S_c =< S_ac C_LC_{H                                                                            (61)}
              C_RC_T
Definition of terms in the above equations is given in Table 1.22.
Tooth strength, equation 58, is essentially a modification of the Lewis formula. The extent of depar-
ture and tie improved accommodation to actual performance is dependent upon the coefficients asso-
ciated with each term
The surface durability equation is related to the well established Hertzian contact-stress formula.
Again, coefficients in the above equations are intended to relate the theory more closely to actual gear-tooth behavior.
The meaning of the coefficients in the above equations are as follows:

Load distribution factors — C_m&K_m 
These factors concern phenomena that cause non-uniform load distribution across the gear width:
profile errors, eccentricity of mounting, non-parallelism of shafts and defiections and distortions.
The effect of these errors is to cause a load concentration.