Bearings to Support Moment from Heavy Eccentric Load 1

[MegaStructures]

Trying to determine the best bearings for a vertical shaft that supports a heavy eccentric axial load. First thought was to use two cylindrical bearings, top and bottom, but realize that cylindrical bearings will resist rotation of the shaft at the ends and moment forces will be transferred to the bearings. Concern is that the moment will concentrate on a small edge at the end of the bearing and plastically deform the bearing. In order to solve this I have a second idea to use a bearing housing that uses a thrust bearing to support axial load at the bottom of the housing and spherical roller bearing at the top of the housing (this is for bottom housing, top housing would only have a spherical bearing). So, couple questions summarized below.

1) Can cylindrical bearings be used to supported eccentric loads that will cause moments at the end of the shaft. If so, why is there not a concern that the bearing will be damaged at a "knife edge" at the shaft-bearing exit point.
2) Can spherical roller bearings work in conjunction with thrust bearings
3) Is there a better bearing to use for this type of system?

Thanks

 

[BrianE22]

I'm not too familiar with cylindrical bearings. Have you ruled out roller bearings? They can rotate a bit and they have some rotational (moment) stiffness. One way to minimize the edge loading is to match the housing moment stiffness with the shaft moment stiffness (called elastic matching I believe).

If you used spherical and thrust bearings you would need to look at the relative stiffnesses to determine which would take the axial load. I'd guess if you preloaded in the axial direction and controlled the locations of all the bearings then the thrust bearings could be made to handle most of the axial load.

If the thrust loads are high you might consider tapered roller bearings.

Angular contact bearings are used in machine tool spindles that react both axial and radial loads.

 

[canmecheng]

Hi,

Depending on your geometry and loading, you may wish to consider a slew bearing. They can take radial, axial and tilting moment loads. If you need the axis to be driven, you can have an external or internal gear.