Long life bearing system 3

[PopeyeTheSailor]

How about a bearing system that will be expected to last a minimum of 25 years under the following conditions:
•Preloaded ball bearings
•Bearing ID will be 2mm with typical OD for this size (~6mm)
•Radial load on bearing = 0 to 5 grams (depending on orientation during operation)
•Axial load will be preload plus or minus 0 to 5 grams (depending on orientation during operation)
•Shaft will rotate back and forth approximately 1/8th of a revolution every 100msec (continuously), it will never make a complete revolution. (Should be equivalent to about 150 rpm)
•Temperature range is about -10ºC to 75ºC

Will the bearing system suffer any from not making complete revolutions?
What is the best lubrication for this bearing system?
Does anyone have any experience with this type of application or have any advice?

 

[sreid]

I assume by Preloaded Ball Bearings you mean a pair of anguar contact ball bearings.

Short stroke oscillatory motion usually kills ball bearings. The balls do not stay greased [oiled], there is metal to metal contact and steel starts transfering from ball to race and vice versa. Early failure.

Using ceramic balls would solve this [spindle bearings]. A very light preload would be required so the race doesn't fail due to metal fatigue. Krytox grease might be the lubricant to use.

Have you considered Jewel Bearings?

http://en.wikipedia.org/wiki/Jewel_bearing

http://www.birdprecision.com/

 

[PopeyeTheSailor]

sreid,
Thanks for the reply. Yes, I did mean a pair of angular contact ball bearings. I was afraid that the oscillation would be a problem for lubrication. I will investigate the Krytox grease.
I did consider jeweled bearings. I made an assumption that the radial play would be unacceptable. I may have been hasty.

 

[sreid]

http://www2.dupont.com/Lubricants/en_US/products/krytox/krytox.html

 

[MikeHalloran]

For just 1/8th of a turn, you might be better off with a flexure.

Ball bearings won't last in that service. I'm guessing less than a month. Really small balls will help some. Magic grease won't make enough of a difference.

;---

I did once see a bearing that had run continuously for 100 years. In continuous rotation, not oscillation. A plain bearing; steel journal running on a steel saddle (like the bottom half of a split pillow block). Load was a few hundred pounds. Rotation not more than 100 rpm. The rotating mass was a waterwheel. The lubricant was a trickle of running water. There was some wear. The shaft had worn its way farther down in the saddle by about an inch.



Mike Halloran
Pembroke Pines, FL, USA

 

[unclesyd]

As posted above you might want to look at these bearings.

http://www.c-flex.com/pivotadd.html

 

[PopeyeTheSailor]

unclesyd,
Thanks, this looks promising. Size and angle of rotation is a question, and I've contacted C-Flex for more information.