Experimental and numerical investigation of the meshing cycle and contact ratio in spiral bevel gears

The load carrying capacity of spiral bevel gears is governed by the way load is distributed between meshing tooth pairs, which is highly dependent on the actual contact ratio as the gears mesh. Previous experimental studies have shown that the AGMA calculated contact ratio is substantially different from that found in practice, because of the shape and dimensions of the bearing pattern produced by the load transmitted between meshing gear teeth. Given the geometrical complexity of spiral bevel gear tooth profiles, a Tooth Contact Analysis computer program is used to determine the location of the path of contact, the dimensions of the bearing pattern under load and the associated contact ratio. The objectives of this paper are to experimentally and numerically study the relationships between the bearing pattern of selected spiral bevel gear sets and their load meshing cycles, to evaluate the actual contact ratio, and to calculate and compare the corresponding AGMA contact ratio to measurements and values calculated by a Loaded Tooth Contact Analysis computer program.