Disk platters and water (was: Re: NOVA4 6070 disk booboo)

[Ashley Carder]

>  Jay> Wonder what the head-disk gap was on a drive of the IBM 1311
>  Jay> vintage.
> 
> Probably not dramatically larger than that of the RK05.  I don't
> remember the number.  It was shown on a drawing on the disk pack bags
> that DEC created to remind people not to put fingerprints on the
> platters.  I remember it showed a fingerprint, a dust particle, and a
> hair, drawn to scale next to the head height.  The fingerprint was
> about 3-5x the flying height, so measure a fingerprint and find
> out...  It also was perhaps 1/50th of a hair.  So perhaps a few
> micrometers?
> 
> paul

I knew I had seen the same diagram, so I looked in my RK05 manual
and found the picture, which shows the following:

Head flying height:  100 microinches
Smoke particle thickness : 250 microinches
Fingerprint smudge: looks  about 2x the size of a smoke particle
Lint and dust: looks about 2/3 the thickness of a hair
Hair :  4/1000 of an inch

Reference : Page 1-17 of the RK05/RK05J/RK05F maint. manual

Ashley