PreCharger Homemade

[Silence]

I'm interested in seeing what else you have to say, but I'll reinforce my opinion now.

Given any specific volume in the air compartment of both a PCgH and an APH--that is, after a specific amount of pumps--you'll always have x times as much air, mass-wise, in the PCgH (where x=PreCharge pressure/15 and x>1). If there is x times more pressure, than you'll always need x times more force to pump.

Given that both the APH and the PCgH have 100 PSI, then the PCgH's air compartment will have x times more volume than the APH will have. This means you have x times more pressure potential and more volume after a specific number of pumps, or that you need fewer pumps, albeit with equivalent force to an APH after x times more pumps, to obtain maximum pressure.

[Silence]

I went out and tested my Argon the other day, and indeed, it did have dropoff similar to that of standard air pressure guns (a fact which has been disputed in other recent threads). However, every measurement was extended (due to extended shot time), so I concluded that it imitated large-PC air pressure soakers, whether by conserving water through narrow streams or through some unknown phenomenon unique to PreChargers.

The flexibility of PreChargers, whether commercial or homemade

To some extent, I've just been throwing the term "flexibility" around when it comes to PreChargers, and its meaning might be a bit vague and its importance lost. Hopefully, the rest of this admittedly short article will dispel confusion concerning the flexibility of PreChargers.

In the previous article, I explained what you do when you PreCharge a soaker--you increase the amount of air inside the PC. When this amount of air is increased, it takes fewer pumps to pressurize the PC to a certain PSI, and the dropoff rate with the total shot time as the unit of time will be the same as with a non-PreCharger air pressure soaker. Naturally, given a fixed time unit for the dropoff rate (as opposed to one that varies directly with the shot time), a PreCharged soaker will appear to have greater dropoff, as its PSI drops more quickly than normal. Does this remind you of something?

Yes, this should remind you of the behavior of soakers with very small PCs. Just like with standard air pressure soakers that have small PCs--say, early Super Soakers and modern air pressure water pistols--you need very few pumps for pressurization, but the shot time is weak and dropoff is somewhat profound. This is because a small standard PC might have the same increase in pressure that a large PreCharger PC might have after a fixed number of pumps. Thus, it is a given that a PreCharger can produce the same short-term performance as a small-PC soaker.*

On the other hand, one could simply choose to not PreCharge the soaker at all, and in that situation, the performance would be identical to that of a standard air pressure soaker with a large PC. This is because the stats are the same--equal PC volume and equal air mass. Thus, it is a given that a PreCharger can also produce the same long-term effects as a large-PC soaker.

Naturally, one would assume that there is minimal battle practicality in switching the amount of air in the PC--and that is true, to some extent. However, while one might not be able to adjust his or her PreCharger's settings on the fly, it is quite possible when the activity is low (perhaps right before filling the weapon); however, one must be aware that it is possible to quickly switch from high amounts of air to low amounts of air. Unfortunately, the opposite switch would be the more useful of the two possible ones, because it would allow one to pump up completely when time allows so, and then quickly PreCharge the soaker and be able to get the pressure back quickly in a fight. Suddenly, I'm not too sure that a PCgH is the best project to do--but it does have some good things going for it, including linear flow and at least partial flexibility. I'm not a person who will give up on this, so I will definitely follow through on the project...although I no longer encourage others to build one yet.

* NOTE: IF YOU JUMPED DOWN FROM THE FOOTNOTE MARKER, FINISH READING THE REST OF THE ARTICLE BEFORE READING THIS
Un/fortunately, there are still a few complex possibilities to think through before the PCgH project is trashed for good. In a small standard PC vs. a large PreCharger PC, are the ratios of plunger movement, volume, pressure, etc. per pump exactly the same? I'll think through all the possibilities numerically, as my brain is currently too dead to do so algebraically. This PreCharger stuff is really wrecking me...

[Silence]

I concluded my last post by saying that I don't trust my algebraic knowledge when it comes down to PreCharging--and indeed, it would appear as if I have little reason to trust myself in those matters. This is because I tested out my Argon today, and compared its performance both with PreCharging and without--and the results are surprising.

First of all, the PreCharging system does not appear very consistent--I'm assuming that's at least partly due to the incomplete release of pressure after pressing the pressure relief button.

Also, I find the pressure meter very unreliable. Sometimes, it actually manages to start at the bottom and go up by thirds with every pump, but most of the time it malfunctions and the pressure readings are just strange. Often, it will start at a starting pressure, so after PreCharging, the needle is about 2/3 of the way up; and then it goes up by 1/9s until the needle hits the maximum point. Because I don't know exactly how it works, I don't know how to get it work every time or whether or not it is actually messed up. Helped would be appreciated here.

When I first went outside, I just messed around with the soaker for a while. Then, I emptied everything and released the pressure. I PreCharged the soaker again, and found the number of required pumps to be 17. For this PreCharge pressure, the soaker could only accept 2.5 pumps before it became very difficult to pump; and after truly exerting myself, I could hear the pressure relief valve squeak as it released the excess pressure. Performance (we're only talking range) was decent, though not more than I had expected; and considering the pump difficulty, I wasn't as impressed as I usually am. Because all the pressure readings and pumping were messed up, I emptied everything and released the pressure once again.

Then, I completed the PreCharging procedure yet again, this time requiring only 16 pumps. However, while it could take three complete pumps this time, the performance (range again) was simply astounding. I'm not sure exactly how many feet of range the shot got, because I was on a slope and because I didn't have a long unrolling tape measure with me, but I just had to pick up my CPS 4100 to compare the range with.

The shot got approximately the same range as the CPS 4100's smallest nozzle, which is very impressive, and thus only a foot or two less than the CPS 4100's powerful middle nozzle. Obviously, the stream far outdistanced the largest nozzle on the CPS 4100. I pumped the soaker up again (not PreCharging) using the same three pumps, and I managed to get identical results. That's why I like the Argon: (when you get everything right,) it gets amazing performance from a tiny sidearm. Additionally, the dropoff rate with individual shot time as the unit of time was similar to that of my XP 270. The Argon has superb stream lamination; I think it's as good as the CPS 4100's, and we all know that the XP 270 has tons of turbulence.

And now for the final test: pumping up the soaker with no PreCharging. I emptied the Argon and released the pressure, then alternated shooting and pressing the pressure release button because that is the best way to remove as much pressure as possible, which was vital for the experiment. It's obvious that the Buzz Bee Toys PreChargers are not intended to be used in the absence of PreCharge pressure; if anything, the pressure gauge problems and pumping unresponsiveness acted up even more. I'm not even sure that I managed to pressurize everything completely (I know I pumped way less than 16 + 3), but I think I stopped when pressurization started to become more difficult.

The obvious results: performance without PreCharging simply sucked. For some reason, I only got about half the shot time, much less range, way more dropoff, a really messed up pressure gauge, and...well, you get the idea. Fact is, PreCharging actually does seem to provide the best of both worlds (that is, small PC and large PC) after all. I'll really have to excercise my brain to find out why, especially after all these apparent misconceptions.

Part of the PreCharge performance boost might have to do with the fact that, even though a PreCharger PC might act like a small standard PC, each pump fills up a smaller percentage of the PC. Thus, the capacity is much greater than expected, so you get some of the benefits of a larger PC. However, I have not deeply analyzed this new theory (I never finished analyzing the old one, either), and the results I got from my non-PreCharged Argon might be messed up due to a design that is meant for PreCharging.

This has been a great revelation, because it means that my PCgH does have hope after all, even if not for the reasons I had originally thought of. More to come.

EDIT on 6/6/06 at 8:48 PM: Well, I tested out my Argon again, and there were even more dramatic performance differences. It took about 12 pumps for pressurization; and the pressure gauge didn't work, though it took only 2-2.5 or so complete pumps for pressurization. I could feel lots of pump resistance, and the pressure relief valve activated with a squeak, which is rare. Performance was decent, but only average; and more importantly, due to the lesser number of required pumps, it's as if my earlier conclusion was correct: PreChargers pick up pressurization from the point where the PreCharging stopped. The Argon accepted fewer pumps, but the stream resembled the standard 3-pump stream, but it seemed cut off at the end. This seems to signify that the dropoff is the same with shot time as the unit of time and resembled a large PC, but the dropoff and the stream ended at the same time as a small PC. Somehow, PreCharger soakers do combine the best of both worlds; and although I'm not the type of person to just leave it at that conclusion with no scientific justification, I am at a loss and will build the PCgH. Expect results this week or the next.

Needless to say, I released the PreCharge pressure and worked the PreCharging process yet again, though this time with a full reservoir as opposed to an empty one (though, since I believe the PreCharge intake is external, it shouldn't make a difference--I just noted this as another observation). This time, it only took 11 pumps; though performance was similar to that from 12 pumps of PreCharge pressure. It clearly appears as if the PreCharge level remains inconsistent, possibly due to the incomplete release of pressure by the depressurization button. Not only will I build my PCgH, but I will complete the charts that I promised concerning the numerical pressure values given after a certain amount of pumps for a small PC, a large PC, and a large PreCharged PC.

[kanigetts]

The precharger is very clearly far superior than any other method seen so far. I think that you and the other members of this board are hesitating to build one because of its percieved complexity. The problem lies in using a piston to separate the air precharge chamber from the water chamber. Don't use a piston! Simply use a bag or latex tube inside a sealed pressure chamber. Kind of like filling a water balloon inside of an already pressurized 2 liter soda bottle. You could really just enclose a rubber PC inside another airtight container, pump up the outer container's pressure, then fill the PC with water through pumping. The chamber or bag that has the water in it does not need to be strong, like a k-mod, because all of the pressure used to push out the water is supplied by the precharge and the extra pressure applied when the water was pumped into the bladder inside. The precharging can even be done using a separate bike tube valve and then left alone. Your increase in pressure due to the addition of water to the bladder in the precharged chamber could be mitigated by using an air chamber that was a few times larger than the water PC. This would help in controlling drop off as well. You could make a relatively small gun if you moved both the water supply and the precharged air into a backpack. I'm sure that you could even put the check valves in the backpack. You could connect both the water and air precharge to your little gun with 1/4" nylon or polyethelene gas tubing. Even your pump could be separated from the gun. Another thing you should look at is the use of Flourescent light safety tubes. The PVC pipe I see in all of the homemade guns is very bulky and heavy. It is also overkill for the pressures needed for a waterfight. These clear lexan tubes are very cheap, strong and light. 1 1/2" PVC fittings glue onto them with PL Premium adhesive and they hold over 200 psi. Look at some of the water rocket sites for further info on these tubes. They have even been wrapped in graphite weave socks and covered with epoxy to create a vessel capable of withstanding over 600 psi. I wouldn't want to get hit by that stream of water though! The other beauty of the precharge system is its adaptability to different situations in a waterbattle. You could use a high precharge, narrow pump, and a relatively small nozzle for sniping, or use a lower precharge, wider pump, and a wider nozzle for high volumes of water. Don't be afraid of using soda bottles for pressure, the 2 liter size can take over 100 psi, the smaller ones even more. They would be ideal as both your precharge ballast air and your water supply. Imagine hiding filled 2 liter bottles of water around the battlefield so you can just screw a new one on when one runs out. The 1/4" tubing is also very easy to work with and is rated over 250 psi. You don't need fancy fittings, just drill a hole in a soda lid or pvc end cap that is a little smaller than the tube, jam it in there and slop a bit of PL Premium on it. You will be amazed how easy this is to work with. I can envision a gun for under $30 using a brass ball valve as a trigger. I'd like to find some check valves for the 1/4" tubing instead of those bulky pvc ones. My son is having a pool party in a couple of weeks, I'll try to make a few guns and see how they work. I'll post back if it works as I think it will.

[Silence]

Very nice points, kanigetts...it's good to see a new tech-oriented member.

I understand your first arguments, and they are very strong indeed. A watertight trashbag or something along those lines would be very effective inside a PreCharge pressure chamber, and as you said, it would remove part of the hesitancy about building PCgHs. However, part of my hesitancy is that I haven't built a homemade yet, but I plan to this week--and other people aren't necessarily obligated to build my design, even though joannaardway had plans to do so.

However, I think a latex bladder in this setup would be unnecessary. People have suggested plugging up the vent holes in their CPS blasters to have compressed air add to the overall power; but in my mind, giving the soaker some air pressure qualities would make the CPS qualities unnoticeable. If you want more CPS power, then use more latex; if you want more air pressure power, just pump more or use a PreCharge design. In this case, the resolution would probably be to just use a bag instead.

However, when you venture into the backpack design, the user might start to find some operational problems. If both the reservoir and the PC are in the backpack, but the pump and trigger/nozzle assembly are on the main gun, then you will need a hose tube that leads to the pump (although the check valves will be operational in the backpack), and an additional one that leads to the trigger/nozzle assembly. Alternatively, you could put the second check valve on the main gun, but then you'd still need a tube from the reservoir and a tube from the PC--so the weight would be even greater with the check valve on board. When you have such hoses (which have been proposed and possibly even built), they twist and turn in unexpected ways, you get a ton of lag from the narrow diameter, and there's just more complexity.

I just love your point about the clear tubing, as they seem to have many pros and few cons. However, part of the reason they might not be popular is they are potentially harder to cut; however, since I don't know, I'll just take your word for it. In fact, I had been thinking of using just such a material for my CPH that I have plans to build (very tentative plans, though--maybe by the end of the summer), so one can see how filled the bladder is, as is possible in the Super Soaker CPS weaponry (air pressure soakers can use pressure gauges instead, though a piston PreCharger soaker can also use a clear case).

Speaking of CPHs, I have started to prefer building an incredibly high-powered CPH (thick bladder layers, 3/8" pump) over a "spliping" (splash + sniping, which I might write an article about--it just means engaging the opponent early, rather than sniping as such) PCgH, due to various factors: a spliper must have tremendous range after even just a few pumps (he might have time for no more), which is entirely possible with CPS; and similarly, the range must be constantly high throughout the shot. As such, I have given up on a spliping-type PCgH, though that might change if I discover why and/or how PCgHs have reduced dropoff.

I understand your point about 2L bottles, but if I do create a powerful PCgH (maybe with a 3/8" inch pump again, which will produce 16/9 the leverage of a standard 1/2" pump), then the pressure will easily top 100 PSI, though I have also heard that such bottles can hold 200 PSI. If I end up doing a piston-type pressure chamber, then the bottle system will be rendered useless--though for the bag system you suggested, it might be possible. However, if you do use a bag inside the bottle, access to the other side of the bag will also be required; though you could have some fancy two-layer seal at the mouth of the bottle if one really wanted it (the price would then go up). However, the bottle would be perfectly fine for a standard APH, so there's no problem there except for possible output limitation.

For bottles as reservoirs, of course, there should be no problem; however, the system might be somewhat clumsy. You could always just hide 2L bottles filled with water everywhere and use them to fill up your reservoir; chances are that a backpack or even a homemade onboard reservoir will be bigger, and there might be some spills as you replace bottle reservoirs.

Excellent points, kanigetts, and I look forward to hearing more about your project(s). Even if I don't incorporate all your ideas, I will certainly look upon PCgHs and other homemade soakers in a new light.

[joannaardway]

I would post the rest of the stuff, but I don't have time right now.

I still intend to build one of these if I can.

I have foreseen the piston sealing leaks that some have mentioned - However, if I can make a pump that can hold that pressure, why not a piston in the chamber?

I can explain why the PCgH has a reduced drop-off tommorrow. (My tommorrow, not yours).

I'll come equipped with graphs.

[Silence]

I plan to visit Lowes, and maybe even some local plumbing stores and the Home Depot, tomorrow. I'll probably get 10 foot lengths of 1/2" ID PVC and 3/4" ID PVC. I believe I already have quite a bit of 4" PVC, though if it isn't pressure rated to at least well over 200 PSI (or at all), then I'll just get 3" or 4" ID PVC instead. I plan to build two or three homemades at once, probably including at least one PCgH and at least one compact APH (or compact PCgH). Later in the summer, I hope to build a sniping CPH as I stated above; it will have a 3/8" pump and three layers of LRT with more layers of bike inner tubing, and it will only be used at extreme distances (more than 50 feet).

By the way, I'm still waiting for joannaardway's PreCharge system explanation...I'm debating how many PCgHs I should make, and the plans for my compact APH can't be flexible for too long.

[Silence]

I ended up building a compact APH instead...but I think I know why there's reduced dropoff in PCgHs. A break from this question really helped.

Given a PCgH with a piston that moves 6 inches and no PreCharging, it will have to move 4 inches to get a certain pressure. And then let's take another that's PreCharged to 30 PSI, or twice the atmospheric pressure of 15 PSI.

Initially, the uncharged one will have 1 atmosphere of pressure. If the volume becomes only a third of the original, then Boyles' Law states it will have three times the pressure, or 3 atmospheres.

The PreCharged one will start off with 2 atmospheres because there's twice as much air (by mass, not by volume) inside. It reaches 45 PSI (the final pressure of the uncharged gun) as the piston gets pumped to allow for only 4 inches of clearance.

Because the ratio of the final pressure to the initial pressure in the PreCharged soaker is closer to 1, it has less dropoff.

But since there's twice as much air behind the piston of the PreCharged homemade, one can assume that the pump area has to be only half as much as that of the regular soaker. In addition, the final PC water chamber capacity is only half that of a regular soaker! This signifies that you will need the same amount of pumps to fill both PCs.

So what does this mean? It means that with commercial PreChargers, you're trading off PC volume for less dropoff. They're throwing you a curveball: they are harder to pump because the pump is wide, which requires less pumps. Fortunately, reduced dropoff means pumping doesn't get too much harder as you go.

A PCgH with a bigger pressure chamber will solve the problem of limited PC capacity due to wasted space, but of course there will be more dropoff since the final pressure will be higher. Next up: is it better to increase the PC's width than it's length if you want more capacity, or not?

EDIT: You can pretty much trash all my older posts. I must not have been remembering that the pressure scale was exponential, or something like that.

EDIT again: Actually, it shouldn't matter whether you change the piston's area or the length for more capacity. As long as the volume change is the same...