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Piston Valve Actuation Speed

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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Piston Valve Actuation Speed

Unread postAuthor: Suppressive Fire » Tue May 29, 2007 6:52 pm

I've had an idea swimming around in my head ever since Spudtech got shut down. I want to biuld a semi auto but I've got one question. How many times can a 2in full port piston open and close in a ten second period? It will dump a 4in dia by 8in chamber to fire a 4oz 2in bore projectile.
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Unread postAuthor: VH_man » Tue May 29, 2007 7:05 pm

however fast you want it to go............. there really is no "set" time. i know that it can open in aorund 10 ms or less, and putting the closing time, which is about 20, i say aobut (however man times 30 milliseconds goes into 10 seconds) would be accurate..... and thats fast BTW
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Unread postAuthor: spudthug » Tue May 29, 2007 7:54 pm

vh man u forgot to add the filling time of the chamber, the turnin on of the compressor(unless its a tank that is always on) and the closing of the pilot...
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: VH_man » Wed May 30, 2007 7:52 am

thats a good point. honestly, it can fill VERY fast if you do it right. still, im pretty sure you can get an ROF nearing commercial Paintbal guns (not the electronic ones).
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Unread postAuthor: Suppressive Fire » Wed May 30, 2007 2:55 pm

The 4in by 8in chamber will have a constant supply of air from a couple massive tanks through .25in air line, the input will be reg'd down to 80psi. This thing is gonna be a beast!! I'm looking for a rof around 1-2 rounds a second.
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Unread postAuthor: iknowmy3tables » Wed May 30, 2007 3:02 pm

so how will you setup the pneumatic on this gun
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Unread postAuthor: Suppressive Fire » Wed May 30, 2007 3:31 pm

I'll post I diagram as soon as I finish it
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Unread postAuthor: Suppressive Fire » Thu May 31, 2007 2:37 pm

Just got a look at clides gb semi
I love the HEAR valve concept
Who knows what I need to put in the GGDT for it?
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Unread postAuthor: clide » Thu May 31, 2007 3:39 pm

Just replied to your PM, but I'll post the GGDT part here in case anyone else is interested.

Modeling requires extensive use of the graphs in GGDT. Basically model your gun as if you were building a barrel sealing tee valve with the outlet the size you plan on using, a large pilot valve, and a pretty heavy piston. Find the approximate opening speed of the valve, and switch to the generic type valve using the opening speed you found. Now you can see what type of performance you get with different dwell times. Find a dwell time you are happy with and take note of what time the valve starts closing on the valve position graph. Then go to the chamber pressure graph and see what the chamber pressure is at the time the valve starts closing. Now you can properly size the middle piston of your HEAR valve based on what chamber pressure the valve will begin to close at. If you need help with how to do that let me know, but I don't feel like writing it up if you already know.

This is not a perfect model by any means, but it should give you a decent idea of what performance to expect and a good basis for your decision on the size of the middle piston.
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Unread postAuthor: fastcannonman » Thu May 31, 2007 3:42 pm

i think that it will fill very fast, so the wait to long or their will be no oxagan left in the chamber
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Unread postAuthor: Suppressive Fire » Sat Jun 02, 2007 7:27 am

Could somone tell me how to post a diagram?
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Unread postAuthor: CS » Sat Jun 02, 2007 8:06 am

<a href="http://www.spudfiles.com/forums/faq.php#38">How-to add a attachment - Forum FAQ</a>
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Unread postAuthor: Suppressive Fire » Sat Jun 02, 2007 2:20 pm

Thats exactly what I did and the page was loading, then it took me back to the same spot as before.
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