eddy current brake

[Steve Ciciora]

<snip>

>   drag force. It's really neat- you can brake the rotating disk without 
>   contacting it. If you happen to have an old hard drive platter laying around 
>   you can demo the effect. Give the platter a good spin and just bring a 
magnet 
>   close to the surface of the upper disk. You'll see the thing slow 
noticeably. 
>   BTW, if you have an older model drive dig out the (big) magnets from its arm 
>   motion control assy; you'll be Astonished by how strong they are if you have 
>   never seen these magnets before. Put two of them together (don't get your 
>   finger caught as they snap together!) and you will not be able to pull them 
>   apart without sliding them parallel! Anyway I think that another app for 
eddy 
>   current brakes was the diesel-electric locomotive?


  The demo I use to do is take a neodinium-iron-boron (spelling, -2) magnet and
drop it down a 3 foot length of copper pipe.  It floated down!  Would take about
10 seconds, vs less than one second to drop a marble down.

Steven Ciciora