MadSci Network: Engineering |
Dear Jerry, There are some very strong magnets out there called "Rare Earth" magnets because some of there composition is from very rare metals. Samarium-Cobalt (SmCo) and Neodymium-Iron-Boron (NdFeB) magnets are the most popular. Neodymium's can be made more powerful than SmCo magnets but are very unstable under higher temperatures, (well above 100°C, which I'm sure you will not have to deal with). Neodymium magnets tend to oxidize (rust) easily so are usually coated with a protective layer. Therefore I would recommend ordering sizes you can use instead of trying to machine or cut them. Also, order extras because if two get away from you they will smash into each other and create an unusable lump. And, keep your fingers out of the way. Here is a warning I copied from Indigo Instruments' website: Neodymium-magnets Warning! Do NOT go anywhere near your computer with them or you could damage your monitor or hard drive. Keep any other magnetic media away including floppy disks, cassette tapes, credit cards, etc. CD-ROMs are unaffected. These are not toys and should be kept away from small children. If two of these magnets come close enough, they will snap together so quickly they could break a bone in your finger or cause a serious blood blister. A pair of the larger disks are strong enough to attract each other right through the thickness of a typical adult hand. Pretty cool, Huh! There are a number of ways to measure magnetic strength, but most will say that Neodymium's are by far the strongest at room temperature. I have some 1"x1" by ½" thick Neodymium's left over from an experiment that I can barely get off the fridge using my fingers. Just to warn you, keep them on the metal sheet they will likely come with or another piece of metal, or tightly in your hand. There is very little to reference except my experience testing these rare earth magnets as mobile composite repair for the Army and what is on the web about them. However, if you want a more detailed explanation of how magnets work or how their strength is measured, I am not the one to ask! Sorry, not my area. Anyway, Indigo at the above sight has some great small magnets that you will likely be able to use. Use the largest that you can since size and thickness of the magnet is the biggest determinate of strength (if made from the same material). Or do any web search for Rare Earth Magnets or Neodymium and you will bring up a number of sights that sell these magnets. Hope this helps and good luck with the film. BK
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