Static shear strength calculation of plastic helical gears mating with steel worm

The mesh mechanism shows the different characteristics of worm and helical gear compared to other kind of gear pairs. A new calculation method is proposed in this paper. With two sorts of design parameters of worms and gears, and two kinds of plastic material, the shear torque of gears were experimentally obtained with a fixture. Compared with the actual test results, the proposed theoretical calculation results only have less than 4% deviation, which were more accurate than the number calculated with DuPont's method.