# Help designing/finding a vendor for this magnetic field

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1. Jan 25, 2017

### 13Nike

I need help find a electromagnet suitable for this http://imgur.com/a/vkm4T
Each electromagnet (the 3 in the center) needs a repelling force of about 20 to 40lbf. I stupidly bought these from amazon http://a.co/aSftIat. Its a holding electromagnet so the N and S poles are essentially on the same plane and are meant to to hold metal sheets. Googling around for other electromagnets bring up hundreds of other holding magnets. Is there a name for the type of electromagnet magnet i have in my design? What do I actually need? Is it even feasible for me to get that much force from each component in the size of say a con of soda?

Last edited by a moderator: May 8, 2017
2. Jan 26, 2017

### Staff: Mentor

Repelling force depends on distance the poles are apart.

3. Jan 26, 2017

### Nidum

What is the actual practical problem you need to solve ?

4. Jan 26, 2017

### 13Nike

In this scenario it would be when the opposing poles are touching.

5. Jan 26, 2017

### Staff: Mentor

Opposing poles? Are these the opposite of opposite poles?

Like when like poles are touching?

6. Jan 26, 2017

### 13Nike

Sorry for the poor English. Say electromagnet #1 is fixed. I need to introduce electromagnet #2 whose say north pole touches the north pole of electromagnet #1 with a required force of 20 to 40lbf (this is a range of whats acceptable)

7. Jan 26, 2017

### Staff: Mentor

Get some iron cylinders that match the diameter of the inner pole and have a length that is about 2-3 times the diameter of the pole. Superglue the iron cylinder onto the center pole to extend it out away from the opposite surrounding pole structure. The magnet won't be as strong, but it will give you an isolated magnetic field source.

But, are you saying that when you bring two of these "holding" electromagnets close to each other and drive them with the same direction of current, they don't repel each other strongly? Both the inner and outer poles will generate repulsive forces that will be pretty strong...

Last edited by a moderator: May 8, 2017
8. Jan 28, 2017

### 13Nike

the ones I bought do repel but its unstable since the poles are in the same plane. Imaging a cup where the outer rim is one pole and a center column is the opposite pole.

9. Jan 29, 2017

### Staff: Mentor

But can you constrain the motion of the magnet to be in the axial direction only? Like with an outer plastic tube?

10. Jan 29, 2017

### 13Nike

Yes this would be the case

11. Jan 29, 2017

### Staff: Mentor

So you're good to go, right?

12. Jan 29, 2017

### 13Nike

Well the issue is that for some reason I cant a simple electromagnet for sale that produces strong forces. Most of the ones I find are holding magnets. Similar to that of the cup formation /horse shoe. I need an electromagnet that is like that of a bar magnet

13. Jan 29, 2017

### 13Nike

Ahh im such an idiot. I need a solonoid.