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flow and piloting

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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flow and piloting

Unread postAuthor: Major Collins » Wed Jun 15, 2011 8:50 am

specifically for a piston valve gun with actuation of a blow gun.
Is it better to bevel and round out inner parts and make all the part have better flow or leave as is for less air to pilot the piston valve
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Unread postAuthor: Labtecpower » Wed Jun 15, 2011 9:04 am

more flow = better.
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Unread postAuthor: Gun Freak » Wed Jun 15, 2011 9:19 am

There won't be a noticeable difference so I wouldn't go through the trouble...
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Unread postAuthor: ramses » Wed Jun 15, 2011 6:15 pm

It is generally accepted that modifying a blowgun by increasing the flow path will allow air to leave the pilot area faster. The actual impact on performance is pretty insignificant, unless your piston valve was honking or closing because the pilot wasn't being dumped fast enough.
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Unread postAuthor: Major Collins » Thu Jun 16, 2011 12:00 am

i see , thanks all another flow question .... what is the optimal travel distance for a piston inside its housing?
more the better or is about 1cm to about an inch good enough ?
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Unread postAuthor: Technician1002 » Thu Jun 16, 2011 12:35 am

A piston should open far enough so the porting area opened is larger than the valve seat area.

Many use 1/4 the valve seat orifice as the minimum distance to be considered fully open as the gap between the piston and valve seat has the same cross sectional area.

I generally view this definition of open as two equal restrictions to flow in series. I prefer to open the piston a little further so the first restriction is negligible and the only significant flow restriction is the valve seat orifice. For this I prefer the piston to move at least 1/2 the valve seat diameter.

For example if you have a coaxial valve and the barrel valve seat has a diameter of 1 inch or a metric value such as 10mm, the minimum using the 1/4 diameter would be 1/4 inch or 2.5mm. Using a larger value of 1/2 the diameter would give 1/2 inch or 5mm for the above example seat diameters.
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Unread postAuthor: Major Collins » Thu Jun 16, 2011 2:42 am

ah alright good explaining Tech, got it . i just came back from modding a blow gun i had.Im not too sure how much it held before (probably more than it does now) but now it only goes up to 80 to 100ish psi before it starts leaking :( ive taken it apart and made sure it put it in as airtight as possiblebut still no luck. Any tips and suggestions ?
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Unread postAuthor: Gun Freak » Thu Jun 16, 2011 8:47 am

How did you mod he blowgun to hold more pressure?
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Unread postAuthor: Major Collins » Thu Jun 16, 2011 8:55 am

i didn't mod it for pressure , if thats even possible , i modded it for more flow to actuate a 1/2 inch piston valve.
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Unread postAuthor: Gun Freak » Thu Jun 16, 2011 12:35 pm

Sorry lol I misread it :roll:
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Unread postAuthor: Major Collins » Fri Jun 17, 2011 3:29 am

okay now update with the vid. pretty much self explanatory .
http://www.youtube.com/watch?v=71ej3HML8bw
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Unread postAuthor: saefroch » Fri Jun 17, 2011 10:07 am

Major Collins wrote:okay now update with the vid. pretty much self explanatory .
http://www.youtube.com/watch?v=71ej3HML8bw


Like this: [youtube]video url[/youtube]
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