APH Design Questions

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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AmaIro18
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APH Design Questions

Post by AmaIro18 » Mon Oct 08, 2018 2:45 pm

I'm thinking of making an APH and I had a few questions.

Consider the two APHs (please excuse my sloppy drawing, drew it on my phone):
Image

Image

If the two APHs have the same volume for their horizontal pressure chambers, and the two were tested at equal pressures, would adding more connections to the pressure chambers (like in the bottom picture) affect the flow rate at the nozzle? Also would it affect the force required to pump the gun?

I would guess that it doesn't affect the pump force but it might affect the flow rate until the bottleneck becomes the nozzle. I'm not 100% sure though.

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Re: APH Design Questions

Post by SSCBen » Mon Oct 08, 2018 2:48 pm

This should not appreciably affect the pumping. Generally the wider the flow path, the higher the flow rate. In this case the main bottleneck is the nozzle as you said, but you might find adding more connections to slightly improve the flow rate.

However, these designs would not work well as-is because you need to keep the water level above the nozzle (when the gun is angled) or else most of the water can't be fired. That's what I used vertical pressure chambers. You also can have chambers angled forward, which is something DX did first as I recall.

AmaIro18
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Re: APH Design Questions

Post by AmaIro18 » Mon Oct 08, 2018 4:24 pm

Thanks Ben. I ask because my hardware stores only carry up to 2" pvc. To get the equivalent PC volume as 3" APHs, the 2" pvc would have to be pretty long in comparison. Do you think it would be alright to have 3 vertical chambers in my case?

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Re: APH Design Questions

Post by SSCBen » Mon Oct 08, 2018 6:30 pm

People have done 3 vertical chambers before. I haven't tried it myself, so I can't comment on whether it has height or balance issues, but I don't imagine it's any worse than the two 3" diameter chambers I used in the guide.

AmaIro18
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Re: APH Design Questions

Post by AmaIro18 » Tue Oct 09, 2018 11:25 pm

The APH guide gives the expected range for 1/4" and 3/8" nozzles, but what kind of shot times / range dropoff should I expect?

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Re: APH Design Questions

Post by SSCBen » Wed Oct 10, 2018 12:51 pm

I don't remember clearly. The dropoff was fairly bad, as it typical for air pressure, so I don't think you have more than a few seconds before you'd want to recharge.

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Re: APH Design Questions

Post by marauder » Fri Oct 19, 2018 7:19 am

Have you considered ordering 3" pvc from online?
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AmaIro18
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Re: APH Design Questions

Post by AmaIro18 » Fri Oct 19, 2018 3:09 pm

I thought about it, but I prefer to just go to a store and buy it. I ended up using 2" pvc. It's strange... some of my local hardware stores sell 3" pvc fittings but not 3" pvc pipes.

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Re: APH Design Questions

Post by SEAL » Sat Oct 20, 2018 10:45 am

That's weird. Pretty much any Lowes or Home Depot that I know of sells up to 6" pipe. But I've made a gun like this with 3" chambers before, and it was the most unwieldy water gun I've ever used. You definitely want to make the blaster as compact as you can. A good nozzle should still give you better range than most stock soakers. I mean if you think about guns like the MD 6000, it can hit 40' and its chambers and tubing are tiny. As a matter of fact, I replaced the PCs on mine with much 1L bottles, and the power did not actually increase all that much.
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Re: APH Design Questions

Post by SSCBen » Sat Oct 20, 2018 5:51 pm

The problem might be pressure rated pipe and fittings. Lowes and Home Depot usually have a good selection of non-pressure rated pipe and fittings. The current APH guide uses non-pressure rated pipe and fittings because I didn't know any better at the time. I intend to fix this next year. Our pressures are fairly low, so there haven't been any problems with this as far as I know, but I'll still fix it.

AmaIro18
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Re: APH Design Questions

Post by AmaIro18 » Sat Oct 20, 2018 9:17 pm

My local Lowes sells up to 1.5" sch 40 PVC pipe but also sells 2" and 3" sch 40 PVC fittings. They do sell non-pressure rated ABS up to 6". My local Home Depot sells up to 2" sch 40 pvc pipe and fittings. They do sell larger non-pressure ABS as well. I wasn't sure how much pressure they could actually handle, especially with using PVC to ABS transition cement, so I just stucked to sch 40 PVC to be safe.

My APH shoots 50-55 ft, but the pump I made out of a wooden dowel leaks at high pressures

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Re: APH Design Questions

Post by marauder » Thu Oct 25, 2018 8:17 am

SEAL wrote:That's weird. Pretty much any Lowes or Home Depot that I know of sells up to 6" pipe. But I've made a gun like this with 3" chambers before, and it was the most unwieldy water gun I've ever used. You definitely want to make the blaster as compact as you can. A good nozzle should still give you better range than most stock soakers. I mean if you think about guns like the MD 6000, it can hit 40' and its chambers and tubing are tiny. As a matter of fact, I replaced the PCs on mine with much 1L bottles, and the power did not actually increase all that much.
The range didn't go up much, but I thought it was a lot more effective in combat. The shot time stock was so little. The added range and definitely the added shot time made it much more competitive.

But your point still stands about homemade. Basically internal size determines a lot. Speaking of which, maybe we could get together sometime and work on a new prototype.
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Re: APH Design Questions

Post by SEAL » Thu Oct 25, 2018 3:45 pm

^Yes, and that coupled with a larger nozzle (3X maybe?) that I drilled out certainly was an improvement over the stock gun. But my point was that larger chambers don't necessarily equal more power. So you don't need massive water tower-sized PCs on your homemade, unless you really want the extra shot time. Guns like the MD6K can still hit 40' even with small internals and PCs. Basically, we should be thinking small in the homemade department. My old APH would probably get slaughtered by a 6K in one-on-one combat.
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Re: APH Design Questions

Post by Drenchenator » Thu Oct 25, 2018 10:54 pm

I think the internal diameter matters more for performance that the chamber diameter. Certainly 4" diameter PCs hold a lot more water, but I don't think they would perform much better on their own. If your gun is designed purely for range and output, you should use the biggest PCs you can buy. But more combat-ready guns would require you to think about the tradeoff between size/weight and the performance.

Also, I don't think people take into account the weight of the guns (and water) though, and that's why I second SEAL's idea of using smaller parts going forward. My homemades tended to use 3/8" brass for the internals, and I was still about to get around 40 feet of range with only a single layer of latex rubber tubing. If I used 1/2" brass, it would have weighed a lot more and probably would have only performed marginally better at best. Anything smaller than 3/8" likely will hurt performance a lot, but 3/8" and up seems fine.
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AmaIro18
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Re: APH Design Questions

Post by AmaIro18 » Fri Oct 26, 2018 10:48 pm

I have to say that I prefer my Pump Action Homemade to my APH that I made. My APH's wooden pump leaks at high pressures, has pretty bad shot time, and is extremely cumbersome. Yeah you can get a 50+ ft shot but you're a sitting duck when you have to deal with a slow/uncomfortable/leaky pump. My PAH is much more maneuverable since there are no pressure chambers. On top of that I can get 47 ft shots every single pump.

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