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full sized GB hybrid

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: STHORNE » Tue Mar 11, 2008 6:13 pm

its a price we all have to pay my friend (if you own a hybrid that is)
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Unread postAuthor: SpudFarm » Tue Mar 11, 2008 6:18 pm

_Fnord i thinking of getting a pipe the size of the burst disks and just put them in a hydraulic press and make like 1000 at 5seconds :)
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Unread postAuthor: Fnord » Tue Mar 11, 2008 6:22 pm

That's not a bad idea actually.


its a price we all have to pay my friend (if you own a hybrid that is)


Not me. I'm above the law! Muahaha.
I just have to fix crap that breaks due to ridiculous mechanical stresses.
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Unread postAuthor: bigbob12345 » Tue Mar 11, 2008 6:27 pm

sthorne wrote:its a price we all have to pay my friend (if you own a hybrid that is)


Or a burst disk pnumatic

And spudfarm I actually really like that idea but I would use a vice instead and clamp it down as hard as I can.
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Unread postAuthor: SpudFarm » Tue Mar 11, 2008 6:29 pm

i got a 10ton hydraulic press so clamping power = no problem :D
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Unread postAuthor: STHORNE » Tue Mar 11, 2008 6:40 pm

bigbob12345 wrote:
sthorne wrote:its a price we all have to pay my friend (if you own a hybrid that is)


Or a burst disk pnumatic


or that. and technically, wouldn't a "burst disk pneumatic" just be an advanced pneumatic?
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Unread postAuthor: DYI » Tue Mar 11, 2008 7:59 pm

Um, you use unrated abs at 500 psi


:lol: Well, make that 50 times the rated pressure... I'm pretty sure that I significantly exceed the burst pressure of the barrel pipes, it's amazing how long they've survived, even in subzero temperatures with heavy (and often completely jammed :roll: ) ammo.

and technically, wouldn't a "burst disk pneumatic" just be an advanced pneumatic?


No. When you're talking about a pneumatic, the valve is the defining component, and a lot of valves fall into the so-called "advanced" category, anything homemade really.
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Unread postAuthor: SpudBlaster15 » Tue Mar 11, 2008 8:18 pm

DYI, 2" nominal diameter Sch 40 DWV ABS pipe should (assuming no molding defects) have a burst pressure of around 1000PSI, so I am not surprised that it resists <500PSI for only a few tens of milliseconds.

I surely wouldn't use it as the barrel of a 10x mix hybrid launcher though.
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Unread postAuthor: DYI » Wed Mar 12, 2008 10:09 am

DYI, 2" nominal diameter Sch 40 DWV ABS pipe should (assuming no molding defects) have a burst pressure of around 1000PSI, so I am not surprised that it resists <500PSI for only a few tens of milliseconds.


Well that's certainly good to know. I'd always assumed it was lower, with all the talk of it bursting at around 150 psi... I guess just another unbased assumption like the whole "mixes over 4x risk detonation" thing. What's the burst pressure of 4" SCH 40 ABS? I may not have to reinforce that barrel after all...

And I'm using DWV copper for the barrel on my hybrid, so no worries there (I hope).
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Unread postAuthor: SpudFarm » Wed Mar 12, 2008 11:45 am

no DYI i also use some really thin walled copper for my hybrid and it is fine :)
BTW with your hybrid are you thinking to go up to like 10x ?
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Unread postAuthor: DYI » Wed Mar 12, 2008 5:26 pm

The goal for my hybrid is 10x air/MAPP. After hydrostatic testing to 1500 psig, 10x will be the normal operating mix. Due to the nature of my meter, I don't expect that fueling will be incredibly accurate below 4x or so, and I see no real reason to use anything other than full power, except maybe for shooting in my yard.
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Unread postAuthor: SpudBlaster15 » Wed Mar 12, 2008 5:28 pm

Burst pressures really are a lot more complex than what a simple formula can model, but assuming no molding defects, 4" nominal diameter ABS pipe should have a burst pressure of somewhere around 800PSI. However, because molding defects are likely in DWV pipe, I wouldn't subject it to any pressure levels greater than half of that figure.
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Unread postAuthor: DYI » Wed Mar 12, 2008 5:41 pm

Thanks. I'll probably reinforce it anyway, because I don't want to risk accidentally bursting a $90 chunk of pipe.
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Unread postAuthor: SpudFarm » Thu Mar 13, 2008 12:34 pm

whhhoa 10x :shock:
you should get to mach two :P

my goal for all of my cannons/hybrids is SOS.
a GB at the speed of sound should be interesting...
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