On Thu, 2 Jul 2020 13:44:59 -0400, Frank Krygowski
wrote:

On 7/2/2020 12:46 PM, Jeff Liebermann wrote:
On Thu, 2 Jul 2020 11:23:43 -0400, Frank Krygowski
wrote:
Ummm... the retention magnets rotate along with the steel spindle.
Everything else is aluminum, carbon fiber, or wood, none of which are
affected by magnetic fields. Actually, you can use eddy currents
through an aluminum disc for magnetic braking but it takes a much
larger magnet:
https://en.wikipedia.org/wiki/Eddy_current_brake

Well, as a cute science demo for a young physics major who was visiting,
I took a high strength magnet about 5mm diameter by 15mm long and
dropped it down an aluminum tube about 10mm ID and a meter long. It fell
very, very slowly. (Try it. It's fun!)

Nice, but I couldn't find a suitable magnet. I think a salvaged
loudspeaker magnet might work if I can find one. All my neodymium
magnets are in the form of salvaged hard disk drive magnets.

Her father is a very smart electrical engineer, but neither of them
understood what was happening.

My point? Eddy currents work well with aluminum. (I don't know about
carbon fiber.) If you have an aluminum frame and this toolkit, your only
hope is that the steel spindle will shield the magnetic fields from the
aluminum.

It should work with any conductive material. The moving magnet sets
up a reflected magnetic field with the same polarity in the aluminum
tube. Like poles (and polarities) repel. The repulsive force opposes
the motion of the magnet, so it slows down.

The water is mildly conductive and can support a magnetic field
sufficient to support mouse in a very strong magnetic field:
https://phys.org/news/2009-09-mice-levitated-space.html
https://www.improbable.com/2009/10/22/mice-levitated-in-lab/
I suppose if it works for a mouse, it might work for carbon fiber.

Otherwise, this braking effect might be enough to overcome the advantage
of even red paint. And as we know, with bicycling, every dyne matters;
nothing is negligible!

Since the sum of all the things deemed negligible often approaches the
whole, discounting negligible effects might not be a good idea. At
some point, we will probably need to consider quantum effects in
bicycle performance.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558