First homemade - improvements?

[zedzed9]

I'm the wrong side of the Atlantic for cheap PVC, so I went for a copper build. The pump shaft goes through the middle of the main shaft, and the pressurised water goes around it. [diagram]

But the performance is a little disappointing. It's currently only slightly better than my xp105 (although with a larger reservoir), and the range is nothing like those boasted by the other homemades around here. I've just been reading through the forums and it looks like my main problem is turbulence. Obviously I can't do anything about getting a more linear flow to the nozzle now, but I was wondering about modding/replacing the nozzle to get a better flow through it.

[Ben]

Welcome to Super Soaker Central!

The combination of ball valves on the PCs, a hose handle as a nozzle, and the fact that the PCs are relatively small reduce your performance. The ball valves appear to be open slightly, which introduces turbulence. They don't introduce turbulence if they are completely open. Typically people add ball valves there as an "improvement" to repressurize the PCs after some are empty, but the pressure drop from one PC to others would be too large. If the other PCs are disabled before, the ball valve system overall is useless because you could achieve the same amount of water being output without the ball valves. I would suggest removing those valves in future designs unless you had them there for another reason.

The garden hose nozzle also is a poor choice for efficiency. Some have actually bored out nozzles, but most have a weird system that is extremely inefficient in terms of range, even more so than the similar pull valve the Super Soakers used a while back. The bends and small diameter tube also limit performance very much here (The combination of the garden hose nozzle and the small diameter tube are your true performance "killers"). The PCs also are relatively small, reducing the total water that can be shot and also the pressure that is easily obtainable.

Much can be improved in this design. You can probably cut off certain parts of the gun and add improved versions. I would suggest removing the bend that leasts to hose handle first. Put a ball valve there. You should see a notable improvement in range by eliminating the very inefficient hose handle. After that I would replace the PCs with something larger and remove the ball valves. There's no reason you shouldn't have a high performance water gun after all that.

[zedzed9]

Hah, indeed.

The ball valves are there so that the pressure chambers can be used independantly to keep a surprise shot in reserve. Most of the time all three are fully open. It should be easy to remove them if necessary.

The pressure chambers were constrained by the fittings available. They have to be either than size, or twice that size, and that affects the balance too much.

I guessed the hose handle would be a problem- there's a reason nobody uses them. For ergonomics, I was hoping to avoid a ball valve trigger. Ah well. Thanks.

[Ben]

The ball valves are there so that the pressure chambers can be used independantly to keep a surprise shot in reserve. Most of the time all three are fully open. It should be easy to remove them if necessary.

That's similar to what I mentioned. Nothing positive about that design has been reported, however, few were made. One was made in 2004 after someone (could be me) suggested it and the user reported it was less than useful. If you find it useful, keep it. Remember however that you always can have a "surprise" shot by not shooting all the water out at once (a large partial chamber shot still is a shot). That keeps the costs down, prevents you from flipping too many switches, and doesn't allow your enemy to guess what you're doing from the valve settings. If you'd would like a surprise shot, I would suggest a large pressure chamber.

The pressure chambers were constrained by the fittings available. They have to be either than size, or twice that size, and that affects the balance too much.

The PCs appear to be 2 inches (about 5 cm) in diameter. Typically people use multiple longer, perhaps as long as a foot (about 30 cm) pressure chambers in that diameter and they report good performance. What matters most is total volume. More mass seems to keep the stream together better perhaps due to an increased ability to resist drag. I would agree that 4 inch chambers might seem a little unbalanced, but a larger single 4 inch diameter chamber probably wouldn't be a bad choice at all. I have not had any balance problems with my 3 inch chamber water guns, however, I do use a strap which seems to negate balance problems. I would suggest a strap if balance is a concern of yours.

Another thing to consider if you wanted better balance is to get rid of the ball valves because they put the weight too far from the center.

I guessed the hose handle would be a problem- there's a reason nobody uses them. For ergonomics, I was hoping to avoid a ball valve trigger. Ah well. Thanks.

Once you become acclimated to a ball valve trigger, the only disadvantage is that two hands are necessary to operate the gun. That can be seen as an advantage if you desire a steady shot and I have not found it to be limiting. Ball valves are readily available, cheap, and have high performance characteristics such as laminar flow and a potential for high flow. The ergonomic disadvantage is outweighed.

[Silence]

Welcome to the Super Soaker Central forums, zedzed9! That's a very nicely-built water gun, I must admit. I like the unique design - most people would have the nozzle on the other side, so the pump is on the same side and the hose tube for the reservoir is in the back.

I'd also suggest using a larger pressure chamber. You could quite easily get 3" or 4" piping but orient it sideways, parallel to the main tube. Although it would drop the ability to turn pressure chambers on and off (which I also agree might not be very useful - your call though), it would vastly increase both the volume and balance, while perhaps reducing cost (although you've already paid for this much anyway). Just make sure the opening for the horizontal pressure chamber is on the bottom and near the rear.

I also agree you'll need a ball valve (and not to mention larger, less turbulent nozzles) for better stream performance. Ben might still be experimenting with high-flow pull valves (which can be actuated like triggers), so I'm surprised he hasn't brought them up yet here.

[Ben]

I'd also suggest using a larger pressure chamber. You could quite easily get 3" or 4" piping but orient it sideways, parallel to the main tube. Although it would drop the ability to turn pressure chambers on and off (which I also agree might not be very useful - your call though), it would vastly increase both the volume and balance, while perhaps reducing cost (although you've already paid for this much anyway). Just make sure the opening for the horizontal pressure chamber is on the bottom and near the rear.

This is a definite possibility. However, I want to clarify what must be done for this design to work optimally. The parallel PC must be facing towards the nozzle and have a water line (the line where the water meets the air) above the pipe to it. Angling the PC towards the nozzle would allow for that, help a potential balance problem, and also reduce cost. Good idea SilentGuy! Perhaps that should be a "standard" design practice. I hadn't really considered angling the PC in that direction until now.

I also agree you'll need a ball valve (and not to mention larger, less turbulent nozzles) for better stream performance. Ben might still be experimenting with high-flow pull valves (which can be actuated like triggers), so I'm surprised he hasn't brought them up yet here.

Sadly I don't have the resources to continue experimenting here at college. Once I figure out how to use the full resources of College Park however I will continue my experiments. Tomorrow I intend on posting something about the Nerf gun I started building with the valve design. I'm also waiting for some sort of lecture on the use of the rapid prototyping equipment here.

Drenchenator has been working on a type of pull valve with mixed results. It's not at all like what I described and is a completely new valve design. It needs some bugs worked out definitely, but right now it is functional. I'll leave posting about it to him.