Paper 4: Measurement of Oil Film Thickness between Rolling Discs Using a Variable Reluctance Technique

Abstract

A variable magnetic reluctance technique has been developed and used to measure the thickness of oil films between smooth rolling discs under various conditions of load, speed, and temperature using two different lubricants. In repeating the experimental conditions of other workers who measured the capacitance of oil films between discs, good correlation is demonstrated between the results of capacitance and reluctance measurements. Since it is unlikely that the two methods suffer from the same uncertainties this correlation can be considered as a recommendation to future users of either method. The main predictions of the Dowson and Higginson theory are verified by the experimental results, apart from a discrepancy in the dependence of h0 upon the dimensionless parameter U0·7 when thick films are developed. In this region observations are qualitatively more in keeping with the thermal theory of Cheng An application of the reluctance technique to the measurements of oil film thickness in gearing is proposed.