So, I’m building a loco with batteries inside. To change the batteries I need to be able to lift the body off without messing about with screws or clips. You may have noticed, I do like magnets and since I have used them with reasonable success on both rolling stock and buildings they are the logical choice.

Having some lights at each end of the loco would be nice. My original thoughts were to use some sort of springy contacts, a trailing wire with a mini connector would get get broken with repeated use.

Anyway I was messing about with some magnets and tinplate to decide what size would be good and the thought stuck me. Tinplate is a conductor and metal magnets should be. A quick test showed that the neodymium magnet had a very low resistance, less than 0.1 ohm, which is as low as I can measure directly. I suspect that may be due to the neodymium core being plated with copper then nickel, but putting one in the lathe to machine the plating off to prove the point seemed a real hassle.

Now there are several ways you can kill a magnet. Repeated mechanical shock, heat it past the curie point or put it in a strong alternating magnetic field for example. A large current might overheat one. But what effect would a small DC current have on these neodymium magnets? I asked the internet, it really hadn’t tried it either. Sometimes you just have to do it the scientific way.

I set up a simple experiment. Tinplate electrodes. A small magnet and some LEDs. Bench power supply. I set the current to 5mA, plenty for my needs.

I left it running for a week with the current passing from N to S through the magnet. I then removed the magnet and tested it against a fresh one from the box by taping a bit of iron to a plastic ruler and gently pushing the magnet to it while noting the pull in distance. As far as I could determine both had the same magnetic strength.

For the next week I reversed the magnet, current S to N. Test repeated, again no change of magnetic strength.

So, I conclude that passing small DC currents through ( or perhaps round the core of ) neodymium magnets does not affect their strength.

Perhaps a bit of a boring blog, but maybe a few folk will find it useful.

I still need to turn that idea into a practical engineering solution but it does give me the confidence to go ahead and try.