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GGDT problems

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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GGDT problems

Unread postAuthor: veginator » Wed Sep 19, 2007 7:16 pm

Can someone help me I'm trying to see if my design will work or not but GGDT isn't working.
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Unread postAuthor: MrCrowley » Wed Sep 19, 2007 7:26 pm

Thanks for searching first, I really appreciate it, instead of making another topic exactly like one that was posted only one day ago.
<A HREF="http://www.spudfiles.com/forums/viewtopic,p,119421.html#119421">Topic you would've found by searching</a>
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Unread postAuthor: veginator » Wed Sep 19, 2007 7:40 pm

thats not the problem the program is working fine it's just once I type in all the stats it looks to be coming out wrong.so get off my back.
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Last edited by veginator on Wed Sep 19, 2007 7:47 pm, edited 1 time in total.
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Unread postAuthor: windshrike » Wed Sep 19, 2007 7:43 pm

Maybe you overlooked something. Once GGDT gave me a negative velocity reading, don't remember why but it was an input data problem.
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Unread postAuthor: veginator » Wed Sep 19, 2007 7:46 pm

could someone input it for me to make sure my computer isn't screwy.
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Unread postAuthor: MrCrowley » Wed Sep 19, 2007 8:08 pm

veginator wrote:thats not the problem the program is working fine it's just once I type in all the stats it looks to be coming out wrong.so get off my back.


Thanks for telling me all that in your first post. Why didn't you give me specifics? There are loads of things that could be wrong.
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Unread postAuthor: veginator » Thu Sep 20, 2007 2:36 pm

MrCrowley wrote:
veginator wrote:thats not the problem the program is working fine it's just once I type in all the stats it looks to be coming out wrong.so get off my back.


Thanks for telling me all that in your first post. Why didn't you give me specifics? There are loads of things that could be wrong.

I hope you know that sarcasism isn't the easiest thing to read. Back to the topic. I want to build a barrel sealing pneumatic with a 48 inch chamber but before I did I wanted to see how well it would preform and how long of a barrel to use. But I don't think I am puting in the right input because the projectile never leaves the barrel. btw i'm sorry I didn't get to the point in the very beginning.
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Unread postAuthor: clide » Thu Sep 20, 2007 10:41 pm

Without more info it is really hard to help you, but my guess would be that you are putting in the chamber dimensions wrong. Inner diameter should be set to 0 and outer diameter should be the ID of your chamber pipe.
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Unread postAuthor: veginator » Fri Sep 21, 2007 2:28 pm

Well I typed that in and it gave me some un expected results. I wound up with a gun that could have a 700 inch barrel. I think it's either the inaccuracy of ggdt or it is your advice or I am bust a moron who accidentally typed in a gun with a 4800 hundred inch chamber. So which one do you think it is.
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Unread postAuthor: clide » Fri Sep 21, 2007 4:13 pm

veginator wrote:Well I typed that in and it gave me some un expected results. I wound up with a gun that could have a 700 inch barrel. I think it's either the inaccuracy of ggdt or it is your advice or I am bust a moron who accidentally typed in a gun with a 4800 hundred inch chamber. So which one do you think it is.


A reasonably large pneumatic can have barrels that long before performance starts decreasing.

Are you using the gun optimizer to see how long your barrel should be? That optimizes so you will have 0 acceleration as the projectile leaves the barrel, which is LONG after the point of diminishing returns for most launchers, and definitely way longer than what is usually practical.

If you are using the optimizer, then you are better off manually changing the barrel lengths until you are happy with the trade off between power and size.

If you really don't think it is giving you the right results then upload your GGDT file and we can look over it (you may have to put it in a zip to use the spudfiles uploader)
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Unread postAuthor: Hubb » Fri Sep 21, 2007 4:54 pm

Redid your input. Put inner diam to 0 (what clide suggested :) ) and changed your valve type to barrel seal. It came to 420fps.
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Unread postAuthor: Hubb » Fri Sep 21, 2007 4:57 pm

Um, dude, what keeps happening with your posts?
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Unread postAuthor: veginator » Fri Sep 21, 2007 4:57 pm

Wow, when I uploaded the file my computer wouldn't let me view so thanks :D I think now all my problems are solved until something else comes up. About my posts disapering. I couldn't view the ggdt so I assumed no else could either so I deleted it. And the post after that you pretty much answered what I saying while I was typing but if you want me to put up the ggdt just ask.
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