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Coil Gun

A place to ask general spud cannon related questions.
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Coil Gun

Unread postAuthor: FishBoy » Thu Oct 30, 2008 7:29 pm

First off, Mods, if this is in the wrong place, feel free to move it, I figured it wasn't non-spudgun related but it isn't quite general discussion either. (this site really needs an electric section)

Anyway, I was wondering, has anyone on here ever made anything like this? - http://www.youtube.com/watch?v=6mobpTrl7cA
If not, how difficult would it be?

I understand that Larda made an ET gun but it is FAR from handheld, also this has a more bullet-like caliber and it's pretty good looking to.

If you don't care about any of this, whatever, I thought it was a cool video.
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Re: Coil Gun

Unread postAuthor: Ragnarok » Thu Oct 30, 2008 7:42 pm

FishBoy wrote:Anyway, I was wondering, has anyone on here ever made anything like this?
If not, how difficult would it be?

Not yet, but I'm hoping to (at least, after 3vo is done) - but with a Ragnarok style twist. :twisted:
I'm reckoning I can give the finger to a decent chunk of the efficiency problems these things have.

If you want to build one, and know no electronics - expect to spend a lot of time learning electronics, and a lot of time building it, mostly in winding coils.
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Unread postAuthor: Davidvaini » Thu Oct 30, 2008 7:45 pm

I agree that we should have an electric section on the site...

Coil guns/rail guns are always cool.
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Unread postAuthor: TurboSuper » Thu Oct 30, 2008 7:56 pm

I built a small coil gun once, it has since broke.

I'll tell you right off the bat that the power is less than impressive- you'd need to multistage it to get any kind of power comparable to that of even the most basic combustion spudgun. A basic one is an easy build but it can get complicated quickly if you're looking for oomph.

Still, it's a neat project. If you've got the cash to build it then it's definitely worth a try. I've heard of multistaged systems breaking the sound barrier.
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Unread postAuthor: Ragnarok » Thu Oct 30, 2008 8:24 pm

TurboSuper wrote:I've heard of multistaged systems breaking the sound barrier.

Multi stage inductance systems perhaps (I know there is one that is at least about 300 m/s). A reluctance system is unlikely to exceed 100 m/s in any practically sized package, unless the designer takes certain... things into account*

*Disclaimer: I may or may not have considered these things.
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Unread postAuthor: FishBoy » Thu Oct 30, 2008 8:46 pm

what kind of power could you get with 2-6 camera caps in parallel? (I know it would be weak, this would just be for giggles)
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Unread postAuthor: rp181 » Thu Oct 30, 2008 8:54 pm

Fish: a BB about 50ft, or a cylinder projectile farther. Making one of these is not difficult at all. Even a multistage is really simple.

Rag: what "other" ideas have you come up with besides the current ramping? I have alot of stuff that would be really expensive normally, and ide love to try out some of your other ideas.
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Unread postAuthor: iemand » Fri Oct 31, 2008 3:14 am

Ragnarok wrote:
TurboSuper wrote:I've heard of multistaged systems breaking the sound barrier.

Multi stage inductance systems perhaps (I know there is one that is at least about 300 m/s). A reluctance system is unlikely to exceed 100 m/s in any practically sized package, unless the designer takes certain... things into account*

*Disclaimer: I may or may not have considered these things.


I remember a Future Weapons episode, in which they had a mortar coilgun, which broke the speed of sound, and it even was a single stage one.

But then you also need a lot of expensive caps :(
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Unread postAuthor: TurboSuper » Fri Oct 31, 2008 5:33 am

The thing is that most people who build these are using those small photoflash boards, which may or may not burn out while charging larger caps than they are designed for. I'm attributing the failure of mine to that anyways- I had two photoflash caps in parallel with a large cap from a CRT. Took about 2 minutes to charge.

One of these days I'll get around to building an HV power supply with a 555 timer and good sized transformer that will be able to give decent output.
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Unread postAuthor: VH_man » Fri Oct 31, 2008 5:44 am

peopel have used Car batteries as their coil drivers before, they seem to work relatively well if you make it a multistage. Then, you can also make it High ROF...... :D

my friend and i are making a multistage gun, after i go through physics and understand magnetism and all the equations that go along with it.
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Unread postAuthor: Ragnarok » Fri Oct 31, 2008 6:46 am

iemand wrote:I remember a Future Weapons episode, in which they had a mortar coilgun, which broke the speed of sound, and it even was a single stage one.

I was deliberately talking just about amateur and semi-amateur coilguns.
No need to get excited over what you need military R&D budgets to build.
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Unread postAuthor: jimmy101 » Fri Oct 31, 2008 10:38 am

FishBoy wrote:what kind of power could you get with 2-6 camera caps in parallel? (I know it would be weak, this would just be for giggles)

A 120 MFD photocap at 330V is about 6.5J (E=0.5cV<sup>2</sup>). Figure a typical single coil coil gun is 0.5% efficient (that's probably optimistic :( ) and using a 1g projectile (equivalent to three 0.177 copper/steel BBs);
Code: Select all
   #        E       Actual    Velocity
Caps    (J)       KE(J)      (FPS)
====================
  1        6.5     0.032        26
  2      13.0     0.065        37
  3      19.5     0.098        46
  4      26.0     0.130        53
  5      32.5     0.162        59
  6      39.0     0.195        65

A $30 cheapo BB gun will fire a single 0.33g BB at about 300 FPS, KE about 1.6J. That's about 8X the KE that you would probably get from six photocaps in a basic coil gun.

YMMV
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