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From: ralf@cad.cs.cmu.edu (Ralf Brown)
Newsgroups: comp.sys.ibm.pc,comp.periphs
Subject: Re: Lot's of questions
Message-ID: <1029@cad.cs.cmu.edu>
Date: Sat, 3-Jan-87 23:24:07 EST
Article-I.D.: cad.1029
Posted: Sat Jan  3 23:24:07 1987
Date-Received: Sun, 4-Jan-87 03:44:30 EST
References: <9073FIB@PSUVM> <2750@osu-eddie.UUCP> <434@catnip.UUCP> <551@brl-sem.ARPA>
Organization: Carnegie-Mellon University, CS/RI
Lines: 31
Summary: Bernoulli Box heads *never* touch the media
Xref: mnetor comp.sys.ibm.pc:775 comp.periphs:91

In article <551@brl-sem.ARPA> ron@brl-sem.ARPA (Ron Natalie ) writes:
>In article <434@catnip.UUCP>, ben@catnip.UUCP (Bennett Broder) writes:
>> The reason that Bernoulli boxes can't suffer from head crashes is because
>> the r/w head always contacts the media, just like a floppy disk.
>Wrong, the bernoulli box is immune from head crashes because it the heads
>are designed to be able to hit the media, but they are not always in contact
>with the media.  They achieve their faster turning rates over floppies by
>forcing air under the heads.

Wrong again:  The Bernoulli Box is so named because it uses the Bernoulli
effect, in which a rapidly moving stream of fluid (either liquid or gas) 
experiences a pressure decrease.

The BB can't have a head crash, because in normal operation, the flexible
media is pulled toward the head by the Bernoulli effect on the air moving
between the head and the disk surface (this is the opposite of hard disks,
in which the heads are shaped so that are flowing under them lifts the
heads off the disk).  If anything interrupts that airflow, such as a piece of
dirt, the Bernoulli effect is lost, the media is no longer pulled toward the
heads, and the media is now safely out of harm's way.  THE HEAD NEVER TOUCHES
THE DISK SURFACE--if it did, the Bernoulli effect would immediately be lost,
again moving the disk surface away from the head.
--
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