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Presta valve = check 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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Presta valve = check valve?

Unread postAuthor: Carlman » Sun Jun 08, 2008 1:50 pm

i have decided to make a homemade stirrup pump.

could i use a presta valve (or 2) for my check valve if i set it in epoxy in a wall elbow?

also i will be using 15mm copper as my chamber for the pump, would i have to glue or solder to use a compression fitting (dont quite get how they work) :oops:

thanks guys
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Unread postAuthor: Sticky_Tape » Sun Jun 08, 2008 2:01 pm

You don't specificly need a presta for a check you can use a shrader you just need to generate enough pressure on the down stroke to open the shrader how much pressure does it take to open a shrader? I think it is 200 psi you should be able to get that because it is impposible to compress a volume of gas to no volume. In other words get the bottom of the plunger to touch the rim of the shrader if you use one.
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Unread postAuthor: psycix » Sun Jun 08, 2008 5:45 pm

Hmm, I dont know about using tire valves as check valves, but why not make your own checkvalve out of something? Just have a tiny piston with a spring behind it and youve got yourself a checkvalve.
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Unread postAuthor: Hotwired » Sun Jun 08, 2008 6:34 pm

Prestas do not have a spring to hold them shut which can cause them to fail to seal if the pressure and flow isn't great enough to slam the poppet shut.
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Re: Presta valve = check valve?

Unread postAuthor: Pyro Ninja » Sun Jun 08, 2008 8:06 pm

Carlman wrote: would i have to glue or solder to use a compression fitting (dont quite get how they work) :oops:


With compression fittings all you need to do is tighten them around the pipe so that the olive squeezes the pipe and holds it in.


wiki wrote:When the nut is tightened, it clamps-down on the olive, causing it to conform to the circumference of the pipe.


Better wording^^^
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Unread postAuthor: VH_man » Sun Jun 08, 2008 8:10 pm

if you wanted better flow you could cluster the schraders so you have 3 or 4 schraders at the bottom of your pipe...............

EDIT: wow you already said that in your original post...... NEVERMIND!
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Unread postAuthor: dongfang » Tue Jun 10, 2008 6:14 am

Hi,

I have used Prestas as check valves many times. Works fine.

If you need it to close at very small pressures, you can install it so that the poppet will drop shut by gravity, or you can use the spring from a ball pen.

Regards
Soren
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Unread postAuthor: Carlman » Tue Jun 10, 2008 9:31 am

thanks all, i will use probably 2 presta valves with springs of necessary set in epoxy all inside a wall elbow :D

thanks for all who helped.
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