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9.2 Bevel Gear Tooth Proportions

Bevel gear teeth are proportioned in accordance with the standard system of tooth proportions used for spur gears. However, the pressure angle of all standard design bevel gears is limited to 200. Pinions with a small number of teeth are enlarged automatically when the design follows the Gleason system.
        Since bevel-tooth elements are tapered, tooth dimensions and pitch diameter are referenced to the outer end (heel). Since the narrow end of the teeth (toe) vanishes at the pitch apex (center of reference generating sphere) there is a practical limit to the length (face) of a bevel gear. The geometry and identification of bevel gear parts is given in Figure 1.45.

9.3 Velocity Ratio

The velocity ratio can be derived from the ratio of several parameters:

          velocity ratio = Z = N₁ = D₁   =   sin g₁                                                  (44)
                                                   N₂       D₂        sin g₂

where:

        g = pitch angle (Figure 1.45)

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