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Nail electromagnet to repel button magnet.

Mikeq666

Jun 6, 2023
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Hello

Is this feasible. Please see attachment. Its a nail will a button magnet attached. I want to be able to repel the button magnet using a coil around the nail powered by a 6v NimH battery. It just needs to push the magnet off when energised, not fire it like a bullet. Its a pretty strong little magnet, I could go slightly smaller.

Feasible or not? Its to create a drop tank on a radio control model. Held on by magnet to nail, but at the flick of a switch, drops off as magnet whcih is part of tank gets repelled.

Cheers

Mike
 

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Delta Prime

Jul 29, 2020
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Why don't you wind the coil on top of the magnet the more windings of the coil the stronger the electromagnet to a point. Then it will attract the magnet upwards towards the coil then when switched off or no power to the coil from the 6 volt battery it'll drop back down trial and error
 

Mikeq666

Jun 6, 2023
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Hi

I guess the magnet will be attracted to the nail head no matter what. I would need to energise the coil to repel it. I’m just wondering if anyone knows that it would be more likely to take a huge number of coils and be impractical.

Cheers

Mike
 

Delta Prime

Jul 29, 2020
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Okay so that magnet must travel the length of the width of the ruler is this correct. The nail head which is inverted right? pointing down we need to know the length of travel of the magnet. And is it a Rare Earth magnet neodymium?
 

Mikeq666

Jun 6, 2023
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Hi

No, the rule is just there for scale sorry.

Its just the nail and the magnet. The magnet is part of the drop tank. The nail head is in the wing.

The drop tank (button magnet) is held on to the wing (nail head) by magnetic attraction. I want to be abke to overcome that attraction to the point the magnet (drop tank) falls off.

Hooe that makes sense.

Mike
 

Alec_t

Jul 7, 2015
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Those little neo magnets are pretty strong. I'd guess you will need many turns of magnet wire and a hefty current to be able to drop it off the nail. Have you considered any alternative approaches, e.g a micro servo to release a catch, or a thermally-released bi-metal catch?
 

Mikeq666

Jun 6, 2023
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Hi

Yeah, there are mechanical ways to do it easy enough. You’re right, they are pretty strong but it would be a neat solution if practicable. That button magnet is probably overkill. I would think a 5mm diameter one would be sufficient. Still pretty strong.
 

Delta Prime

Jul 29, 2020
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That's great can you take it some more photos I'm still trying to get a mental image of what you're trying to do here but if you're up for ideas that's great
You try ceramic magnets or kitchen magnets those flat ones layer them together or even aluminum ring like this
photo_1686086382049.png
 

Bluejets

Oct 5, 2014
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Feasible or not?
There is a certain brand of mains electrical safety switch which uses the same principle and it works very well.
Idea behind this particular application is, a trip mechanism is held using the small rare earth magnet so obviouslt it is held firmly.
When the coil is energised, it opposes the current magnetic field and the mechanism releases.
Might add this usually trips in around 10 milliseconds.

In your application, much would depend on the physics involved to determine the overall design, however the idea is not new and, it does work.

As far as using it for an R/c aircraft drop tank, I wouldn't.
For one thing, these days, dropping anything from R/c aircraft is illegal in many countries.
Yes, I know, we used to as well but things change................................:(
Secondly, a servo can do the job and everything is in place to control it, just need a mechanism as in the video link below.
Weight of the load in the below link becomes less of an obstacle or need for consideration perhaps.

 

Delta Prime

Jul 29, 2020
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Yes, I know, we used to as well but things change................................:(
I understand now thank you for the information to the thread starter. Apologies I could not be of assistance. Looks like fun.
 

Mikeq666

Jun 6, 2023
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Hi

Thanks for the ideas guys. The mechanical option is straightforward but the electronic approach doesnt look as straightforward as I thought. Re dropping the drop tanks, would only be just before touch down to avoid cracking the wings. No wheels. These are slope soaring gliders that land on their bellies. Its actually a scale model of an F86 so with droo tanks gives you the idea. I’ll risk the wrath of the law . They’ll be too busy monitoring peoples ‘right think’ on line to be out on the moors in a 30mph wind
 
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