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piston seat?

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 seat?

Unread postAuthor: subterranean » Thu Jun 28, 2007 12:28 am

i feel like a complete idoit asking this(considering i have bilt a fairly large cannon with a 2" barrel sealing piston valve that works very well)but what is the "seat" of a piston valve? i want to calculate ,on ggdt, performence of a cannon im working on and i need the "seat" diameter.

PS-as soon as i get my digital camera working ill post the cannon o and modds, feel free to delete this when the question is answerd
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Unread postAuthor: hi » Thu Jun 28, 2007 12:45 am

i think it is what it seals against. so if you have a 1.5'' barrel, then the seat is a 1.5'' pipe.

note the words "i think".
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Unread postAuthor: homedepotpro » Thu Jun 28, 2007 12:47 am

hi wrote:i think it is what it seals against. so if you have a 1.5'' barrel, then the seat is a 1.5'' pipe.

note the words "i think".

i am 95% sure thats it
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Unread postAuthor: subterranean » Thu Jun 28, 2007 12:47 am

ok, thanks for clearing that up for me :oops:
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Unread postAuthor: MrCrowley » Thu Jun 28, 2007 1:05 am

On the note of GGDT, when it asks for the diameter of the pipe do you guys put the real I.D or the nominal diameter?
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Unread postAuthor: Modderxtrordanare » Thu Jun 28, 2007 11:01 am

MrCrowley wrote:On the note of GGDT, when it asks for the diameter of the pipe do you guys put the real I.D or the nominal diameter?


I put the pipes I.D. because it's actually asking the outer diameter of the air space inside the chamber. That's why there is an inner diameter input box for the chamber, incase you are modeling a coaxial. Because then you would put the O.D. of the inner barrel running through the middle of your chamber.
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Unread postAuthor: schismatized » Thu Jun 28, 2007 11:02 am

agreed with modder, also for seat; i usually put the inner diameter there too. think of the seat as what the piston sits on. :D
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Unread postAuthor: Modderxtrordanare » Thu Jun 28, 2007 11:06 am

schismatized wrote:agreed with modder, also for seat; i usually put the inner diameter there too. think of the seat as what the piston sits on. :D


For the piston seat, I always use the barrels O.D. Piston seat is the sealing face correct?
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Unread postAuthor: Gepard » Thu Jun 28, 2007 11:20 am

No, I'd disagree, 'cos the OD of the seat doesn't in any way affect performance, only the ID, and if it doesn't affect performance then I don't see why you would have to enter it...

Michael
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Unread postAuthor: Modderxtrordanare » Thu Jun 28, 2007 11:24 am

Gepard wrote:No, I'd disagree, 'cos the OD of the seat doesn't in any way affect performance, only the ID, and if it doesn't affect performance then I don't see why you would have to enter it...

Michael


Usually the pipe I model is thinwalled metal (copper) so it wouldn't matter. But yes, I suppose it would make more sense to use the I.D. of the barrel as the piston seat.
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Unread postAuthor: RDX, » Thu Jun 28, 2007 1:32 pm

Seat is the pipe that your piston seals against. I always use seat ID for GGDT, and Gepard the OD of the seat does affect performance :wink:
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Unread postAuthor: Gepard » Thu Jun 28, 2007 1:37 pm

You sure?

I can't see that it would....

Michael
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Unread postAuthor: MrCrowley » Thu Jun 28, 2007 2:47 pm

Yeah it should, because it would affect the surface area of the piston that has pressure forcing it back.
Like in one of my guns I used a small bushing as a sealing face, being the idiot I am I glued it in the wrong so the reducing part is the seat, so now the seat is about twice as thick as a normal barrels wall, meaning it takes up more surface area of the piston then it needs to, therefore effecting performance.

Modderxtrordanare wrote:
MrCrowley wrote:On the note of GGDT, when it asks for the diameter of the pipe do you guys put the real I.D or the nominal diameter?


I put the pipes I.D. because it's actually asking the outer diameter of the air space inside the chamber. That's why there is an inner diameter input box for the chamber, incase you are modeling a coaxial. Because then you would put the O.D. of the inner barrel running through the middle of your chamber.


Yeah same, I was just checking that D_hall hadn't programmed it to recognize say 40mm pipe having an I.D of about 44mm.
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Unread postAuthor: Gepard » Thu Jun 28, 2007 3:30 pm

Ah yeah - sorry I was thinking that the seat had to be at least the diameter of the piston. But obviously that's not always the case...

Michael
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