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Registered Member #2457
Joined: Thu Nov 05 2009, 02:34AM
Location:
Posts: 1
First off I have very little overall knowledge about magnetism and just about anything that has to do with coil guns so I'd be more then happy for you to point out everything that is wrong with this idea!
Well recently I've been interested in making a coil gun and had an odd idea. I've read that you want a tube to be as thin as possible to improve efficiency and that's when I had this odd idea. Why don't you use magnets for tubing? What I mean is making circular magnets that aren't strong enough to capture and hold the projectile used but strong enough to keep it steady and in the center to make a "magnetic barrel". And then I was thinking...why don't you make it so that not only are the coils pulling on it but the magnets to add a bit of energy. So when the projectile is placed in the "magnetic barrel" you attach it to something to make sure it doesn't go shooting out but when you press the trigger it is released and pulled by the coil and the magnets.
My idea must be horribly wrong if nobody has tried it out yet...so please tell me everything that is wrong with it!
EDIT
Oh and I was thinking the design would be a multi stage coil one.
Registered Member #882
Joined: Sat Jul 07 2007, 04:32AM
Location:
Posts: 103
just to clarify the construction: like a stack of toroidal perm. magnets, with the coil wrapped around that?
My thoughts:
a coil gun doesn't really need passive centering of the projectile, since it gets centered real fast once the discharge hits the coil. and i'm not sure how the magnets would center the projectile anyway; it would just stick to the side.
if anything, the magnets might help to confine the field. but a steel barrel, steel endcaps, and a steel pipe surround would give more confinement for the buck wouldn't they?
and what about the perm. magnet applying drag as the projectile leaves the coil? it doesn't turn off like the coil does, and so the projectile is going to feel that pull as its trying to leave. just seems like it provides minimal benefit while reducing velocity. especially in a multi-coil setup.
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Actually, I was just tinkering with a new coilgun design and my research pointed out the problem with such an approach karma. Magnets, particularly really potent ones, don't behave in quite the way you might expect when exposed to another powerful magnetic field.
The coils would have a very hard time transferring energy to the projectile while inside a magnetic tube. Not only could there be opposition between the coil and magnetic barrel, but the magnetic barrel would also actually act to shunt magnetic lines of force around, rather than through, the projectile.
Similarly, the problem with encasing coils in steel to 'contain' the magnetic field is that while you may keep the total volume of the magnetic field somewhat smaller, what you're actually doing is pulling flux density out of the center of your coil (and away from your projectile) and pushing them into the outer regions of the coil. You're also significantly increasing the coil's inductance, decreasing current capacity and increasing ramp-up time and the potential for harmful transients.
The ideal means of concentrating the field of the solenoid would actually be to dispose of a traditional barrel all together instead have a ferrite or low carbon steel rod passing through all of your coils, upon which rode a donut or tube shaped projectile.
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Random coil gun idea....
