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new valve design?

A place to ask general spud cannon related questions.
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Unread postAuthor: MrCrowley » Thu Jun 03, 2010 8:15 pm

Potatoflinger is right, even with a spring the piston will go no where until all the chamber pressure has been piloted out the schrader (depending on spring force). As is, the hole is too big. Make it small enough, then your valve has no flow and would suck. Potatoflinger's suggestions would probably work.

IS NO ONE READING MY POSTS ABOUT THE SPRING THAT WILL PUSH THE PISTON BACK?!?!

DID YOU NOT READ POTATOFLINGER'S AND HOTWIREDS POST ABOUT 5 POSTS BACK?!?!?! :roll:
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Unread postAuthor: Technician1002 » Thu Jun 03, 2010 8:57 pm

With the spring as indicated, the launcher will work up to a maximum that is limited by the spring. The spring would prevent filling with a pressure below the maximum working pressure as it will not open to the chamber below that pressure. If the chamber is filled above the maximum pressure set by the spring it won't fire until the chamber pressure is below the maximum pressure where the spring can push against chamber pressure.

It would be dangerous below a minimum pressure as the pilot would be required to hold the valve closed. If it bled off into the chamber or outside, the piston would open on it's own. Only at the maximum working pressure will the piston reliably remain closed without a perfect rear piston seal.
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Unread postAuthor: saefroch » Thu Jun 03, 2010 9:11 pm

Just extend the piston to cover the hole, or at least partially with a small fill hole or employ a floating o-ring on the back of the piston to allow air to flow into the chamber when it is pushed forward.
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Unread postAuthor: tghhs » Fri Jun 04, 2010 4:03 am

OR...

Build Techs QDV, no spring to create turblance too...
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Unread postAuthor: Crna Legija » Fri Jun 04, 2010 4:43 am

yes but the QDV that tech build needs two orings to work, there not to hard to make if you have a drill, drill press or lathe. the problem is that not many people have them

a simple tee or colax piston valve are grat because they work with out high tech equipment.
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Unread postAuthor: Technician1002 » Fri Jun 04, 2010 11:00 am

Look at my ABS cellular core test cannon. No drill press, lathe, or any power tools was used in the construction. A hand saw, hand drill, sandpaper, glue, and torch were the only tools used. It is true the better piston was made with better tools.
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Unread postAuthor: ramses » Fri Jun 04, 2010 4:18 pm

It would work with a few modifications.

Make the piston cover the holes to the chamber in the "forward" position.

Induce a leak in the back floating O-ring like in Gippedo's shock pump. This will act like a check valve, allowing air to enter the chamber from the pilot, but not enter the pilot from the chamber. Once the piston slides back, the port will be open to the barrel, and you will have decent flow.
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