Ian Iveson wrote:

Phil wrote

R-cores have so many practical advantages it is a surprise how few you see
being used.

Yes, and come to think of it, why haven't they *always* been used?

They were only 'invented' in relatively recent times.

What are the problems?

More expensive than common E-I.

They seem to be common when cast or pressed cores are used,

Eh ? Please give an example of a cast or pressed core !

but
winding strip into anything other than a toroid is fundamentally problematic.
How are the strips kept squashed together in the straight runs, and how does the
core keep its shape during and after the winding of the strip? Presumably it
must be annealed after winding and clamping, or bonded somehow. There is also
the need for precision-cutting of strip to a shape peculiar to each core size,
without leaving a burr on the edge. I wonder if that is done before or after the
insulating coating? That's quite a lot of tricky processing dedicated to each
core size.

The guys that make the cores and accesories have it sorted for sure. You need to buy
a special winding machine too.

Graham