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Homemade Directional Control Valve?

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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Homemade Directional Control Valve?

Unread postAuthor: Tantum » Tue Nov 17, 2009 11:51 pm

First off, I'm really sorry if what I'm asking for can be easily found elsewhere. I've spent about 15 minutes searching the site and combing stickies. I haven't found anything.

What I'm asking is, is making a homemade DCV valve possible and/or practical? I'm hoping to emulate the function of this valve. That valve has one input, 2 outputs. One of the outputs would lead to a piston valve / qev, or whatever you want to call a valve that requires a pilot valve. The other would act as the pilot, venting to atmosphere. The input leads to a high volume tank. Button is depressed, pressure vents and input is closed, firing the piston valve but keeping air in the secondary tank.

I have a dremel, a drill, and various saws at my disposal. I'm guessing the answer will be "you need a lathe", but maybe someone on here has another way.
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Unread postAuthor: btrettel » Wed Nov 18, 2009 12:04 am

Lathes would help, but I don't think they are necessary.

The simplest valve might use telescoping brass tubes (also available from McMaster-Carr). You'd have to be careful about putting flow paths in the tubes such that they can still slide and seal well. I could see this going wrong more often than right so...

Something from cast epoxy would probably be your best bet. See the threads below for some ideas.

http://www.spudfiles.com/forums/epoxy-c ... t8916.html
http://www.spudfiles.com/forums/making- ... t8919.html
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 18, 2009 12:09 am

Not to be a pedant (yeah, right...) but for 10 bucks, shouldn't you just buy one?
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Unread postAuthor: POLAND_SPUD » Wed Nov 18, 2009 7:49 am

jack is right... building one might cost you more than 10$ (when you take into consideration materials & time spent) and the result won't be as good

If you are lucky you might find some good deals on ebay...
for just ~3.6$ I bought 6 valves in excelent condition...

to a piston valve / qev
what size are we talking about??

you see, a 1/8" DCV (it seems I introduced a new naming convention :) ohhh well at least this one seems to be better) can pilot a 1/2" QEV but some of them might not offer enough flow to pilot it if you squeeze (like a firearm trigger) the button/lever instead of pressing it

the ones that should work ok as triggers are indirect acting DCV (with an in built smaller valve that aids switching the valve) and poppet valves...

flow rates given by manufacturers are measured when the valve is fully 'switched'... what I am referring to here is the flow that you get the moment the valve is switched as this is the most important thing for piloting a QEV

so it might be a good idea to buy a larger valve or an indirect acting DCV (but they might leak when you use them above their rating) or a small QEV to help pilot the larger QEV/piston valve

don't worry, it's not that's a serious problem with a QEV but piston valves are not as well built so they might require higher flow rates
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Re: Homemade Directional Control Valve?

Unread postAuthor: velocity3x » Wed Nov 18, 2009 10:08 am

I guarantee it takes a lathe and more if you build it yourself. If you can do it with off the shelf parts......do it.
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Unread postAuthor: ramses » Wed Nov 18, 2009 5:07 pm

edit: wrong topic

on that note, a drillpress and some creativity should suffice.
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