3.5 FDD head size: size of the gap of the read/write heads

[SMD1990]

3.5" FDD head size: size of the gap of the read/write heads

I doubt anyone here knows the answer, but I thought I would ask anyway. I mean, I know not of a better forum on which to ask...

Anyway, does anyone happen to know the size of the gap of the read/write heads of a 3.5" floppy disk drive? Unless I am mistaken, the size should vary depending on what density of disk the drive supports.

I have tried Google, but failed to find anything of relevance. Surely, somewhere out there, the answer is recorded. Still, I was not able to find it.

So, yeah, if anyone knows the answer to this, I would appreciate them sharing the answer with me.

Oh, and if there is any sort of resource containing gap sizes for hard drives, as well... I would be interested in that, too.

 

[MATLABdude]

I believe these heads were in physical contact:
http://web.mit.edu/2.972/www/reports/floppy_drive_read_write/floppy_drive_read_write.html

However, they also only spun around 300 RPM:
http://hypertextbook.com/facts/2005/GennaAbleman.shtml

As for modern hard drives, Wikipedia says around 3-5 nm:
http://en.wikipedia.org/wiki/Disk_read-and-write_head

As noted, 'disk flying height' gets smaller and smaller with higher and higher bit densities. 4 years ago, the bleeding edge was 13 nm (0.5E-6 inches):
http://www.storagereview.com/guide/opHeight.html

 

[rcgldr]

Note that in some cases, the gap size in the direction of data can be bigger than the bit density, which is accomplished by changing the field of the gap faster than the media travels across the gap, leaving a higher density pattern once past the edge of the gap.

 

[SMD1990]

MATLABdude, I was not asking about the "flying" height. I was wondering about the size of the gap in the electromagnetic "head" (i.e., 19 µm for an EP VHS head).

In none of your links did I see anything specifying the size of the gap. In the links relating to floppy disk drives, only the speed of rotation was listed (unless I overlooked something, in which case, please correct me).