The efficiency and friction of plastic cylindrical gears Part 2: Influence of tooth geometry

Abstract In Part 1 the influences of materials and material combinations on the efficiency of plastic gears were investigated. In this paper, the effect of changes to plastic gear tooth geometry is investigated. Using a gear tooth form of standard proportions as the benchmark gear, gears were moulded to a number of different specifications. These changes in geometry included speed ratio, module, pressure angle, addendum, integer contact ratios and tip relief. Sensitivity to centre distance variations was investigated on the benchmark geometry. A helical gear was also tested for comparison with a spur gear of comparable specification. Using measured efficiencies, coefficients of friction were determined for a number of the gear geometries examined.