This page written circa 30 December, 2010.
This holiday season has caused me to reflect upon two of the most important things in the world: toys and pioneer idiots. These two pretty much make my life livable.
Let me start by considering neodymium. Neodymium surely must be the stuff of today. It is not a rare element, despite being a "rare earth" element or lanthanide. The vast majority of the world's current supply is mined in China. This instance of Chinese dominance causes some concern. Neodymium makes the most powerful permanent magnets known, and they are used in disk drives, microphones, loudspeakers, headphones, generators in aircraft, high-efficiency electric motors for electric vehicles, and even starter motors for go-karts like our Blue Typhoon. However, I mostly think of toys when I think of neodymium magnets.
The motors in model trains, boats and cars are inevitably permanent-magnet, brushed dc motors (PMBDC). They may soon change to the astonishingly high power-to-weight brushless ac type found in the current generation of radio-controlled helicopters and aeroplanes, but they all use neodymium. Older-design model trains used magnets that were not as strong as the current neodymium ones, and if you foolishly dismantle the motors you have to remagnetise them when you reassemble them in order to recover sufficient torque. Old trains also had difficulty pulling more than a few carriages, since the magnets set the torque. Neodymium obviates these problems.
Many slotcars depend upon neodymium magnets to hold them to the track. T-scale trains depend upon neodymium magnets for sufficient grip to run at all, they are so tiny that without magnetic wheels, grains of sand or dust would lift them off the rails.
Eric introducd me to a new "executive toy" that consists entirely of 5mm-diameter magnetised metal balls. These things are powerful magnets, and they make and hold fascinating shapes. You can make a bracelet that you cannot shake apart, as well as a range of fascinating objects, such as these.
Edwin spends his money on "Bakugan". The toys in this series consist of transformer-like miniatures that fold out from spheres, cubes, etc., in response to touching a steel surface. They contain latches that use tiny neodymium magnets to release springs when the magnet senses steel outside the plastic shell. This line kept a few mechanical engineers happy in the designing.
My keychain crank-flashlight no doubt uses neodymium magnets.
There is an all-new warning on the packets of some toys Edwin got this Christmas. It runs something like "contact a doctor if swallowed", but not because of poisonous nature. The toys are ones that contain tiny but powerful magnets, and the risk is that, if swallowed, they will "stick to metal or another magnet in a separate fold of the intestine, causing infection" in the gut, "and possibly death". I doubt that this risk occurred to many people before it happened to some poor pioneer idiot. I have nearly lost blood from my finger fooling with disk-drive magnets, but I had not contemplated the consequences of swallowing them. Ooh-er, scary.
The little magnetic balls come in sets of 216 at $5--10 a set ex HK (or $30 in NZ), the variation being in the colour and the tolerance. (Dissimilar-sized balls do not readily hold interesting shapes.) Add a sugar coating and you could hospitalise an entire kindergarten and have leftovers. For all I know the characters on the packaging of Eric's "NeoCube" magnetic balls may be Korean for "Handle with care---magnetic assassination kit---for distribution in US only".
Where would we be without those pioneers who discover these risks for us? Who discovered that hemlock was poisonous? Who documented the consequences of not cooking your kidney beans enough, or using the wrong part of the rhubarb plant? (Denis loves to tell the story of Kay's mother substituting rhubarb leaves for spinach one night when the fridge was light, thank goodness he knew better.) Who figured out which bit of the puffer fish to not use, or the recipe for making a zombie? How do we know that 100mA is the most lethal a current when my student cannot even mention the impact of accidental shocks in his thesis without ethical approval. OK, that last bit only affects New Zealand.
Come to think of it, Australians had better buy up magnetic balls while they can, it is only a matter of time before their politicians ban them.