[Amps] Resistors

[Colin Lamb]

I used to want ball bearing fan motors for computers.  However, even though they may have a longer period without service, they can become noisy.  I have found that the sleeve bearing fans can be oiled quite easily and continue for a long time.  The sleeve bearing depends upon lubrication.  In effect, the bearing is the oil itself.  Without oil, there is no bearing.  Annual lubrication by removing the label and plug covering the bearing can keep the bearing going for a long time.  I can often bring a seized bearing back to life with a removal of the bearing and cleaning of the burned residue and relubrication.  

A few years ago, I came upon a small hydroelectric power plant undergoing annual maintenance.  The generator used sleeve bearings.  I asked the fellow how long the sleeve bearings lasted at 24/7.  His answer was "about 30 years".  But they regularly lubricate them.  I no longer make slanderous comments about sleeve bearings.  

73,  Colin  K7FM

-----Original Message-----
From: David Kirkby <david.kirkby at onetel.net>
Sent: Apr 25, 2005 12:30 PM
To: Ian White GM3SEK <g3sek at ifwtech.co.uk>
Cc: "amps at contesting.com" <amps at contesting.com>
Subject: Re: [Amps] Resistors

Ian White GM3SEK wrote:

> Even a small low-noise fan (ex-PC power supply, for example) will do 
> wonders in keeping the whole thing cool. 

Just be aware the mean time before failure (MTBF) of small fans is 
orders of magnitude smaller than most components, and considerably 
shorter than decent fans.

Most PC power supplies have fans with sleeve bearings, which generally 
have even lower MTBF's than those with ball bearings. Couple that with 
the fact the fan is used, and generally made very much to a price, I 
personally I would steer well clear of them.

AC fans normally have much longer lives, but they tend to be bigger and 
more expensive.

I have a PC here, which I bought from work for £25 or so. Two fans had 
failed - one on one of the two 450MHz CPUs, another on the hard drive 
caddy.

On my Sun workstation, two small of its 5 fans have failed on that too. 
One was on the Celeron processor of a "PC" that fits on a PCI slot of 
the Sun (a PC inside a Sun) and the other was on the DC-DC converter 
that supplies power for the CPUs (I think). The former fan I removed 
(decided it was next to useless and Celerons are dirt cheap) and the 
latter I replaced with another fan.

*Generally*, I find Sun workstations run fine for years without fan 
trouble, despite the fact they run 24/7, but fan failure on PCs seems 
very common.

-- 
Dr. David Kirkby,
G8WRB

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/


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