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Simple homemade pilot valve

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Simple homemade pilot valve

Unread postAuthor: Selador » Tue Nov 09, 2010 8:13 pm

This morning an idea for a pilot valve occurred to me.

Based on a gate valve.

I spent a few hours designing and drawing it out.

After all that time, a new idea occurred to me. Much simpler. And can be made with things that most of us already have.


You can buy valve seat repair seals. Little pieces of rubber that are round. With one flat side, one domed side, and a hole in the center.

VERY cheap.

If you get the right size, it will seal the end of a piece of 1/2" sch40 PVC pipe.


Parts needed:
*One of those stem seat repair rubbers.
*Some scrap 1/2" sch40 PVC pipe.
*A 1/2" PVC fitting.
*A bolt. 10-24 will do. Get the appropriate length for the size you decide to make this.
*A piece of wood dowel that fits inside the 1/2" PVC pipe.
* A spring.
*Some JBWeld, other epoxy, plumber's goop, whatever you decide to use as an adhesive.
*Optional: Something to use as a button.


Drill a hole in the center of the piece of wood dowel. (Or fill up part of the 1/2" pipe with epoxy, or bondo, or whatever, and drill a hole in that.)

Glue the wood into the pipe. Drop the bolt through the hole. Add a nut to the bolt. Then the stem seat rubber, with the dome toward the wood and the pipe. Then another nut. (I would use a nylock for the last nut.)

Glue the pipe into a fitting.

Place the spring into the fitting, below the stem seal.

Glue a second piece of 1/2" pipe below that.


Now, you'll have to play around with this.

You'll have to be careful with the seal face, on the 1/2" pipe, etc, the same as you would, with a piston valve.

You decide how long you want it to be. Etc.

You can make a button and JBWeld it to the top. Or just leave the bolt head, and make some sort of trigger to push on it.

None of this is written in stone. Make it work with materials you already have. Play around with it. You get 8 or more of those pieces of rubber in a package. The rest is mostly stuff that you already have anyway. So if you screw up, you can just toss it and make another.

Just like I like it. Cheap and easy !


The spring helps to seat the rubber seal against the bottom of the pipe. The air pressure will do the rest.
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Unread postAuthor: Gun Freak » Tue Nov 09, 2010 8:26 pm

The problem I see with this valve is that it is unballanced and will be a !@#$^@ to push at pressures over 40 psi. At 120 psi, it would take 60 pounds of force. I like the design itself, but not the dementions. Scale it down and you got a nice little valve.
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Unread postAuthor: Selador » Tue Nov 09, 2010 8:47 pm

Gun Freak wrote:The problem I see with this valve is that it is unballanced and will be a !@#$^@ to push at pressures over 40 psi. At 120 psi, it would take 60 pounds of force. I like the design itself, but not the dementions. Scale it down and you got a nice little valve.


Very good point.

I would have no problem pushing it with a simple button on the end, myself. (I'm kind of a distant cousin to Jorge the slingshot builder. LOL) But I can see that it would be a problem for others.


One reason I decided to go with the 1/2" stuff, is because most of the available pilot valves all have too much restriction.

Doing it this way, you can open up that restriction, a lot.


Leverage is your friend. (Give me a big enough lever and a place to support it, and I'll move the world.)

The right trigger system would leverage 60 pounds or more, on the end of the shaft, with much less force needed on the trigger itself.


And this is part of why I said you'll have to play with it.

I didn't intend to post this as a 'cast-in-stone', do it my way or the highway, design. I intended only to present an IDEA, and let all of you run with it.

I wanted to "de-mystify" the pilot valve. Let people know they are not stuck with blowguns.

I like that you thought about it, and the different forces at work.



Make it smaller.

Use different dimensions on different parts of it. Etc.

Do what it takes to make it work for you.
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