Modified experimental procedure to determine the output variable in an optimum range – A case study: Pulley belt experiment

Abstract

The pulley-belt experiment for determining coefficient of friction (μ) between belt and pulley surface is a standard experiment in engineering mechanics laboratory of undergraduate engineering programs (freshman year). It is used as a measure to establish the relation between the loads applied, angle of lap (θ) and coefficient of friction between the contact surfaces of pulley and belt. The value of coefficient of friction is calculated from friction equation by using measured load ratios and angle of lap. However, the value of coefficient of friction shows significant variation as angle of lap varies from one extreme to another, as this variation leads to a deviation from the theoretical model of the experiment. This further compromises the quality of the output, i.e. coefficient of friction, in addition to its inability to be experimentally measured. Also, no quantitative measure is available to validate the results of the experiment on the basis of measurable variables, which if present could serve as an indirect measure to check the quality of the output (μ). In the present work, parameters are identified to validate the experimental results based on the measurable variables of the experiment, i.e. load ratios and angle of lap. These parameters, i.e. difference in standard deviation of μ, load ratios for forward and reverse loading, help to determine a range for angle of lap, for which this experimental setup shall yield results which are closest to the theoretical framework of the same, giving a quantitative measure to validate the results.