Accession Number : ADA318693

Title :   Effects of Planetary Gear Ratio on Mean Service Life.

Descriptive Note : Technical memo.,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Savage, M. ; Rubadeux, K. L. ; Coe, H. H.

PDF Url : ADA318693

Report Date : JUL 1996

Pagination or Media Count : 9

Abstract : Planetary gear transmissions are compact, high-power speed reductions which use parallel load paths. The range of possible reduction ratios is bounded from below and above by limits on the relative size of the planet gears. For a single plane transmission, the planet gear has no size at a ratio of two. As the ratio increases, so does the size of the planets relative to the sizes of the sun and ring. Which ratio is best for a planetary reduction can be resolved by studying a series of optimal designs. In this series, each design is obtained by maximizing the service life for a planetary with a fixed size, gear ratio, input speed power and materials. The planetary gear reduction service life is modeled as a function of the two-parameter Weibull distributed service lives of the bearings and gears in the reduction. Planet bearing life strongly influences the optimal reduction lives which point to an optimal planetary reduction ratio in the neighborhood of four to five.

Descriptors :   *PLANETARY GEARS, *TRANSMISSIONS(MECHANICAL), LOAD DISTRIBUTION, OPTIMIZATION, LIFE EXPECTANCY(SERVICE LIFE), COMPUTER AIDED DESIGN, TRANSMISSION GEARS, TORQUE, BENDING STRESS, GEAR TEETH.

Subject Categories : Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE