Spur gears with contact ratio less than unity

The objective of this research is to evaluate the design of a pair of spur gears and another analogous pair with a contact ratio of less than unity. Considering two pairs of normalized gears with equal diametral pitches and pressure angles, as well as equal pitch radii in their driving gears and equal pitch radii in their driven gears. For the first pair of gears with normalized tooth numbers, the contact ratio greater than unity es obtained. For the second pair of gears, the number of teeth is proportionally reduced, consequently obtaining a contact ratio of less than one. For both pairs, the maximum von Mises stresses are obtained using the finite element method. The pairs are compared qualitatively and quantitatively. This work contributes with novel elements of judgment for a better decision making of the industrialists interested in reducing the problems of normalized spur gears such as noise, abrasive wear, adhesive wear, temperature, and efforts induced by the overlapping relationship between coupled teeth; proposing them a practical solution that will open new avenues of research.