Recent thoughts on water gun design

Build a homemade water gun or water balloon launcher and tell us about it.
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SSCBen
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Recent thoughts on water gun design

Post by SSCBen » Sat Jan 17, 2009 4:53 am

I've been thinking a bit over the past few months about water gun design. This year I will have access to rapid prototyping equipment, be able to use engineering analysis and CAD effectively, and have a more real job so I can afford more, so I'm rather excited. What was unachievable before is very achievable now. I'll explain some of my thoughts on my next water gun concept. Any comments would be appreciated.

Range: Capable of at least 65 feet. Typically gets about 60 feet without issue.

Nozzles: Rotating nozzle assembly made with rapid prototyping equipment.

Water reservoir: Polycarbonate water jug--strong, light, clear, available in reasonable sizes, and not too expensive.

Pressure chamber: LPD with a pressure ratio of at least 70%. Water pipe is 3 inch clear PVC. Air chamber is 4 inch normal PVC. Will have pressure gauge and schrader valve for bike pump.

Valve and trigger: At the moment I'm thinking of using an air cylinder to open a ball valve like 6061's water gun. This has some advantages and some disadvantages. The biggest disadvantages would be cost and that using the trigger would use air. But, the trigger always would be easy to operate and the valve would open very quickly. With a pressure regulator the air usage can be minimized, but that adds more cost to an already costly system. I'm still thinking about this. If I can make some sort of trigger actuated gate valve with rapid prototyping equipment that would be ideal.

Frame: Will be made of polycarbonate pieces cut somewhat like THR (which still hasn't been completed), and 6061's water gun. This basically would be slices like THR with a solid bar at the bottom to attach a handle and the pump.

Pump: The seal assembly will be made with rapid prototyping equipment. I'd like to experiment with some atypical pumps like dual-action pumps but that might not happen.

The main problem with what I've described is that it'll be expensive as hell. This might be a $300 water gun. But it'd be an extremely good water gun, which is all that matters (other than having fun building it of course).

I'd like to investigate water gun efficiency so I have to pump less to get a certain level of performance. Simply energy efficiency might not make too much sense because the vast majority of the input energy would be returned. Or maybe not. I haven't looked into it yet. :p

ben@sscentral.org / Please read this before emailing or PMing me

Do not ask me water gun questions by email or PM. Please post the question at the forum. Private questions and suggestions are welcome by PM and email. Also, I do not sell or buy water guns online.

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cantab
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Re: Recent thoughts on water gun design

Post by cantab » Sun Jan 18, 2009 6:12 pm

Will your trigger system be reliable? Fancy stuff might help performance, but if it breaks a la Max-D valves it's no good.

For a case, why not try vacuum forming? You can make moderately complex and fluid shapes with the technique, and it's relatively easy to make the formers (typically from wood). The only drawback might be I'm not sure how thick a plastic you can use.
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SSCBen
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Re: Recent thoughts on water gun design

Post by SSCBen » Sun Jan 18, 2009 6:39 pm

I can't see how the trigger system would be unreliable because it's basically using compressed air to open the trigger rather than a hand. My biggest worries are that it wouldn't respond fast enough in some configurations, would use air too quickly, and could be too expensive. All concerns depend greatly on the configuration.

A pneumatic trigger also wouldn't directly help performance, though it can allow you to change your design for better performance. If a pneumatic trigger permits you to use a larger valve that originally would have been hard to turn, it'll help performance. This brings up the primary advantage of such a system--the trigger is always easy to pull.

Vacuum forming sounds interesting, but I don't know how useful it would be. I was thinking I might try that for a water reservoir originall, but I then thought about 4 liter polycarbonate jugs. The main goal is to make a frame rather than case because frames are a little simpler.

ben@sscentral.org / Please read this before emailing or PMing me

Do not ask me water gun questions by email or PM. Please post the question at the forum. Private questions and suggestions are welcome by PM and email. Also, I do not sell or buy water guns online.

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Silence
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Re: Recent thoughts on water gun design

Post by Silence » Mon Jan 19, 2009 10:21 pm

Water guns have become progressively more ambitious, and I'm waiting to see what this one will look like.

Cantab, I don't know if vacuforming's worth the trouble for Ben if he's only building one of these. And with that price tag, selling them won't be practical, either. I'm not familiar with the process, but I expect it's a little time consuming to hack and scrape out all the chunks of wood, especially if you're looking for symmetry. Sounds cool, though.

Ben, I'm a little surprised you're not going the constant air pressure for this one. At the very least that would help justify a pneumatic trigger valve. :p

Like cantab, I agree that trigger sounds overkill, and complexity alone makes it potentially unreliable. But I'll admit the ability to easily use valves ranging from one to two inches in diameter is promising, as far as performance goes.

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