Duxburian's Attempt at a CAP

[DX]

Well, I would like to make a CAP homemade, however, with the battle practicality restraints. Overall size, weight, etc. do matter. It has got to be pump-based rather than compressor-based, have an onboard reservoir, and be as compact as possible. I don't care whether it has to be a hand pump or bike pump, but a manual pump nonetheless. This gun has to be designed for the local terrain, meaning it can be long, but it can't be too tall. Materials and cost are not too big of an issue due to me getting my paycheck a few days ago. I have plenty of 3" and 4" pipe. However, if I need a regulator, it has to be cheap, and I don't know much about them in the first place.

[isoaker]

CAP and being hand-pumped as opposed to CO2 cartridge/compressor based seems fairly hard to do since I'm not sure you can achieve as high as pressure with a hand-pump needed to maintain pressure in the rest of the blaster. Any thought on what your maximum pressure you can achieve with a hand-pump?

[DX]

I could get in 100 PSI via bike pump. A regular soaker pump probably won't work well enough.

[SSCBen]

In my design for you Duxburian, I'm making it a water gun that'd have a good capacity and no backpack. I'm assuming that you don't want a backpack. The CAP system is much easier to build with a backpack of course, but you'll only run into regular water cannon design problems without one.

Right now I'm debating whether or not to design one for you based upon the inverted-T or U shape or a piston. A piston would be the absolute best option in my opinion because there would be so much unused water in another system. I'm thinking that you're partial to inverted-T however and wouldn't want to spent $20 on seals.

The system is rather simple and best explained in m15399's animation: http://www.geocities.com/m15399/cap.html

The cheapest air pressure regulator that you'd want would be part number 4956K11 at McMaster-Carr for $17. The 3/8" one I bought was serious overkill actually. In the future, the cheaper one will be the only regulator I'd suggest. I'm also assuming that you have pressure gauges - you'll want two ideally.

I'll draw up a modified APWC design with the air tank, pump and regulator to make it use the CAP system tomorrow. I'm actually fairly sure that you'll understand the basics once you see m15399's animation, so I'm holding off on the drawing for a bit.

This really works too. I was a little skeptical before firing an extended shot, but I was getting fairly constant output and range from my SuperCAP water gun when it was working! The word drop-off wouldn't work very well because there was none. In fact, range fluctuated a bit during the shot, increasing a bit and decreasing a bit. I'm assuming that's because my regulator regulates within 5%. It was nothing of a problem however. By the time the water ran out, there was a very dramatic drop. Lots of air shot out too, so I added the parts needed to save that air and actually refill the water chamber when the air chamber was pressurized (a simple ball valve before the regulator).

You also could make a design which uses a regular water pump but re-regulates the air. I believe I told you about that via PM last year. I was initially really excited about that design, but I'm not sure how well it'd actually work. Sounds like it'd work much better as a Pre-charger/CAP hybrid. In fact, that'd be a great idea. I think I'll make one actually.

Don't underestimate the air reserve either. People would be seriously surprised how long a good air reserve would last. No pumping for maybe 5 shots is better to me than pumping between each shot, especially when each shot is larger. Of course, in the design I'll make for you, you'll get multiple shots from a single pressurized air chamber.

[DX]

Right now I'm debating whether or not to design one for you based upon the inverted-T or U shape or a piston. A piston would be the absolute best option in my opinion because there would be so much unused water in another system. I'm thinking that you're partial to inverted-T however and wouldn't want to spent $20 on seals.

I've ditched the inverted-T for water cannons and replaced it with a wye,with the top of the wye hanging over the nozzle. I've realized how much efficiency matters with high powered, high output guns. I would agree that a piston would be the best way to go, however, I'm not quite sure how I would go about constructing one this large and how it would stay attached inside the chamber. If the parts could be found locally [and if I knew what I needed for that], you bet I would go piston, since that uses all the water.

I'm hoping this will work well enough that I could go quite a while before having to refill it and/or re-pressurize. No longer can covering fire protect a man while they re-pressurize with a bike pump. When you go to pump something like a Douchenator, water cannon, etc., you get rushed. There only a few situations/areas where one can fill and pressurize without enemy pressure.

This gun also has to be able to fit through the reeds. I'm going to the park to take pictures so you guys can see the thickness of these reed groves I always talk about. SuperCAP would get stuck, simply because it's so tall. Thin guns are best when fighting in that kind of terrain. My CPS 2500 looks like a reed stalk when I hold it perpendicular to the ground while in an ambush position. :laugh:

I just looked up some regulators locally, and found a 1/4" for $19. How do you attach it to the rest of the gun? It has female threads, but 1/4" is not a findable PVC size here.

[SSCBen]

Attaching 1/4" sized threads to larger threads takes only the right bushing and pipe nipples. In both the old SuperCAP air delivery system and the new redesign, I have used a small brass 1/2" to 3/8" bushing. A bushing to convert to 1/4" is the same size as a lot of air compressor fitting and is much easier to find actually. I was worried that I wouldn't get enough flow with 1/4", so I bought the slightly more expensive 3/8" regulator, but I'd say that it was too powerful. Close up image: http://www.sscentral.org/images/supercap/img_0055.jpg

You can also look at the steel pipe section if you want small pipe. You'll need a pipe wrench however if you do use steel pipe (we've got one). You'll only need an adjustable wrench if you choose the brass bushings.

[DX]

I will probably use brass if they have 1/4" to 1/2" bushings in stock. I've never seen such a small fitting, so I have my fingers crossed. :laugh:

[wetmonkey442]

The CAP I will most likely make before the end of the summer will be piston based. Using 3" PVC for the chamber, a standard size American hockey puck makes an almost perfect seal and using a lathe, or alternatively a simply drill and dremel, you could quite easily create grooves in the plastic for o-rings.

I look forward to Duxburian's progress as well as the development of the CAP as a popular homemade in the world of water warfare.

[SSCBen]

I will probably use brass if they have 1/4" to 1/2" bushings in stock. I've never seen such a small fitting, so I have my fingers crossed. :laugh:

I doubt you'll have any trouble finding that fitting. Just check all of the aisles next to PVC. I bought most of my brass fittings in the same place where tubing barbs and tubing are located. Also check the air compressor section. These fittings are used in both plumbing and air tools.

CAP piston water guns would actually be the way to go. The piston would not only solve the angle problem, but also the problem of air being released at the end of a shot. A piston will save you a bit of air.

Of course, the pressurized air behind the piston will have to be released in order to refill the water chamber, but that's just another efficiency improvement to be made. The only solution to that problem I can see is to power another device from the air behind the piston, possibly a water balloon launcher to help you get to the water. Good idea actually. I wish I thought about that earlier.