G'day all,

@Hans. There is a big tool and metal suppliers somewhere near Blacktown, I can't remember their name at the moment. They can cut you any length of soft iron rod up to 5cm diameter. But I agree ferrite would be a better choice. I think if Stubblefield could have got hold of ferrite he would have used it. Perrigo used bundles of thin rods to make his cores, similar to laminates in a transformer. Sharper hysteresis too.

Ian

G'day Ian,

I had thought about using a bundle of fence wire for the core, that would have worked, but it is messy to do. That is why I settled for the ferrite. I agree with you that if ferrite had been available then, Stubblefield and Tesla would have made extensive use of it.

Hans

@ Freezer:

Fantastic!  That's a new record for us here.  56mA!  Now my coil looks like a little toy compared to yours.
Great job!

@ Hans:

Ferrite eh?  Ferrite is nothing more than iron oxide and I don't understand why this should work.  I had thought earlier about trying a carbon core (from my cell outside) but I have no idea why this would work either.  I do agree that we have many things now that Tesla and NS would have loved to have had.  I have machined a lot of ferrite in my day for wave guides for microwaves and other such devices.  I was not aware of soft or hard ferrite.  All of the materials we had required diamond tooling as did the rest of the ceramics we machined.  I will have to check on this somewhere.  Do you have any way to post pictures of your device?  I can't wait to see the results.  I am hoping to find that beer increases the output of my coil.

Bill

Newcastle gave me a new record bill 

G'day Bill,

The main difference between the ferrites colloquially known as soft and hard ferrites (this does not refer to the hardness of the material) is that the "soft" one magnetises and demagnetises quickly, which is why it is used in transformers, RF coils and so forth, while the "hard" ferrite, once magnetised, holds its magnetism, which is why it is used to manufacture ceramic magnets. Because both materials are a ceramic and very hard, rehaping them is very difficult, if not impossible. Diamond tools are needed.

I think the terms soft and hard come from a time when people talked about soft iron and hard iron (steel), which have the same respective magnetic properties.

Hans von Lieven