Triggered water gun valve

SSCBen · Post by **SSCBen** » Thu Jun 14, 2007 1:03 pm

A goal of many builders has been a triggered homemade water gun. Drenchenator did it with his ball valve water gun, but I think some people are looking for something more like the typical pull valve.

Interestingly enough, I have come up with a design that uses no O-rings at all and will definitely provide a perfect seal with everything. A big problem before was the seal on the back end of the valve. I remember in my first attempt at making a triggered water gun (back in 2004, before the APH), I had trouble getting a seal that would move easily and provide a perfect seal. The other end was easy--just use a rubber O-ring and a washer to seal against a flat PVC hole from a reducing hex bushing. I've done that before and it works great.

Well, I do know something that provides a good seal and can move. It's piston seals. I can't believe I never considered this before. This makes making a triggered water gun easy, though perhaps a bit on the expensive side at more than $10 per valve. However, potential for flow is not limited, making this a valve to seriously consider.

I apologize, but I do not have the time to post a drawing of the concept, but I think some here should understand what I'm talking about enough. At the moment, I am constructing a Nerf gun to use a similar valve... while Nerf is not water guns, the valve is nonetheless similar and I will post the results here.

Silence · Post by **Silence** » Thu Jun 14, 2007 1:53 pm

Sounds good. Interesting how Drenchenator crafted a neat ball valve system and the pull valve for his second Nerf homemade.

Ben wrote:However, potential for flow is not limited, making this a valve to seriously consider.

By that do you just mean that the valve has large inlets and outlets so as not to restrict the flow? Or is the design completely out of the box? Sounds interesting. I guess I'll wait for your drawing.

Good luck with your projects!

all_washed_up · Post by **all_washed_up** » Sat Jun 16, 2007 2:48 am

Interesting post--piston seals. I'm not familiar with them. I looked at Google Images, but didn't find anything that appeared applicable. I'll look forward to seeing more details here.

I'm about to post a drawing of my first APH design. I've drawn it with a metal ball valve, but I'm actually thinking of another trigger design, something that will allow a more conventional trigger pull.

My idea is inspired by the illustration at howstuffworks. It shows a simple metal clip cutting off water flow. So, what if I incorporated some tubing between the pressure chamber and the nozzle, and pinch it off in between with a mini-clamp. Something like this:

If I mount the clamp in a position with the point on top, with one side secured to an upright, it'll operate much like a trigger.

Any feedback on this idea?

a_w_u

PS: I don't mean to hijack the post; I'm looking forward to a piston seal discussion.

SSCBen · Post by **SSCBen** » Sat Jun 16, 2007 11:33 am

Pinch valves are not a very good idea. Super Soaker stopped using that idea for a reason. They're unreliable, making a seal that apparently is relatively easy to break without pulling the trigger. They typically doesn't allow for good flow and a good flowing version would be hard to make. The fact that Super Soaker stopped using them in favor of a more expensive valve tells me that these valves were unreliable enough to stop production of them, even if they were cheaper.

I'll have a detailed drawing of my design soon, and I don't think too many people will try something else given something this simple.

all_washed_up · Post by **all_washed_up** » Sat Jun 16, 2007 3:09 pm

Yeah, I was worried about those aspects of the pinch valve, though the theory was appealing in its simplicity. I'm looking forward to your drawing.

a_w_u

Scavenger · Post by **Scavenger** » Tue Jun 19, 2007 7:09 pm

Ben wrote:The other end was easy--just use a rubber O-ring and a washer to seal against a flat PVC hole from a reducing hex bushing. I've done that before and it works great.

I don't quite understand how that works, is the o-ring on the rod, or stationary on the bushing?

I can see how the piston seals would be set up, only requiring two seals and no o-rings, though there might be a simpler way than what I'm thinking of.

About the price, I don't think it would be $10 a pop unless it's a large diameter. The smallest diameter on McMaster is 1 1/2" at $3.67 each, and that's still too big for 1" pipe. Also, the piston cups on McMaster are fabric-reinforced, and some triggers probably won't need that for such a small diameter.

By the way, I just found a local (around 20 miles) store that has piston seals, though I haven't seen their selection yet.

Silence · Post by **Silence** » Tue Jun 19, 2007 9:16 pm

The O-ring can be attached to either surface, but you'll want to make sure the washer is on the other one. However, I'd put a bit more faith in a neoprene sealing disc - does the same thing, but it's flat.

You can get piston cup seals that aren't fabric-reinforced. Even the massive 4" ones that Ben used for SuperCannon II have variants without the fabric, I think.

SSCBen · Post by **SSCBen** » Wed Jun 20, 2007 1:31 pm

I don't quite understand how that works, is the o-ring on the rod, or stationary on the bushing?

Hmm... I didn't mean to say O-ring. I mean rubber washer and a regular washer. The rubber washer is on the rod.

I can see how the piston seals would be set up, only requiring two seals and no o-rings, though there might be a simpler way than what I'm thinking of.

The seals needed are one piston seal and one rubber washer. Nothing else. That's the beauty of simplicity.

I probably need to draw a picture. I had planned to draw a picture this Monday, but I wasn't feeling too good, so I never got around to it. I'll see what I can do later today if I remember. Don't let me forget.

About the price, I don't think it would be $10 a pop unless it's a large diameter. The smallest diameter on McMaster is 1 1/2" at $3.67 each, and that's still too big for 1" pipe. Also, the piston cups on McMaster are fabric-reinforced, and some triggers probably won't need that for such a small diameter.

You're probably right. Though I think the price including the allthread, rubber washers, spring, piston seal, PVC and couplers, among other things would add to $10 or more. The little parts add up and I took that into account in my estimate.

The piston cups I used before were fabric-reinforced and I only used them because the others were not big enough. I'm thinking the smaller "Buna-N U-Cups" would be better suited for this valve. With this being said, in my Nerf gun valve I am using a 2 inch fabric reinforced piston seal because I already had one.

all_washed_up · Post by **all_washed_up** » Wed Jun 20, 2007 3:20 pm

Yes, Ben, I'm waiting eagerly for the picture. I am going to dry fit my gun today, with a PVC ball valve, but I may change the design if I can see your trigger in time.

a_w_u

Scavenger · Post by **Scavenger** » Wed Jun 20, 2007 5:46 pm

Something like this?

Unless you mean a threaded rod when you say allthread, then the wooden rod would be threaded and the piston seal and such would be held on with nuts and washers.

I actually have some faucet washers right now and tested them on a trigger, but (since they're faucet) they seem a little harder than rubber and I was testing it against inset 1/2" pvc, not a metal washer. They didn't work, by the way.

SSCBen · Post by **SSCBen** » Wed Jun 20, 2007 6:41 pm

That's very similar to what I meant. Mine uses two inch diameter pipe for the valve part due to the fact that the 1 inch to 2 inch bushings have a flat 1 inch hole, eliminating the need for the washer (and probably helping flow and the seal). My trigger was located differently too, but I like this one better. Thanks a bunch for the image. It's always interesting to see someone's interpretation of some wording. I think it helps the creative process sometimes, as it did here in the trigger setup.

Allthread is a metal threaded rod that can be cut to any length. It's very convenient to cut the rod to whatever length is wanted. Threaded rod is very useful and I think it needs to be used more often in homemades.

Perhaps allthread with one of these seals isolated on the end with hex nuts would make a good pump? I'm liking that actually because a handle can easily be threaded on to the other end.

all_washed_up · Post by **all_washed_up** » Thu Jun 21, 2007 3:54 pm

Sweet design. I'm going to stick with the ball valve for the gun under construction, but the next one will be for my son and I'll give this trigger design a try on that one. Thanks.

SSCBen · Post by **SSCBen** » Thu Jun 21, 2007 4:48 pm

Okay, I'm going to buy the parts for my Nerf valve today. This valve is very similar to this one and I'm buying a variety of parts to test different things out. We need to know which pieces work well and which ones don't.

I also want to say something I had not said earlier. Scavenger's drawing needs an important washer/aligner to be installed to keep the seal in alignment or else it would be movable and not sealing. This aligner is important obviously, so I thought I should mention it for anyone who wants to try out this type of valve before I do.

Scavenger · Post by **Scavenger** » Thu Jun 21, 2007 4:49 pm

I just realized something. Allthread would work, but how would you get a trigger on? Maybe a peice of metal and some nuts? Or you could drill a hole in another rod (wood or metal) and then use nuts and washers to hold it on. But then the trigger would be really wide, hmm.

Silence · Post by **Silence** » Thu Jun 21, 2007 6:48 pm

You've changed my mind about sealing plunger faces. I'd always been more keen on O-rings sliding in tubes with holes, but sealing faces look better in most applications now. Easier to build, takes less space, perhaps cheaper, no friction, more flow, instantaneous opening...the list goes on and on.

Of course, for valves like the one on Drenchenator's second Nerf homemade, you'll have to use a sliding plunger so that no two ports are open at the same time.

EDIT: What if you had both the inlet and the outlet on the face that the trigger face seals? That way, you could have the plunger the size of the valve chamber and use an O-ring on the plunger itself. That'll center the plunger and it might make the valve a bit more compact. Having two holes in one face would require drilling and epoxy though.

My only concern is the way the forward/backward forces on the trigger rod and plunger will change as you open and close the valve. The surface area on the plunger's face that contacts pressurized air changes often, so the trigger rod might jump around a bit.

EDIT again: Nevermind. I guess the forces would change similarly for a sliding plunger valve anyway.

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