Self-closing piston valve (brass fittings)

jhalek90 · Tue Nov 10, 2009 4:31 pm

Where in the world do you find the hose barbs like that?

All the ones i can find, in michigan have a hexagonal part on them, and will not thread into the hex bushing...?

Also.... every hex bushing that i cna find is only threaded half walk down on the inside... and therefore i can not thread anything in backwards... not even a nipple....

Am i just looking in the wrong section of the store??

I am looking where they have all the cast steel, and copper parts for gas lines... ect.

Any help would be awesome.

Major Collins · Wed Nov 18, 2009 6:40 am

this is very similar to what im trying to achieve but my piston completely fails and i cannot fix it

but i dont have a spring at all mine only relies on the air pressure to close and open ... can anyone help?

rikukiakuchiki777 · Wed Nov 18, 2009 6:59 am

Major Collins wrote:this is very similar to what im trying to achieve but my piston completely fails and i cannot fix it but i dont have a spring at all mine only relies on the air pressure to close and open ... can anyone help?

You'll have to give more details than that. Try posting some pictures of your piston and valve and we'll see what we can do.

jackssmirkingrevenge · Wed Nov 18, 2009 7:44 am

Major Collins wrote:mine only relies on the air pressure to close and open

weird for a piston valve

Major Collins · Wed Nov 18, 2009 7:49 am

ok umm the 2 pistons are : the top one is hot glue and the bottom one is fiberglass resin and i got 2 end thingies to choose from im recently experimenting with the top one but in the past ive used the bottem one and it is the end of a hose fitting for gas. umm yeah

jackssmirkingrevenge · Wed Nov 18, 2009 9:11 am

Looks like a fairly neat setup, what exactly is the problem you're having?

Wed Nov 18, 2009 4:16 pm

outside diameter of seal= outside diameter of piston..

?

Anyway..it should close when filled from the back...actuating is a different thing..

there needs to be a difference in surface area between the sealing face and the diameter of the piston, wich should be LARGER...

The less difference the more potential for a valve that opens later, but faster, when is finally does..
This requires a pretty tight fit though.
Air should not be allowed to flow back out the pilot valve, or at least asa little as possible.

Major Collins · Wed Nov 18, 2009 9:12 pm

jackssmirkingrevenge wrote:Looks like a fairly neat setup, what exactly is the problem you're having?

well i cant find a good sealing gasket or so . and air will still leak through the front where the barrel should go with the little through the end thingie .

the black line shows where it leaks .

Major Collins · Wed Nov 18, 2009 9:19 pm

"Brian the brain"outside diameter of seal= outside diameter of piston..

?

Anyway..it should close when filled from the back...actuating is a different thing..

umm the gasket or sealer thing is bigger than the hole but couldn't be too big or else it would not be able to be retracted back in , my "actuator" for now is just a ball valve and my fill valve (bike shrader) IS behind the piston. so yeah :/

rikukiakuchiki777 · Thu Nov 19, 2009 1:16 am

Major Collins wrote:well i cant find a good sealing gasket or so . and air will still leak through the front where the barrel should go with the little through the end thingie .

My local plumbing store sells gaskets and rubber washers of various shapes and sizes. Just have a look around, ask them about it, or try another plumbing store. You should be able to find something.

niglch · Thu Nov 19, 2009 11:16 am

Could anyone please link to suitable hose barbs and/or 1" - 3/4" reducer bushings (maybe on McMaster.com) that can be used to construct this valve? I can't seem to find any that look like they can be threaded into one another the "wrong way" so that the hose barb can protrude into the tee. For example, all of the bushings that I can find have an unthreaded portion on the inside which would prevent anything from threading in from the opposite end that they are supposed to.

Also, wouldn't doing this with NPT fittings be nearly impossible because the tapering of the threads would not match up. Or is this done with non-NPT fittings?

This how-to should be made specific as to exactly what types of fittings need to be used since it seems clear that any old hose barb and reducer will NOT work.

cannon monkey · Thu Nov 19, 2009 11:38 am

this is what i think would work i been saving and i dont have enought to make a new piston so ya.... use one of these for the seal face..

http://www.fdsons.com/images/plumbing/b ... derson.jpg

sombody please answer this
wouldnt this fitting work for the front end let the piston moved up onto here and seal?
i need to test it i got all the parts just no money for a chamber and fittings to put all together

jeepkahn · Thu Nov 19, 2009 11:59 am

For those of you havingissues finding nipples and bushings, try looking fore hose thread threading, ie, bushing would be 3/4"mpt x 1/2"fht, and the nipple would be 1/2" hose x 1/2" mht(fht= female hose thread, mht= male hose thread)... they will be near the pex fittings in your local hardware store.

edit: Ijust reread the OP, you'll use 1" mpt x 3/4"fht bushing and 3/4" hose x 3/4"mht nipple, if you want identical size valve...

niglch · Thu Nov 19, 2009 1:43 pm

Thanks for the help, jeepkahn. I have been trying to figure out how to put together a valve for use in a piston hybrid, and I was hung up on how to get the barrel to protrude into the valve to form a seat. I'll have to look around the hardware store to see what I can find as far as the hose thread fittings. My only concern would be whether or not the valve could handle the pressure of a 4x mix. I'm not sure how those fittings are rated for pressure since the thread engagement is so short. All I'm looking for is a way to get a valve seat in the valve and this looks like a very clean way to do it so long as you can find the right fittings.

jhalek90 · Thu Nov 19, 2009 5:41 pm

Well... i got tired of not being able to find my fitting...So i made one.

I have limited access to a lathe and a mill, so i bought a 1-3/4 hex bushing, and a 3/4 npt tap, and simply faced off the back of the bushing... and ran the tap in through the back... whole process took about 5 minuet, and works great.

I then had a piston made out of some high strength plastic, slapped a few o-rings on it... and all together the piston weighs under 20g

My only problem is a sealing face.... bolting a neoprene washer to the piston causes leaks.... and silicone-ing one on fails after the second shot.

Mind you that i am testing this all at 120psi, but after i fix all leaks/errors.. i plan to take my all steel valve up to 500-600 psi (or as high as my friddgy will go... whatever is less.)

Any tips on a reliable sealing face? and method to attach it to the piston??

Self-closing piston valve (brass fittings)

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