SpudFiles

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!

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.

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.

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.

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?

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.

It just appears, nice. If you were to fire a pointed steel projectile, how deep do you think it could penetrate, say, a tree?

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-hyb ... html">Thar we go!</a>

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?

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.

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.

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?

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.

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.

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.