Design and Development of a Free Planet Transmission

This paper presents a brief description of an advanced technology power transmission arrangement designated as "free planet transmission", and a summary of results obtained from testing two prototype free planetary transmission modules. This new transmission can be generally classified as a quasi compound planetary containing such major elements as a sun gear, planet spindle assemblies, ring gears and rolling rings. All internal gear forces are balanced between the free-floating planet subassemblies and cylindrical support rings. Since the planet spindles are not restrained, the conventional planet carriers (spiders) are not required. The elimination of this component and the associated planet bearings has numerous favorable Implications on such parameters as weight, reliability, cost, and survivability. The work accomplished to date, including endurance testing of two 500-HP 20:1 reduction ratio transmissions, indicates that the concept is stable, that it has high mechanical efficiency and excellent load distribution, and that significant potential advantages and benefits might be obtained by its use.