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Simple Coil Gun

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Well-Known Member
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Someone Electro said:
You certainly wouldn't be able to blow an hole right through 8 sheets of alu foil whith 5A.
Current doesn't do anything by itself. It is the amount of power that does work.
You have about 300V, which times the 5A current equals 1500W!

If you had a rediculously high 500A, then at 300V would burn a hole in a 1metre thick piece of steel! That's 150kW! :lol:


Active Member
I can get my hands on some rather large caps from work. I think they are like 200,000 uF with a working voltage of 63VDC.

Have you thought about rewinding your coil? you might be able to gain alittle more if you had it wound nice and tight.

Also, how exactly are you measuring the velocity? I saw you had a microphone in the picture on the previous page.

I think I might have to start playing around with something like this. :twisted:
Thread starter #23
You may have an problem whith such big caps becose you wont be able to fuly discharge it in the coil.It may be porsible if you wire then in serial for an higher voltage.
Thread starter #24
Oh and how i mehure the speed.

Simple realy.I just record the fireing.Then whith audio edidting software i meshure how many miliseconds is betwen the fireing click of the coil and the sound of the projetile hiting a box. Then i can cauclate the speed.


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With a huge value cap then the coil will still be energized when the projectile is trying to leave the coil. Therefore the coil would try to pull it back, putting on the brakes big-time.
The most effective way to control the coil would use a photo-detector to turn off the coil when the projectile reaches its center. Then all the power of the coil would be used to accellerate the projectile.

If the projectile is magnetized, the polarity of the coil could be switched to pull it in then push it out, doubling the thrills. :lol:
Thread starter #26
Yea the puling back.But the problem is if you thurn off a lot of the charge will stay in the cap. You cod serial more caps for an higher voltage.

My projetile got magnetised becose of the strong pulses.It can get magnetise prety good after one fireing. But that is nothing compared to the huge field around the coil.So for this you wod need an rare earth magnet,wich are extremly powerful.
Thread starter #29
I can see it. Its DivX encoded.

Check the you have an DivX codec.The audio is an MP3 stream.

Media player says "conecting" and firefox is saying "transfering from putfile.com"Then sudenly it starts playing.

You have to give it time to load
Thread starter #30
I made some biger projetiles out of nails.And on one i left the sharp point.

It makes holes in thin cardboard and makes a hole in a can.But the hole is litle so that the projetile cant go trough.

I had to use an new barel becose the nail was way too big for the old one.So i had the floor full of wire from the unwinded coil that i had to wind around the new barel.

Also i wod not like to put my hand in front of a big nail traveling at 21Km/h.

The nail is 11,5 cm long and 4 mm thick.
Thread starter #34
Yea dengerus if your stupid and stick your fingers around wen there charged.

I once acsidetaly was toching the output wen i trigerd the SCR and it only stung a litle bit.That was 100V.My hands ware dry so codnt coduct much.If they ware wet i wod cetarnly get a painful shock.

There is a way by stacking a lot of car baterys in sersis to get an high volatge.This is very dengerus if you short it becose an cap will only make an pulse of high curent but a car batery will make continues high curent that can make wires realy realy realy hot and melt them.

Whith an coligun you have to have high volatge to get enugh curent trough the coil (Ohoms law)
Thread starter #36
You cant stack transformers one after an nother.But some voltage multiplyers can.I dont recomend this becose as you multiply the voltage you decresre the curent and therfore the caps take longer to charge.

I have an mains transformer that outputs 50V but i neded 100V so i put in an voltage dubler.
An Idea!

I think you could make the weapon more powerful with little difficulty, i think that if you use a slightly longer pipe and 2 seperate coils (with a reasonable gap between them) one fired after another then you could gain more speed.

the first coil needs to turn off before the second turns on, the first one should get initial momentum in the projectile and the second one should boost the speed.

if you try it then let me know how well it works.
Thread starter #40
I know thats called an multistage coilgun.You can have an open or closed loop desing.Open loop is just an timing circuit fireing the coil one after an nother.An closed loop has feadback.there are LEDs and phototransistors in the barel to detect at exsactly what moment to fire it.
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