New idea: homemade pressure regulator

Homemade water gun threads that are notable.
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aEx155
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New idea: homemade pressure regulator

Post by aEx155 » Tue Jun 10, 2008 10:27 pm

I was thinking about this idea while I was taking a shower (no kidding) and I came up with a nice small design for a low pressure regulator (rated to the pressure of the pipe). I'm not sure what it would be called, but for now I'm calling the design "Homemade Pressure Regulator"

Here it is:

Image

I'm going to have a better diagram once I have the chance.

EDIT: here's a nice closeup of the piston part; I only got the piston part because I accidentally (arrgh!!!) deleted my unsaved diagram of the whole thing. (it took a while too!)

Image

The top part is when the the output pressure is lower than the set pressure. The set pressure is set by how much the spring is pushing against the piston. The bottom port is held open by the spring, and so, air goes into the regulator and out the output.

The bottom part is when the output pressure is greater than or equal to the set pressure. The output pressure is enough to compress the spring so that the piston covers the output. That way, the pressure can't increase.

I'm pretty sure that it won't work as I expected; if there is equal pressure on both sides of the piston (like there always will be), then the piston won't move to cover the input hole. If there was some way that it would work, then suggestions would be appreciated.
Last edited by aEx155 on Wed Jun 11, 2008 12:23 am, edited 1 time in total.

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Silence
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Re: New idea: homemade pressure regulator

Post by Silence » Tue Jun 10, 2008 11:23 pm

That's exactly how real regulators work. HowStuffWorks had a really good animated diagram of how one works on this SCUBA page, but it's since been replaced with a similar diagram. They substituted a bulb with water pressure instead of a spring to push on the piston - that's the best way underwater, where the pressure should match the ambient pressure anyway. But for surface applications, most regulators use springs.

You may want to work on making the design a bit more compact. You could probably do the entire thing in a single 3/4" or 1" tee with 1/2" plug bushings stuck in the sockets.

aEx155
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Re: New idea: homemade pressure regulator

Post by aEx155 » Wed Jun 11, 2008 12:27 am

SilentGuy wrote:You may want to work on making the design a bit more compact. You could probably do the entire thing in a single 3/4" or 1" tee with 1/2" plug bushings stuck in the sockets.
I don't know how it would be more compact; that's the only way I could fit it, and I don't really know a way to design one that would. Given time I probably could, but the fact that it's homemade makes up for it's size. (Wouldn't this be cheaper too?)

If someone can tell me if this idea works, it would be appreciated:

If I put a check valve in between the output and the input (on the long pipe that runs over the main assembly in the first picture), and added a small hole in the input section before the check valve, the pressure would be lower than the output, causing the piston to move to cover the input hole, right?

EDIT: I found a picture of a "Straight Stem Style Direct-Operated Regulator" (from here), which I believe is the same version used in Ben's SuperCAP (this is just some info for people who want to try and make their own regulators, like me):

Image

After looking at it, I believe this is how it works (all of the names I'm using are made up, so don't look for them anywhere else):

The large spring in the yellow spring is the pressure set spring (I'll refer to it as the PSS). The PSS keeps the input open and allows air to flow into output; it does this by controlling the output plug (OP), which blocks the output in its up position. The PSS pushes on a diaphragm connected to chamber fed by the output; when the pressure of the output is enough, it will push against the PSS, pulling the plug up and shutting off the airflow.

I believe that's how it works; I hope that this explains things. (if it sounds like I'm explaining things to myself, that's because I am...)

Now, to apply this to a new design...
Last edited by aEx155 on Wed Jun 11, 2008 12:45 am, edited 1 time in total.

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SSCBen
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Re: New idea: homemade pressure regulator

Post by SSCBen » Wed Jun 11, 2008 1:25 am

There's nothing wrong with the design. If built correctly I'm sure it will work. But, building a regulator will obviously be a lot more work than buying one, and they can come rather cheap so I don't think there's any reason not to buy one. McMaster-Carr sells a plenty adequate regulator for $18 that'd be much more compact than this design. This design would have much higher air flow however, but higher flow isn't necessary.
If I put a check valve in between the output and the input (on the long pipe that runs over the main assembly in the first picture), and added a small hole in the input section before the check valve, the pressure would be lower than the output, causing the piston to move to cover the input hole, right?
That makes sense, so yes.

aEx155
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Re: New idea: homemade pressure regulator

Post by aEx155 » Wed Jun 11, 2008 2:13 am

I was actually going to use the regulator for something else not related to water guns, I just though that I should put my idea here since it would be helpful for people here to use if they were going to make a CAP gun.

As for price, which is why I designed this: I'm not sure, but wouldn't this be cheaper than a commercial regulator?

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SSCBen
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Re: New idea: homemade pressure regulator

Post by SSCBen » Wed Jun 11, 2008 2:33 am

It definitely would be cheaper than all but the cheapest commercial regulators (which are nothing more than glorified ball valves). But, the time and effort it would take to build one would be make it more worthwhile in my opinion to fork over the extra $5 to $10 for a commercial regulator. That's all I was saying.

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Drenchenator
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Re: New idea: homemade pressure regulator

Post by Drenchenator » Wed Jun 11, 2008 2:35 am

It's a good idea and should work; it's basically the same design as the rest of the air pressure regulators. But I'm gonna have to say that it's not really needed because air pressure regulators are not only available but also cheap--I think I remember seeing some at Sears, though McMaster also stocks a good selection.

If you build it correctly, it can be very cheap. I had a similar project part-wise with my air pressure gun, and I believe the final cost came out to about 30 USD because it only used one prepared valve, the large check valve in the handle. The rest was pipe, fittings, wood, O-rings, and nuts and bolts. But remember that what you save in parts you'll have to pick up in labor. The beauty of buying a regulator is that you don't have to built it.
The Drenchenator, also known as Lt. Col. Drench.

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