Release a certain amount of air pressure from tank?

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Luke31
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Mon Mar 01, 2021 4:48 pm

I am thinking about some concept designs for an air cannon . I would like to build a cannon that can rapidly fire and can control how much pressure its releasing.

Say I want to fire the gun 7 times at 100 psi before having to refill the air tank. I presume I would fill an air tank with 700 psi and release 100 psi every time it shoots. But what would be required in order for it to stop at 600, 500 etc.. psi for the next round?

Also, would releasing the pressure from 700 down to 600 psi be any different than releasing it from 100 to 0 psi? I'm thinking the air would be released much quicker at higher pressure levels. Which could lead to inconsistent results.
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jackssmirkingrevenge
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Tue Mar 02, 2021 12:24 am

The only way you can really regulate it is by using a valve that opens for a fixed time. If you're mechanically inclined, then a hammer valve would be the obvious solution.

If you're a little handy with electronics, then solenoid valves would be a good choice.

If you're starting from 700 psi, naturally if you open the valve for the same interval every time, then the shots are going to get increasingly weak as the pressure goes down.

Therefore if consistency is important you either need to adjust opening time accordingly or use a regulator.
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mrfoo
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Tue Mar 02, 2021 1:17 am

What you're wanting to do, in order to get consistent shots, I think, is release a fixed amount of air at a fixed pressure.

This is more complex, and yet more simple. Have one high pressure tank of large size. This feeds a small chamber, perhaps of variable size so you can tune it, via a regulator. You can now dump your chamber entirely on every shot, which simplifies valve design considerably (QDV?). However, between shots you have to rearm the valve if it doesn't do so automatically, and refill the chamber via the regulator.
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