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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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Supersonic?

Unread postAuthor: noname » Sat Jun 02, 2007 8:43 pm

Well, I've been trying different types of high pressure burst discs lately. My gun stopped working as a hybrid, no idea why. I have my meter length and pressure set correctly according to SpudTool (AdvancedSpuds) and FuelTool (BurntLatke). It's all steel, so I've been shooting it at ridiculous pressures as a pneumatic. I used two layers of aluminum soda can today, as a burst disc. They held 350 psi! I couldn't pump further with my bike pump (I was literally jumping on it), so I waited. After a minute or two, the thing went off, totally randomly. The steel ball bearing went through 6 soda cans, two layers of 1/2" plywood (the backstop :lol: ), through my tin shed, out the other side, and finally left a 1/2" deep dent in my 3/4" plywood fence. It was extremely loud, louder than anything I've ever heard. Usually the gun sounds like a rifle, but this shot was louder than a shotgun. I can barely hear now.
Give me your opinion, was it supersonic or not.

Almost forgot, this gun's barrel is 10 feet of 1/2" PVC for those who don't know.
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Both layers on top of each other
Hybrid 009.jpg
The burst was PERFECT!
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Unread postAuthor: pyromaniac » Sat Jun 02, 2007 8:45 pm

i say hell yeah is was. horay for a sale at OSH.
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:pottytrain3:
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Unread postAuthor: hi » Sat Jun 02, 2007 8:58 pm

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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: Redcoat » Sat Jun 02, 2007 9:04 pm

wow :shock: . thats is a massive! It went through all that?

Thats AWESOME!
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Poo.
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Unread postAuthor: SpudBlaster15 » Sat Jun 02, 2007 9:06 pm

GGDT says you hit somewhere in the vicinity of 900fps.

That was one hell of a shot, but I am not surprised. A 10 gram piece of steel traveling at 4/5 the speed of sound will do a ton of damage to most things.
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Unread postAuthor: spudthug » Sat Jun 02, 2007 9:42 pm

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..
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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: VH_man » Sat Jun 02, 2007 9:58 pm

wow.................... that sounds pretty powerful. i would invest in a shock pump and send things at the speed of sound with simple pneumatic pressure, and prove that it can be done............
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Unread postAuthor: SpudBlaster15 » Sat Jun 02, 2007 10:10 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..


How did you come up with that number? I am doubtful that your JME-45 could accelerate a 1" diameter marble (probably on the order of 20 grams) to within 50fps of the speed of sound, at 100psi.
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Unread postAuthor: noname » Sat Jun 02, 2007 10:16 pm

I'll keep trying, as soon as I can get it to work as a hybrid. 6 or 7x will produce enough pressure to get it going that fast. Over the summer, I also plan on doing hybrid C:B ratio tests, with a 40 or 50 foot barrel, and replicating Latke's tests (cutting 20% off after ever round of shots).
I plan on starting with a 50 foot barrel, shooting 3 shots at 1x, 3 shots at 2x, 3 shots at 4x, 3 shots at 5x, then cutting off 20%. I'll keep doing this until I get to a 1 foot barrel.
Damn, I'm gonna go through soooo many burst discs. :?

Oh, forgot to mention, check out that amazing burst!
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Unread postAuthor: spudthug » Sat Jun 02, 2007 10:19 pm

my marble was 10 grams...idk i didnt come up with it ggdt did...but anyway..no name u say that u only put 350 psi of air in there? wow...try a 5x mix and u could probably get around 1000 fps...im not a hybrid expert but isnt it pretty easy to reach 350 psi with a hybrid?
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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: PVC Arsenal 17 » Sat Jun 02, 2007 10:20 pm

That sounds like one hell of a shot! Lucky that crap didn't bounce off something and fork you up.

Burst disc guns continue to fascinate me. I have yet to see any valve match the speed of burst discs. The only trouble is finding the perfect one for your gun.
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Unread postAuthor: noname » Sat Jun 02, 2007 10:27 pm

By sticking on a peak pressure guage, I figured (when it worked as a hybrid) 1x would get me about 90 psi, 1.5x would give about 140 psi, 2x would get me about 170, 2.5x got around 215, 3x about 250, 4x about 310, and I didn't test past that.
I wouldn't recommend using soda can burst discs for PVC guns, because one layer takes around 170 psi to burst.
PVC Arsenal, I got hit by one of the bearings once. At a 2.25x mix, the ball bearing got shot through 4 soda cans and hit a piece of steel pipe that was lying around. It gave the pipe a 1/4" deep dent, bounced back, and tapped me on the kneecap.
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Unread postAuthor: spudthug » Sat Jun 02, 2007 11:01 pm

@noname: what is the best burst disk u have used at a 4x mix? also waht mix are milk bottles good for?

also does anyone know how to wire up a stun gun to 2 spark plugs?? i will be posting a thread asking this question soon reply there..
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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: A-98 » Sat Jun 02, 2007 11:11 pm

hm.... i need to build a hybrid.....badley....

also....

spudthug.

i

cannot

allow

you

to have an avatar cooler than mine....

i marvel in the presence of your avatar.
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Unread postAuthor: Velocity » Sat Jun 02, 2007 11:14 pm

I elaborated on the gangsta theme....

anyways...

PVC Arsenal, I doubt that there IS a valve faster than a burst disk. Full flow, rapid opening... can't beat it.

The only valve better than a burst disk valve... is a BIGGER burst disk valve.
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