S-gears: From metal to polymer solution

Abstract

The paper addresses the gradual development of S-gears from a heavy industry start up to the present state with polymer gears. The curved and half symmetric path of contact implies a concave-convex contact in a vicinity of the meshing start (and end), higher reduced radii of curvature and improved lubrication conditions. Specimens of both gear geometries, which were made of tempered and nitrided alloyed steel, were tested on an FZG testing machine, and results confirmed the theoretical foundations of S-gears. Lastly, the rack profile is defined by a parabolic-type function, which in turn defines the path of contact and finally gears with arbitrary number of teeth. This concept is considered for polymer gears as well. A special testing machine was built to enable testing of small plastic involute (E-) and S-gears. Initial results combining gear pairs made of polyacetal and nylon confirm the theory of S-gears. Improved performance of S-gears, compared to E-gears, is based on the fact that S-gears exhibit a lower amount of sliding.