air filters

From: Peter C. Wallace <>
Date: Tue Oct 14 16:06:53 2003

On Tue, 14 Oct 2003, Jay West wrote:

> > Though this does make one think that it may not be that hard to steal the
> > paper filter from an existing (larger) HEPA filter , cut it to the proper
> > size, and hot melt it into the old filter casing...
> Of course, bear in mind you're in for some spectacular crashes if the filter
> media you get at home depot doesn't have exactly the same airflow (density)
> as the one you replace. The air flow through the filter media is very
> carefully calculated to get the right amount of air into the media cavity so
> the heads can fly on that cusion of air. I seem to recall the head disk gap
> on a 7906 is about 20 microinches or so? I don't think I'll be playing "test
> the unknown filter media" games anytime soon.
> Jay
> ---
> [This E-mail scanned for viruses by Declude Virus]

Actually thats not true at all, there is very little you can do that will
change the air pressure in the HDA (short of moving to a different altitude).
The air pressure/media speed/head geometry/head loading pressure determine the
flying height, the filter will have little or no affect on that. The filter
pressure drop will determine how much of the circulating air goes through the
filter and how much bypasses it...

Peter Wallace
Received on Tue Oct 14 2003 - 16:06:53 BST

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