Comments on: From the "ball-bearing motor" file http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/ the blog that is not dansdata.com Fri, 10 Feb 2012 19:14:43 +0000 http://wordpress.org/?v=1.5.1-alpha by: Thuli http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2882 Thu, 21 Aug 2008 09:18:22 +0100 http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2882 Rubber rim brakes get quite warm, and I've read that on long downhill stretches it's not unknown for them to get so hot they can blow tires, so it's much of a muchness. Pity, liked the idea of non-wearing brakes. Rubber rim brakes get quite warm, and I've read that on long downhill stretches it's not unknown for them to get so hot they can blow tires, so it's much of a muchness. Pity, liked the idea of non-wearing brakes.

]]> by: Alex Whiteside http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2880 Thu, 21 Aug 2008 06:47:56 +0100 http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2880 Who <i>wouldn't</i> want a bicycle with brakes that glowed red with latent energy when you arrive at the office? Who wouldn't want a bicycle with brakes that glowed red with latent energy when you arrive at the office?

]]> by: Daniel Rutter http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2879 Wed, 20 Aug 2008 16:12:05 +0100 http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2879 Even if you used a few kilos of magnets and a nice thick solid-aluminium wheel rim, I think it'd be quite difficult to tell when the "brake" was operating :-). You could maybe come up with some geared contraption that, say, spun a copper disk past magnets much faster than the wheels were rotating. But if you're going to go to that much trouble, you might as well do it properly and make an electric-motor-assisted bike with regenerative braking. Also bear in mind that conservation of energy applies, here. The energy you dump by eddy-current braking goes into heating up the conductive disk. If you're just waving a magnet over a slab of copper or damping the oscillation of a balance beam then the temperature change in the metal will be too small to notice, but if you want to bring a bike and rider to a halt, any form of energy-dump brake will turn your joules of momentum into joules of heat, and get rather hot. Even if you used a few kilos of magnets and a nice thick solid-aluminium wheel rim, I think it'd be quite difficult to tell when the "brake" was operating :-).

You could maybe come up with some geared contraption that, say, spun a copper disk past magnets much faster than the wheels were rotating. But if you're going to go to that much trouble, you might as well do it properly and make an electric-motor-assisted bike with regenerative braking.

Also bear in mind that conservation of energy applies, here. The energy you dump by eddy-current braking goes into heating up the conductive disk. If you're just waving a magnet over a slab of copper or damping the oscillation of a balance beam then the temperature change in the metal will be too small to notice, but if you want to bring a bike and rider to a halt, any form of energy-dump brake will turn your joules of momentum into joules of heat, and get rather hot.

]]> by: Thuli http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2878 Wed, 20 Aug 2008 15:13:21 +0100 http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2878 Any reason eddy current braking couldn't work on a bicycle? Or would it be too slow/not enough aluminium? Any reason eddy current braking couldn't work on a bicycle? Or would it be too slow/not enough aluminium?

]]> by: Daniel Rutter http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2877 Wed, 20 Aug 2008 13:58:53 +0100 http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2877 On his <a href="http://www.eskimo.com/~billb/maglev/magroll.html">page</a> for this contraption, Bill mentions that the magnet should float either way, but should float much <b>higher</b> if the cylinders are spinning so as to "blow" it upward rather than "suck" it downward. On his page for this contraption, Bill mentions that the magnet should float either way, but should float much higher if the cylinders are spinning so as to "blow" it upward rather than "suck" it downward.

]]> by: loseweightslow http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2876 Wed, 20 Aug 2008 09:15:50 +0100 http://dansdata.blogsome.com/2008/08/19/from-the-ball-bearing-motor-file/#comment-2876 Does it matter which way the cylinders are rotating? because they seem to be spinning so that they will draw in anything toward the table. It might (only a little) safer if they span so that they expelled anything away from the table. In that way the table could act as a bit of a guard. I dont undestand the physics so it may not work that way. Does it matter which way the cylinders are rotating?
because they seem to be spinning so that they will draw in anything toward the table. It might (only a little) safer if they span so that they expelled anything away from the table. In that way the table could act as a bit of a guard.
I dont undestand the physics so it may not work that way.

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