[Amps] Resistors

[Karl-Arne Markström]

I certainly can vouch myself for the longevity of the "Oilite" bearings.

In the blower motors of our ex-Air Force 208U-10's  these sleeve bearings are used,
and to date only one single bearing failure has occurred.

The amplifiers have accumulated about 110000 hours of 24/7 operation since late 1988,
and they were far from unused when they were acquired.

73/

Karl-Arne
SM0AOM


----- Original Message ----- 
From: <G3rzp at aol.com>
To: <k7fm at teleport.com>; <david.kirkby at onetel.net>; <g3sek at ifwtech.co.uk>
Cc: <amps at contesting.com>
Sent: Tuesday, April 26, 2005 11:51 AM
Subject: Re: [Amps] Resistors


> 
> In a message dated 25/04/2005 20:50:57 GMT Standard Time, k7fm at teleport.com  
> writes:
> 
> But they  regularly lubricate them.  I no longer make slanderous comments 
> about  sleeve bearings.  
> 
> 
> 
> Ball bearings have lower friction for a given load bearing capability, but  
> are noisier. For heavy loads (like steam locomotive axle boxes), roller 
> bearings  (in the small size, needle bearings) are better. But for things like small 
> fans,  an 'oilite' (sintered phosphor bronze) sleeve bearing, well impregnated 
> with  oil, is in my opinion, going to take a hell of a lot of beating, 
> because of  its lower noise, lower cost and longer life.
>  
> Back in 1996, a Boeing 747 - 400 on a BA flight from Johannesburg to London  
> was over Abbeville in northern France at about 0630 when a passenger called 
> the  flight attendant and complained about sparks, smoke and flames coming out 
> of a  ventilation grill by his feet. The cabin crew moved him to another seat 
> (!), and  called the guys up front. The co pilot shot a fire extinguisher 
> through the  grill, the Captain declared a Mayday, made an emergency landing at 
> Heathrow, and  the passengers evacuated. The problem turned out to be a  ball 
> race in the three phase fan of a humidifier, which had seized after  only 3000 or 
> so hours. The situation was was exacerbated because  Boeing had managed 
> (quite accidentally) to fit a 25 amp breaker to protect  wiring rated at 4 amps, 
> instead of a 2.5 amp breaker. Now if aircraft quality  bearings can fail that 
> soon, what does it say for cheap fan bearings? (Can't  remember if it was 
> lubrication failure - anyone wanting full details can find  them in the AAIB 
> accident reports for 1996)
>  
> 73
>  
> Peter G3RZP
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