In the formulation of Lewis equation for toothed gearing, the load W_T acts on:

Concept:

In the Lewis analysis, the gear tooth is treated as a cantilever beam. The tangential component (WT) causes the bending moment about the base of the tooth.

The Lewis equation is based on the following assumptions:

1. The effect of the radial component (Wr), which induces compressive stresses, is neglected.
2. It is assumed that the tangential component (WT) is uniformly distributed over the face width of the gear. This is possible when the gears are rigid and accurately machined.
3. The effect of stress concentration is neglected.
4. It is assumed that at any time, only one pair of teeth is in contact and takes the total load.