New Linear Flow Valve

[Drenchenator]

Sorry for the double post, but I finally edited out a small section of a video demonstrating how the valve works. Enjoy.

http://images.sscentral.org/valves/linear_valve.mov

In the video, I pull down on a length of steel rod to open the valve. The spring pushes the cylinder back up again, closing the valve.

I'm a still trying to think of a good name for this kind of valve. "Rod valve" and "cylinder valve" just don't seem as good as "ball valve." Does anyone else have any good ideas?

[Silence]

"Gate valve" is probably the best name...took me a moment to remember it though.

I'm wondering how you'll make sure the rod stays aligned. I feel it could easily twist, which could suddenly induce turbulence in a full-bore valve. Any solutions, besides a groove or square guide rod or something?

[Drenchenator]

It has linear guides that limit the cylinder's motion. It won't twist as long as the steel rod is in. Plus, I made an "alignment hole" to properly align in the first place. I have video of the assembly of the valve that could demonstrate this but it is big (~60 MB). Furthermore, it didn't twist during testing. The spring doesn't provide a rotational force; it can't see how it would twist unless someone actually grabbed it and twisted it.



The guides also limit vertical motion; the cylinder cannot be removed without the removal of the steel rod. I thought the design through.

[scupper]

I've been looking for something like this for my gun.

I've been looking for weeks trying to come up with something that would open the valve and also be inexpensive.

I try to make alot of these for my kids, nieces, nephews and friends when we have get togethers. It gives them something to do and since it's out of my pocket, and never charge anything, I need all the help I can get

[Drenchenator]

I've been looking for something like this for my gun.

I've been looking for weeks trying to come up with something that would open the valve and also be inexpensive.

I am assuming that from your other post you are trying to build marshmallow guns. This valve would not do them justice; it was designed for linear flow. In water guns, the turbulence of the stream plays a big role in a gun's performance. In an air gun, like a marshmallow gun, valve opening time is much more important. A cheaper and more available option for a marshmallow gun is a garden hose handle.



The bottom handle accepts 3/4" female PVC fittings at the nozzle and 3/4" male PVC fittings at the other end. As shown, a simple PVC fitting threads cleanly onto them. The trigger is also included in a hose handle; my valve is just a valve. I've made a hose handle gun for Nerf darts and it works great with marshmallows as well. Look around at a local hardware store or Lowes or Home Depot. They should still have a good selection of handles.

[scupper]

Drenchenator,

Thanks for the hint. I started making mm guns around easter of '06. It's still too cold for soakers in NJ. I've just begun trying to make soakers.

Do you think though on your valve, if I was to make the hole bigger it would work? I thought with a rubber gaskets on either side of the hole they would keep the air pressure intact. I would then release the pressure by rapidly pressing down on the cylinder. I would have to place a stop or something to keep the plunger from popping out.

What do you think?

[Drenchenator]

Do you think though on your valve, if I was to make the hole bigger it would work?

Yes, it should work as long as the hole is not as wide as the pipe (the cylinder would split into two at that point). This valve is a prototype for a later version that I will build using rubber rod and a larger hole as discussed earlier. Since the pipe is 5/8" wide, I would probably try a 7/16" hole at most. The hole in the prototype is 5/16" wide.

I thought with a rubber gaskets on either side of the hole they would keep the air pressure intact.

I don't think that rubber gasket would work. Unless you carefully roll it into a cylinder, a valve like this one would leak. However, if you could find a way to just block the hole, it would work. In the end, I will use rubber rod as the cylinder in my final valve. It is available in the correct size (5/8"), does not require any work to make it fit, and will not leak.

I would have to place a stop or something to keep the plunger from popping out.

As stated several posts ago, the cylinder will not leave the housing unless the steel rod holding it in is removed. I left the top of the cylinder open for easily removal later during repairs. The linear guides prevent removal from both directions (up and down) when the steel rod is inserted; furthermore the bottom grey section does not allow the cylinder to enter. It serves only as a housing for the compression spring.

(Below: the spring housing, disassembled)



Since I assume you are a first time homemade water gun builder, I would highly recommend that you use a simple ball valve instead. This valve is more or less on the "cutting edge" of Super Soaker design and quite frankly, I haven't even built the final design yet. But if you would like to build it, go for it! I would be flattered. Just remember to use rubber for the cylinder and you should be set. The valve should be leak free as long as the cylinder is rubber.

I don't have access to the valve at the moment. I am at college and the valve is at my parents house. From memory though the materials include:

• 1/2" schedule 40 PVC cross
• 1/2" schedule 40 PVC
• 5/8" rubber rod (available at McMaster-Carr)
• 3/8" PVC sheeting
• 1 1/2" long 3/8" wide compression spring
• 1/8" steel rod

You will have to figure out the needed dimensions; I do not recall them at the moment. If you would like a higher flow valve, I would build it out of 1" schedule 40 PVC because the internal diameter is almost exactly 1" and 1" rubber rod is available for a cylinder. If you need more specifications, don't hesitate to ask.

[WaterWolf]

This is an excellent innovation.
I have long wondered whether it would be possible to make something that could open and close near instantly with good linear.
Yet another item for me to experiment with this winter, which is when I usually do most of my homemade work.

A larger version of this prototype could also make for a perfect water balloon launcher firing mechanism. Imagine a 2-inch diameter valve, that could be opened almost as easily as a real trigger, while remaining within people's budgets.
It would be like a cheaper version of the SGTC Supah-Valves, but with better flow.

[Drenchenator]

I have long wondered whether it would be possible to make something that could open and close near instantly with good linear.

It does open quickly. Another advantage of this valve is that it closes automatically. Though ball valves offer the maximum flow, they do not close automatically like this one. I tried for a long time while building my CPS homemade to make a ball valve close with a spring. No matter how I oriented the spring, it would not close the valve all the valve. I was able to get the trigger system to open the valve all the way, but if the valve can't close all the way the gun is pretty much useless. I still have to figure out a trigger system for this valve though (pullies come to mind).

A larger version of this prototype could also make for a perfect water balloon launcher firing mechanism. Imagine a 2-inch diameter valve, that could be opened almost as easily as a real trigger, while remaining within people's budgets.

I would still prefer a solenoid but larger sizes of this valve should not cost too much and could be used in a variety of applications. This valve would be preferable to a ball valve in a launcher because it opens easily and quickly. On McMaster, the prices of rubber rod vary greatly, but many lengths of rod are very cheap.

If anyone is interested in building one of these, the list below should prove useful in determining which pipe sizes should fit which rod sizes.

• 1/2" schedule 40 PVC uses 5/8" rubber rod.
• 1" schedule 40 PVC uses 1" rubber rod.
• 1 1/4" schedule 80 PVC uses 1 1/4" rubber rod.
• 1 1/2" schedule 80 PVC uses 1 1/2" rubber rod.
• 2" schedule 40 PVC uses 2" rubber rod.

[WaterWolf]

One way to cut down the price and up the availability of this valve would be to use silicone sealant instead of the rubber rod.

Fill the inner 1/2" pipe with the silicone, let it harden up, then drill the hole through.

I don't have hands on experience, but I think this would most likely work since there isn't much pressure being put on the rubber section itself. Its just keeping the water from spraying up or down the inner pipe piece.

Again, I don't actually have experience with this, but to make a cleaner "spring-stopper", would be to possible to simply continue the piece of 1" pipe downwards a little farther and put an end-cap on it?

[Ben]

Silicone sealant doesn't work well with any pressure. Moving the rod of silicone also would be problematic because it would tear up as it is moved. Silicone sealant should be avoided in most water gun situations.

I also would imagine that enough silicone sealant to make a rod would be more expensive than a comparable piece of rubber rod. Rubber rod isn't hard to find either--it is available for cheap on McMaster-Carr.

The cheapest and best option in my opinion would be the gate valve I mentioned before. The problem is that you are only given two choices for size and they both are rather large. At College Park in an engineering demo, I saw one of these valves being used and it was easy to pull, so I know that much is good. I think this would be good for larger, "water cannon" type guns mainly.

I like your spring stopper idea. I don't know why he didn't do that actually. Sounds way simpler.

[Drenchenator]

One way to cut down the price and up the availability of this valve would be to use silicone sealant instead of the rubber rod.

Fill the inner 1/2" pipe with the silicone, let it harden up, then drill the hole through.

I appreciate the idea, but the big reason I am going for the rubber rod is to ease construction. I spend the majority of the time working on the cylinder for this valve. My cylinder leaks right out of the top still because it's filled with foam backer rod and epoxy. Rubber rod is expensive but it is the correct part for the job.

Again, I don't actually have experience with this, but to make a cleaner "spring-stopper", would be to possible to simply continue the piece of 1" pipe downwards a little farther and put an end-cap on it?

I like your spring stopper idea. I don't know why he didn't do that actually. Sounds way simpler.

In retrospect, I should have done that and didn't think about that until now. To tell the truth, I used a "short pipe" for only two reasons: it made drilling the "valve holes" much easier and with the bottom section installed, the cylinder can't go past the open position. I didn't just pick an arbitrary point to end the 1/2" pipe; I picked the point where if the cylinder was in the open position, it's end would be at the end of the pipe. I can drill a hole through both the pipe and cylinder, resulting in a cleaner drilling (they would align better in the future). This method made sure that I could drill the hole correctly.

Instead, I should have just continued the pipe and have then used a short but accurate length of dowel to push the cylinder to the correct position so that I drill the hole in the right spot. The guides would make sure that the cylinder doesn't go past the open position then.

Thanks WaterWolf, I don't know why I didn't think of this before. It will be implemented into my final design.

[Silence]

By using a pulley system, are you looking to have a horizontal motion instead of a vertical one for the trigger? It seems easier to have a lever with the trigger perpendicular to the piece that pulls the valve open.

WaterWolf, no hand-actuated system is effective for launchers. Your finger can only apply a few pounds of force, whereas pressure-actuated systems use hundreds or thousands of pounds of force to open the valve. Also, whereas pressure-actuated systems perform even better in larger sizes (because more area = more force), hand-actuated systems perform worse (because more circumference = more friction).

[Drenchenator]

By using a pulley system, are you looking to have a horizontal motion instead of a vertical one for the trigger? It seems easier to have a lever with the trigger perpendicular to the piece that pulls the valve open.

Yes, I want a horizontal motion (like a trigger pull) instead of the vertical motion of the valve. I tried messing around with some pullies briefly before I left but I couldn't get anything to work. Could you elaborate your idea? I'm really stumped about how to solve this.

[WaterWolf]

I'm about to buy several items from MCMaster and I would like your input as to which rubber to get.

I'm buying a 1" rod, but what "Hardness", Tensile Strength, etc would you suggest?
I don't think it needs to have a very high temperature resistance, but what about stretch.

Having never dealt with this rubber before, help would be appreciated before I make my order.