Strong Magnets

I have a pair of magnets 25 x 6 mm ,they are the strongest magnets I have known for there size, and can give a nasty nip If they are not handed correctly. The photo shows them holding on to a 35 .5 mm thick book, has any one got any stronger for the size.

Bob

They are almost certainly Neodymium type. This site:

https://www.kjmagnetics.com/calculator.asp

**LINK**

...has a calculator which will give he force between magnets. I buy magnets from

https://www.first4magnets.com/

**LINK**

...who have a large range at reasonable prices - you could find a comparable size and check what the force is.

We had a project at work a few years ago. It used some very large magnets, to pull these parts together, and then to separate by rotating one of the magnets. They came with alot of warnings and had a large container for each. One guy had his swipe card too close to the magnet and it ruined it. Lucky there were new cards on site. I can recall the instructions mentioning not to allow another Neodym magnet to become too close as permanent damage could occur to both magnets. The magnet had a holding power of around 100kg. Our new lifting magnet can hold 350 kg and is the same size as the old 200kg magnet for lifting steel plates etc.

These magnets gave me a nasty nip the other month when playing around with them, I had to pull the magnets that had pinched my skin rather than pulling them apart which was impossible. Definitely not a toy to play with,keep well away from children.

Bob

One might take a look at rotors (for workshop made wind turbine generators. Extreme care needed when handling those! A ‘nasty nip’ would not be relevant if they got out of control!!

Rare earth magnets are remarkably strong, but they're weeds compared with superconducting electromagnets. Superconducting used to require temperatures close to absolute zero, not very practical, but after 50 years of research the technology can run close to room temperature.

Two years ago an American warm superconducting electromagnet broke the record with 25 Tesla, but progress is rapid - the current record holder is a 45 Tesla magnet in China.

Small permanent magnets are usually about 4000 gauss. As there are 10000 gauss in a Tesla, the Chinese magnet is roughly 100 times more powerful than Neodymium.

The march of technology is fascinating. In my lifetime science fiction becoming common include: microprocessors, mobile telephones (with video!), the internet, green energy, 3D printing, drones, bionics, artificial intelligence, high definition media streaming and home lasers. At the same time a bunch of other technologies have disappeared or are going: gas lighting, trolley buses, telegrams, shortwave radio, analogue TV, high street shopping and early day closing, ocean liners, sodium vapour street lights, cast-iron fingerposts, motorbikes that leaked oil, steam locomotives, factory chimneys, railway signal boxes, public telephones, milk floats, and mum's electric iron plugged into the light socket.

Dave

Talking of magnets, a friend recently had his stationary engine magneto re magnetised, he said it wasn't cheap. After reading the above, I wonder if by simply attaching several large powerful magnets to these original engine horse shoe magnet, the spark would be restored. I am aware of AVO enthusiasts attaching extremely small magnets to the original magnet within an AVO meter, in doing so, restoring the meter accuracy. It is of course essential to get the polarity correct in both cases. John

Only in the UK were we unwise enough to destroy our tramways and trolley busses. They are still used in the rest of Europe and even in the USA. I put it down to short term thinking, they did little mainainance on the systems until they needed major spending, then the money had been spent on something else.

My grandfather lived through the arrival of the motor car to seeing men on the moon, he just missed the personal computer.

Mike

Hi Mike, my late elder brother saw all the moon landings and was quite knowledgeable about electronics and had some understanding about mainframe computers, be he sadly missed out on the personal computer, of which he would have probably been in his element with, but he did get to use one of Clive Sinclair's first electronic pocket calculator.

Regards Nick.

When I was an apprentice at Fawley Power Station in 1971 we had an experimental superconducting motor on one of the cooling water pumps - about 3000 horsepower if memory serves. I never saw it running because the refrigeration plant was so unreliable. I was intrigued to discover that it used copper as an electrical insulator for the superconductors.

George

Well the superconductors had zero resistance so the copper would be shorted out. It would however have good thermal conductivity for cooling.