無料の面白動画・画像・ゲームの特集ブログ｜ふらぶろ

お父さんの75歳の誕生日プレゼントに作ったという強力な磁力を持つ「マグネットボール」を運ぶ面白からくり装置の動画をご紹介。

[YouTube] A Magnet Machine

This machine manipulates small spherical rare earth magnets, slicing one at a time from the end of a long chain, moving it around a bit, then dropping it back to re-connect at the tail end of the chain.  It also demonstrates a little snippet of science called eddy currents. Watch how slowly the magnet falls through the aluminum tube compared to falling through air: the falling magnet generates an electrical current in the tube, and that current in turn generates a magnetic field that opposes the movement of the magnet, slowing it down dramatically. See http://en.wikipedia.org/wiki/Eddy_current if you want more.  I made this machine for my father-in-law for his 75th birthday: astute viewers equipped with video analysis software and way too much time on their hands might find that the magnet drops 75mm from the tip of the slicer until caught by the lifter, and that the lifter then drops it through a 75mm long aluminum tube.  These magnets are currently a popular toy, and can be purchased on the web or in stores (usually in a set of 216, which makes a 6x6x6 cube). Many different brands exist: Zen Magnets (http://zenmagnets.com/), Buckyballs (http://www.getbuckyballs.com/), nanodots (http://www.thenanodots.com/), Neo Cube (http://www.theneocube.com/), and more. I highly recommend this toy! Watch some videos at the above sites.  I used a plastic drywall anchor for the main screw drive that pulls the chain of magnets through the machine. The 2 other driven axles — the slicer and and the lifter — are geared directly to the screw drive. (Steven Garrison's gear cutting method was invaluable to make the gears operate smoothly, see http://www.stevengarrison.com.) The lifter is based on a standard four bar linkage (a film advance mechanism) but was modified to dip very low before lifting back up and stroking its straight vertical line at the top.  See http://www.flickr.com/photos/dogrocket/sets/72157626544506603/ for still photos of building it.  I don't know who first figured out that 5mm spherical rare earth magnets could be so much fun, but whoever they are, I thank them.

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