dc fan rotational speed vs. life

[noslo21]

While observing L10 life expectancy fan test data, I notice that there is approximately a 5% increase in the rotational speed of the unit from the time the test start and ends. This is for a ball bearing unit with a max flowrate of 23 CFM and runs at about 13,000 rpm @12v. It would seem to me that the bearing somehow get "broken in" to allow faster operation? Is there any truth to this? or is there some other reason for this change. It would seem to me that the bearings would run slower, not faster as more and more dirt, etc. gets in the bearing.

 

[noslo21]

Just though that I would add that this is after approx. 1400 hours of total fan testing

 

[ko99]

Never heard of this. 1400 hours isn't very long so maybe it's just smoothing out tiny burrs. I'd still guess the same as you: eventually wear would take over and speed would slow.

Have you contacted the fan manufacturer?

ko (

http://www.ecooling.biz)

 

[johnfitzgerald]

Assuming the fan has ball bearings, it might just be the grease packing getting cleared away. I've always notice new bearings are more difficult to turn when new that after they have had some life put on them. I would expect this to happen within the first few hours.

 

[Heckler]

Are you a fan manufacture? or are you using a commerical fan in a mil project and are just running a rating life test? What are the specifics of the fan & bearings, sleeve bearing or ball type?

Best Regards,

Heckler
Sr. Mechanical Engineer
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Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

 

[noslo21]

No, I'm not a fan manufacturer. The L10 data was provided to me by the fan manufacturer. I did talk to the rep. while they were here about it and they did not know at the time. The fan has two ball type bearings. Its a dc brushless axial flow fan (40x40x28mm).

 

[sreid]

I wonder if the Neo Magnets could be losing field strength with time. That could cause the motor to speed up. There has been some China based Neo material that is real junk.