Home Page

Dynamic factors— Kv & Cv 
 These relate to speed and gear errors which lead to dynamic loading. As pitch-line velocity increases, the dynamic load increment increases linearly. However, the dynamic effects of tooth errors is much more complex. Tooth-to-tooth errors, which arise in a variety of forms, have a different dynamic effect than runout errors. Also, elastic tooth deflections cause apparent errors.

Life factors — KL & CL 
 These factors are primarily intended to take into account performance of gears the life of which can
be finite.

Factors of safety — KR & CR 
 Although factors of safety are old in engineering practice, in this case they identify the degree of reliability sought in a clear fashion.

Temperature factors — KT & CT 
 These factors modify the design in accordance with adverse temperature effects on lubricant performance. Usually this factor does not become significant until temperature exceeds 200’F.

Surface factors—CPCH& CP 
 The three durability factors, C,, C & C for surface condition, hardness ratio and elastic coefficient rates the resistance of the gear-tooth surface to wear.

Size factors — KS& CS 
These reflect the non-uniformity of material characteristics, such as hardness, and the dimensional parameters of the gear. The latter include: diameter, face width, tooth size and ratio of case depth to tooth size.

Geometry factors — J & I 
These relate to the tooth proportions, primarily concerning radii of curvature and parameters controlling load sharing. They are somewhat akin the Lewis Y factors. For standard tooth
proportions, these have fixed values.

Allowable stress — Sat & Sac 
 This is the rated stress value of the material as specified by the manufacturer or standards, or obtained from material testing. This value takes into account cyclic stressing and is the nominal endurance stress rating of the material.

Numerical values of factors — Specific factor values are available from AGMA publications, or duplicated extracted information. Procedures for determining these factors are given in the AGMA literature. When conditions are such that a given factor is unimportant or insufficient information
exists for its adequate evaluation it is usually safe to equate the factor to unity. In most cases, this results in a conservative or mid-value rating.

Evaluations of equations — The above information constitutes an outline of the procedures offered by AGMA for determining strength and durability ratings. As an outline it cannot include detail;and to apply the procedures the reader should refer to the references.

Additional design equations — The AGMA beam strength and durability equations have been custom modified and refined by a number of gear designers and manufacturers, creating a variety of design techniques and equations. Often this may be proprietary information, but will be available for specific use with customers’ needs. In addition, there are a host of varied design equations used by

                                   T90      Prev Page