electromagnet construction question

[OPABolt]

first of all i would like to appologize if this is in the wrong place. That said, I need help building 2 small opposite pole electromagnets to move a pair of small rare earth magnets back and forth approx. 1-2 inches along a rail.

|e-mag1| -rail--|perm.mag|--rail--|e-mag2|
|<------approx 1.5"------>|

the rare earth magnets I've been using are 4lb pull and 8lb pull. (sorry that's the only info i have on them)

unfortunately, the amount of space i'm limited to is a hollow cylinder 1.5" Inner diameter and about 8"long. and i need the e-magnets to run off a pair of 9v or a couple AA/AAA batteries.

I've been tinkering for a couple weeks but have been getting nowhere. any help would be greatly appreciated.

also, what would be the best type of wire to use for the coil? i have a lot of 20awg copper, silver, and stainless.
for the uninsulated wires, what would be the easiest way to insulate them. time is no concern since i have it in abundance.
thanks in advance for any help.
Joe

 

[Warpspeed]

I can see a few problems with this. The permanent magnet will want to "stick" at each end, and may not wish to "jump" to the other end. Making it work is possible, but it will probably take a lot more electrical power than you have available.

A better solution might be to have a fixed magnetic field and make the coil move along (through) this fixed magnetic field. Have a look at how a loudspeaker works to get the general idea of this.

Also do some research on "linear motors". These go back and forth, not round and round.

 

[OPABolt]

thank you Warpspeed for the ideas, however, the linear motors I was finding can't produce enough force over enough distance or are too loud.

my last idea was to use wire with a lower resistance than the copper I'm currently using. The projectile I'm trying to launch with this setup is very low mass, I think <.5g.

the reason I chose this setup was because it would be nearly silent, lightweight and i thought easy to construct.

 

[Warpspeed]

Only wire available with lower resistance than copper would be solid silver wire.

About the only other way I can see to do this would be a linear actuator that uses a leadscrew that goes through the centre of a motor. That could produce relatively high force with little electrical power, but it would be slow.

Something along these lines perhaps:

http://www.hsi-inc.com/

 

[TDew]

As for what you have already stated the limiting factor is your power source. You simply cannot generate the type of field needed generate that much force.


More turns will help you produce a larger magnetic field up untill a point. Also a marerial used in the core of the magnet will play some part, but with out substantial ampers.

http://en.wikipedia.org/wiki/Electromagnets

I did noth check the equations but they will get you headed in the right direction.