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Electromagnets

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Electromagnets

Unread postAuthor: squeaks » Thu Jun 07, 2007 12:50 am

Has anyone made powerful electromagnets before? According to my calculations, if I could make an electromagnet from a pipe that is 2.4" ID and 2.792" OD, 3" long and will hold 800 newtons (81 kilos or 180 lbs) I could make a 2" porting, electromagnetic piston valve. Does anyone know if this could be made and how much current I would need to accomplish it?
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Unread postAuthor: hi » Thu Jun 07, 2007 1:11 am

my friend made one just by taking a nail and wraping wire around it and simply pluged it into the wall outlet and it was very strong, so my guess is twice what ever the wall puts out.
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Unread postAuthor: squeaks » Thu Jun 07, 2007 9:40 am

Anybody with a much more scientific and/or experienced answer. Sorry, bud, but everyone has made a magnet with a nail before.
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Unread postAuthor: Hotwired » Thu Jun 07, 2007 9:54 am

Well I've made a pretty powerful electromagnet but only for a fraction of a second.

Dumped 1160uf at 330v through a tiny coil of wire for my coilgun ^_^
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Unread postAuthor: mopherman » Thu Jun 07, 2007 10:11 am

Hotwired wrote:Well I've made a pretty powerful electromagnet but only for a fraction of a second.

Dumped 1160uf at 330v through a tiny coil of wire for my coilgun ^_^

could we see it? coilguns are cool.

When the magnet is turned off, the piston would stay in place because of high pressure air on both sides right?
Unless theres no pressure behind the piston?
more details on your design would help

I hope it works :D
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Unread postAuthor: Hotwired » Thu Jun 07, 2007 10:41 am

It's not new, I made it either last year or the year before. Pings bits of nails across a room :)

It literally is just a coil of magnet wire around one end of a little plastic tube, a manual switch and 12 camera flash capacitors wired in parallel.

Charge the capacitors with a camera flash circuit, stick a bit of nail halfway into the coil, flick the switch and *ping*.

I really don't think a coilgun type thing would be useful for you though - it would only provide force for a very short time.
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Unread postAuthor: Modderxtrordanare » Thu Jun 07, 2007 11:35 am

Hotwired wrote:It's not new, I made it either last year or the year before. Pings bits of nails across a room :)

It literally is just a coil of magnet wire around one end of a little plastic tube, a manual switch and 12 camera flash capacitors wired in parallel.

Charge the capacitors with a camera flash circuit, stick a bit of nail halfway into the coil, flick the switch and *ping*.

I really don't think a coilgun type thing would be useful for you though - it would only provide force for a very short time.


You'd only need the force for a fraction of time, to force the piston backwards. Then pressure takes over and holds it open for the rest of the time till it dumps the chamber.
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Unread postAuthor: joannaardway » Thu Jun 07, 2007 3:34 pm

A proper coilgun coil for a properly made coilgun will chuck out whole numbers of Teslas if it's working properly.

I've got a joint project lined up with Ragnarok for a proper Gauss rifle (similar to a coilgun, but with magnetic rifling, and shrouded coils) in the near future, which should get up to 12 ft lbs - the same as most air rifles.

But, back on topic - an 800 newton electromagnet would have to have very high current, and could damage any nearby electronic devices if the pulse length was too short.

And for it to be portable, the pulse length would have to be very short - and then, basically what you're planning on building is a big EMP device.
It could be made if you had a huge capacitor bank, and a pre-magnetised piston (think rare earth magnets), but it wouldn't work very well.

My advice - I don't think it's worth the sheer trouble - and if it ever did work, you'd have a fairly nasty electromagnetic bomb.
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Unread postAuthor: TurboSuper » Thu Jun 07, 2007 10:02 pm

Those already exist...in the form of solenoid valves. Pneumatic ones actuate faster.

I built a coilgun too, it's pretty sweet how it launches an object using magnetics.

...and like Jo said, you'd need alot of current. Watch your tongue arond them capacitors...
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Unread postAuthor: VH_man » Thu Jun 07, 2007 10:32 pm

yeah, i dont reccomend using an electromagnet to hold back your piston. use a mechanical catch/sear, you will be much happier.......
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Unread postAuthor: Hotwired » Fri Jun 08, 2007 5:28 am

TurboSuper wrote:...and like Jo said, you'd need alot of current. Watch your tongue arond them capacitors...


WTF?

I'd be looking for atomised tongue if I licked the contacts on my coilgun capacitor bank. It makes a godawfully loud bang when shorted out.
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Unread postAuthor: VH_man » Fri Jun 08, 2007 6:41 am

coilgun question:

hotwired: when you stated that you wiried multiple camera flash capacitors in series, is that completely safe? like have you ever been shocked with it?

i dont want to risk my life building a coilgun whose power is horribly low for the amount of work put into it.
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Unread postAuthor: joannaardway » Fri Jun 08, 2007 7:00 am

I wire caps in parallel normally for a CG, unless the voltage is insufficent.

I've been shocked by coilgun caps. Usually rather uncomfortable, but not fatal. After the 2nd shock, you start to take more care.

Which is of course why I've shocked myself 19 times with them.
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Unread postAuthor: ShowNoMercy » Fri Jun 08, 2007 7:10 am

And this may be a bit random but if you want to lower your current needed just increase your voltage input, pickup a transformer and jump your 120 volt to 240 or use two hot lines and bump that up to 480? That may give you the nessacery power.
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Unread postAuthor: Hotwired » Fri Jun 08, 2007 7:18 am

Hmm, I don't remember saying series.

Hotwired wrote:...and 12 camera flash capacitors wired in parallel.


It's safe as long as you make dam sure the capacitors are shorted out before you do any work with them - a screwdriver blade between the terminals works fine as long as your nerves don't mind the noise and light or a large resistor for a slower but safer way of discharging them.

I discharged all of them then used a couple of lengths of thick, stripped copper wire as bars for the terminals of the capacitors to be soldered to and covered everything in black electrical tape once it was all fixed up.

I've only ever been shocked by the camera charging circuits when I accidentally put a finger in the wrong place while dismantling them. I'd never be that careless with the whole capacitor bank - at the very least it can give you a nasty shock. At worst - going through both arms it could screw your heart up.

About as dangerous as a spudgun really except the danger is more in the device than the projectile.
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