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(News.com.au)   Best Mach 1.2 ping pong ball cannon you'll see this week (w/ video)   (news.com.au) divider line 48
    More: Cool, speed of sound, mach, paddles, mechanical engineers  
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3234 clicks; posted to Geek » on 05 Feb 2013 at 11:17 AM (1 year ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2013-02-05 10:08:25 AM
Great double negative there, "do not, do not try this at home". Ok, if you insist! I'm going to try it at home and blow my face off, then we'll see who's laughing, all the way to the bank, scaring children on the way.
 
2013-02-05 10:27:25 AM
Even better than the actual gun firing is the awesomely awkward moment at 6:38.
 
2013-02-05 10:31:25 AM
"Do not do this at home."  That just makes me want to do it at home!!
 
2013-02-05 10:42:24 AM
This technology has the potential to revolutionize the pumpkin chunkin' world.
 
2013-02-05 10:45:36 AM
Wonder how far it would go. With that little mass at that high a velocity, the aerodynamic deceleration it would go through once it leaves the barrel has to be really prodigious.
 
2013-02-05 10:47:23 AM
"Don't Try This At Home".

Meh.  I've got a device at home that was invented back in the early 1600's that propels a much heavier sphere (14.9 grams, vs. 2.7 grams) at a significant higher velocity (1,755 KPH vs. 1,448 KPH).

Mine is also more portable.
 
2013-02-05 10:58:52 AM

vossiewulf: Wonder how far it would go. With that little mass at that high a velocity, the aerodynamic deceleration it would go through once it leaves the barrel has to be really prodigious.


Should be easy enough to calculate using this:

http://www.handloads.com/calc/

Let's see, a ping-pong ball has a diameter of 40mm, or 1.575", a weight of 42 grains, and a velocity of 1320 fps.  Ballistic coefficient would be about 0.002.

That calculator only goes down to ballistic coefficients of 0.005, but using that number instead of the more accurate 0.002, the ball would lose nearly half it's velocity in the first 10 yards.  It would probably actually lose half, or more, of it's initial velocity in the first 10 yards.
 
2013-02-05 11:01:55 AM
If you follow the link to the explanation they say that the ping-pong ball exits the barrel with the same kinetic energy as a .32 ACP bullet.
 
2013-02-05 11:02:40 AM

dittybopper: It would probably actually lose half, or more, of it's initial velocity in the first 10 yards.


Thanks, and yeah, now someone more awake at this point should calc the G load of that deceleration. I'm guessing somewhere around jumping off a 30 foot building onto concrete.
 
2013-02-05 11:15:02 AM

Fubini: If you follow the link to the explanation they say that the ping-pong ball exits the barrel with the same kinetic energy as a .32 ACP bullet.


Let's see, common energy of a .32 ACP is around 125 ft/lbs.

Formula for muzzle energy is (M*V*V) / 450400 = ft/lbs energy.

(42 * 1320 * 1320) / 450400 = ~162 ft/lbs muzzle energy, or about 30% more energy than a .32 ACP.

/Can't imagine Leroy Brown having a ping-pong ball gun in his pocket for fun.
 
2013-02-05 11:22:24 AM
That's the most boring air gun video I've ever seen.

Perhaps the DoD would like to use that technology.
 
2013-02-05 11:40:28 AM

Quality Unassured: Even better than the actual gun firing is the awesomely awkward moment at 6:38.


yeah, i think they could have maybe spent another 5 min in the editing bay to work out some of those cuts....
but yeah for science anyway
 
2013-02-05 11:52:18 AM
Lemme see.  I have a vacuum pump and an air compressor and some tape.  And I can cut apart my old potato gun. Now I'm off to get some balls.
 
2013-02-05 12:05:22 PM
No slo-mo?
 
2013-02-05 12:21:01 PM

Kuta: No slo-mo?


img268.imageshack.us
 
2013-02-05 12:21:39 PM
been done before

Link
 
2013-02-05 12:36:03 PM

abhorrent1: been done before

Link


If you were paying attention you would know that that BYU cannon is of the standard simple subsonic variety, and that this vid gives modifications (nozzle, compressed air) to become supersonic.
 
2013-02-05 12:47:08 PM
"What you need to know is not to try this at home. "

Too late, already gathering fellow physics grad students.
 
2013-02-05 12:50:46 PM

Felgraf: "What you need to know is not to try this at home. "

Too late, already gathering fellow physics grad students.


Actually, that gives me an idea:  Shooting a bunch of ping-pong balls out of my muzzleloading mortar.

Or *PAINT BALLS*.

Oh, that would be awesome:  Load up a can full of paint balls in some sort of matrix so they don't burst on firing, and just let them come down on a "beaten zone" down range.  I might have to actually try that.
 
2013-02-05 01:04:51 PM

dittybopper: Kuta: No slo-mo?

[img268.imageshack.us image 600x600]


That produced a laugh that woke my cats.

An actual laugh, out loud. Nicely done, black-powder man.
 
2013-02-05 01:52:23 PM

dittybopper: Felgraf: "What you need to know is not to try this at home. "

Too late, already gathering fellow physics grad students.

Actually, that gives me an idea:  Shooting a bunch of ping-pong balls out of my muzzleloading mortar.

Or *PAINT BALLS*.

Oh, that would be awesome:  Load up a can full of paint balls in some sort of matrix so they don't burst on firing,



Maybe some sort of closed-cell foam sabot?
 
2013-02-05 02:01:27 PM

dittybopper: vossiewulf: Wonder how far it would go. With that little mass at that high a velocity, the aerodynamic deceleration it would go through once it leaves the barrel has to be really prodigious.

Should be easy enough to calculate using this:

http://www.handloads.com/calc/

Let's see, a ping-pong ball has a diameter of 40mm, or 1.575", a weight of 42 grains, and a velocity of 1320 fps.  Ballistic coefficient would be about 0.002.

That calculator only goes down to ballistic coefficients of 0.005, but using that number instead of the more accurate 0.002, the ball would lose nearly half it's velocity in the first 10 yards.  It would probably actually lose half, or more, of it's initial velocity in the first 10 yards.


I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....
 
2013-02-05 02:03:42 PM

Embden.Meyerhof: dittybopper: Felgraf: "What you need to know is not to try this at home. "

Too late, already gathering fellow physics grad students.

Actually, that gives me an idea:  Shooting a bunch of ping-pong balls out of my muzzleloading mortar.

Or *PAINT BALLS*.

Oh, that would be awesome:  Load up a can full of paint balls in some sort of matrix so they don't burst on firing,


Maybe some sort of closed-cell foam sabot?


I hadn't thought of using a sabot, but it would be PERFECT for this thing.

I wonder what happens to a carrot at mach 1.2?
 
2013-02-05 02:13:31 PM
This is a fantastic demonstration of how all that airy foam destroyed Columbia's wing during launch, resulting in its fiery destruction.
 
2013-02-05 02:18:56 PM

Marcus Aurelius: I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....


Hey, you may be on to something there....
 
2013-02-05 02:21:39 PM

Embden.Meyerhof: Maybe some sort of closed-cell foam sabot?


I was thinking more along the lines of Cream of Wheat.
 
2013-02-05 02:25:25 PM

dittybopper: Embden.Meyerhof: Maybe some sort of closed-cell foam sabot?

I was thinking more along the lines of Cream of Wheat.


Remember, we're talking about a mortar with a 3" bore.  I generally shoot 15 oz tin cans half-full of cement for projectiles (they weigh 1 lb) over 400 grains (just under an ounce) of Fg black powder.  They go approximately 300 yards.

My idea is to talk one of the cans and split the sides so it will open up like a plastic shotgun cup does.  Inside would be multiple projectiles sitting in that matrix in order to keep them from being distorted or broken upon firing.
 
2013-02-05 02:30:01 PM

Marcus Aurelius: dittybopper: vossiewulf: Wonder how far it would go. With that little mass at that high a velocity, the aerodynamic deceleration it would go through once it leaves the barrel has to be really prodigious.

Should be easy enough to calculate using this:

http://www.handloads.com/calc/

Let's see, a ping-pong ball has a diameter of 40mm, or 1.575", a weight of 42 grains, and a velocity of 1320 fps.  Ballistic coefficient would be about 0.002.

That calculator only goes down to ballistic coefficients of 0.005, but using that number instead of the more accurate 0.002, the ball would lose nearly half it's velocity in the first 10 yards.  It would probably actually lose half, or more, of it's initial velocity in the first 10 yards.

I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....


You will probably have to use heavier duty materials than PVC pipe and packing tape though, as the pressure built up in the pressurized chamber wouldn't be enough to launch a much heavier projectile. How about trying some kind of metal tubing and nylon filament tape?
 
2013-02-05 02:51:47 PM
I think you are missing the part where the accelleration would be much slower with a heavier projectile.  You would need a much longer tube.  But with a really long tube the heavier object should really fly farther.  Also the pressure wouldn't be that great.  What makes the speed is the lack of resistance in front of it.
  ( or at least that's how I have it figured )
 
2013-02-05 03:11:40 PM
So that's how Chinese Ping Pong Olympians train!
 
2013-02-05 04:14:43 PM

mudpants: But with a really long tube the heavier object should really fly farther.


Should? Of course it will, it has much more mass and therefore much more inertia to be overcome by drag, assuming it has the same muzzle velocity as the ping pong ball.
 
2013-02-05 07:03:02 PM

dittybopper: Marcus Aurelius: I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....

Hey, you may be on to something there....


I just looked at the numbers and I'm pretty sure that a lead sphere with a good seal on the PVC pipe would create enough pressure to create and exploding PVC tube spewing shrapnel at about mach 1.

So make sure your wear safety goggles, and have a friend make the video and send flowers to the funeral.
 
2013-02-05 07:04:58 PM

Genju: Marcus Aurelius: dittybopper: vossiewulf: Wonder how far it would go. With that little mass at that high a velocity, the aerodynamic deceleration it would go through once it leaves the barrel has to be really prodigious.

Should be easy enough to calculate using this:

http://www.handloads.com/calc/

Let's see, a ping-pong ball has a diameter of 40mm, or 1.575", a weight of 42 grains, and a velocity of 1320 fps.  Ballistic coefficient would be about 0.002.

That calculator only goes down to ballistic coefficients of 0.005, but using that number instead of the more accurate 0.002, the ball would lose nearly half it's velocity in the first 10 yards.  It would probably actually lose half, or more, of it's initial velocity in the first 10 yards.

I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....

You will probably have to use heavier duty materials than PVC pipe and packing tape though, as the pressure built up in the pressurized chamber wouldn't be enough to launch a much heavier projectile. How about trying some kind of metal tubing and nylon filament tape?


Listen to this farker.  They know what they're talking about.

Maybe some aircraft grade wing spar tubing, that might fit the bill.
 
2013-02-05 07:11:55 PM
GGreat. Now where's my dodgeball cannon?
 
2013-02-05 07:35:54 PM

Genju: Marcus Aurelius: dittybopper: vossiewulf: Wonder how far it would go. With that little mass at that high a velocity, the aerodynamic deceleration it would go through once it leaves the barrel has to be really prodigious.

Should be easy enough to calculate using this:

http://www.handloads.com/calc/

Let's see, a ping-pong ball has a diameter of 40mm, or 1.575", a weight of 42 grains, and a velocity of 1320 fps.  Ballistic coefficient would be about 0.002.

That calculator only goes down to ballistic coefficients of 0.005, but using that number instead of the more accurate 0.002, the ball would lose nearly half it's velocity in the first 10 yards.  It would probably actually lose half, or more, of it's initial velocity in the first 10 yards.

I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....

You will probably have to use heavier duty materials than PVC pipe and packing tape though, as the pressure built up in the pressurized chamber wouldn't be enough to launch a much heavier projectile. How about trying some kind of metal tubing and nylon filament tape?


My personal preference is steel tubing that is milled octagonal, 15/16" across the flats, with an internal diameter of .54", and with internal grooves that spiral once every 66".
 
2013-02-05 07:37:24 PM

Marcus Aurelius: dittybopper: Marcus Aurelius: I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....

Hey, you may be on to something there....

I just looked at the numbers and I'm pretty sure that a lead sphere with a good seal on the PVC pipe would create enough pressure to create and exploding PVC tube spewing shrapnel at about mach 1.

So make sure your wear safety goggles, and have a friend make the video and send flowers to the funeral.


Maybe I'll just use this to propel that lead sphere:

img236.imageshack.us
 
2013-02-05 09:58:19 PM
"Do not try this at home"....uh, okay.....then why the heck did they explain it AND then show it?  With this, I WILL win at the next beer pong tournament I participate in!!!!!!
 
2013-02-05 10:18:46 PM

vossiewulf: mudpants: But with a really long tube the heavier object should really fly farther.

Should? Of course it will, it has much more mass and therefore much more inertia to be overcome by drag, assuming it has the same muzzle velocity as the ping pong ball.



What I was saying is these other folks were making it sound like if ya only made the pingball out of lead it would go farther with out changing any thing else,
 
2013-02-05 10:27:31 PM

mudpants: vossiewulf: mudpants: But with a really long tube the heavier object should really fly farther.

Should? Of course it will, it has much more mass and therefore much more inertia to be overcome by drag, assuming it has the same muzzle velocity as the ping pong ball.


What I was saying is these other folks were making it sound like if ya only made the pingball out of lead it would go farther with out changing any thing else,


That's actually true:  If the initial velocity is the same, a solid lead ball will go much farther and lose velocity at a much, much, *MUCH* slower rate.
 
2013-02-05 11:08:27 PM

dittybopper: Marcus Aurelius: dittybopper: Marcus Aurelius: I bet it would go a lot farther with a lead sphere.  I'm going to have to try that at home....

Hey, you may be on to something there....

I just looked at the numbers and I'm pretty sure that a lead sphere with a good seal on the PVC pipe would create enough pressure to create and exploding PVC tube spewing shrapnel at about mach 1.

So make sure your wear safety goggles, and have a friend make the video and send flowers to the funeral.

Maybe I'll just use this to propel that lead sphere:

[img236.imageshack.us image 582x181]


That is a very nice weapon.  Which is why I know it's not yours.

And neither is this one mine:
www.gatling-gun.com
 
2013-02-06 09:07:42 AM
The method is how you prep a space railgun for operational tests in the hypersonic range.

If you try to fire enclosed channel rail guns at very high velocities the differential density between the top and bottom of the air inside the accelerationway will cause the projectile to diverge through the top of the assembly.  So you gotta vac em down to dead near zero.


Thank you.  I invented this.
 
2013-02-06 09:23:50 AM
dittybopper:
That's actually true:  If the initial velocity is the same, a solid lead ball will go much farther and lose velocity at a much, much, *MUCH* slower rate.


But with the same barrel length and the same vacuum you will not have the same acceleration/initial velocity.
 
2013-02-06 02:18:51 PM

Marcus Aurelius: That is a very nice weapon.  Which is why I know it's not yours.


Yes it is:

i39.tinypic.com

You must be confusing my gun with "the gun that shall be mine":

i51.tinypic.com

Here they are together so you can distinguish them:

i54.tinypic.com

Top one is mine, and the bottom is the gun that shall be mine.
 
2013-02-06 02:21:56 PM

mudpants: dittybopper:
That's actually true:  If the initial velocity is the same, a solid lead ball will go much farther and lose velocity at a much, much, *MUCH* slower rate.


But with the same barrel length and the same vacuum you will not have the same acceleration/initial velocity.


Given the same amount of energy, the solid lead ball will still go much farther because it won't be slowed down nearly as much by air resistance.

In a vacuum, you'd be correct, of course.
 
2013-02-06 02:22:37 PM
Applied Physics:  It's what kills dinner.
 
2013-02-06 03:16:34 PM

dittybopper: dittybopper: Embden.Meyerhof: Maybe some sort of closed-cell foam sabot?

I was thinking more along the lines of Cream of Wheat.

Remember, we're talking about a mortar with a 3" bore.  I generally shoot 15 oz tin cans half-full of cement for projectiles (they weigh 1 lb) over 400 grains (just under an ounce) of Fg black powder.  They go approximately 300 yards.

My idea is to talk one of the cans and split the sides so it will open up like a plastic shotgun cup does.  Inside would be multiple projectiles sitting in that matrix in order to keep them from being distorted or broken upon firing.


Paintballs are frail things meant to rupture. It's gonna be tough to keep them from doing so. You had better give some thought to keeping the heat/flame from the powder charge out of the "shot cup" as it were. Solid bottom comes to mind or maybe some type of over powder wad? I also wonder about the "matrix" material. If the material grains are too large they will create points of concentrated pressure where they touch the paintball. I wonder if a finer grained material might work better. My first thought was flour but it is flammable so a non flammable powder like clay might be a better choice.
 
2013-02-06 03:55:57 PM

IAMTHEINTARWEBS: dittybopper: dittybopper: Embden.Meyerhof: Maybe some sort of closed-cell foam sabot?

I was thinking more along the lines of Cream of Wheat.

Remember, we're talking about a mortar with a 3" bore.  I generally shoot 15 oz tin cans half-full of cement for projectiles (they weigh 1 lb) over 400 grains (just under an ounce) of Fg black powder.  They go approximately 300 yards.

My idea is to talk one of the cans and split the sides so it will open up like a plastic shotgun cup does.  Inside would be multiple projectiles sitting in that matrix in order to keep them from being distorted or broken upon firing.

Paintballs are frail things meant to rupture. It's gonna be tough to keep them from doing so. You had better give some thought to keeping the heat/flame from the powder charge out of the "shot cup" as it were. Solid bottom comes to mind or maybe some type of over powder wad? I also wonder about the "matrix" material. If the material grains are too large they will create points of concentrated pressure where they touch the paintball. I wonder if a finer grained material might work better. My first thought was flour but it is flammable so a non flammable powder like clay might be a better choice.


This is the mortar in question:

i46.tinypic.com

See that tin can on the rack on the right front of this image?  That's a projectile for the gun.  It's half-full of cement.

My idea is to take tin snips and cut lines all the way down to near the bottom.  I'd put in a layer of some sort of matrix to cushion the bottom, then some paint balls, then some more matrix, more paint balls, etc. until I've got the thing at the proper weight for shooting.

A paintball that is supported around it's entire outside surface is much less likely to burst.

The mortar itself doesn't *PUSH* the projectiles that hard:  I've calculated the muzzle velocity as somewhere around 300 FPS, which is about the velocity of a paintball gun anyway.
 
2013-02-06 08:19:29 PM

dittybopper: Embden.Meyerhof: Maybe some sort of closed-cell foam sabot?

I was thinking more along the lines of Cream of Wheat.


Actually I think gelatin/Jello would be best. It is fairly clear so you could see your paintballs and you could probably add enough sugar or other chemical to make it match the density of the paintballs. If the density of your matrix matches then the objects within it, they will have no relative acceleration.
 
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