Churning losses contribute significantly, both to overall inefficiency and
to oil heating, in many dip-lubricated transmission systems, notably in aut
omotive applications. For this reason, a reasonably accurate estimate of ch
urning loss is often desirable at the design stage. However, the published
literature contains several empirical calculation methods that give widely
different results, even within the claimed range of accuracy. For example,
a single 72-tooth, 3 mm module spur gear rotating at 4500 r/min immersed in
20W50 motor oil to a depth of 54 mm would be predicted to exert a churning
torque of 75 N m by the method of Boness but less than 5 Nm by the method
of Terekhov. In order to resolve the discrepancy, churning torques have bee
n measured on a range of meshed and single spur gears with different speeds
, lubricants and temperatures. Results are compared with the predictions fr
om various literature sources.