Static tooth load

Machine Design

Gear Drive

Static tooth load

Introduction:

The static tooth load (also called beam strength or endurance strength of the tooth) is obtained by Lewis formula by substituting flexural endurance limit or elastic limit stress (σ_e) in place of permissible working stress (σ_w).

Static Tooth Load

∴ Static tooth load or beam strength of the tooth,

W_S = σ_e.b.p_c.y = σ_e.b.π m.y

Values of flexural endurance limit

For safety, against tooth breakage, the static tooth load (W_S) should be greater than the dynamic load (W_D). Buckingham suggests the following relationship between W_S and W_D.

For steady loads,

WS ≥ 1.25 WD
For pulsating loads,

WS ≥ 1.35 WD
For shock loads,

WS ≥ 1.5 WD

Note : For steel, the flexural endurance limit (σe) may be obtained by using the following relation :

σ_e = 1.75 × B.H.N. (in MPa)