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Hooting Potato Gun, Silencers? Resonance?
http://forum.spudtech.com/viewtopic.php?f=38&t=2039
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Author:  Spudtech [ Thu Jul 17, 2003 9:00 am ]
Post subject:  Hooting Potato Gun, Silencers? Resonance?

Originaly posted by pacogoatboy,
I have a pneumatic potato gun as follows.
2"x5' chamber
1.5"x5' barrel
1" sprinkler valve (electrically activated)

when i fire, i get a honking noise that is incredibly loud. i was wondering if this is normal, or if i am just lucky like that. i've watched videos of other pneumatic spudguns and they have more of a wet smacking sound when they fire. do you think the barrel or chamber could be resonating to produce this? i've tried weighting both in various places, but with little effect. has anyone come up with an effective silencer for this sort of noise?

Author:  Spudtech [ Thu Jul 17, 2003 9:00 am ]
Post subject:  this is what to do...

Originaly posted by someguynamedchris,
Pneumaticly operate you valve. It will open 10x faster and you will not have to have all those batterys and wires. you can find how to do it bye clicking here

Chris

Author:  Spudtech [ Thu Jul 17, 2003 10:00 am ]
Post subject:  this will fix the noise?

Originaly posted by pacogoatboy,
?

Author:  Spudtech [ Thu Jul 17, 2003 10:00 am ]
Post subject:  it should...

Originaly posted by someguynamedchris,
i had the same thing with my eletric valve since i pneumaticly operated it there is no sound at all.

Chris

Author:  Spudtech [ Thu Jul 17, 2003 11:00 am ]
Post subject:  Makes sense...

Originaly posted by Freefall,
The solenoid valve doesn't let air out fast enough to fully open the valve. As soon as air begins to flow, you get low pressure on the valve face (venturi effect - high speed air has lowered static pressure and raised dynamic pressure.) This makes the valve try to close itself. Air continues to flow out the solenoid valve, valve opens, venturi effect, valve closes, etc. This happens at a rate well within the audio range, hence the loud "hoot" sound. If this frequency happens to coincide with the resonant frequency due to barrel length, it'll be even louder.

Author:  Spudtech [ Thu Jul 17, 2003 11:00 am ]
Post subject:  question 2

Originaly posted by pacogoatboy,
thanks for the info, i'll give this a try. i do have one question still though. i checked out the page you suggested for converting the valve to pneumatic actuation. it said to attach one end of a hose to the valve and the other end to a "blowgun rated for at least 100 PSI." i'm not familiar with blowguns, except as weapons used by amazonians, what is it? how does this open the sprinkler valve?

is it equalizing the pressure on both sides of the valve, allowing it to open, or what?

Author:  Spudtech [ Thu Jul 17, 2003 12:00 pm ]
Post subject:  Blowgun

Originaly posted by IzzyDoesIt,
It's a pneumatic device normally used to clean out dust, dirt, or whatever. It has a 1/4" NPT input port.
You can attach it with a hose or directly to the modded sprinkler valve.
Here is a picture of one (Ace Hardware)

http://www.acehardware.com/product/index.jsp?productId=1279171&cp=&searchId=10294052174&keywords=blowgun&parentPage=search

You can find them at most hardware stores for about $10 each.
I.D.I.

Author:  Spudtech [ Thu Jul 17, 2003 3:00 pm ]
Post subject:  Valve opening

Originaly posted by Freefall,
When the valve is closed, there is high pressure over the entire back surface and a portion of the front, with atmospheric pressure on the center of the front surface. This difference in pressure over the center holds the valve closed. When the valve is actuated (electric or pheumatic), the pressure behind the valve is released, leaving the high pressure on a portion of the front of the valve. This acts to very quickly open the valve.

Author:  Spudtech [ Thu Jul 17, 2003 6:00 pm ]
Post subject:  $3.99 at home depot...NT

Originaly posted by someguynamedchris,
NT

Author:  Spudtech [ Sat Jul 19, 2003 9:00 am ]
Post subject:  NO SILENCER NEEDED!!READ!!

Originaly posted by GisMo,
The sound comes from the sprinkler vavle you bought. You need to exchange the vavle you bought for a rainbird or a watermaster, the one you have is a black one, correct me if I am wrong..sounds like an air horn when you fire it...its a bad vavle it restricts flow.

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