Can anyone help me out with how to build a STRONG and LIGHT electromagnet? The metal center has to have a hole in the center so I can draw a shaft up into it.

I've built some with 2 AAA batteries, a bolt, and some 18 gauge wire I had lying around, but it doesn't seem strong enough, even with the wire doublewrapped. I need to be able to pull a shaft with a spring on it inside so I can turn off the magnet and have the spring propel the whole device in the air. So, the magnet also has to be light. Any suggestions?

sounds like a rail gun idea ...

No, no... Not a railgun at all... If I wanted to build a railgun, I'd just buy a 6 pound, 50 dollar electromagnet.

I want to make a little thing that hops, haha.

why?

Yours is not to question 'why', insertnamehere. As for Turbo, use commas when you try and further explain your idea. What are you trying to accomplish? Post some pictures if you can aswell, that would be cool.

Lokil, thank you!

Basically, all I want is an electromagnet that is strong enough to pull a metal shaft with springs on it into the center of the magnet. This would be mounted vertically into some sort of body. Then, when I turn off the magnet, the springs push the shaft out, hopefully hard enough to cause the whole contraption to be shot an inch or so into the air.
It's not the rest of the device I have questions with, simply the electromagnet. How do I build a stong, lightweight electromagnet that can compress a spring? Like, what type of wire and what core makes the best magnets, and should I use any resistors or anything in the circuit? I've done a bit of research, but everything explains the theory behind electromagnetism, which I already know. Nothing tries to teach the MOST EFFICIENT way to construct one.
There really is no purpose to the device, other than my own amusement in building it and making it work.

Oh, and insertnamehere, may I ask why not? I enjoy learning things and building things. This presents an excellent way for me to build something while learning why it works, even if it is a strange idea.


Why does everyone on here have a railgun fetish??

The electromagnet you want to make should use a hollow tube as the core, it will suck the metal rod in nice'n good. I think they're called SOLENOIDS. You sould be able to buy them at the store. If you can't find any, I've found some in old dooorbells. I think that power-locks in the doors of cars might have them, you could check at a auto junkyard. I used to play around with them, and I found that what worked best to power mine were two 9v batteries connected together to make 18v. Good luck on your project!

Another thought: a McDonalds straw would make a good core. sturdy yet thin.

Bunghole, you're right. It's called a solenoid. However, thr straw would be really weak, because the core should be soft iron. I found some more information that said to use soft iron, but I don't know if there are any other tricks I'm missing. Also, I don't want to buy anything. This is a half-assed commitment, come on now!


Edit: Spelling error

[This message has been edited by Terbo (edited 12-11-2002).]

Maybe you could find a good core in the plumbing section of a hardware store. I get ideas for all sorts of things when I go there...