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Posted: Sun Jun 26, 2011 11:42 pm
by Jolly Roger
MrCrowley wrote:Oh yeah wow, I didn't notice how much the chamber pressure increased with the extra 9 ignition points. Jumps up to around 20,000PSI, for an increase of about 10ms.
Is there a problem with sticking a longer barrel on it? Hybrids aren't very portable to begin with, especially one like this.
No I think that's what I'll do, put a longer barrel on it. This is really just a concept design so I shouldn't be too concerned with those sorta things anyway.
ramses wrote:All right, I got 799 m/s. But for a real design IT WILL NEVER WORK. suffice to say that the aspect ratio of the chamber is... well... *em*
HGDT reports the maximum chamber pressure as 221ksi, but the graph only shows a peak at around 16ksi. It is also extremely inconsistent in that the velocity varies 200m/s between runs with identical parameters./quote]
I've noticed that as well. After running the sim I change an input, run the sim, then change it back and run it again, different results... But for now I think it is still the best way to optimise the gun.
Once I get Solidworks down pat I'll upload the design for you all to have a look over
Posted: Mon Jun 27, 2011 12:37 am
by MrCrowley
After running the sim I change an input, run the sim, then change it back and run it again, different results...
I thought I was going crazy. Noticed that in the past as well, never mentioned it though.
Posted: Mon Jun 27, 2011 2:16 am
by Jolly Roger
David did say when things quieten down again for him that he'll be combining GGDT and HGDT together, and will hopefully solve some of these errors. Someday
Posted: Mon Jun 27, 2011 12:24 pm
by Ragnarok
I can't get more than about 615 m/s within those limits and a practically achievable real world design - and that's using some of the dirtiest cheats I can think of.
ramses wrote:HGDT reports the maximum chamber pressure as 221ksi, but the graph only shows a peak at around 16ksi.
Bear in mind that the graph does not show all data points, just every 25th one (I think). It's perfectly possible to have a peak between those that doesn't show on the graph.
Posted: Mon Jun 27, 2011 6:04 pm
by ramses
Ragnarok wrote:I can't get more than about 615 m/s within those limits and a practically achievable real world design - and that's using some of the dirtiest cheats I can think of.
ramses wrote:HGDT reports the maximum chamber pressure as 221ksi, but the graph only shows a peak at around 16ksi.
Bear in mind that the graph does not show all data points, just every 25th one (I think). It's perfectly possible to have a peak between those that doesn't show on the graph.
I realized that shortly after I typed most of the post, but I still wanted to get the meme in there. Also, I misspoke (mistyped) when I said the chamber pressure exceeded 221ksi. That was actually the peak barrel pressure. A 0.25cm chamber opening into a 2.1cm barrel would not produce such peak pressures.
Posted: Wed Jun 29, 2011 1:25 am
by Jolly Roger
ramses wrote:Ragnarok wrote:I can't get more than about 615 m/s within those limits and a practically achievable real world design - and that's using some of the dirtiest cheats I can think of.
ramses wrote:HGDT reports the maximum chamber pressure as 221ksi, but the graph only shows a peak at around 16ksi.
Bear in mind that the graph does not show all data points, just every 25th one (I think). It's perfectly possible to have a peak between those that doesn't show on the graph.
I realized that shortly after I typed most of the post, but I still wanted to get the meme in there. Also, I misspoke (mistyped) when I said the chamber pressure exceeded 221ksi. That was actually the peak barrel pressure. A 0.25cm chamber opening into a 2.1cm barrel would not produce such peak pressures.
Technically it may be able to but if the chamber diameter is smaller than the barrel, I dont see how the barrel pressure would be higher than the chamber.
Posted: Wed Jun 29, 2011 7:19 pm
by ramses
Jolly Roger wrote:ramses wrote:
...
I realized that shortly after I typed most of the post, but I still wanted to get the meme in there. Also, I misspoke (mistyped) when I said the chamber pressure exceeded 221ksi. That was actually the peak barrel pressure. A 0.25cm chamber opening into a 2.1cm barrel would not produce such peak pressures.
Technically it may be able to but if the chamber diameter is smaller than the barrel, I dont see how the barrel pressure would be higher than the chamber.
I know
