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piston set up q

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 set up q

Unread postAuthor: homedepotpro » Sun Apr 22, 2007 12:40 am

i was wondering if some of the more experienced spudders could check out my design and tell me what they think.
p.s. never mind the top left conner, thats just prices of parts
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1'' thredded venting port and fill up is at the top of the diagram.
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Unread postAuthor: PneuJose » Sun Apr 22, 2007 12:43 am

welll, im not the most experienced, But i think its horrible!!!(joking 8) 8) ) iits realy good desing. i think it has been done(i think) but oh well it might work the best.
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Unread postAuthor: clide » Sun Apr 22, 2007 1:11 am

The piston needs to be a larger diameter than the outlet, otherwise I won't fire.
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Unread postAuthor: hi » Sun Apr 22, 2007 3:06 am

i agree with clide. i also think that i needs to be a solid piston that fits in the pipe. other than that, it looks good. you will need a thick peice of rubber the way you have it set up. i would suggest a larger tee or a smaller barrel.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: jrrdw » Sun Apr 22, 2007 6:48 am

Looks good on paper, the real test is done after you build it and find out does it work.
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When life gives you lemons...throw them back they suck!
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Unread postAuthor: chaos » Sun Apr 22, 2007 7:55 am

hi wrote:i agree with clide. i also think that i needs to be a solid piston that fits in the pipe. other than that, it looks good. you will need a thick peice of rubber the way you have it set up. i would suggest a larger tee or a smaller barrel.


no actually it doesn't, mine isn't and it works flawlessly, all i sugest is that if you are filling from the chamber put a spring that holds teh piston against the barrel.

i believe it will work, good job.
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Unread postAuthor: super spuder » Sun Apr 22, 2007 8:50 am

i may be compleetly wrong but if the thing pointing down is the barrel shouldn't the piston go into the barrel or am i just confused again :joker:
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2007 9:06 am

clide wrote:The piston needs to be a larger diameter than the outlet, otherwise I won't fire.


As the man says, if your barrel and piston sleeve are the same diameter, then emptying the pilot chamber will have no effect on the piston.
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Unread postAuthor: chaos » Sun Apr 22, 2007 9:14 am

in his picture they are not the same, one ins slightly larger diameter than the other
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Unread postAuthor: keep_it_real » Sun Apr 22, 2007 10:14 am

I'm pretty sure they are the same diameter. It's just that the sealing face is bigger, not the actually part that slides back and forth.

Is this right?: You need a bigger diameter piston (than the barrel) so that when you pilot it, there is more of a vacuum behind the piston rather than in front. If they were the same the force on each side would be equal and the piston would stay where it is.

chaos: do you have a diagram of the one you made that works. Is it your triple s?
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Unread postAuthor: chaos » Sun Apr 22, 2007 10:54 am

Yea man its off mi new *debut name announcement*: "The S260"

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Unread postAuthor: homedepotpro » Sun Apr 22, 2007 11:10 am

keep_it_real wrote:I'm pretty sure they are the same diameter. It's just that the sealing face is bigger, not the actually part that slides back and forth.

Is this right?: You need a bigger diameter piston (than the barrel) so that when you pilot it, there is more of a vacuum behind the piston rather than in front. If they were the same the force on each side would be equal and the piston would stay where it is.

chaos: do you have a diagram of the one you made that works. Is it your triple s?


ok thats what i though. i can make the rear of the piston 3'' in a 3'' pipe apposed to a 2''. do you think that would work
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Unread postAuthor: Velocity » Sun Apr 22, 2007 11:12 am

I have a question about barrel sealing piston valves. In another thread, either on spudtech or spudfiles, someone commented about how barrel sealing piston valves open faster when the piston seat diameter is closer to the sealing port diameter (I THINK that clide said this). However, once the two were equal, the piston does not actuate... I was not really sure why.

The only explanation that I can come up with has to do with the pilot pressure. While chamber sealing valves begin to actuate as soon as the pilot valve is triggered (resulting in poorer performance), barrel sealing piston valves actuate when they reach a certain pilot pressure. This must decrease according to the size of the piston. If you are using a 6" piston with 1.5" porting, the pilot pressure would only need to drop a little to get the piston moving back (to overcome the forces holding the piston in place), and therefore the piston would move back relatively slowly, because only a small amount of the pilot pressure has been released. If you use a 2" piston with 1.5" porting, you need a much less pilot pressure. Once this pilot pressure is attained, the piston will begin to move back. It will move back much faster, for as soon as it leaves the sealing port, the pressure in the chamber will force it backwards much faster, for it will not have any pilot pressure to resist its movement backwards.

If you use a 1.5" piston with a 1.5" sealing port, once the pilot pressure reaches 0 PSI, the forces will still not be great enough to overcome the sealing of the piston, and it will remain there. I would think that if you used a vacuum, and brought it to -x psi, the valve would actuate.

This is all speculation, and could very well be completely wrong (it probably is; never taken any physics or anything like that). If so however, I think that the builders of barrel-sealing piston valves should strive to build valves which actuate at as low of a pilot pressure as possible to achieve maximum performance. If my bullshit theory based on absolutely nothing is true, then possible installing a vacuum would help to actuate piston valves whose piston diameter is equal to the diameter of the sealing port

Once again, I apologize to all of those who I offended with my ridiculous statements, lack of common sense, and ideas based on nothing.
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Unread postAuthor: keep_it_real » Sun Apr 22, 2007 11:47 am

That actually sounds pretty darn cool. Maybe you could have a tank on the exhaust side of the pilot valve and make a pump that creates a vacuum so when you pilot it, it's sucking the piston back even more. You'd need a really good bumper.
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Unread postAuthor: scatdawg » Sun Apr 22, 2007 11:56 am

rmich, i too would like to know the physics and equations that prove or disprove your theorys. right now i have a coaxial with a .800 inch barrel housed in a 2.5inch chamber. my piston is the full 2.5 inch diameter. i was wondering if i sleeved the space of the chamber where the piston is to a closer diameter to the barrel size would i get better performance because this would or could shrink my pilot volume.
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