thrust or contact ball bearings

[Saut]

ANSI C50.41 states that vertical motors shall have thrust bearings designed to carry all specified axial thrust conditons imposed by driven load. Can contact ball bearings achieve the same function? Is the thrust bearing more advantageous than the ball bearings?

 

[Metalguy]

If you mean angular-contact ball bearings, they are ideal for the combo of axial and thrust loads.

Whatever you do, do not end up with a situation where any ball/roller bearing isn't preloaded.

 

[Saut]

Metalguy, are there any issues I have to worry if ball bearings are used instead of sleeve bearings. Also, as I'm not very familiar with bearings, I'd like to know if thrust bearings refer strictly to sleeve type bearings or can refer to ball bearings? What does the standard refer to?

 

[Metalguy]

For electric motors, ball bearings are usually considered to be better than sleeve, although sleeves can be VERY good. But sleeves are suited for radial loads, not thrust (axial). A thrust bearing simple means it takes the axial loads of a shaft. Sleeves aren't usually used for vertical-shaft motors.

A plain "ball bearing" is usually a "Conrad" or deep-groove type, and can take loads in both directions, but load can be higher in the radial direction.

 

[Metalguy]

Correction to my first messgae--meant to say the combo of axial and radial loads!

 

[GusD]

Hi Saut

Angular Contact ball bearings are the norm for vertical
installations.On large equipment, they may be used in tandem on Back to Back ,In series or any combo depending on the expected Axial Thrust forces.
As a rule, the 40 Deg Angular Contact Ball bearing is the most commom.I know of applications where they use a 2 bearing assembly,one bearing is a 40 Deg the other a 15 Deg.The reason for this arrangement,is because on a 2 bearing assembly,if they are both 40 Degs ,one bearing carries all the load the other very little causing it to fail.When one bearing was 40 Deg and the other 15 Deg ,they seem to share the load without problems to either bearing.

GusD

 

[Metalguy]

GusD,

Interesting point on the angles. But the "unloaded" bearing must be preloaded all the time, or the balls skid instead of rolling-regardless of the angle.

 

[GusD]

Hi Metalguy

What you said is true.The "unloaded condition" of the bearing is mitigated by the use of the 2 different angles of contact 40 and 15.The failures were very common when we used 2 -40 Deg ang.cont ball bearings.Somebody was thinking on this one.It does work.
Roller bearings are much more susceptable to skidding than ball bearings,but you are right,ball bearings also fail for the same reasons.
Thank you


GusD

 

[diamondjim]

Clearance in bearings are often desired
in many industrial applications. It reduces
turning torques and allows more discrepancy
or inaccuracies in mounting surfaces. If
a bearing is preloaded too high it will fail
early. Preloaded bearings are stiffer and
may require overheating in fast rpm bearings.

 

[gunnarhole]

Thread,

I'm not sure who invented the dual contact angle concept but the firt I heard about it was at a TAMU Pump User Symposium when an engineer from MRC gave a presentation about their new Pumpac bearings. MRC have since been integrated into SKF but I am sure that they have enough information on their website to satisfy any of you who are looking for more information.

Regards,

Gunnar