Fluid Dynamic Bearing on semi-passive PSU

anderson9987

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Corsair RM1000x and RM1000I have diferrent fans.
The RMX is rifle bearing and the RMI is is fluid dinamic bearing..
I know that FDB is better, but as pointed out on this article:

http://www.tomshardware.com/reviews/power-supplies-101,4193-18.html

"The only problem with this type of bearing, besides increased production cost, is that during the start-up phase and until the lubricant is pumped all the way up to the bearing's top, there might be increased friction, meaning that these fans aren't suitable for applications involving lots of starts and stops (in PSUs featuring a semi-passive mode)."

So the FDB is not good for semi-passive PSU..
But FDB is better than Rifle.....


If you going to start/stop several times, which one would have longer lifespan ?


thx in advance


 

BFG-9000

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This question does not make any sense, because a rifle bearing is a type of FDB.

FDB are just sleeve bearings sealed in a pool of oil, often with grooves to circulate that oil around (the "rifling"). The quality of their seals to a large extent determines their lifespan because once those go, it just becomes a plain sleeve bearing...that you cannot add oil to.

Like any sleeve bearing, they last longer if not mounted horizontally (like in a PSU) because there's a larger bearing surface along the axle instead of the tiny thrust surfaces at the ends. When stopped these surfaces actually touch because there's no spinning motion to float them on oil (the sleeve bearings in your car's engine also suffers ~90% of wear on startups for the same reason--there's no oil pressure then).

Ball bearings do not care about orientation because the surface area of the angular contact with the races is the same no matter which way gravity pulls on them.
 

anderson9987

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Thx for your answer, it was very good
.
But what happens if I get and RM1000X and the system crosses the 400 W limit several times a day.
(400w is the limit to make the fan spin) . It reaches lests say 700w, then goes back to 200w several times a day.

The fan would suffer a lot wouldnt it ?
 

BFG-9000

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As I said, the lifespan is mostly determined by the seals, which have no spec you can look at or compare. Several times a day doesn't sound like much either--I mean think of a pizza delivery driver who starts their car 50x a day, yet the engine still easily lasts >100,000 miles.

Theoretically a ball-bearing fan will be unaffected by starts/stops, but they are only rated ~60,000 hours. Some FDB fans are rated 300,000 hours so you'd have to lose 80% of their life from startup friction from those to match the lifespan of ball bearings.

In any case, you are overthinking this because they are guaranteed to work for the duration of the PSU warranty. After the warranty is over, you can break any warranty seals to replace the fan with a better one if you like.
 

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