this book is really fascinating. there's a whole chapter on the physics of rotating disks
ALT
ALT
Replying to @gloriouscow@oldbytes.space
this is a good illustration of how the flux direction is recorded - the current direction through the coil will induce a directional magnetic domain through the magnetic coating directly beneath the tip.
ALT
Replying to @gloriouscow@oldbytes.space
i'm gonna have to model that in blender aren't i
Replying to @gloriouscow@oldbytes.space
This is one of two magnetic heads in TEAC FD-55BR high-density floppy drive. It's the beige plastic bit in the middle.
The actual head is on the right side - the black tuning-fork looking thing. Writing occurs at the 'stem' of the fork, where it splits, those are the two erase heads, which neatly trim the magnetic signal by laying down a gap to either side of the track, like a tractor tilling furrows in a magnetic field.
ALT
Replying to @gloriouscow@oldbytes.space
The 'lip' on the left provides a backing pressure pad for Head 1 when it descends and the two heads clamp the floppy.
The heads are in physical contact with the floppy disk, which is why they are so important to keep clean.
Replying to @gloriouscow@oldbytes.space
You can see the 'furrows' here as the vertical stripes. These are written by the erase heads.
This is an image of a floppy disk taken by a special magneto-optical microscope. I'd love to have one to play around with, but they're a few thousand dollars.
ALT