STEORN DEMO LIVE & STREAM in Dublin, December 15th, 10 AM

[0c]

Real quick, so if you say, "Well, if the Finemet core is like 2.5 times Metglas cores in the same space, then just move it farther away."  Of course you can do that, but moving it farther away you end up with the same force.  If moving the core farther away has other side effects that are good, then the Finemet is a better choice. We'll have to see.

... or use a smaller, easier to saturate core to get the same torque?

[haithar]

Can someone probably answer my question which optical sensor to use when timing the pulse? Over an hour of internet search didn't bring me results.
Like the optical sensor in this image: http://jnaudin.free.fr/steorn/images/steornv3b.jpg
Anyone? Name, Part number, shop link, whatever. thanks.

[0c]

If the metglas retains 79% of its magnetization when the coil is de-energized and 79% of the energy stays inside the core, then PL can't possibly recover up to 95% of the energy from the pulse.  The most that could be recovered from the pulse is 21% in the perfect case. 

That is a 174% gain just by energizing and de-energizing the metglas core if you can re-capture 95% of the pulse according to PL, which is close to PL's 170% efficiency claim for his tiny Orbo replication.  We have OU just by energizing and de-energizing the metglas core.  I don't think so, lol.

PL, you're calculations don't add up. 

GB

The energy recovered from the pulse has nothing to do with remanent magnetization. It has everything to do with the change in inductance (permeability) between coil on and off times. The permeability ratio at these 2 moments is what will determine how much energy is returned when the coil is deenergized.

[wings]

Immediately after deenergizing, the core will retain a remanent magnetization, oriented in a circular polarity that is not externally detectable. This "biased" core will have very near the maximum permeability and attraction to an approaching magnet (permeability is higher near the knee of the BH curve than it is at zero). As the magnet approaches, the domains in the core will be rotated to align with the field of the magnet and the core will essentially become a diametrically magnetized magnet, oriented for maximum attraction to the approaching magnet.

@ OC
oops
I forgot this step, thanks for the explanation

[gravityblock]

The energy recovered from the pulse has nothing to do with remanent magnetization. It has everything to do with the change in inductance (permeability) between coil on and off times. The permeability ratio at these 2 moments is what will determine how much energy is returned when the coil is deenergized.

It has to do with both remenance and coercivity.  Let's say you used a pulse with enough energy to magnetize it to 100%. If the metglas core is 79% magnetized after the pulse, then it is holding 79% of the energy from the pulse.  If you re-capture 95% of the pulse, then you lost 5%, but the core is holding 79% of the energy it took to magnetize it.  (79-5=74% above unity or 174%).

So, you're saying it only took 5% of the energy from the pulse to magnetize the core to 79% while the 95% that could be recovered only magnetize the core 21%?

GB