Stacked Thrust Bearings

[PhilBW]

I have an application that currently requires a tapered roller thrust bearing. I am having difficulty fitting a thrust bearing in my bearing housing because the available space limits the diameter of the thrust bearing. One of my co-workers suggested stacking thrust bearings to handle more load using smaller diameter bearings. I have spent the last 3 hours searching on the internet and can find practically no information on stacking bearings.

Does stacking thrust bearings require special bearings? How does the load get distributed among all bearings in the stack? Can you divide the total load by the number of bearings in the stack? Are there any good resources on the internet or to purchase that cover bearing design issues such as this?

 

[ischgl99]

This document is probably what you are looking for

http://www.timken.com/industries/to...97959782931D6C=0&bcsi_scan_filename=e3_69.pdf

The load rating is not linear as you increase the number of bearings. The formula used in the document above is:

fb=(ib)^0.7

ib is the number of stacked bearings and fb is the correction factor for the life calculation.

 

[dimjim]

I think stacked bearings in a thrust situations simply
passes the load from the first stacked to the second
stacked bearing, ie, no gain.

 

[sreid]

Can you use angular contact bearings? The 60 degree types make good thrust bearings. Ground for preload they can be stacked 2, 3, 4, etc.

 

[volpegrigia]

To increase your system load ability you can use angular contact ball bearings, as long as they are suitably matched for stacking, or specially produced thrust cylindrical roller bearings (called "tandem"). The latter were specifically designed for applications with limited radial space but high thrust forces (such as in a twin screw plastic extruder).
the link below will get you to a company website where you will see these bearings.

http://www.unitecbearings.com/

 

[Fugeguy]

Phil,

The correction factor listed is correct for ball bearings. For roller bearings the exponent is 7/9 not 0.7.

I am an application engineer for a bearing manufacturer and the design process you are using will most likely result in failed bearings. I would be happy help. Please upload a sketch and load diagram for your system and I will make some recommendations.

Good luck to you.

 

[dimjim]

Call Timken, or any major tapered roller bearing company
and explain you load situation and application. There is a big difference in life calculations and simple static
load calculations. They are happy to sell you bearings and offer free application information.

 

[PhilBW]

Thanks to all who replied. I have been out of the office the past several days, but will be digging into this more in the next few days.

Phil