Altair Fan

[Cini, Richard]

Dave:

	Rules-of-thumb like this are great to know. The fan, I'm sure, was
installed (like the IMSAI) blowing IN because the inside was caked with
dust. So, I made it an exhaust fan (no filter).

	As I work on the IMSAI, which has no filter either, I will swap it
around, too.

	To answer another comment at the same time, the fan does indeed have
an arrow but the arrow itself doesn't tell me if it should be facing IN or
OUT.

Rich

=============================
Richard A. Cini, Jr.
Director
Wachovia Capital Finance
1133 Avenue of the Americas
New York, NY 10036
W: 212-545-4402
F:  212-545-4589
 
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Dave Dunfield
Sent: Friday, June 17, 2005 7:01 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Altair Fan

At 21:31 16/06/2005 -0400, you wrote:
>All:
>
>	OK, this is a stupid question. I'm fixing up the 8800b that I got
>recently and I removed the fan to perform some work on the power supply.
>Unfortunately I didn't mark which direction the air blows. Can someone tell
>me if it blows inward or outward?
>
>	Thanks.
>
>Rich

Hi Rich,

Both of my 8800s have the fan blowing out.

The general rule is:

If the fan has a filter, then it should blow in.:

  By maintaining positive internal pressure, and
  filtering the air that comes in, you keep dust
  from entering the box.

If it does not have a filter, it should blow out:

  A fast moving stream of air will carry more dust
  than a slow one. If you blow the fan in, it will
  carry dust into the box which will drop out before
  it exits at slower speed (because of the much larger
  area of all the vents and other openings) - it also
  causes dust buildup to concentrate that certain
  points bacause of sudden changes in airflow (you can
  often see bands of thick dust in boxes with fans
  improperly installed). Going the other way reduces
  the entry speed (same reason) and thus the amount of
  dust that enters - what does get in tends to settle
  out in a more uniform distribution.

Regards,
Dave
-- 
dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Collector of vintage computing equipment:
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