In this work, a profile modification technique was used in design of a spur gear. In this technique, the tooth-sum is varied to obtain the desired contact ratio and low contact stress for a specified center distance. A program has been developed using C language to compute the contact stresses by varying the amount of profile shift for a tooth-sum of 100 teeth ( §4%). The selected tooth-sum of 96, 100, and 104 gears was subjected to cyclic loading using a back-to-back test rig. The morphology of the damaged gear tooth surface after cyclic loading was examined by scanning electron microscopy. The morphological investigation reveals that the degree of damage observed in negative number of teeth alterations is less compared to standard and positive alteration tooth-sum due to lower contact stress.

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The effects of sliding velocity in a spur gear for a tooth sum of 100 (altered by ±4%) with constant centre distance have been studied. The product of contact stress and sliding velocity (σ Vs) factor is calculated for varied profile shift. The effect of Hertzian compression, bending and shear deflection on sliding velocity at points along length of the path of contact has been computed. The scanning electron micrographs at pitch point C show that negative alteration in tooth‐sum gears is better compared with standard and positive alterations in tooth sum. Copyright © 2016 John Wiley & Sons, Ltd.

Asymmetric gears have evolved from the rising demand for power transmission drives with high load-carrying capacity, surface durability, and service life. Direct design and S± profile shifted system are the most common approaches used for enhancing design features by geometry modification in asymmetric gears. This paper aims at establishing asymmetric gear geometry modification using tooth sum alteration for a family of gears running on a specified center distance as a feasible design approach. A complete mathematical treatment of the design approach is provided, and an in-house developed computer program is used for numerical simulation. The paper explores the influence of dynamic load factors, location factors for bending, specific sliding on load-bearing capacity, and surface durability on different tooth sum alterations. The study concludes that tooth sum altered asymmetric gear geometry can be employed as an effective design technique that offers designers flexibility in designing gears for surface wear, load-bearing, and tooth life.

Contact stress between the gear teeth in mesh determines the ability of the gear to transmit the power safely. In improving the contact strength of gear teeth, profile shift is found to be the best option beyond the use of high strength materials and surface treatment techniques. This paper discusses an alternate yet simple method of improving contact strength by the way of altering the tooth-sum. Altering the tooth-sum working between a specified center distances for a given module changes the operating pressure angle and hence necessitates profile shift. Using this profile shift gears can be designed to advantage. Few cases are considered for the purpose of discussion for clear understanding of the presentation. Large volume of monographs are developed which the practicing engineers can use.