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Does 6x + a 20 foot barrel = 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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Does 6x + a 20 foot barrel = Supersonic?

Unread postAuthor: noname » Fri Aug 17, 2007 2:10 pm

Just trying to get confirmation on this, because I'm pretty sure the gun is shooting supersonic but have no way of telling for sure. GGDT predicts that using an 8 gram ball bearing as a projectile, the gun shoots at 1700-2000 fps, depending on generous or crappy values.

Chamber diameter: 2"
Chamber length: 11"
Pressure: at least 575 psi
Temperature: It's like 2000-3000*, right?

Valve Type: Burst Disc
# of Valves: 1
Flow Coef: a good piston valve is like 40% or something, right? So a burst disc would be 50-60%?
Seat diameter: .7"

Dead Volume: .3 in^3

Barrel Bore: .63"
Length: 240"
Projectile Friction: Almost none, 1 psi or less
Projectile mass: 8 grams (measured on a triple beam balance)
Diameter: .62"
Initial Position: .5"


Does it all sound right?
I know it shoots a hell of a lot harder than with the 6 foot barrel; I can put a ball bearing through 5+ inches of wood. If I shoot without a projectile, I hear a sound like air being released, kind of like a quieter piston valve. With a projectile, I get a massive rifle-like CRACK! sound.


Edit: Almost forgot the best part: Pictures!
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A triple layer of soda can burst discs holds 550+ psi in a 1/2" union.
hybrid20ft 003.jpg
hybrid20ft 002.jpg
Suffering from extreme BBS (Bendy Barrel Syndrome)
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Unread postAuthor: paaiyan » Fri Aug 17, 2007 2:21 pm

Wow, I like it. I don't know about supersonic, hybrids aren't one of my specialties. I do, however, know that if you're putting a ball bearing through 5 inches of wood, I WANT ONE!

That barrel is crazy long and bendy, could you shoot around a corner with it? That would be sweet.
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Unread postAuthor: noname » Fri Aug 17, 2007 2:25 pm

It's no ttoo hard to make one; just use steel and you won't kill yourself. I think I could shoot around a corner if I had a thicker barrel, but then it wouldn't bend, would it? :? The force from a ball bearing going around the curve would probably crack/shatter the barrel.
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Unread postAuthor: mopherman » Fri Aug 17, 2007 2:26 pm

paaiyan wrote:That barrel is crazy long and bendy, could you shoot around a corner with it? That would be sweet.

lol, I'm pretty sure it would just blow a hole in the side of the barrel.
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Unread postAuthor: paaiyan » Fri Aug 17, 2007 2:27 pm

mopherman wrote:
paaiyan wrote:That barrel is crazy long and bendy, could you shoot around a corner with it? That would be sweet.

lol, I'm pretty sure it would just blow a hole in the side of the barrel.


Poop, I wanted to shoot around corners. I figured that would be what happened.

So about how long is the delay between firing and the projectile exiting the barrel?
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Unread postAuthor: noname » Fri Aug 17, 2007 2:33 pm

A hole just appears in the target when you click the igniter. I don't know how fast that is, but it's pretty damn quick.
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Unread postAuthor: paaiyan » Fri Aug 17, 2007 2:36 pm

It just appears, nice. If you were to fire a pointed steel projectile, how deep do you think it could penetrate, say, a tree?
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Unread postAuthor: noname » Fri Aug 17, 2007 2:39 pm

I was thinking about making some darts out of the remaining 10 inches of 1/2" aluminum rod that I have...
I think it would go frickin' deep, there's no telling just how deep though. At least 8"?

Edit: There's a few damage pictures in the gun's thread:
<a href="http://www.spudfiles.com/forums/the-hybrid-update-8-11-damageandnew-pics-t9879.html">Thar we go!</a>
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Last edited by noname on Fri Aug 17, 2007 2:40 pm, edited 1 time in total.
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Unread postAuthor: paaiyan » Fri Aug 17, 2007 2:40 pm

Sweet, now what about accuracy? I would think with that much barrel, there might be a bit of jump. Or do you have the muzzle strapped down somehow?
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Unread postAuthor: noname » Fri Aug 17, 2007 2:43 pm

I could always duct tape it to the ground, I guess. There isn't too much recoil, surprisingly. If you want any accuracy, it has to have the 6 foot barrel on it; with the 20 footer, you just put stuff in front and watch it get blasted to oblivion.
Click the link in the above edit.
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Re: Does 6x + a 20 foot barrel = Supersonic?

Unread postAuthor: joannaardway » Fri Aug 17, 2007 2:50 pm

Handing the numbers over to Ragnarok... the offical verdict is:

Ragnarok wrote:Well, I can't say for absolute certain that it's shooting above 340 m/s... but judging by the 13% required efficency between the minimum kinetic energy for that and maximum potential kinetic energy, I'd say that - with reasonable confidence - it's probably firing at at least that. But nearly Mach 2 seems optimistic.


So to cut through his jargon, yes, you're probably going supersonic.
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Re: Does 6x + a 20 foot barrel = Supersonic?

Unread postAuthor: mopherman » Fri Aug 17, 2007 3:03 pm

joannaardway wrote:Handing the numbers over to Ragnarok... the offical verdict is:

Ragnarok wrote:Well, I can't say for absolute certain that it's shooting above 340 m/s... but judging by the 13% required efficency between the minimum kinetic energy for that and maximum potential kinetic energy, I'd say that - with reasonable confidence - it's probably firing at at least that. But nearly Mach 2 seems optimistic.


So to cut through his jargon, yes, you're probably going supersonic.

does he talk like that all the time? :lol:
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Unread postAuthor: noname » Fri Aug 17, 2007 3:28 pm

I wasn't expecting Mach 2 or anything like it, I just built the gun to shoot supersonic, so if it does, I'm satisfied.
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Unread postAuthor: jimmy101 » Fri Aug 17, 2007 7:40 pm

noname wrote:I wasn't expecting Mach 2 or anything like it, I just built the gun to shoot supersonic, so if it does, I'm satisfied.

So you really don't know if it does or not. Ragnarok's calculation is very crude and assumes that you get the same efficiency out of a gun shooting supersonic that you do with a gun that shoots at 300 FPS.

Build a chrono and measure the muzzle velocity.

Extraordinary claims require extraordinary proof.
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Unread postAuthor: noname » Fri Aug 17, 2007 7:51 pm

I'm telling you, there's no way I'd ever be able to put anything electrical together that has more than 3 parts.
Plus, don't you have to have it hooked up to a computer or something? I'm sure as hell not going to shoot inside.
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