Back Pack guns - What's out there, or build my own?

[frankenbike]

Brief intro:
I'm old. By the standards of this group, really, really old. But I hang with a fun bunch of people, and my wife is in a roller derby league.

Well, a challenge has been called, and at this summer's roller derby convention, a water war has been declared between leagues. In Downtown Las Vegas in August.

I have no idea what to expect, but this is a pretty resourceful group of people, and there is sure to be some Monster Garage style weaponry.

My opinion is that water carrying capacity is a primary factor. In this year's guns, that seems to leave two choices: Aqua Pack Devastator and Hydra Pak. I've had no luck locating a Hydra Pak, and the APD doesn't really have that big a capacity.

Neither measures up to a CPS 3000, and while those can be found used on Ebay, I can't imagine them not being worse for wear after all these years. Rubber stuff deteriorates over time and it seems to me that the diaphragm would weaken with repeated cycles at some point.

So, for current guns, the WW Hydra Pak would seem to be the hot ticket. Except that no one carries it and I haven't found a source on the web yet.

On top of that, I'm thinking...I have a machine shop in the garage, suppose I wanted to make one. Use aluminum tubing, which would take a lot more pressure than plastic and is still fairly light, a really large charge chamber, put a piston that pushes the water out the charge chamber through a nozzle, and on the other side of the piston, charge it with a CO2 cartridge, so all I have to pump is water. I could make the pump really high volume too, so I could fill the chamber in a couple of pumps. Would a CO2 cartridge even be adequate?

But the lazy middle aged guy in me says, "If you can find the Hydra Pak, why not leave it at that? Building a water gun is a pretty big engineering project." Oh, and I'd have to build two, since my wife must be armed similarly.

So...whaddya guys think? Any net resources for build your own guns? I'd prefer to find a prebuilt pump, maybe a bicycle pump, and high pressure valves than machine my own.

Or, does anyone know a source for the WW Hydra Pak's? I sent email to Buzz Bee, but haven't heard back.

Anyway, thanks in advance. Sorry for the long run-on.

[DX]

SSCentral is the best source for information about homemade water weaponry.

Building a water gun is a pretty big engineering project

Using the CO2 makes it a little complicated, but building an air or constant pressure homemade out of pvc and fittings is very easy. I would reccommend making one of those [Full instructions at SSCentral] because they are cheap, can be made quickly, and can be very powerful. Making a homemade allows you to also make your own backpack, or make a custom reservoir, so you could make that as big is you need. But whatever you decided to do, definately pursue making some kind of homemade, as it will outpreform that Hydra Pack you were thinking about in just about every stats category.

[frankenbike]

SSCentral is the best source for information about homemade water weaponry.

Building a water gun is a pretty big engineering project

Using the CO2 makes it a little complicated, but building an air or constant pressure homemade out of pvc and fittings is very easy. I would reccommend making one of those [Full instructions at SSCentral] because they are cheap, can be made quickly, and can be very powerful. Making a homemade allows you to also make your own backpack, or make a custom reservoir, so you could make that as big is you need. But whatever you decided to do, definately pursue making some kind of homemade, as it will outpreform that Hydra Pack you were thinking about in just about every stats category.

Thanks Dux. Some great designs there, much simpler than what I was thinking.

A couple of 4" dia. or larger tanks maybe 18" long mounted to a backpack frame (with waist support to take the weight off the shoulders), a Shrader valve on the top to pressurize it using a bicycle pump or a CO2 pump, and a garden hose handle type thingie as the trigger.

All I'd have to do is machine a couple of different size screw-on nozzles and I'll have some seriously pissed off roller derby chicks and refs ready to kill me

I told my wife about this. She gave me the "wife look". Might have to go with something more conventional for her

So my question about the Hydra Pak stands, if anyone knows where they can be obtained. Plus, there is the rest of the league to outfit

Thanks a lot for the pointer to SSCentral. Great site. Just the sort of thing I was looking for

If anyone has any other suggestions, I'd really appreciate them.



Edited By frankenbike on 1118895192

[BlueMage]

actually you could build such a contraption out of your average household PVC pipe. i think some can handle up to 400 psi. although if the trigger valve were to be in a handle, you would have to seal the tubing going from the PC's to the gun pretty tightly. anyways, there's no reason not to try it, PVc is cheap. if you do try and build one, tell us how it goes!

oh yeah, what's a roller derby?

Stay Cool!

[frankenbike]

BTW, I notice you're active on a bunch of lists where people use bike pumps to pressurize their homemades. Instead of a bike pump, they could use the CO2 inflators you find in this Froogle search:

http://froogle.google.com/froogle....oring=p

I think if I build mine, I'll put a pressure guage on the tank. You could easily over pressurize a tank with those things. I like the 2nd Wind one which has a bicycle pump and CO2 filling capability, but I might go for the Red Zeppellin and a higher volume pump. I'm getting a plan together :blues:

[emperor_james]

So your not just going to build the Air Pressure Homemade described in SSCentral? Thats what I would reccomend, those are extremely powerful. It would take a lot of CO2 to have your water gun last for long, and it probably wouldn't be that powerful, either.

[frankenbike]

So your not just going to build the Air Pressure Homemade described in SSCentral? Thats what I would reccomend, those are extremely powerful. It would take a lot of CO2 to have your water gun last for long, and it probably wouldn't be that powerful, either.

I'll probably build something that's a riff off that backpack one. I'm thinking of three shorter tanks and a slightly different hardware arrangement to utilize the space better (that one has a big empty gap in the middle) using something like this with some modifications as my valve and a laminar flow guide to modified brass sweeper nozzles of varying diameters (maintaining their interchangeability).

If it works, I'll post it at SS Central

Don't know yet about how effective the CO2 things would be, but with a Shrader valve it's worth a shot, using the bigger cartridges. I'll have a hand pump as an backup, maybe in a scabbord. If I can get the CO2 thing working, I can make it so I don't have to take the pack off to pressurize it.

I'd probably have the 25g cartridges on a bandolier, and just pump the CO2 in until I hit 90 PSI. Maybe higher (those things are pressurized at over 600 PSI). That would have some pretty good throw if the tanks are only 3/4 full. I figure I'd like to get 2-3 gallons as my capacity at 3/4 full.

If I had access to a water hose, I could use that to pressurize the system. But it's pretty unlikely on Fremont Street where the battle is set to take place.

Anyway, I'm pretty sure that along the way I'll have to do a redesign. I've got a backup plan to incorporate pressure chambers and a pump in addition to the pressurized tank if I can't get the power and flow I want. I've got over two months to work out the bugs

If you know of any other sites with some different homemade designs, I'd like to check them out for more ideas.



Edited By frankenbike on 1118995642

[SSCBen]

Let's get this straight - the Air Pressure Homemade water gun is a low-powered homemade. I made it for simplicity, but I knew that people would call it complex regardless of it's actual complexity.

Try utilitizing Constant air/gas pressure. Also please read a few other articles I wrote in that Water Gun TechLog.

I'd highly recommend constructing some air chambers and using an air compressor over CO2. Those small cartridges are meant for paintball and other similar sports. They are not designed to handle the appetite of a water gun.

[isoaker]

Due to the direction of this thread, I'm pushing it into The Workshop.

[emperor_james]

I didn't say that the APH was complex, but the fact that it is considerably more powerful than all stock guns made is undeniable.

I'm not quite sure what the advantage the Constant Air Pressure has over any other water gun, though.



Edited By emperor_james on 1119045262

[SSCBen]

I didn't say that anyone said the APH was complicated. I only said that it's extremely simple as far as homemades go.

Constant air pressure is CPS, but using air pressure. :;):

[emperor_james]

I'm afraid then that I don't understand how this Constant Air Pressure system works. Is it similar to the Water Warriors precharcher line? An expanation or diagram would be helpful...

[frankenbike]

Try utilitizing Constant air/gas pressure. Also please read a few other articles I wrote in that Water Gun TechLog.

Thanks for the advice. It would be easier to visualize the CAP system if there was a drawing or something to illustrate the water/air circuitry. I'm guessing you have a water tank, and an air pressure tank. You pump the water into a kind of firing chamber, and you have a trigger that allows the air to drive the water out. Originally I was thinking of doing something like that with a piston on one side of the chamber which would push the water out, but getting the piston to return to its original position is a trick.

Otherwise, forcing the air into the water chamber would turbulate the water as it drains from the chamber, wouldn't it? That's why I'm having a hard time visualizing it as you've written it up. Sometimes a drawing is worth a thousand words

Do I have the right idea of what you're saying, or am I way off base?

I'd highly recommend constructing some air chambers and using an air compressor over CO2. Those small cartridges are meant for paintball and other similar sports. They are not designed to handle the appetite of a water gun.

That's most certainly a good possible way to do it. I'd have 3 different tanks hooked together in my design. I could easily use two for water and one for air. But at the end of the cycle, when the water is used up, the air pressure will be considerably down. I don't know how much pressure those tanks will be able to take, but you just can't avoid that loss of pressure whether you have water in all the tanks and pressurize them all, or you have pressure in a separate tank and regulate it.

I am giving some thought to how I can maintain the highest possible pressure without having to pressurize an ever increasing volume of air.

The main problem with your suggestion is that I won't have access to a nearby air compressor. We'll probably be taking a cab from the convention or bar to Fremont, so I won't even have access to a cig lighter to plug one of those car compressor things into. I wouldn't have anywhere to stash anything. It's pretty much a "whatever you can carry" kind of deal.

I can pressurize it at the hotel initially, though, and use the cartriges to suppliment it as pressure goes down, or if I can get an opportunity to refill the tanks. The only thing I don't like about pre-charging the tank, is the possibility that mishandling in the cab could make it explode

I wasn't thinking of using a single cartridge to charge it up. I was thinking multiple cartridges of the largest size available. 25g at 690PSI is the largest I've seen in conventional cartridges. There may be some that are the size of soda cans, and I'm looking into those. As the water is depleted, I could recharge the pressure as it goes down. That was the thinking, anyway. Not a cheap way to go, by any means, but a quick and efficient way in the field.

If you're unfamiliar with Fremont Street in downtown Vegas, it's sort of a covered mall with a lot of casinos and food places. The battle will cover several blocks, and I wouldn't bet against the police getting involved. Which happens all too frequently with these girls.

Let me just summarize my design goals:

1. Small front profile. I'd like the gun to be no larger than say, an Uzi, because we'll be in a crowded situation. This means that the gun would be more likely to be a remote control than the actual pressurizing/firing mechanism. It's the small front-of-the-body size that rules out the APH design as I've seen it in pictures.

2. Large water capacity. 2 gallons would seem to be the ideal. Reloading is going to be problematic as there is unlikely to be a public water supply.

3. Self contained. No external compressors or pumps if possible, unless they can be easily carried.

4. Elimination of pumps if possible to keep firing time up as long as possible.

5. Rapid repressurization with minimal physical effort (it'll be 110 degrees even at night).

6. Repressurization without removing the backpack if possible.

7. Distance is unlikely to be the primary goal. Short, high volume blasts would seem to be the most effective, and the target would probably be within 10 feet most of the time.

8. Water pressure should be in the same range as a garden hose. Around 80-90 PSI would be adequate. If they tanks and system can take it, I might pressurize to 120 PSI. I could probably still get adequate pressure when the tanks have emptied. I'm guessing this could be as low as 30 PSI. On the fly repressurization might raise this.

You can see why I'm heading in the direction I'm heading design wise. I may not be able to choose the most efficient or powerful design for this particular project. Of course, I could deploy the tanks on a different gun with a better design for a less "assault" style commando waterfight.

I would like ideas on how to integrate separate pressure chamber designs if it doesn't compromize my other design goals too drastically.

Sorry for the long posts. I'm trying to get my thoughts out on this.

[Dacca]

the way a CPS system works is that the pump pumps air and water (from the tank) into the pressure chamber. when the trigger is pulled, it opens the valve to the PC and the water exits. there is a good diagram of this somewhere on SCC (dont know the link) but it was gor a water machine/gattling gun that shows the setup in a larger scale by using a water tank, a kickball and a bike pump.

[isoaker]

I am giving some thought to how I can maintain the highest possible pressure without having to pressurize an ever increasing volume of air.

Without a pump system to move water into the firing chamber, I can't think of any way to create a system based on air-pressure continuously shooting without the need to deal with needing to pressurize an ever-increasing amount of space as water empties.

The nicest concept air-pressure system, IMO, is the one employed by the Aqua Master Pre-Charge line by Buzz Bee Toys. Basically, they have a piston/movable plug that separates the pressurized air from the water. Thus, the water can be under pressure without actually having air being pushed directly against it, resulting in less gas in the liquid and smooth streams. However, one still needs to pump water into the firing chamber side that, for the large version, becomes rather hard to do due to the higher pressure on the back side.

I've seen pics of some homemade soakers that had a pressure regulator and CO2 tank to pressurize a larger reservoir and appears to behave like an oversized (and more powerful) garden herbicide sprayer. The only way to eliminate pumping is to either pre-pressurize the system or use a large CPS-type chamber that is also prepressurized (i.e. SC Power Pak, Big Trouble, or WW Hydra Pak) or use another form of pressurizing such as compressed CO2, but you've already brought that up.

Apart from the pressuziring/pumpless issue, I do believe the rest of your soaker-desires shouldn't be too hard to accomplish if building your own soaker.

[SSCBen]

Misconceptions are everywhere... ???

First off, rubber CPS systems should not pump air into the pressure chamber. Air pumped in there would be a waste of space for water. The rubber itself powers the shot in that - no air is needed or will air help.

I'll get to making a drawing of the Constant air pressure setup and making the rest of my explanations at a later date. I am far too busy at the moment to make a few drawings and writings. Read and reread the Constant air pressure article and I do not see why you will not be able to understand the concept. Remember that I picked up this design from a short few sentences describing it - it's not hard to understand at all.

[frankenbike]

the way a CPS system works is that the pump pumps air and water (from the tank) into the pressure chamber. when the trigger is pulled, it opens the valve to the PC and the water exits. there is a good diagram of this somewhere on SCC (dont know the link) but it was gor a water machine/gattling gun that shows the setup in a larger scale by using a water tank, a kickball and a bike pump.

OK, I understand that. The vertical chambers on top of the barrel get water pushed into them and the chamber has a very small space of air in it at the top that has high pressure. Since the air "floats" to the top, it doesn't mix with the water in a turbulent stream, it just pushes down on it.

Has anyone measured that pressure? This isn't quite irrelevant.

Obviously, as the chamber empties out, the pressure drops and the stream becomes less aggressive. Have I got that right?

BTW, I've been doing some research on CO2. The opinions on CO2 at SSC are out of date. Heck, my knowledge was out of date.

This moves into "don't try this at home" territory. The kind that can kill you if you screw it up.

The current hot rigs in paint ball technology use refillable high pressure tanks between 9oz and 48oz in volume. There are three gasses that can be used and different ratings for the tanks. CO2 is the lowest of them, with pressures running between 850psi and 1000psi. HPA (High Pressure Air) is the highest, and runs up to and above 4000psi.

That's why knowing the pressures people get in APH designs is sort of relevant.

While the initial rigs and regulators are expensive by water gun standards, they're pretty cheap to refill. About $3 for a 16oz tank of CO2 at your local paintball shop.

Which should hold about .75 lbs of CO2. If I've done the math right, this is enough to pressurize 25 liters of air to 100psi, which is the pressure of a moderately strong garden hose. The general safety guide among air cannon afficionados is that even high pressure PVC shouldn't be run above 150psi.

So a single tank of that sort should be able to power about 6 gallons of water at a constant garden hose strength. Larger tanks are available.

You could make a very dangerous water weapon using CO2 or HPA technology. For example, using higher pressure materials in the gun and mounting the CO2 tank to the top of the gun with an isolated water cartridge chamber, you can try to push a burst of water out at the full 850psi! I'm not ready for that kind of design work yet.

Here's a link to some inexpensive CO2 tanks:
http://www.paintball-discounters.com/cgi-bin....1007.d0

I'm still working on finding an appropriate regulator for something like this. But I expect that the bottle and regulator alone will run around $60 togetherat the low end. Expensive by water enthusiast standards, but cheap by paint ball enthusiast standards. Cost is only slightly relevant to me (I'd like to keep the whole project for this round at under $100).

I'll be making a trek to the local paint ball store to see what they've got and maybe see if they have anything to add.

In any case, this is where I'm leaning. Comments?

[SSCBen]

Pressures higher than 150 psi are extremely dangerous and should be avoided at all costs (unless you're insane). Xray tried 350 psi in a metal tank and reportedly it shot out the entire contents in less than a second on a nozzle about 1/8" if I remember correctly. I'm talking about a gas tank for a grill too, on a small nozzle, in less than a second. That's dangerous to say the least.

I personally do not feel that CO2 or HPA will be worth the money in the long run, but given that you do not have an air compressor, you could use either. I would use an air compressor because I have several.

I doubt that you will be able to make this water gun for less than $100 unless you have connections to parts manufacturers. You'll spend probably near that in the regulator alone.

[frankenbike]

Pressures higher than 150 psi are extremely dangerous and should be avoided at all costs (unless you're insane). Xray tried 350 psi in a metal tank and reportedly it shot out the entire contents in less than a second on a nozzle about 1/8" if I remember correctly. I'm talking about a gas tank for a grill too, on a small nozzle, in less than a second. That's dangerous to say the least.

I hear ya. I have no intention of pressurizing the system above 100psi. I'm going to put a guage and regulator on it if I use one of the 16oz CO2 cans, that's for sure.

I'm currently looking for a source for CPVC locally, which will give me a little operating "squish" room, you might say.

As I said, this is definitely a "don't try this at home project." I have a fair amount of machine shop experience, my father's an engineer (with a fair amount of experience in hydraulics) and will probably be going over my design, and I also have minor experience working with explosives for a special effects company (though I most certainly wasn't in charge).

I personally do not feel that CO2 or HPA will be worth the money in the long run, but given that you do not have an air compressor, you could use either. I would use an air compressor because I have several.

I've got a large air compressor at home. I'll be using it for testing the integrity of the system and working out bugs in the design. I'll probably test it at 125psi.

I've got one in the car too. I just can't carry it around with me at the event. HPA definitely isn't worth it. CO2 isn't that expensive once you have the rig. The refillable tanks are pretty cheap and still compact enough for my purposes, but the regulators are expensive. Worth it if I don't want a big plastic granade on my back.

But I don't know what all that I need yet for the CO2 rig. I'll probably know by Tuesday.

I doubt that you will be able to make this water gun for less than $100 unless you have connections to parts manufacturers. You'll spend probably near that in the regulator alone.

I'm afraid that might be true. I'll be doing some research. I've seen regulators for the $40 range, but I'm going to talk to the paint ball guys to see what they think would be necessary for this since they have all the catalogues on hand and there's a paint ball superstore near me.

I don't know yet what CPVC schedule 40/80 4" pipe costs yet. But that'll probably be amortized over multiple guns. If we just go with pressurizing and replenishing, the cost of the CO2 bottle, regulator and hardware would also be amortized. Over time, it'll be a hell of a lot cheaper than using a bunch of non-refillable CO2 cartridges.

BTW, do you know of any pressure gauges that might be suitable for a mix of 100+psi air and water? Maybe a water pressure gauge?



Edited By frankenbike on 1119146250

[Aquarius]

A good, used 3000 or new 3200 would make this much more simple. Unless the thing is just ragged out, been used to shoot organic solvents, or exposed to excessive ozone or UV, the rubber components will be fine. Granted, they're rather hard to find but can be had for under $100 on eBay.

110 F at night in Vegas? I had no idea it got THAT hot. Last time I walked the strip at night I nearly froze. This was December though, and all I had on was a pair of jeans and a t-shirt. :wacko:



Edited By Aquarius on 1119149632