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Assessment of Lubrication Conditions in a Big End
It's where this chart can be obtained.
Whole bunch of test oils, and big end bearing equipped with thermocouples, operated at different loads and RPM.
14 test oils across the board, interestingly including including 4 Newtonian oils with no VII...
5W20 synthetic
15W30 High VI GrIII
15W20 and SAE50 solvernt refined (GrI)
Table III shows the temperature rises in the big end bearings for different viscosities at different RPM...will show the Newtonians here for e.g. The 80C sump temps are shown, but they are also at 125, and 150C in the document...the chart I use above shows the general trend anyway.
Code:
RPM 5W20 10W30 15W40 15W50 SAE50
2,000 7C 10C 12C 14C 17C
3,000 14C 19C 25C 20C 27C
4,000 20C 30C 37C 30C 40C
5,000 31C 37C 52C 42C 54C
Quote:
IV-2 Influence of Operating Conditions on Big-End bearing temoerature
Figure 6 (the one that I use) shows the variation of the bearing temperature versus speed and load at different sump temperatures. As expected, speed is an important parameter. The temperature increase induced by the load is maximum at low speed, but rarely exceeds 10C. At 5,000RPM the variation of temperatures with load is only 3 or 4C, except when a sharp peak of temperature occurs (*)
.
.
.However, it is well known that bearing failures occur mostly at both high speed and high load. This means that under boundary lubricating conditions, small variations in load and/or temperature can have dramatic consequences.
(*) subsequently explains this as the onset of metal/metal.
Quote:
IV-4 Bearing Temperature Rise
The absolute value of bearing temperature is imprtant in connection with bearing failure.
But the increase of oil temperature in the bearing provides information on the energy dissipated in the bearing by viscous heating or metal to metal contact.
Quote:
IX - Summary
1) results for big-end beaings seem to correlate with results for main bearings, which are much easier to evealuate.
2) under hydrodynamic conditions it is possible to derive an effective viscosity from temperature measurements.
.
.
.
4) the viscosity limit for safe operation of a bearing depends on the bearing surface conditions, operating conditions and additive package. With a worn bearing, failure can occur even with an SAE50 oil.
5) comparison of the results of the present work with other published data suggests that for current values of viscosity index, occurences of bearing problems is not certain, but possible for some SAE20 oils as defined by their high shear rate viscosity or better by their effective viscosity.
Assessment of Lubrication Conditions in a Big End
It's where this chart can be obtained.
Whole bunch of test oils, and big end bearing equipped with thermocouples, operated at different loads and RPM.
14 test oils across the board, interestingly including including 4 Newtonian oils with no VII...
5W20 synthetic
15W30 High VI GrIII
15W20 and SAE50 solvernt refined (GrI)
Table III shows the temperature rises in the big end bearings for different viscosities at different RPM...will show the Newtonians here for e.g. The 80C sump temps are shown, but they are also at 125, and 150C in the document...the chart I use above shows the general trend anyway.
Code:
RPM 5W20 10W30 15W40 15W50 SAE50
2,000 7C 10C 12C 14C 17C
3,000 14C 19C 25C 20C 27C
4,000 20C 30C 37C 30C 40C
5,000 31C 37C 52C 42C 54C
Quote:
IV-2 Influence of Operating Conditions on Big-End bearing temoerature
Figure 6 (the one that I use) shows the variation of the bearing temperature versus speed and load at different sump temperatures. As expected, speed is an important parameter. The temperature increase induced by the load is maximum at low speed, but rarely exceeds 10C. At 5,000RPM the variation of temperatures with load is only 3 or 4C, except when a sharp peak of temperature occurs (*)
.
.
.However, it is well known that bearing failures occur mostly at both high speed and high load. This means that under boundary lubricating conditions, small variations in load and/or temperature can have dramatic consequences.
(*) subsequently explains this as the onset of metal/metal.
Quote:
IV-4 Bearing Temperature Rise
The absolute value of bearing temperature is imprtant in connection with bearing failure.
But the increase of oil temperature in the bearing provides information on the energy dissipated in the bearing by viscous heating or metal to metal contact.
Quote:
IX - Summary
1) results for big-end beaings seem to correlate with results for main bearings, which are much easier to evealuate.
2) under hydrodynamic conditions it is possible to derive an effective viscosity from temperature measurements.
.
.
.
4) the viscosity limit for safe operation of a bearing depends on the bearing surface conditions, operating conditions and additive package. With a worn bearing, failure can occur even with an SAE50 oil.
5) comparison of the results of the present work with other published data suggests that for current values of viscosity index, occurences of bearing problems is not certain, but possible for some SAE20 oils as defined by their high shear rate viscosity or better by their effective viscosity.
