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GGDT? help from the pros?

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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Unread postAuthor: saefroch » Sun Jan 09, 2011 10:15 pm

Slugfoot wrote:What would I enter for a given CV of 7.5, say?
File -> Configuration -> Valve flow parameter -> CV
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Unread postAuthor: Mr.michael.2468 » Sun Jan 09, 2011 10:21 pm

ok cool i got about that performance and for a sprinkler valve should i use the generic valve setting? it seems a lot more applicable to what a sprinkler valve does
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Unread postAuthor: Slugfoot » Sun Jan 09, 2011 10:23 pm

saefroch wrote:
Slugfoot wrote:What would I enter for a given CV of 7.5, say?
File -> Configuration -> Valve flow parameter -> CV


Okaaay...Thanks. :confused1:
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Unread postAuthor: saefroch » Mon Jan 10, 2011 7:44 am

For a ball valve I'd use the generic valve setting, if only because it allows you to dial in your own opening time.

Slugfood wrote:Okaaay...Thanks.
Did you manage to change the units on Valve flow to CV?
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Unread postAuthor: D_Hall » Mon Jan 10, 2011 11:14 am

Technician1002 wrote:Then to complicate things, the CV in GGDT is a % of CV, not the actual CV value you will find on a valve manufacture site.

Yes and no.

In the configuration screen for GGDT there is an option wherein you can choose how you'd like GGDT to behave.

Cv = Use the manufacturer-listed Cv (common on valves made in USA).
Kv = Use the manufacturer-listed Kv (common on valves made in Europe).
Eff = Use a % of full flow. Useful for when you have no manufacturer data, you're building your own valve or scaling a valve up/down.

Note that if you have a Cv of X and you change the configuration to Eff, GGDT will do the conversion from X to % based on other valve parameters. Similarly, if you have a valve operating at Y% and you want to know the Cv, if you change the configuration the conversion will be done for you.
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Last edited by D_Hall on Mon Jan 10, 2011 11:23 am, edited 1 time in total.
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Unread postAuthor: D_Hall » Mon Jan 10, 2011 11:19 am

saefroch wrote:So ignore that last post by me, but oddly enough GGDT gives a higher muzzle velocity (127fps) when I increase opening time to 100ms. :?

Nothing odd about it. You said you set the dwell time to 0. That means GGDT is opening up the valve and then immediately closing it again. If you want the valve to stay open, you need a dwell time that reflects that. A nice and simple 1 second would work wonders there.
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Unread postAuthor: D_Hall » Mon Jan 10, 2011 11:21 am

Mr.michael.2468 wrote:ok cool i got about that performance and for a sprinkler valve should i use the generic valve setting? it seems a lot more applicable to what a sprinkler valve does

No. A sprinkler valve is yet another take on a barrel sealing piston valve with a light weight piston.
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Unread postAuthor: Slugfoot » Tue Jan 11, 2011 12:53 am

Thanks for the help. After using my head a little, I came up with some figures which I think are reasonable.
Is there anything in the screenshot which looks unrealistic to anyone?
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