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Newbie Project : Coilgun ?

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Take a fork strap it to your closed fist and jam it in an electrical outlet, that lethal enough for ya axl?

What more help do you want? There have been several links that provide plenty of usable information on coil guns and their designs, and a simple Google search will find you more, the onus is on you to teach yourself electronics we can't hold your hand and it's not possible to teach a course through a forum, you need either one on one time with a tutor or to follow some other introductory electronics courses, which again there are plenty of if you look on Google.

You seem to just want answers and a working product in your hands like magic, not gonna happen, that coilgun you linked from Youtube was very well put together, and probably cost the guy that built it a couple hundred dollars of material and many hours in fabrication and testing, and he obviously knew exactly what he was doing. Also you'll notice how close range all those shots are, it has no distance and no practical power, it's basically nothing more than a very controlled thrown rock, all the stuff that it broke was hard materials and the shot was a blunt point. If you wanted any kind of range you'd have to use a very tiny shot and the total delivered power would drop VERY quickly with the increased range. You can buy for probably less than the total cost in both time and materials, a hand pumped BB gun that will deliver 10 times more energy, and that's at distance, a paintball gun would work better.

All you see is a neat gimmicky little toy and you want it and you want to build it yourself, you have no clue how to go about it, so aside from what links have been provided so far you're not going to get anymore help here.
 
For some reason, I've been thinking about coil guns. I've figured out the equations needed to design one, and in a simple enough form to not require advanced math. For example, we can use simple kinemetic equaitons to calculate the force that's necessary, acceleration length, etc, and simple coil equations to calculate the magnetic fields. But something I've never understood is how does one calculate the force on a ferrous object by a magnetic field. In Physics, we learned how to calculate B fields, how to calculate induced voltages, how to calculate force of a moving charge from a B field, etc, etc.. but never this problem. Has anyone ever come across a simple equation?
 
Take a fork strap it to your closed fist and jam it in an electrical outlet, that lethal enough for ya axl?

What more help do you want? There have been several links that provide plenty of usable information on coil guns and their designs, and a simple Google search will find you more, the onus is on you to teach yourself electronics we can't hold your hand and it's not possible to teach a course through a forum, you need either one on one time with a tutor or to follow some other introductory electronics courses, which again there are plenty of if you look on Google.

You seem to just want answers and a working product in your hands like magic, not gonna happen, that coilgun you linked from Youtube was very well put together, and probably cost the guy that built it a couple hundred dollars of material and many hours in fabrication and testing, and he obviously knew exactly what he was doing. Also you'll notice how close range all those shots are, it has no distance and no practical power, it's basically nothing more than a very controlled thrown rock, all the stuff that it broke was hard materials and the shot was a blunt point. If you wanted any kind of range you'd have to use a very tiny shot and the total delivered power would drop VERY quickly with the increased range. You can buy for probably less than the total cost in both time and materials, a hand pumped BB gun that will deliver 10 times more energy, and that's at distance, a paintball gun would work better.

All you see is a neat gimmicky little toy and you want it and you want to build it yourself, you have no clue how to go about it, so aside from what links have been provided so far you're not going to get anymore help here.

You are right. But what I asked was not like that. I was asking for some voltage equation so that I don't hurt myself because right now I haven't got one voltmeter. And it's pretty expensive compare to a Vietnamese student income. Let me remind you that a normal Vietnamese has income of about 150 bucks per month (income tax subtracted) . A voltmeter's about 10 bucks already. There are much more to spend on you know. And I asked if anyone can suggest me a way to improve (there are lots of ways to try) so that I can speed up the process. Those lines about building lethal guns were just kidding. BB and Air-soft aren't illegal to use in our country but illegal to ship in.

For some reason, I've been thinking about coil guns. I've figured out the equations needed to design one, and in a simple enough form to not require advanced math. For example, we can use simple kinemetic equaitons to calculate the force that's necessary, acceleration length, etc, and simple coil equations to calculate the magnetic fields. But something I've never understood is how does one calculate the force on a ferrous object by a magnetic field. In Physics, we learned how to calculate B fields, how to calculate induced voltages, how to calculate force of a moving charge from a B field, etc, etc.. but never this problem. Has anyone ever come across a simple equation?
This is exactly what I've been thinking for weeks. I've calculated energy needed to move the projectile. Since most coilgun are 3% efficiency, I calculate the energy needed is : x= kinetic energy / 3 x 100. Then I come to the E= ½CV². Is x = E ? If it is then I can easily choose an upgrade option without wasting money.

Note that 3% means I've skipped lots of equations converting kinetic to magnetic then to electric...
the force on a ferrous object by a magnetic field
 
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Then I come to the E= ½CV². Is x = E ?

If this were an electrostatic gun, then x=qE, where q is the charge. But it's a magnetic one, and I don't know the equation. Tried to look it up, but no luck so far.

Correction: I should have written x=qV. There is an analog in the magnetics realm to potential, and it's MMF which is

MMF=NI, where N is the number of turns of a coil, and I is the current. But what to multiply MMF by to get potential energy, I haven't a clue.

But anyway, thanks for getting me to think. It's been way too long since freshman E&M classes.
 
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The main problem you're going to have is finding out how the magnetic fields interact with the load itself, this isn't easy. You need to know what the load is made out of, it's dimensions and then you have to figure out all the forces in play, because aside from the simple magnetic attraction this field is actually a pulse which means there are eddy currents in the load itself which are being dissipated as heat, add to that the fact that as soon as the field starts to build the load starts to move the actual dynamic fields and currents involved are nearly chaotic.

I don't know what resources you have but for simplicity practice with cylindrical loads, or as close as you can get to one, length and diamater are going to be the two things you want to play with, the load can be tuned for the gun if you can't tune the gun.
 
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If we're talking small projectiles, shot for example, the secondary effects can most likely be ignored. I'm not really interested in experimenting, I would like to be able to estamate the required magnetic field to send a projectile over a pre-determined distance. Still looking for the equation though...
 
Then I come to the E= ½CV². Is x = E ?
That E is for Energy in the Cap Bank. Not E = F/q.

IMO If you want to use F=qE then you have to know the charge of the projectile. First calculate the force needed for the projectile to be lethal :D Then combine with environmental forces to get the Electro Magnetic Force needed.

Since these are very complicated I think we can take the 3% efficiency we see in most coilgun.
 
That E is for Energy in the Cap Bank. Not E = F/q.

Yes, I corrected my post with the right equation. We used the equations to build an electron gun in Physics lab many, many years ago. It's not complicated at all really. We could use the same methods for the coil gun, if we knew the forces. I suspect it will end up being something like the magnetic permeability and the volume of the shot . I could probably come up with it if I put forth more effort. The more we bump the thread, the better chance we have of someone providing the equation :)
 
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