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zerooftheday
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27 Mar 2009, 11:31 am

Anyone have any experience with these or know of a couple good websites?

My cousin and I are into geeky science stuff, and these somehow ended up on our list of stuff to build, along with Wolverine claws, a tank, a forge, a smelter, and a trebuchet. Anyways, we're thinking something that will smash 1/2" steel ball bearings into rocks fast enough to be dangerous to anyone watching.

First, can we use steel ball bearings? A few of the websites mention non-ferrous materials, but none of them say why.

Second, how do we go about building one? Most of the plans on the 'net aren't much for the step-by-step, they're just blueprints.



iceb
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27 Mar 2009, 2:22 pm

Rail guns use magnetic fields to accelerate the projectile which must be a good conductor and not magnetic. they are basicly the same as an a.c. induction motor or linear accelerator they were certainly covered in a book by Professor Eric Lathwaite from which I built a linear accelerator and a levitator as an apprentice many years ago.
Rail guns are used in test laboratories to accelerate projectiles to simulate very high speed impacts like meteoroids on a space station for example.


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ruveyn
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27 Mar 2009, 3:29 pm

zerooftheday wrote:
Anyone have any experience with these or know of a couple good websites?

My cousin and I are into geeky science stuff, and these somehow ended up on our list of stuff to build, along with Wolverine claws, a tank, a forge, a smelter, and a trebuchet. Anyways, we're thinking something that will smash 1/2" steel ball bearings into rocks fast enough to be dangerous to anyone watching.

First, can we use steel ball bearings? A few of the websites mention non-ferrous materials, but none of them say why.

Second, how do we go about building one? Most of the plans on the 'net aren't much for the step-by-step, they're just blueprints.


Look here:
http://en.wikipedia.org/wiki/Rail_gun

It turns out explosive missiles are more cost effective.

ruveyn



zerooftheday
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27 Mar 2009, 3:49 pm

Iceb:

Ok, so the ball bearings are out. "Test laboratories" are a great excuse, I'll remember to use that.

Ruveyn:

Aye, missiles are more cost-effective, but they're kinda illegal to build in a garage. Railguns, so far as I know, aren't even limited by firearms laws. And even if they are, firearms laws (concerning "destructive devices") are centered around the size of the projectile, not muzzle energy.

F=1/2(m+v*2)

we don't really need big, what we need is *fast*.



ruveyn
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27 Mar 2009, 6:08 pm

zerooftheday wrote:

we don't really need big, what we need is *fast*.


Don't forget accurate. One has to be able to hit what one is aiming for.

What good is a fast flying mass that doesn't hit the target?

ruveyn



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27 Mar 2009, 6:09 pm

zerooftheday wrote:

we don't really need big, what we need is *fast*.


Don't forget accurate. One has to be able to hit what one is aiming for.

What good is a fast flying mass that doesn't hit the target?

ruveyn



zerooftheday
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27 Mar 2009, 6:24 pm

I thought that was implied. In any case, that's more a derivative of the construction of the device than the projectile size. Once we had a working model, then we can refine it endlessly.

The projectile would have to be designed pretty well in any case, since spheres aren't known for their high ballistic coefficient.



kip
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28 Mar 2009, 4:44 am

ruveyn wrote:
zerooftheday wrote:

we don't really need big, what we need is *fast*.


Don't forget accurate. One has to be able to hit what one is aiming for.

What good is a fast flying mass that doesn't hit the target?

ruveyn


Machine gun anyone?

See if you caint bundle together smaller projectiles, like a shotgun blast. Then you don't have to worry as much about accuracy. And also, you're more likely to cause just pain, not death, should one of your family members be dumb enough to get in the way.


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ruveyn
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28 Mar 2009, 4:59 am

kip wrote:
ruveyn wrote:
zerooftheday wrote:

we don't really need big, what we need is *fast*.


Don't forget accurate. One has to be able to hit what one is aiming for.

What good is a fast flying mass that doesn't hit the target?

ruveyn


Machine gun anyone?

See if you caint bundle together smaller projectiles, like a shotgun blast. Then you don't have to worry as much about accuracy. And also, you're more likely to cause just pain, not death, should one of your family members be dumb enough to get in the way.


Rail guns are single shot weapons. Of course if a rail gun can launch a cluster bomb then it need not be pin point accurate.

In any case an explosively launched cluster bomb or one dropped from a plane is still more cost effective than a rail gun. Rail guns are technologically cool but no one has yet found a more cost effective method a hurling a mass than by explosive force.

Linear motors are better used to propel trains than ammunition.

ruveyn



zerooftheday
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28 Mar 2009, 7:47 pm

Kip:

There's no way in hell we're gonna test this thing with anyone in the way. I live in Idaho, USA. I can point in any direction, and in 50 miles be out of side of any sign of humanity excepting dirt roads. If I blow myself up, that's OK. I'm not going to risk hurting people. It's all fun and games until the charges are read by a judge, we always say.

Ruveyn:

It wouldn't be much of a garage project to make something logical, efficient, and technologically simple. Gotta do something pointless, overly complex, and very bad from a cost-benefit perspective. :D



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28 Mar 2009, 7:53 pm

Considering the time and money you'd have to spend on making on that'll launch a projectile farther than 2 feet, you'd probably be better off doing something like making a potato gun, but with a smaller PVC pipe to launch ball bearings or pipe harpoons.



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29 Mar 2009, 9:27 am

zerooftheday wrote:

Ruveyn:

It wouldn't be much of a garage project to make something logical, efficient, and technologically simple. Gotta do something pointless, overly complex, and very bad from a cost-benefit perspective. :D


Jobs and Wozniac did not have this p.o.v.

ruveyn



zerooftheday
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29 Mar 2009, 11:58 pm

DNForrest:

I've got a spud gun, I can reach 150 yards out. It's on my list of things to do to change my 2" barrel out for a 1.5", 2" spuds are hard to find.

Ruveyn:

I don't care if this ends up making me money, I just feel like making one. It's a hobby, like anything else, I do it for entertainment, not profit. My money-making project is never mentioned outside close friends and family.