Rapid Firing Coil Gun

[The Thing]

Hi all. I am considering making a rapid-firing coil gun for a school project. NO it will not be a gigantic man-slaughtering weapon of mass destruction - I doubt whether it will even break the sound barrier (more like dropping like a stone after travelling 2 feet). Honestly, I'm happy if I get the projectile out a meter before it hits the ground.

 

So, can anyone suggest some ideas or plans or sites to help me? I've googled around, but they all are either camera flash cap powered or gigantic cap more than capable to kill a person powered. And they're all one shot, then wait for the cap to recharge style. Are there any rapid fire ones? I saw a few movies of a very low power but rapidfiring coilgun. It was awesome.

 

So, should I go around messing with caps? One thing is certain, a cap-powered coilgun will NOT give me rapid firing abilities. So, should I build a slow-firing cap coilgun, or a rapid firing battery coil gun? I am leaning towards the latter, but then, where can I get a 12v battery with an appreciable amount of current?

 

So, help and ideas please?

[Pleiades]

You would probably need to have multiple banks of capacitors and cycle through them, its going to be a problem finding components that can handle continuous switching of that much energy though. Check out http://www.powerlabs.org/emguns.htm if you haven’t already.

 

Rapid firing also brings the problem of heat buildup; witch will increase the resistance of your coils further decreasing efficiency.

[The Thing]

Well, thanks everybody. I've decided against the coil gun because our teacher absolutely refuses to allow me to have even a few hundred volts built up across the circuit. So, I'm just gonna do a much safer Gauss Rifle! Basically its a bunch of magnets spaced out on a wooden stick (120 cm in my case, yea!), and 2 steel balls in front of each magnet. When a steel ball is attracted to the first magnet, it will transfer its energy, push the 2nd steel ball in front of the magnet, which will hit the magnet in front of it, and transfer its energy, and so on, so the device is accelerating and at last, the final steel ball will burst through the muzzle.

Any tips for making this way-too-simple-to-hand-in rifle more advanced and fancy? Like adding some further electronic functions?

Also, I can't see this thing being rapid fired, cuz each steel ball requires moving back to the magnet by hand.

[Cap'n Refsmmat]

Use electromagnets and a series of switches that can also be run in reverse, which would allow you to move the balls back to their original position (with a bit of fancy switching) without actually touching them.

[The Thing]

That's a good idea, and I've thought about it. However, how can I make the electromagnets as strong, if not stronger, as a neodymium magnet? That's what I'm worrying about, because I DON'T think I'll have an AC supply.

[Cap'n Refsmmat]

That's an interesting question, and probably out of my knowledge. Given that you don't think you'll have an AC supply, then it's probably not viable.

 

However, you can go for something else, like a system of little plates connected to a servo that will pull the metal balls back to firing position.

[The Thing]

Yea I've thought of that too . I thought of a manual one, so each magnet will have a little thin plate sticking out behind it. So when the ball hits the plate, the energy will be transferred, but I can have a handle on the side and I'll pull it back using manual force. Is that what you're suggesting as well?

Our teacher would not let us use anything above 12V . She's scared of caps, so AC's definitely out of the question.

Incidentally, are there any other electronic add ins or just plain addins to add to my rifle to make it fancier?

[flyboy]

http://www.powerlabs.org/

 

go here

 

theyve got forums for help but watch it

they banned me for no reason at all

[calbiterol]

Just use a halbach array. I've used the principle behind a gauss rifle to develop (unfortunately, not create) an electric-powered paintball gun. The trick is getting the return mechanism right (and, in the case of paintball, the loading mechanism).

 

Be extremely careful, because gauss rifles are incredibly powerful. 120 centimeters could, depending on the number of magnets used and the spacing between them, potentially kill someone.

[The Thing]

Thanks. Could you explain to me how the returning mechanism will work?

 

I will probably cut the length of the wood to 1m, and the magnets I have are not TOO powerful. They're for hanging hand tools, yes, but I don't think they're the N40 bone-breaking ones.

 

EDIT: Incidentally, can I build a smaller scale gauss rifle? Like everything's smaller so smaller magnets, smaller ball bearings, and build it minature scale?

Oh yeah, and please explain how the returning mechanism works. As I said above. Thanks!

[flyboy]

http://www.powerlabs.org/coilguns.htm

[The Thing]

@ flyboy: That's a coil gun, and I've decided against building one of those. Now I'm building a Gauss rifle. Thanks for the link though.

 

I've seen your design on the electromagnetic gauss gun paint ball shooter thing that you were discussing with D22k, calbiterol. However, I have just about 4 or 5 days to build this thing before handing it in, and how much time would it take to wrap about 100 electromagnets? They're too weak - I only have a maximum power source of 9V batteries.

[calbiterol]

To be honest, the easiest way to wrap nearly-perfect coils is with a power drill. For example, grip a nail with the drill, duct tape the end of the wire to the nail, and SLOWLY (that's the key this is where multispeed locking drills are amazing) wind the coil. Speed-wise, I don't know. I don't remember, however, if the design I put up here @ sci forums was the EM one or the halbach array one. Either way, it should work.

[lightwave]

See the oufit MetalStorm. They made a launcher/machine gun which fires 1 million rounds per minute.

[The Thing]

Thanks calbiterol. For the project I'm handing in I'll just build a magnetic gauss rifle, instead of the automatic, because I don't think I'll have enough time for it. However, I will make the automatic Gauss rifle! Probably during spring break, summer, or some other long weekend. I have lots of 3 meter long square lumbers (like the sticks for holding up signposts and stuff) lying around my school's wood shop and I can cut a section using the table saw and dig a groove in it using the milling machine, then work on the electromagnetic one!

Thanks for the help!

[The Thing]

Okay, I've met a problem that I never thought I'd run into:

I don't have any ball bearings!!!!11!1

What can I use to substitute for the ball bearings?

 

EDIT: I'm going to an automotive parts shop tomorrow to look for ball bearings. But, to prepare for the worst case scenario, what can I replace them with in my gauss rifle?

[calbiterol]

Cheapest way to get pseudo-ball bearings that work is to buy steel "slingshot ammunition." It's identical in every respect to ball bearings except precision (a lot less perfect of a sphere) and price (immensely cheaper).

 

If you need to find something else, you're severely limited. It must be a paramagnetic material in the shape of a sphere.

[The Thing]

Well, that's the problem. I can't find steel balls anywhere. I've asked for everything: steel balls, ball bearings, steel marbles, steel BBs, steel pellets, you name it. I've went to every shop I can find - hardware shops, Home Depot, craft shops, auto parts shops... Basically, I can't find a sphere that is made of metal. .

I have one last resort: my teachers. Going to ask them tomorrow.

 

Incidentally, yesterday I built a very crude coin launcher on my dining table. I had 3 stages only, but it worked, and the penny was launched off the table. It wasn't very far - think it was 5 inches. But I used coins lying flat on the table, and obviously it was very crudely done - did it in about a minute.

[The Thing]

I got ze bearings! Got an entire jar of them now .

I'm thinking of a launching mechanism for the Gauss Rifle, one that I can control from a distance through a wire. I'm thinking of an electromagnet controlling a little "gate" which blocks the first ball, and when I press the switch the gate is attracted upwards, letting the ball roll to the first magnet. However, are there ay other ways to create a launching mechanism?

Thanks a lot!

[calbiterol]

Yep. Pneumatics. Otherwise known as an air cannon. PVC, a spare bike tire nipple, and a bike tire pump, connected to a ball valve and something to launch the bearing. This setup gives you a lot more oomf than normal, for two reasons. First, the magnet doesn't have to overcome static friction, and two, the first bearing has added momentum to give to the next ball.

[The Thing]

Well I'm done my Gauss rifle. It didn't work as well as I would have liked.

The ball was slooooooow. It had 10 stages and the exitting ball is so slow that you could stick your hand in its way and feel absolutely nothing and the ball will just slide off your hand. I can barely feel it hitting my hand. And instead of everything happening at once and you hearing an almost uniform loud clink when the thing fires, mine you could track the sounds as it went clink-clink-clink-clink. I am pretty sure that I have optimal spacing - 6cm, as any closer would send the ball hurtling towards the magnet in front of it prematurely. I estimate that I could have placed just one other ball bearing in front of each group of 2 balls. That was my spacing. The ball just made pass my table and fell like a stone. All very fast of course.

But I think the reason that why it, well, failed, was because my ball bearings were infinitely bigger than my magnets. They were 3/4" in diameter, while my magnets were 1/2" in diameter and 1/4" thick. So the size wasn't all too ideal. I think that my magnets, however strong the shop advertises, are really not all that strong. Okay, I could open my fridge door with one, but I'm pretty sure they aren't the N48 ultra powerful NIB magnets that everyone else uses. AND they're small, as mentioned.

So, is that why it would not go faster? It's actually pretty pathetic, the speed. You don't feel a THING as the ball hits your hand. But the ball at the end is moving, so I guess that's something...

Incidentally, I've increased the speed of the last ball by using a smaller bearing. It's still very slow though. It travelled like maybe 30 or 40 cm before dropping like a stone. I'm pretty sure it could have rolled much further if I let it roll on the table instead of firing it at the edge of the table though .

[calbiterol]

If your first ball (the one you push/shoot/whatever at the first magnet) is LARGE, and all the rest are smaller, you'll have a much, much, much faster gun.

 

Also, the ideal bearing size is about the same size as the magnets (but in a sphere instead of a prism).

[The Thing]

Thanks calbiterol. It still fires, but is just not satisfactorily powerful. In the future, should I have a series of ball bearings, each smaller than the one behind it?

And I blame all my failures on the small sizes of my magnets!!!

[calbiterol]

Yes, that would increase the end speed.