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Piston valve seat construction question

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Piston valve seat construction question

Unread postAuthor: niglch » Sun Nov 22, 2009 2:03 am

I've been trying to come up with ideas on how to get 3/4" OD copper or aluminum tubing (barrel) into a 1" iron or steel tee so that it extends inside and can form the seat for a piston valve. So far, the only thing that makes sense to me is to maybe use a compression adapter and get the tubing to somehow extend all the way through the fitting. This would probably be difficult and involve griding down steel with I don't know what.

I also read the how-to (http://www.spudfiles.com/forums/self-closing-piston-valve-brass-fittings-t17609.html) on this forum that shows a hose barb threaded the "wrong" way into a bushing which holds both the hose barb and the barrel. However, I have been having trouble finding fittings made in such a way that would allow me to construct something similar.

However, since so many metal pneumatics use piston valves (as well as some hybrids), I figured that there must be some easier way to do it. I did some extensive forum searching but for some reason couldn't turn much up (must have been looking in the wrong places or something). So how do you guys solve this problem?

Thanks guys.
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Unread postAuthor: jackssmirkingrevenge » Sun Nov 22, 2009 2:30 am

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Unread postAuthor: MRR » Sun Nov 22, 2009 3:56 am

There are are two things, that come to my mind which you can use as a substitute for the hose barb.

There are these fittings (don't know the name in english), one side is for soldering and the other side has threads...
Image
If the fitting is to short you can always solder / glue a piece of pipe into it.

The other option would be a threaded piece of pipe that you cut to your needs.
Image

In both cases you might need to shorten the threads.
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Unread postAuthor: john bunsenburner » Sun Nov 22, 2009 4:02 am

What i found you can do, if you are as useless at using epoxy as I am, is to do as follows:

Find those bits of steel that have internal threads in them, they are usually very thick walled and come in loads of sizes, I have no clue what they are for but hey, if it works...Check the nuts and bolts section of a hardware store for them.

Then get a die that will thread the outside of said fitting, and one that will thread your pipe so that you can screw the end into it.

Now what you do is find a T that had internal threads that are the same size as those you will cut ont he outside of your fitting.

You then thread the barrel, remembering that you need to thread the length of the fitting + the amount the barrel should stick out at the end. Then you thread the out side of your fitting and turn it onto your T. Then you screw your barrel into the fitting in the T, use teflon tape to seal it all.

If the fitting is too long for what ever reason, use a hack saw.
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Unread postAuthor: cannon monkey » Sun Nov 22, 2009 12:20 pm

why not use a flare fitting?
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Unread postAuthor: c11man » Sun Nov 22, 2009 12:30 pm

i own pipe taps up to 1/2inch so so far i take a hex bushing going from my tee size to my desired seat size and taped the back of the bushing so the barb/nipple can thread into it and the bushing just goes right into the tee.
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Unread postAuthor: ramses » Sun Nov 22, 2009 2:11 pm

you could use a copper reducing bushing and a male NPT thread adapter . Through McMaster, you can get up to 2" porting, at a cost of over $80.

ex: barrel into

copper .75-1" bushing (file down the nub inside so the pipe can go all the way through, so the reducing bushing will fit like a ring)

Put the "ring" that is the reducing bushing into a 1" copper tube to 1" NPT adapter.

This could be done with a reducing bushing, but it would require a short section of 1" copper tube.
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Unread postAuthor: cannon monkey » Sun Nov 22, 2009 3:07 pm

flare fittings :D <a href="http://s119.photobucket.com/albums/o124/monkey083192/?action=view&current=Untitled-2.jpg" target="_blank"><img src="http://i119.photobucket.com/albums/o124/monkey083192/Untitled-2.jpg" border="0" alt="Photobucket"></a>

this is what im talking about....



http://www.ec51.com/uimages/r/ra/rajlax ... roduct.jpg
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