Continued from page 20


Figure 5. Energy efficiency measurement of components


Measuring the small torque losses in a single highly efficient small sized (6204) deep groove ball bearing is very challenging. Yamamoto (4) carried his measurements out on a pair of 6204 bearings to improve the sensing and separation of different greases tested. His initial results showed that after running-in there was no measurable difference in the friction torque of two greases with different fibre structures, but confirmed that the amount of thickener influences the churning losses, showing that the higher the thickener content, the less efficient the grease was. He also confirmed that by optimising the base type and viscosity, as well as thickener system and amount, improved, more energy efficient greases could be developed for deep groove ball bearings.


In many applications, tapered roller bearings are used. These have significantly more sliding contacts than in deep groove ball bearings. A pair of tapered roller bearings were run for 500 hours in an FE8 test under a 20 kN load at 750 rpm to simulate a commercial vehicle wheel bearing test. The friction torque and temperatures of the two bearings were monitored throughout the test and are reported in Figure 6. The results show that it takes more than 150 hours to reach steady state in this test. A second wheel bearing grease was tested and gave similar torques and temperatures.


Figure 6. Friction torque and bearing temperature in an FE8 tapered roller bearing test Continued on page 24


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LUBE MAGAZINE NO.129 OCTOBER 2015


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