Technical > Torque

There are two basic kinds of torque: Starting torque and Running torque. Starting torque comprises of two main elements which need to be overcome before rotation occurs:
(1) Metal to metal contact between Raceways and Balls, and
(2) Lubricant shearing
Running torque is comprised of retainer drag (on both rings and balls) and lubricant churning caused by couplings between balls and retainer, and retainer and raceways.
Torque has a direct effect upon the following: temperature generation, speed variation, power consumption (at start-up and during running), and also power consumption variations caused by unstable rotation, etc.
• Temperature Generation
The primary cause of temperature generation in ball bearings is due to churning from several lubricant couplings. Churning type lubricants cause temperature generation because of the shearing effect. Countermeasures for this problem are to reduce the lubricant quantity or to change to a channeling type of lubricant.
• Failure to Reach Speed
Sometimes motors cannot reach the designed nominal speed because of problems caused by:
(1) Excessive grease quantity, or
(2) Selection of a soft churning type of lubricant
• Excessive Power Consumption
The reasons for this are the same as "Failure to Reach Speed" above. Lubricants with high Worked Penetration can also add to the problem.
• Excessive Reach Running Current
The high running current of the motors during operation is considered due to:
(1) Grease Quantity
(2) Worked Penetration of lubricant
(3) Softness level of a churning type of lubricant
• Speed Fluctuations
this is caused by grease "slumping" into the pathway of the ball. The solutions to this problem are:
(1) Reduce grease quantity
(2) Use a channeling type grease
(3) Use a much softer type of churning grease
• Relationship between Speed and Running Torque
Torque increases with speed.
• Relationship Between Grease Quantity and Running Torque
Generally, if the lubricant quantity is increased, the running torque is increased.
• Relationship Between Temperature and Running Torque
Generally, as temperature decreases, Bearing Torque increases.