D . Are you going to have to step up your piping to sch 80 or go with more metal parts

Good luck on that paper. I am glad I am done with school

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SSCBen
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Re: Engineering Challenge

Post by SSCBen » Wed May 13, 2009 2:20 am

I don't know how expensive the ram will be. I also don't know what I'll use to store the energy in the ram or what parts I'll use. The idea is just that, an idea. I do know that it's not likely to be very efficient in most configurations. That's where the engineering challenge comes in.

This likely will only be practical for hose powered water guns and in that case a few changes should be made to prevent water hammer where you don't want it.

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Silence
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Re: Engineering Challenge

Post by Silence » Wed May 13, 2009 3:32 am

Ben, I've always wondered how they build such compact pulsating nozzles – they're used on the XP 90, the HydroBlitz, and the Pulse Master/Blaster. The XP 90 has neat retro aesthetics, but some power to go with the pulse would be neat, too.

Typical of you to turn it into an efficiency issue.

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cantab
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Re: Engineering Challenge

Post by cantab » Thu May 14, 2009 8:32 pm

The HydroBlitz works by having a secondary CPS chamber, at a lower pressure than the primary. When the blitz mode is activated, pulling the trigger allows water to flow from the primary to the secondary. Once the secondary is full, the nozzle valve is opened (I think mechanically, by the expanding bladder) and the water is shot out. Then the nozzle valve closes and the cycle repeats.

The Pulse* guns don't fire a pulsating stream. It's just a name.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

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adronl
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Re: Engineering Challenge

Post by adronl » Mon May 25, 2009 2:41 am

I did some testing on the gum rubber that I had mentioned in another forum and the results were great. I put water in at 105psi and the hose held quite well, I drained and checked for fatigue and there did not seem to be any at all.

I did a several more tests at the same psi and the rubber seems a little softer but no significant signs of fatigue. I cut open a section of the tube and examined the inner walls. There was no tearing and the walls were the same thickness as before.

As advertised it stretches twice its length, unadvertised this means all directions. Pressurized it grew to almost 4" in diameter.

My idea make a homemade pump and make it far more efficient than an average homemade for maximum psi.

What is the highest psi of the best performing homemade pump on the site?

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Silence
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Re: Engineering Challenge

Post by Silence » Mon May 25, 2009 3:34 am

Wow, neat results. Keep us updated on the durability.

What do you mean by an "efficient" homemade pump? If you just want high PSI, remember: pressure = force / area. Given that a user can pump with no more than a fixed, maximum amount of force, you need to reduce the pump's cross-sectional area – via its diameter – to increase the maximum pressure. However, that reduces the volume pumped and increases the number of pumps you'll need to make.

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SSCBen
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Re: Engineering Challenge

Post by SSCBen » Mon May 25, 2009 11:09 pm

Very interesting. Keep us informed.

One important thing to note is that the pressure the tube will exert on the water is often lower than what pressure you pumped it in at. In fact, if the pressure in the pump wasn't higher than the pressure in the tube, you wouldn't be able to pump at all. So the 105 psi number might not be representative of what pressure the tube itself generates. Put a pressure gauge on that side to see what it actually is. ;)

The tears are small and you're not likely to notice any of them without a microscope. Measure the thickness with calipers and see how it changes as you cycle the tube more. Latex tubing gets very noticeably thinner with use.

Also, I don't know the highest pressure anyone's operated a homemade water gun on our site at but I'd guess it's around 100 psi. I recall a guy named Xray several years back running some tests at 300 psi.

Let me reiterate that higher pressures aren't necessarily a good thing, in fact, I'd say they are generally a bad thing. Higher performance can be achieved without high pressures. High pressures require stronger materials, which in turn increases cost if the same level of safety is desired (and it should be).

I'd suggest repeated cycles of pressurization to find a relationship between tube thickness and number of cycles to get an idea of the fatigue characteristics of the tubing. The same procedure done with LRT should be done to have numbers to compare against. I might try this myself.

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adronl
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Re: Engineering Challenge

Post by adronl » Tue May 26, 2009 12:32 am

So what is the highest psi you have generated with a home made pump like on your SuperCPS. I figure I can try and improve on an existing design by going for better seals lubes etc to and make improvement

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SSCBen
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Re: Engineering Challenge

Post by SSCBen » Tue May 26, 2009 1:51 am

I don't know the highest pressures I've generated because I haven't measured them for something like that. I'd guess around 60 to 70 psi.

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