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A piston valve that could be filled from chamber side.

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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A piston valve that could be filled from chamber side.

Unread postAuthor: Leonard » Tue Jul 29, 2008 5:49 pm

Just a quick question for you fellow spudders, would it be possible to make a piston valve that could be filled from chamber side (barrel sealing piston valve) so that the rear of the tee is used only to exhaust air, not to fill? Mainly like a sprinkler valve, but in the form of a piston.

Thanks for the input, if my question is unclear feel at ease to tell me
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Last edited by Leonard on Tue Jul 29, 2008 5:57 pm, edited 1 time in total.
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Unread postAuthor: SpudFarm » Tue Jul 29, 2008 5:52 pm

no it wont
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Unread postAuthor: jrrdw » Tue Jul 29, 2008 5:53 pm

Yes, you can fill from the chamber side of the piston valve. You will need a spring to aid in piston sealing.
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Unread postAuthor: Leonard » Tue Jul 29, 2008 5:58 pm

jrrdw wrote:Yes, you can fill from the chamber side of the piston valve. You will need a spring to aid in piston sealing.


Do you realy think that only a spring could do the job? I was thinking that it could work by drilling a very small hole in a sleave (wich would contain the piston) that would be INSIDE the tee, but i might be wrong.
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Unread postAuthor: jrrdw » Tue Jul 29, 2008 6:04 pm

Why would you drill a small hole in the piston sleeve? Equiliztion from chamber to pilot? Typicly members who have filled from chamber side of the valve made their pistons fit loosely so the air could slip by.

Yes, a spring with the proper tension will work.
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Unread postAuthor: SpudFarm » Tue Jul 29, 2008 6:04 pm

it simply wont work since the spring has to be so strong that it will hold the piston there after it is piloted..
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Unread postAuthor: jrrdw » Tue Jul 29, 2008 6:11 pm

SpudFarm wrote:it simply wont work since the spring has to be so strong that it will hold the piston there after it is piloted..


No,no, no. Once the piston seals the pressure is equilized no matter how much more air you put in.

It is a bit harder to get the piston to seal, but it does work.
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Unread postAuthor: Leonard » Tue Jul 29, 2008 6:26 pm

Humn... allright, thanks for the answer, i'll try that setup!
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Unread postAuthor: SpudFarm » Tue Jul 29, 2008 6:35 pm

but it wont seal since the pressure from the chamber side will open it no matter what you do, and if you set in a spring so it does not open it will have to be strong enough to hold the peak pressure and then it wont open ever..
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Unread postAuthor: clide » Tue Jul 29, 2008 6:40 pm

SpudFarm wrote:but it wont seal since the pressure from the chamber side will open it no matter what you do, and if you set in a spring so it does not open it will have to be strong enough to hold the peak pressure and then it wont open ever..


The spring only has to be strong enough to let the valve seal initially. After that the pressure leaking through the equalization hole does the sealing just like any other piston valve. A sprinkler valve works on the exact same principles as a piston valve and it has a wimpy spring.
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Unread postAuthor: brogdenlaxmiddie » Tue Jul 29, 2008 6:51 pm

clide wrote:
SpudFarm wrote:but it wont seal since the pressure from the chamber side will open it no matter what you do, and if you set in a spring so it does not open it will have to be strong enough to hold the peak pressure and then it wont open ever..


The spring only has to be strong enough to let the valve seal initially. After that the pressure leaking through the equalization hole does the sealing just like any other piston valve. A sprinkler valve works on the exact same principles as a piston valve and it has a wimpy spring.


I have to agree with spudfarm... plus, Sprinkler valves are diaphragm valves... not piston valves.
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Unread postAuthor: Mr.Sandman » Tue Jul 29, 2008 6:58 pm

brogdenlaxmiddie wrote:
clide wrote:
SpudFarm wrote:but it wont seal since the pressure from the chamber side will open it no matter what you do, and if you set in a spring so it does not open it will have to be strong enough to hold the peak pressure and then it wont open ever..


The spring only has to be strong enough to let the valve seal initially. After that the pressure leaking through the equalization hole does the sealing just like any other piston valve. A sprinkler valve works on the exact same principles as a piston valve and it has a wimpy spring.


I have to agree with spudfarm... plus, Sprinkler valves are diaphragm valves... not piston valves.



but they do have springs in them
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Unread postAuthor: brogdenlaxmiddie » Tue Jul 29, 2008 6:59 pm

Mr.Sandman wrote:
brogdenlaxmiddie wrote:
clide wrote:
SpudFarm wrote:but it wont seal since the pressure from the chamber side will open it no matter what you do, and if you set in a spring so it does not open it will have to be strong enough to hold the peak pressure and then it wont open ever..


The spring only has to be strong enough to let the valve seal initially. After that the pressure leaking through the equalization hole does the sealing just like any other piston valve. A sprinkler valve works on the exact same principles as a piston valve and it has a wimpy spring.


I have to agree with spudfarm... plus, Sprinkler valves are diaphragm valves... not piston valves.



but they do have springs in them

But a diaphragm valve is very different than a piston valve. A piston requires an actual object to move backwards. A diaphragm valve uses a piece of rubber to move. Last time I checked, rubber moves a helluva lot better than anything I've seen used as a piston.
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Unread postAuthor: Mr.Sandman » Tue Jul 29, 2008 7:06 pm

i know that i was just saying that clide was right about the spring
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Unread postAuthor: mobile chernobyl » Tue Jul 29, 2008 7:12 pm

It will work. Clide and Jrrdw are smart fellows, don't be so quick to shut them down.


The spring will need to work in accordance with the blowby of the piston, towards the exhuast side. You will need to match this to the input flow. If you are filling with a bike pump, a light spring and minimal blow by tolerance is needed - however a really good seal is needed as well to compensate for the lighter spring. Upgrade to a compressor and you will need more blow by, and a slightly heavier spring - seal will still be important, but it can seat at 5-10 psi vs 2-5 psi with the bike pump (numbers are examples)

Blow by and springs are indirectly related. More blow by will mean a lighter spring can be used, more spring weight means less blow by is needed.

Pressure barrel (exit) side is constant 1 atmosphere, so you dont need to worry about a little pressure leaking out in the beginning ruining everything. You will accumulate pressure in the tank, and it will press against the barrel just like normal. It will need to be an especially good seal to avoid having an overly heavy spring, so you can fill it efficiently without having to have a high flow fill system combined with more blow by on the piston just to create pressure on the piston to press against the barrel.

Think about something a little harder before dismissing it all together. You just may discover something new that way. :shock:
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Last edited by mobile chernobyl on Tue Jul 29, 2008 7:15 pm, edited 1 time in total.
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