Help with an unconventional water gun design

Build a homemade water gun or water balloon launcher and tell us about it.
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Egg
Posts: 2
Joined: Mon Mar 26, 2007 5:41 pm

Help with an unconventional water gun design

Post by Egg » Mon Mar 26, 2007 5:46 pm

Hi guys. I'm looking for a water gun with a few particular and unique qualities, and judging from the garbage I've seen in stores for the past 5-10 years, I'm resigned to the fact that it will need to be a homemade design.

I'm new to building water guns, but not new to building pressurized devices with PVC. I've built a few potato guns in the past with good success (combustion models).

Anyhow, the qualities I'm looking for are a bit unconventional, as this gun isn't to be used in water fights. Because of this, I doubt any suitable designs are out on the net. The features I'm looking for are as follows:


- small overall design (think pistol-size, up to maybe SS-30 size)

- powerful to very powerful blast

- fairly accurate

- small amount of water dispersed with each shot (less than 4 ounces)

- safe design (i.e., not going to blow apart)

- ability to charge gun using some sort of electronic air pump (tire pump for instance)



So basically, I'm looking for a 1 or 2 shot wonder, ideally pistol-sized, with a very brief and powerful blast. I'm not completely opposed to using a hand-pump, but for the sake of simplicity and maintaining a small overall design, it would be much preferred if I could use something like an electronic tire pump (I have one with a built-in pressure gauge). This is basically to be a stealth model.

Before anyone gets worried, know that I'm 26 years old, and not some irresponsible kid who's going to intentionally injure somebody. Even if an accident were to somehow occur, I would take full responsibility.


So, I'm looking for any help, opinions, insights, or general building wisdom that can be given.

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Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Post by Silence » Mon Mar 26, 2007 8:54 pm

There are some really nice blasters out from Buzz Bee Toys. Last year's Blazer, Lightning, and Piranha were good, but this year is even better--the Orca and the Tiger Shark. iSoaker.com should have complete reviews in the next few weeks.

However, none of them suit the type of gun you're looking for.

The 2-liter homemade is a small, one-shot device filled and pressurized from the hose.

If you want real power using a compressor, a mini version of SuperCannon II sounds appropriate. Water cannons are filled with water and then pressurized with air; SuperCannon II has a piston separating the water and air. Otherwise, the chamber would have to have the opening at the bottom to allow only water to exit.

Note that SuperCannon II gets its power, even at low or medium pressure, from the wide piston area. Force is pressure times area, and the massive area gives it tons of force. 0.625 tons of force, to be exact. A pistol would probably have no more than a 2 inch diameter, or 1/4 the force. However, you could use higher pressures with the smaller tubing, maybe 150% of what SuperCannon II uses--150 PSI--if you want to. That would give you a good amount of force.

Good luck!

Egg
Posts: 2
Joined: Mon Mar 26, 2007 5:41 pm

Post by Egg » Sun Apr 01, 2007 6:45 pm

The Supercannon looks pretty cool, but I would need to shrink it to about 1/10th of that size, so it would basically be a new design.

I'm envisioning something along the lines of a 5/8 - 3/4" ID pipe, about 12-18 inches long, with a standard tire air-stem protruding from the rear cap. I'd want to fashion a "pistol grip" to the underneath, but that would be the easy part. Here are my next questions:


I know absolutely nothing about triggering mechanisms. I'd actually prefer the traditional trigger location, but I don't know if this is feasible. What do you guys suggest?

In place of this piston mechanism, I was thinking something like a marble or ball-bearing would be a better alternative because of the difficulties involved in making something so small. However, what is to stop the marble/bearing from blowing the front off the barrel? Any idea how the creator of the Supercannon avoided this??


Lastly, what do you guys suggest for a front-end nozzle? In order to get more pressure, smaller would probably be better I'd imagine. I was thinking of one of the screw-on pump nozzles for inflating rafts, but I don't know if the diameter would be small enough.

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SSCBen
Posts: 6449
Joined: Sat Mar 22, 2003 1:00 pm

Post by SSCBen » Sun Apr 01, 2007 9:35 pm

Welcome to Super Soaker Central!

I apologize for not coming by earlier. I have been very busy and understandably that affects how often I check my forum.

In Supercannon II, the piston does not exit the nozzle because the pipe reduces in size. The piston is 4 inches in diameter, while the pipe is 1 1/2 inches in diameter. The problem with this design for your purposes is that the large diameter piston is necessary to achieve the high force. This may not be small enough and certainly making would be a big waste of money due to the lack of capacity.

There are a few options here. Limiting yourself to air pressure designs, you essentially have two options: piston or non-piston design. A non-piston design is simpler and cheaper, but can be fired on a limited range of angles and is not as efficient as a piston design. In contrast, the piston design can be fired at any angle and is more efficient.

I would make a small, about 6 inch long piston chamber with a 3 inch piston to make a small pistol water gun. This wouldn't be too large and could be very powerful. You will not have trouble achieving 55 feet of range with this design.

For simplicity, you essentially are limited to using a ball valve as a trigger. One question I often get from spud gunners is "Isn't a ball valve less efficient than a solenoid/etc.?" The answer for water guns is no. In fact, ball valves are perfect performance-wise for water guns due to their high and straight flow. Air pressure spud guns only need a fast opening valve to get high initial flow to push the projectile out at a faster initial speed. That is not necessary in water guns.

Ball valves can take some getting used to though, but once used to them, there is essentially no difference between them and regular triggers.

For nozzles, threaded caps typically are used due to their price. They're not the best for performance, but they're good enough for most purposes. A cone-shaped nozzle is the best. More on this later.

I am leaving for dinner right now and will write more later (I am not done yet)... let us know if you have any more questions. I'll write some more on the 3 inch piston design in my next post.

:)

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