WaterWolf - Question about PCs

[WaterWolf]

Well, recently I dug up some old designs I had for an APH and started making revisions. Then I began wondering about the pressure-chamber/s.
So my question is, what are the advantages/disadvantages of having two pressure chambers instead of one? (Eg: One 10" chamber vs two 5" chambers)
I'd searched around on the other forums and found conflicting data, so I thought I'd ask people here.

I'm designing this homemade to be compact, powerful, tough, high-shot-time, long-range and a relatively low price tag. (Compared to other APHs) Code named: Paladin.
So far, my design on paper has achieved all of these goals and I was in the process of putting the finishing touches on it when I ran into this issue.

I'm not sure when I'll start construction of it, probobaly sometime this year.



Edited By WaterWolf on 1171981938

[isoaker]

Two chambers lets you potentially have greater amounts of pressurized water, but also introduces another layer of complexity into the design, reducing the laminar flow where the T-joints are. An advantage is that for the same total volume, dual (or more) PCs lets the overall form factor of the soaker to take on a longer, more balanced (weight-wise) shape than a single, large chamber would allow. Consider an XP 270 versus a Pool Pumper Blaster. One could theoretically swap on a 1L PC onto the XP270, but then it'd get much more front-heavy. The PC could be moved more towards the rear for better balance, but you'd still have a top-heavy issue whereas the Pool Pumper Blaster has its weight of PCs evenly distributed along the top, making the soaker feel less prone to tipping when the PCs are filled. A soaker with a single, taller PC (the SS 200 comes to mind, does feel more unstable to hold when the PC is filled. Then again, the whole design of the SS200 is top-heavy, but I'm referring to when the reservoirs are empty and the PC is filled.

That said, the turbulence issue shouldn't be neglected. It really depends on how much you want to maximize your soaker's range. From my understanding, a single PC should be able to generate better flow than two or more, thus if you can pressurize it, you should be able to form a better stream. Not sure how much decrease a dual (or more) system loses in range compared to a single PC, though, so it may not necessarily be a huge difference.

[HBWW]

It also has to do with surface area, with more surface area it's more powerful. Regardless of volume, more surface area means more air pushing on the surface of the water. The extra PC's are a way to increase that surface area. (doesn't really matter what the volume is here) Picture a 3" PC that's really short, vs one that's 1/2" and really tall, tall enough that it holds the same amount. Same concept, except it's going throughout different PC's. As for just one thick PC (as in really big, like over 5" if it's possible), the reasons iSoaker mentioned come in.



Edited By C-A_99 on 1171987493

[isoaker]

@C-A_99: surface area! Forgot about that one, too; Good point! Then again, one could increase surface area in a single PC by using a much larger diameter chamber, but then there's the problem of directing the water (and only the water) into the hole that connects the PC to the nozzle.

[WaterWolf]

So basically, two 3"W x 3"H PCs is better in that they have more range and balance, but worse flow and more expensive to build.
While a single 3"W x 6"H PC will have better flow and is cheaper to build, while making the gun less balanced and possibly having slightly less range.

I'm leaning towards building it with two, but the biggest problem I have with that is that it means more parts to glue, while raising the price-tag from $42.50 to $52.20, and I'm trying to keep it fairly cheap.

Heres an idea though, what about using one of these as a single PC? It could give you lots of surface, while keeping it cheap. The only issue I could see with this is that it might be a little hard to get all the water out.



Edited By WaterWolf on 1171995683

[SSCBen]

The advantages of price by the single PC are outweighed by the advantages of balance and the small increase in power by the dual PCs in my opinion.

The flow from one single chamber compared to two chambers are about as turbulent as each other. The streams appear about as laminar as each other. Of course, the advantage of having less turbulent flow is increased range. The problem with having one PC is that there is half the surface area, which means half the power at the same pressure (force is the surface area times the pressure). Half the force is significant.

And of course, having laminar flow is no replacement for high force. Force matters for the majority of water gun performance, followed by potential for flow (the diameter of the pipes essentially, and what matters is that the diameter is larger than the nozzle really), and having laminar flow. Perhaps in the past I pushed laminar flow too hard. Not having perfectly laminar flow isn't bad. What is bad is having turbulent flow. Laminar flow mainly is an efficiency issue.

With that being said, achieving the same pressures that you would achieve with a single PC water gun on a dual PC water gun will be difficult. What work you put in, you get out (basic physics). If you do the same number of pumps on each PC, they should be similarly powered. The dual PC design will get more force on higher pressures, but for the same number of pumps as the single chamber, it will have lower pressures. Essentially, how the PCs are set up on a water gun that uses a hand powered air pressure pump doesn't matter for the actual power in the end. What you put in is what you get out. Surface area matters much more on water guns that have an external pressure source, such as Supercannon II.

However, in my experience a dual chambered APH is a little bit more powerful than a single chambered one. For some reason, you can put more work in easier with dual chambers. The dual PC versions of my APH shoot perhaps a foot more than my single single chamber version.

The most major problem with having one big 10 inch PC is balance however, as iSoaker noted. If you make a water gun like that, it will be very unbalanced. I would consider one like that nearly unusable. I would recommend dual PCs for the balance reason alone.

Using a tee isn't a good idea because you won't get much of the water out, as you noted. Also note that the water gun will achieve maximum range at about a 45 degree angle (actually slightly less due to the starting height, but I always get too technical). For that reason, the surface where the air and water meet would be an ellipse even on the tee, reducing the potential surface area by a lot. And as I said before, due to the work principle, what you put in is what you get out, so for hand pumped water guns, surface area matters a lot less anyway.





Edited By Ben_ on 1172008459

[SilentGuy]

Here we go again...

Two PCs allow for greater volume though, and that means less dropoff. They also have better balance. I'll work out some figures regarding the actual maximum pressures and dropoff.

Check out Duxburian's homemades, probably at SM or SSC, to see how he used sanitary tees.

EDIT: Just saw Ben's post.

sbell25's homemade has two large PCs, but expect a single PC to be that size if you want a lot of volume.

I'm wondering whether or not you get equal pressures with homemades with different numbers of PCs. Does it act like Pascal's principle? Or not? In other words can you get twice the pressure with a single PC? I'll have to think about it.



Edited By SilentGuy on 1172009020

[WaterWolf]

Ok then, I've put the changes for 2 PCs on my design and recalculated its costs.

It looks somewhat like this homemade, with the standard APH configuration, but mine's more compact, has fewer parts, bigger pressure-chambers, a lower price tag ($52.20 instead of $62.00) and a 1/2" pump rather than the 3/4" pump. (This is part of what gave his the poor range stats, the pump on his was too wide)
Another major difference between Peppers design and mine, is that on mine I'm making it so that all the major parts can break-down, allowing you can replace or repair individual sections without having to build another gun from scratch.

I think this is going to be an excellent assault-rifle, with high range, power and shot-time, while retaining a low(ish) price-tag and high battle practicality.

[SilentGuy]

I wouldn't bother with the whole replacement compatibility deal. I really don't think it's worth it--I doubt there'll ever be any repairs, and little will probably be salvaged for any future guns. Unless you mean that you're leaving space between the components, which still probably isn't necessary.

My APH isn't really as battle-practical as I thought, but there are some definite improvements to be made...especially ergonomically.

[WaterWolf]

Thats why I'm building mine this way.
I built my recent WBL with that in mind and I am VERY thankful that I did, I had to make several revisions of the trigger and the secondary PC, so having had that experience, I think its definitely worth it.

In what way was your APH impractical in battle?

[SSCBen]

The largest problem with homemade water guns in battle is the trigger. Most homemade water guns use a ball valve for a trigger. At first, this will be akward to use because most everyone who is building their own water gun has used a manufactured one before that operates with a pull trigger. However, you'll get used to the ball valve trigger relatively fast, that is, after about a battle's worth of use.

At the moment I'm used to both pull triggers and ball valves. I wouldn't know which I am faster with. I do prefer ball valves however because they're cheap, much more reliable, and have the best laminar flow possible from a valve.

Other things like positioning of handles, the existence of pump handles, and such are really more up to the user. If you'd prefer a softer grip than the PVC plastic, there's some really great bike handle bar grip tape that you can wrap around the handle.

I would actually highly suggest putting extra pipe length between each fitting and using threaded fittings for the parts that you can use them on. Repairs are less likely in homemade water guns, but you may want to change the way you designed something later either because it didn't work right or you want to upgrade your water gun.

For example, on my CPS homemade water gun I am considering upgrading the diameter of the pipes for everything from the PC to the valve. This upgrade would allow me to use larger diameter rubber tubing which has much more force and also allow higher outputs and larger nozzles to be used.

[WaterWolf]

Well the ball-valve trigger shouldn't be a problem for me, I've had experience with them before.

I like the idea of making the parts of a homemade able to break-down partially because as you use it, you may find that you want to make some small changes.
A little more water here, a little less weight there, a different grip.
By building them this way, you can configure the gun to whats right for you, instead of having to start from scratch again.

Good luck with upgrading your CPH, that thing is a beast.

[SilentGuy]

My APH seems impractical for a number of reasons. The balance is terrible, the pump isn't that great, the nozzles are terrible, the backpack is unreliable and leaky...and it's not ergonomic at all. Plus I still have to get used to tap shooting with a ball valve. The whole thing is probably a little too big and heavy anyway.

Also, I doubt I'll ever bother with using any diameter over 1/2" for the tubing. The riot blast seems a waste, and the 1/2" ball valve will likely be easier to turn. And I'm thinking that using smaller tubing will actually allow for small CPS tubing and the powerful larger tubing.



Edited By SilentGuy on 1172098359

[WaterWolf]

The other problems I can understand and have taken into account on mine, but what do you mean when you talk about terrible nozzles?

[SilentGuy]

None of the homemade nozzles I've drilled so far have had good lamination. But that might just be my skills (or lack thereof, if that's the case) or my drill. Anyway, if you can create a good nozzles, then that really shouldn't be a problem.

Note that I'm still happy I built my APH. It was just fairly hard to predict what it would turn out to be like, especially in battle. We'll see though, yours might be a silver bullet homemade. Good luck!

[WaterWolf]

O I doubt that its going to be THAT good, its basically just a step up from the standard design, by combining the positive aspects of several APHs that I've seen, while doing everything I can to keep it compact and low-priced.

If I was so inclined to (and I might be someday), I could design one to be the very best that my mind can come up with, but it would probably be quite expensive and right now I'm focusing on designing equipment that can be built/operated by basically anybody with a little skill in PVC.

If I were to attempt the construction of a Silver-Bullet, I would probably spend at-least year designing it and get everybody in the community in on it, so as to have a massive brainstorming of ideas.



Edited By WaterWolf on 1172107914

[DX]

The largest problem with homemade water guns in battle is the trigger

IMO, the trigger is the least-problematic thing about a homemade. The flip motion or a ball valve has become engraved in my memory equally to that of the pressing motion.of a normal trigger. You can easily tap/pump with a ball valve, which is a key part of Battle Practicality [which needs a new article due to changes in what that means]. My biggest problem with homemades has been range, stiff pumps, and reservoirs. I can't get them out of the high 40s, can't get my pumps to stay constant, and can't get large reservoirs to balance well enough. Compared to the 1100, which has 50ft, a perfectly sliding pump, and great balance, my most practical homemade still falls flat. I've probably wasted hundreds of dollars chasing the perfect battle practical homemade, and still am far from it. There's also the slight problem of it being quite "chilly" at home. PVC cement is not allowed inside the house, and it freezes when left in the barn, so I simply can't have any until the nightly lows get out of the damn teens. I've made no progress in homemade building since October or so.

@Waterwolf: Make the topic! I'm serious too, I've GOT to have a homemade more powerful than my modded guns that is more practical as well. You wouldn't believe how many stupid stand-offs and kill opportunities could have been solved by 10 more feet of range. In my mind, that's the main reason homemades are not as popular as they could be. Not the fear of injury, or pricing, or building, or any of that. They simply are not as practical as they should be. You've probably got terrain up there in Vermont that, like the Ridgewood battlefields, that demonstrate the faults in the homemades of today.

[WaterWolf]

I have that same problem with the PVC Cement.
Luckily, part of our current house just got designated as my work area, so I can glue and paint in there now.

Sure, I'll start the topic right away.
To fix the problems you've had on yours, have you tried 1/2" track-pumps or more pressure chambers? Those could potentially fix the range and stiff pump issues.

[DX]

The main problem is my seals. They suck, even with the perfect sized o-rings. For some reason, the PPPs don't leak whatsoever, yet these same sized pumps sometimes do with enough pressure. After the initial lubing, the pumps work alright, and then after a night of no use stiffen up. Wooden dowels expand when wet, so they make the O-rings get ever-so-slightly larger as well. Cutting a little trough sometimes helps, but then the seal is ever-so-slightly too small, resulting in leaks.

[SilentGuy]

I've had a bunch of pump problems too. I'll try the pump design on SSC now though, and use aluminum rods.