Study of Loading in Point-involute Gears

Abstract

The main limiting factor in high-speed aviation gear systems is contact strength. There are two main ways for reducing contact stresses in gears with involute tooth profile: 1) by using a standard basic rack profile with increased pressure angle; 2) by using a non-standard basic rack profile i.e. increasing the overlap ratio. However, contact stresses can also by reduced by implementing point gearing; Novikov's gears in which the relative radius of curvature is much more larger than it is in involute gears. On the basis of an involute and Novikov's gears, an point-involute gear was created which has a mixed engagement. An attempt was made to apply this design in the spur gear of the central gear box of gas turbine engines. But due to the point nature of the tooth profile, the limiting factor for the gear becomes its bending strength. Hence there was a necessity to conduct comparative tests with the usual spur gear of the central gas turbine engine gear box. A pulsator test bed was created for these tests and comparative tests were carried out.