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How does this dcv design look?

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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How does this dcv design look?

Unread postAuthor: Matt_NZ » Fri Oct 08, 2010 2:57 am

Here is a modified version of "Iknowmy3stables" dcv design from this thread


Image

I'm hoping to create a push button dcv with 1/4" ports.
This will allow a short button press to exhaust the chamber, then it will spring to back into position and continue filling.
I will probably construct this from two identical brass rods, which i can get for about $10NZ.

Anyway what do you guys think, is this going to work effectively and/or could there be some improvements.
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Unread postAuthor: POLAND_SPUD » Fri Oct 08, 2010 3:49 am

Not the best idea... you see, the moment air starts to flow from the pilot side to vent air is still allowed to pass from the input to the the pilot side
That's why there are 2 orings in the original design

Your modification does not improve anything. In fact it just makes it work worse

EDIT
So to sum it up - you need two orings because ports are not just dimensionless points in space - they've got diameter. Both of them have to overlap the diameter port - otherwise the valve won't work correctly
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Unread postAuthor: Matt_NZ » Fri Oct 08, 2010 4:46 am

POLAND_SPUD wrote:Not the best idea... you see, the moment air starts to flow from the pilot side to vent air is still allowed to pass from the input to the the pilot side


I see now. I didn't fully understand how the dcv works hence this failed design. :oops:
I would think by adding an additional o-ring, then it would work. However now I would have to move the "button" further and it would no longer be what i was hoping for. Any ideas?
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Unread postAuthor: POLAND_SPUD » Fri Oct 08, 2010 5:33 am

You don't need an additional oring - you'd end up where you were before modifying this design

Any ideas?

Who said you have to use circular ports? Use slits instead.
Take a pipe that matches the ID of the T and cut relatively narrow slits exactly there the ports are (in this design you just need one slit). Put the pipe inside the T and find a way to seal it with it


Ohh and finally - don't forget that used DCVs are pretty cheap. In most cases it's cheaper to buy one than to build one
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Unread postAuthor: Matt_NZ » Fri Oct 08, 2010 3:47 pm

POLAND_SPUD wrote:Use slits instead.
Take a pipe that matches the ID of the T and cut relatively narrow slits exactly there the ports are (in this design you just need one slit). Put the pipe inside the T and find a way to seal it with it.


I could probably put a thread on the whole pipe and then screw it in. But one slit for this design? (I'm sorry i don't see it :? )


Ohh and finally - don't forget that used DCVs are pretty cheap. In most cases it's cheaper to buy one than to build one


I have looked on NZ auction site trademe and there is nothing there.
I guess if I could find something on ebay, although postage to New Zealand is usually insane.
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Unread postAuthor: POLAND_SPUD » Fri Oct 08, 2010 11:02 pm

The only port where the slit should be is the one you marked as pilot port. That where the switching actually takes place.

Of course, you need a hole to let air flow from the input/source into the valve, but its size isn't as important
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