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Supersonic?

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: spudthug » Sat Jun 02, 2007 11:17 pm

burst disks are the fastest openning valves, AND teh most effective...basically because it puts a gigantic hole there within a millisecond...it just happens instantly...

oh and about the new cat thing...if pyro is keeping that list he is going to have to keep up with all of us changing :wink:
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: jackssmirkingrevenge » Sat Jun 02, 2007 11:23 pm

I'll join the naysayers, I've used 400 psi+ in long barreled small calibre launchers with extremely efficient piston valves and still never exceeded 1015 fps with 0.12g BBs
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Unread postAuthor: spudthug » Sat Jun 02, 2007 11:25 pm

but ur gun has a tiny ass chamber..mine has two 7 inch chambers...
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: SpudBlaster15 » Sun Jun 03, 2007 1:27 am

spudthug wrote:my marble was 10 grams...idk i didnt come up with it ggdt did...


I ran your gun through GGDT, and even after tweaking certain variables in an attempt to maximize the theorized output, the maximum velocity I could achieve was 760fps at a chamber pressure of 100psi, using a 10 gram projectile.
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Unread postAuthor: jackssmirkingrevenge » Sun Jun 03, 2007 4:37 am

spudthug wrote:but ur gun has a tiny ass chamber..mine has two 7 inch chambers...


It's a question of barrel/chamber ratios - once you reach a certain limit, increasing chamber volume has absolutely no effect on performance.
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Unread postAuthor: spudthug » Sun Jun 03, 2007 9:37 am

well sb15...

1 thats what i got when i typed in the specs of my gun...maybe i did something wrong..

2. lets not get into a fight over my gun... we decided we werent going to fight anymore..
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: veginator » Sun Jun 03, 2007 10:12 am

i now of a pneumatic that went supersonic :D http://www.spudtech.com/content.asp?id=10
look near the bottom
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Unread postAuthor: schmanman » Sun Jun 03, 2007 12:31 pm

spudthug wrote:i almost got supersonic with my jme-45 gun...i got 1054 fps with a 1 inch marble....at 100 psi...if i went to 120 there is no doubt i would have gotten supersonic..

sadly my compressor wont fill the massive gun over 105 psi..




bullshit.
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Unread postAuthor: spudthug » Sun Jun 03, 2007 12:34 pm

schmanman we dont need u putting ur 2 cents in when we already established that i made a mistake....why are u always jumping to conclusions? read the other messages..
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Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: Velocity » Sun Jun 03, 2007 12:51 pm

I personally don't believe spud gun velocity figures unless (1) The poster shows a GGDT picture of what they input and what the results are (2) An actual chronograph photo with the speed (which has become less convincing in the last year or so, considering a lot of people have gotten over 900 FPS (one guy allegedly broke Mach 2) because they put their muzzles too close to the chronograph) (3) The poster is actually someone reliable who I doubt would bump up their velocity figures just to gain more respect; people like clide, jack, Neospud, SB15, Gort, etc posts the data (note: thats not ALL of the people who I think are reliable; there are a couple more).

I'm not trying to be a jerk here or insult anyone, but it seems like there are too many "mistakes" made when a velocity figure is posted. I'm not ripping on you only spudthug... just placing a general complaint; there are many perpetrators (I myself might have done this too)
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Unread postAuthor: ammosmoke » Sun Jun 03, 2007 3:01 pm

I think the archive that included co2 not being able to propell an object to supersonic speeds was interesting. According to that archive, it isn't possible to make a gun that uses co2 or compressed air to go supersonic because the expanding gas only cannot make a projectile go faster than its speed. However, the guy continues to say that helium could work because it is lighter. I am not sure that this applies to hybrids though, no offense to hi who posted the link. I don't think so because the guy goes on to say that some "real" guns can because they use heat, which can expand faster. And, hybrids use heat when they are ignited, so I don't think it applies to hybrids. Although, noname didn't say he ignited it, so in your case, you are probably right.
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<img>http://www.speedtest.net/result/309559995.png</img>
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Unread postAuthor: spudthug » Sun Jun 03, 2007 3:04 pm

I'm not trying to be a jerk here or insult anyone, but it seems like there are too many "mistakes" made when a velocity figure is posted. I'm not ripping on you only spudthug... just placing a general complaint; there are many perpetrators (I myself might have done this too)


i was telling the truth 100 percent when i said i put that in...i must have made a msitake..i am not sure everything about the valve but i know igot the pressure,chamber, and barrel right...so the only thing i could have messed up on would be the valve...
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: CpTn_lAw » Sun Jun 03, 2007 4:34 pm

you can go supersonic with compressed air as long as it is hot. basicly, you need a quick fill, and immediate fire.
I've done it. It worked. I was happy. My neighbors weren't. I idn't do it more.
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Unread postAuthor: noname » Sun Jun 03, 2007 4:57 pm

I'll do it again, except blowtorch the whole cannon for a few minutes first! And maybe add another 10 feet of barrel?
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Unread postAuthor: SpudBlaster15 » Sun Jun 03, 2007 5:14 pm

I think it would be much more effective to first pressurize the chamber to a pressure that you know will not cause the disks to rupture (200psi or so), then heat the chamber until thermal expansion causes the pressure to increase past the threshold of the disks.
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