Remagnetising a tiny rod magnet

[polygonum]

Might do - thanks.

[The Natural Philosopher]

Oh the curie point of most magnets is a lot less than that.

Neodymium is barely 100C and a bit.

standard failure mode of electric model planes. Motor gets hot. magnets lose magnetism a bit, motor draws more current and gets even hotter...traiil of magic smoke, gasps of ooh ahh and with luck you throtlle back enough for a dead stick landing.

[Dave Liquorice]

Ought to be a bit better quality than my Oregon WM918 system then. Mine was installed mid 1999 and has worked well but is showing it's age. It's not the electronics but the mechanical bits. Reed switches giving up is expected over that time period but the wind vane pot could also do with being replaced.

I was lucky in that about 6 years ago Carlisle Ski Club replaced their WM918 system and they gave me all the external sensors. I'm just down the road from their ski slope on Yad Moss and they used to look at my station to get a guide about conditions up here.

Not sure there is much choice if you want a decent system. There are ones about for winter gales and salty atmosphere we get down here on the coast.

Mines handled the weather well and it does get a tad breezy up here, sustained 50mph, gusts to mid 60's mph are not unknown, accompanied by heavy rain. But we don't have salt, that's probably the real killer.

[Tim Streater]

Nah, more like some of the local oiks been practicing their ack-ack skills. Local dweeby librarian used to fly his models planes over the rec when I was a kid, thass what happened to them.

[harryagain]

The other way you can do it is to stick your duff magnet on the neodymium magnet and put on hard (ideally non-magnetic) surface and tap the (duff) magnet with a hammer. Hammering ferrous materials in a magnetic field was how permanent magnets were made in days of yore.

[Martin Brown]

How about chipping a flake off the small brittle Nd magnet and putting it at one end. You can get Nd magnets 1-2mm thick with self adhesive on one side and N or S pole on the other. I'd suggest buy one shatter it and stick a piece just big enough to induce the right level of magnetism in the host. Neater job if you buy round ones the right size.

What you want is a tiny Nd magnet attached to a soft iron nail!

Probably didn't get it above the Curie temperature.

Try this lot and hope that one is the goldilocks solution:

Or a ferrite one and hope you can patiently cut it down to size

[Dave Plowman (News)]

One I have here - there are other types - has a rectangular bar magnet measuring 25.5 x 8.5 x 8.5mm

[Chris Hogg]

Many thanks for doing that, but too big in all dimensions to be immediately useful. ATM I'm pursuing other solutions. If I ever get it right, I'll post here. Thanks again.

[Dave Plowman (News)]

Might be worth giving the dimensions of your one - may ring a bell with someone. Although a reed switch usually doesn't need much in the way of magnetic field to work - depending on distances.

[Chris Hogg]

You missed it in my OP? A circular rod 4mm dia. x 8mm long.

[Dave Liquorice]

I wonder if the shank of a 4 mm steel wood screw or a bit of 4 mm wire nail would be easier to magnatise to a suffcient strength than the orginal ferrite? Stroking with the neodynium one you have.

[John]

There's a magnet of around that dia in this kit:

Can't be sure how long the magnet is because of the brass mounting.

[Chris Hogg]

A RESULT!

Initially I tried TNP's method of a few turns of thick wire (actually about 20 turns and 1mm^2) on a small plastic bobbin (a wheel 'borrowed' from one of the trays in the dishwasher!), connected it via a 'Quicktest' connector (see

to a cooker type panel supplying a 7.5 kW pottery kiln. Banged down the lid, quick flash from the neon, blew the 13A fuse, tripped the 50A MCB and the RCD in the dedicated CU, recovered the little magnet, but zilch! Not a Gauss (or should that be an Oersted), well, nothing significant, anyway!

On to plan F (or is it plan G now?) Whichever, it was a combination of Bob Minchin's and Martin Brown's suggestions of getting a much smaller Nd magnet and/or chipping a bit off one that I'd got. The Nd magnets I had were 4mm dia. and 6mm long, and I'd bought a pack of 10 from First4Magnets so plenty to play with. I chopped one into three more-or-less equal lengths by holding it in the wire-cutting section of a pair of pliers at the point I wanted it to break (2mm) and then squeezed the pliers in a small bench vice. They snapped/cleaved perfectly in just the right place, pretty much straight across. So I now had three Nd magnets, ~2mm long. I tried two together, but they were still too strong, but one on its own, with a couple of short bits of mild steel rod to provide the extra length and weight, and Bingo! it works perfectly, and the gauge calibration is still OK.

I'm delighted. Many thanks to everyone for their helpful suggestions.