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air release problems...

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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air release problems...

Unread postAuthor: Spud Destruction » Mon Feb 13, 2012 7:55 pm

Hey guys im having trouble with our new air powered cannon. It has a 3" barrel 2' long. Attached to that is a 1 1/2 sprinkler valve. Problem even at 80psi when i squeeze the trigger release which by the way is a 4' long hose.. quite a bit of air comes out the valve first before it open the diaphram. Is this normal? With a valve this big shoild i be operating at around 150psi instead of 80-100. Most people use 1" valves so im thinking that is the issue. Any help is appreciated.
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Unread postAuthor: jrrdw » Mon Feb 13, 2012 8:06 pm

Pilot the sprinkler directly from the top of the sprinkler and see if it makes any difference. Play with the different pressures, it's the kind of experimentation that really adds to the fun!
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Unread postAuthor: Spud Destruction » Mon Feb 13, 2012 8:35 pm

Pilot the sprinkler? You mean modify. Yeah i modified the valve plugged up all the holes. if there is a pinhole leak anywhere will that cause the slow opening. I pressurised it went to eat and went back and the pressures gone..

Not completely gone but down to 20 psi from 80
I'm filling up the tub right now to submerge the chamber under water to find the air leaks :idea:
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Unread postAuthor: Spud Destruction » Mon Feb 13, 2012 10:06 pm

Now i figured what you meant jrrdw... I took off the hose plugged the hole with my thumb, pressured to 40psi all my thumb could hold.. Moved my thumb bamb 162.95 MPH hahhahah 40 psi.. Oh my Goodnesss, my wife was helping me and she was turning the valve to let the air in, she was amazed at the speed with such little pressure. This gun by far rules over any combustion i have ever made. too bad i didn't discover this site sooner. thanks guys for all your help we should have video up soon on our show, debuting the new cannon.. :o
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Unread postAuthor: mobile chernobyl » Tue Feb 14, 2012 12:11 am

I'm guessing the 2 foot long barrel is temporary?
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Normal

Unread postAuthor: Technician1002 » Tue Feb 14, 2012 12:34 am

quite a bit of air comes out the valve first before it open the diaphram. Is this normal?


This is normal. To open the valve, a pressure drop is required. Air compresses. To drop pressure, air is released before the valve opens. This is why long trigger hoses and large volume pilot areas are discouraged. A smaller volume to release = a faster release of less air to trigger the valve.

In air cannons, this is referred to the hiss-boom. If you record the sound and examine it, you can see the hiss before the bang.
Image

A 3 inch pipe makes a great T shirt barrel, but on a 1.5 inch sprinkler valve, the distance it can reach is quite limited. A longer barrel on a 1.5 inch valve won't gain much due to the max flow of the valve.
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Unread postAuthor: Spud Destruction » Tue Feb 14, 2012 10:54 am

mobile chernobyl wrote:I'm guessing the 2 foot long barrel is temporary?


No i meant 2' chamber. The barrel is 4' like all of you encouraged..
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 14, 2012 10:59 am

I would suggest a 1/2" or 3/4" ball valve directly on the sprinkler valve as a pilot go get the most bang for your buck.

You can attach a chord to the handle in order to fire it from a distance and it won't affect performance (as well as looking like a real cannon ;))
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Unread postAuthor: Spud Destruction » Tue Feb 14, 2012 11:08 am

That actually sounds like it would look cool.. im going to look into that. Thanks.
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 14, 2012 11:10 am

Spud Destruction wrote:That actually sounds like it would look cool..


,... as long as the launcher is firmly mounted and you don't pull the muzzle towards you ;)
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Unread postAuthor: High-PSI » Wed Feb 15, 2012 8:03 pm

jackssmirkingrevenge wrote:
Spud Destruction wrote:That actually sounds like it would look cool..


,... as long as the launcher is firmly mounted and you don't pull the muzzle towards you ;)


Awesome response! I almost laughed out loud at that....... :D

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Unread postAuthor: MrCrowley » Wed Feb 15, 2012 10:22 pm

If you want to keep the blowgun trigger, mount a 3/4" sprinkler valve to the pilot of the 1.5" sprinkler valve and have a blowgun to pilot the 3/4" valve which in turn pilots the larger 1.5" valve. I did something similar with a 2" and 1" sprinkler valve.
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 16, 2012 12:55 am

MrCrowley wrote:If you want to keep the blowgun trigger, mount a 3/4" sprinkler valve to the pilot of the 1.5" sprinkler valve and have a blowgun to pilot the 3/4" valve which in turn pilots the larger 1.5" valve. I did something similar with a 2" and 1" sprinkler valve.


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