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using both induction and reluctance for coilgun

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Maz

Mon Apr 17 2006, 12:23AM

Registered Member #111 Joined: Fri Feb 10 2006, 01:04AM
Location: Menasha,Wisconsin
Posts: 65

is it possible to almost double the efficiency of a coil by making the projectiles out of three parts?

the back, a ferrous material, to be sucked into the coil.

the middle, up to the center of the coil. something that isn't affected either way. I'm thinking epoxy cast.

and finally, aluminum. to be pushed away from the center of the coil.

for some reason this seems way too easy but if it works, it should be of great benefit.

Electroholic

Mon Apr 17 2006, 12:41AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

u mean you want to pulse the same coil twice?
never heard of anything like that,
it should work, in theory. don't know about efficiency, tho.

Simon

Mon Apr 17 2006, 05:58AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Using two principles doesn't equal doubled efficiency, in fact, it sometimes means compromise efficiency. I suggest you try it and see what happens but I doubt you'll get much benefit. The epoxy will just be dead weight.

evilgecko

Mon Apr 17 2006, 08:47AM

Registered Member #288 Joined: Mon Mar 06 2006, 07:52AM
Location: Palmerston North
Posts: 32

I think he means that you but the bullet at the center of the coil so that you pulse it once and half the bullet is attracted and the other half repelled and the same time

FastMHz

Mon Apr 17 2006, 05:26PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Fascinating idea! You should definitely try it. Has anyone ever tried firing an all-aluminum slug from a CG?

Bjørn

Mon Apr 17 2006, 06:53PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Except in special cases the efficiency will be worse than the best of the two.

If you have a very efficient coil gun and the projectile is about to saturate, then you can reach higher powers more efficiently by adding reluctance than by increasing the current for the coil gun.

Madgyver

Tue Apr 18 2006, 07:15PM

Registered Member #177 Joined: Wed Feb 15 2006, 02:16PM
Location: Munich, Germany
Posts: 214

Why should a Mag. field, strong enough to repell Aluminium not attract the iron too? unless your Epoxy spacer is VERY long.

...

Tue Apr 18 2006, 10:37PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Madgyver wrote ...

Why should a Mag. field, strong enough to repell Aluminium not attract the iron too? unless your Epoxy spacer is VERY long.

That is the idea, you have the Fe being attracted to the coil while the Al is being repelled, doubling? you eficiency

Self Defenestrate

Wed Apr 19 2006, 12:08AM

Registered Member #87 Joined: Thu Feb 09 2006, 01:36PM
Location: San Jose
Posts: 191

I bet tuning the thing would be terribly hard. Seems like an interesting idea though. I'd give it a go.

Xyth

Wed Apr 19 2006, 01:55AM

Registered Member #285 Joined: Mon Mar 06 2006, 02:37AM
Location: Fairfax VA
Posts: 3

I guess this isn't too bad of a place to make my first post...

I've been messing around with this idea for a little while recently. Using a 2 section bullet, front being aluminum and the back being steel (I was calling it a "Hybrid" bullet, since it's pretty accurate and sounds cool). I haven't had much luck so far, alot of it being because of how many variables seem to come into play. Such as the length of the aluminum bullet, the length of the steel section, distance between the two, how far each one was put into the coil, etc. There also seems to be the inherent problem of the ideal firing conditions for a reluctance coilgun are different from that of an induction coilgun. Since with a reluctance CG you need a slightly longer pulse since it has to be pulled into the coil and more slowly accelerated, where with induction you want a very fast pulse to dump as much energy into the projectile before it is pushed to far.

Anyway, I haven't done a whole lot of testing with the idea, espically since I don't have a chronograph currently (Though it is coming in the mail!) and have had to judge power by eye.

Also, not totally sure why this is, but the bullet had a tendancy to break apart. I was first just using tape to hold the two sides together, and they would rip off of each other pretty frequently. They survived a few more shots after I started super glueing them however. Im not totally sure whether this has to do with the eddy currents on the aluminum repelling the steel, or just the shock of the impact jarring the pieces... As well as the overall results seemed to point to a lower efficiency then with just a steel projectile.

Well, I look forward to seeing what kind of results you come up with.

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