Coil gun 3

[daviddoria]

here are pics of the working gun... however, some questions.

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A) when i measure the DC out of the rectifier, It reads 170v when the switch is closed, and 120v when the switch is open... shouldn't it say 0v when it is open??

B) my trigger design is very unsafe... lol. look at the picture where i am holding 2 wires near each other. that is the trigger. how can i make this a more normal switch without melting the switches??

c) that coil look ok? it is factory wrapped wire... should i unwrap it and rewrap it?

d) it breaks the breaker about 1 in 3 times... why would it do this?

enjoy!

 

[daviddoria]

bump

 

[Dave the Embalmer]

Jeebus, get a new coil, stat!

First of all, its really bad if the wires aren't coiled uniformly (all turns going in the same direction, none overlapping). Second, use magnet wire. That beefy insulation is only taking up valuable space that could instead be used for more wire. Use some small magnet wire, and wind a coul about half again as long as the projectile you plan to shoot. It should be 1 wire thick, and should be tightly packed (no gaps between the wires). Next, wrap another coil around the first one (all with independant leads, so 2 coils would have 4 leads) just as you did the first coil. Do this until you have a coil that is phat enough for your satisfaction. Hook all the coils up in parallel (so you'll get low resistance, ands lots of current. Using small wire, you'll get a ton of inductance, which will produce a whoopass magnetic field).

As for a switching method, I've found a good no-spark way for discharing capacitors. Take one aluminum rod and duckape it to some wood for the first terminal. Next, use electrical or ducktape (Duck® Brand Ducktape preferred) around part of a second aluminum rod for a handle on it. Wrap some uninsulated copper wire around the rod. Wire them up. So you should be grabbing the tape-handle of a rod, and smaking the other rod with the part of the first rod that has copper on it. Works like a charm, no spark if you smack it nice and hard.

 

[daviddoria]

every time i have used small (30 AWG) magnet wire, or not alot of wire, it has just melted. should i just use a couple of wraps of this stuff? i guess i am missing how to throw this much current through any less than this size this much wire.

???

lol

any comments are appreciated

david

 

[compute_a_nerd]

I have a few questions also on my coil gun.
Design:
I made the coil from 10y of 22gauge magnet wire
2 fender washers on the outside with a straw going through the coil.
a 1 time use camera board (big capacitor, volts somewhere from 250-300)
and a switch.
I one end of the coil wire to the neg. of the capacitor, and the other end of the coil to a switch and then to the posotive of the capacitor.
It is powered by a AA battery.
So theoretically when you charge the flash like normal and then push the switch it should shoot your projectile, But ever since I soldered my leads the capacitor doesn't charge, and the projectile won't shoot.
Does anyone have any questions
Thank you
Chris
:wink:

 

[compute_a_nerd]

ps. david that coil gun looks pretty awesome
Chris

 

[Dave the Embalmer]

Are you powering the coil using rectified DC from an outlet? Of course that will melt the wire, among other things. You're pretty much shorting an outlet out, which is bad. Secondly, the coil gun won't work anyway, the projectile will just stay in the center of the coil. You need to use a big capacitor that will give the coil 10,000+A for a few microseconds. That way the coil won't melt (I mean, a really big 350V 7500uF cap only contains only 460J. Thats not even enough to raise 1 Liter of water a tenth of a degree C.). I DID see a capacitor in one of your setups though. Make sure ONLY the capacitor is connected to the coil, no other power source.

Compute_a_nerd, are you sure all the charging current isn't just going through your coil instead of the capacitor?

 

[daviddoria]

Dave, how else would i power this beast?

also, i am using a 200v 10,000uF cap. that should be plenty eh?

I also have a 23,000uF 16v cap. when i tried using that, a 9v battery to charge it, and a much smaller coil, i hardly saw results.

With the current setup it does fire the projectile (about 3 feet), it does not get stuck in the center, however it seems like it should be going alot further.

recommendations?

 

[thebigbasicq]

Well, you could do something like this...

Instead of using just one coil. You could use say 3 or 4 coils. The projectile can contain a magnet at a certain point. When the first coil produces the magnetic field, it will repel the magnetic field of the projectile. The projectile will then move forward where it will encounter the second magnetic field, then third, fourth... and so on. So u could get the projectile fired at really high velocity.

 

[daviddoria]

thebigbasicq, i am satisfied with a single stage design, however, i need to make more clear what i am aiming for (coil wise).

is this correct:
1) if projectile is 1 inch, make coil 1.5 inches long.
2) wrap a single layer of small (30AWG) magnet wire
3) wrap several layers of 14AWG insulated wire as much as i want

then it will work much better??
david

 

[daviddoria]

why 2 different size wires?