Pull Valve Instead of Ball Valve?

Build a homemade water gun or water balloon launcher and tell us about it.
Locked
User avatar
Captain Galaxy
Posts: 35
Joined: Mon Aug 04, 2008 9:09 pm

Pull Valve Instead of Ball Valve?

Post by Captain Galaxy » Tue Sep 02, 2008 4:27 pm

I know that almost all homemades use ball valves. These can be a pain to use and make it impossible to pump and shoot at the same time. Even though ball valves are more efficient, I believe making a pull valve could make a great homemade trigger system. I realize pull valves can cause the flow to be turbulent, but they worked for the CPS series, didn't they? The design would be based on WaterWolf's check valve, with the proper tweaks. This would make homemades much more practical and easier to use.

User avatar
cantab
Posts: 1492
Joined: Fri Oct 19, 2007 1:35 pm

Re: Pull Valve Instead of Ball Valve?

Post by cantab » Tue Sep 02, 2008 8:09 pm

Pull valves have the advantage that they seem to scale better and still have the trigger not too hard to pull. "Linear flow is good, but high flow is better."

The drawback is, of course, that you gotta build one.

Also, if you're doing it to make the gun easier to use, you also need to consider ergonomics.

Triggers CAN be made for ball valves, but are a bit of a pain in the butt.

I can't think of any time I'd pump and shoot simultaneously anyway. It buggers up my aim.

My Granta design (build expected October/November) still uses a ball valve, but will hopefully be nicely balanced around the handle, allowing easy one-handed aiming, though not firing unless I make a trigger.

One other idea I've had - distinctly unorthodox. Make the pump the torque arm! Might be tricky to hold steady when pumping though.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

User avatar
SSCBen
Posts: 6449
Joined: Sat Mar 22, 2003 1:00 pm

Re: Pull Valve Instead of Ball Valve?

Post by SSCBen » Tue Sep 02, 2008 10:41 pm

Yep, linear flow is good but high flow is better. Well put cantab.

People have thought of pull valves before, but the problem is that you have to make them unless you're satisfied with garden hose nozzles. Ball valves are the highest flow valves that can be obtained easily.

Once I figure out stereolithography equipment or the other CNC equipment at my disposal at my university I might make available some precision machined pull valves, but I wouldn't expect them to be available forever or be cheap. I don't know if they charge me for machine time, but I suspect they don't.

User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Re: Pull Valve Instead of Ball Valve?

Post by Silence » Wed Sep 03, 2008 1:35 am

Pull valves actually don't scale that well. As you increase the diameter, you increase the change in force between the open and closed positions (thanks to pressure acting on the exposed, sealing face). With high pressure and diameter that could be 20-50 pounds of force.

Ball valves get tighter and tighter at higher diameters. A bit of lubing and a torque arm should do the trick.

User avatar
Captain Galaxy
Posts: 35
Joined: Mon Aug 04, 2008 9:09 pm

Re: Pull Valve Instead of Ball Valve?

Post by Captain Galaxy » Wed Sep 03, 2008 2:26 am

I think I've figured out the general idea, the only problem would be keeping it from leaking. I'm considering a piston similar to a pump. Not all of us like to pump and shoot, but it is nice to be able to do it. It's not clear though, if you guys think it could work. By the way, I'll be gone for the next 2 weeks, so I won't be able to reply for a while, so hopefully you will have lots of suggestions by the time I get back.
Last edited by Captain Galaxy on Wed Sep 17, 2008 3:47 pm, edited 1 time in total.
Image
Live Long and Prosper

User avatar
cantab
Posts: 1492
Joined: Fri Oct 19, 2007 1:35 pm

Re: Pull Valve Instead of Ball Valve?

Post by cantab » Wed Sep 03, 2008 9:46 pm

Actually, assuming the coefficient of friction is the same on all sizes of ball valve, the force/torque to open both pull and ball valves scales linearly with flow area.

So it just comes down to which is stronger: pressure or friction?
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

klrluvr
Posts: 7
Joined: Tue Jun 17, 2008 3:45 am

Re: Pull Valve Instead of Ball Valve?

Post by klrluvr » Mon Nov 10, 2008 5:28 pm

I went through this to some extent already. However my LRT blew and it p*##ed me off a bit and I went on to different projects. This thread contains alot of info on one type of pull valve. Good luck...

http://forums.sscentral.org/t5152/

Chris

devvo
Posts: 19
Joined: Sat Jun 14, 2008 12:43 pm

Re: Pull Valve Instead of Ball Valve?

Post by devvo » Fri Nov 14, 2008 6:41 pm

I know its a little off topic but its something I've been meaning to ask for a while. has anyone on the boards tryed using a solenoid valve? I was also thinking of using a pull valve until I acquired a solenoid which if all goes to plan should mean I can press a button without the hassle of messing with a ball valve

User avatar
SSCBen
Posts: 6449
Joined: Sat Mar 22, 2003 1:00 pm

Re: Pull Valve Instead of Ball Valve?

Post by SSCBen » Fri Nov 14, 2008 7:33 pm

Solenoid (sprinkler) valves would work, but they're not for very high flow and would add turbulence to the stream. They're far from ideal and aren't a very good compromise in my opinion. Not to mention that unless you modify the valve batteries will be involved, and we know that batteries and water usually don't mix well.

Modifying the valve would work fine with air pressure, but with rubber CPS or a spring system you'll need to have some pressurized air somewhere to pilot the valve. That's getting rather complex, especially considering the case is far from ideal. It's not worth jumping through hoops for, in my opinion, at least.

Locked