Analysis of Large-Scale Hybrid Aerospace Spur Gear Drivetrains

The hybrid gear concept, which combines a metallic outer rim of gear teeth with a composite web, has shown potential to reduce the weight of small-scale spur gears without negatively affecting vibration performance for low- and medium-speed applications. In this paper, the hybrid gear design and tooth microgeometry optimization technique that had been applied to small-scale spur gears was adapted for application to spur gears of aerospace-relevant scale, speed, and load. A single reduction drivetrain model was developed featuring large-scale hybrid spur gears, which was used to determine optimal tooth microgeometry modifications that minimized peak-to-peak transmission error. Static and dynamic transmission error analyses were then performed using the optimal microgeometries. Results were compared to those predicted for a similarly-optimized all-steel drivetrain. The application of optimal tooth microgeometries to large-scale hybrid gears led to a more significant decrease in a peak-to-peak transmission error than was observed for the small-scale gears. Similar to results for small-scale hybrid gears, the drivetrains featuring large-scale hybrid gears predicted similar dynamic transmission errors to their all-steel counterparts at low and medium speeds, while significantly different transmission errors were predicted at high speeds.