Robert C. Bill

Multi-Plate Dry Clutch Design and Analysis for Dual Speed Rotorcraft Applications

This paper describes the analysis and minimum weight design of a multi-disk clutch system for application in a two-speed rotorcraft transmission. The analysis and design method presented account for component stress limits and thermal requirements for a specified shift profile. The stress analysis is based on idealized structural models with closed-form stress field approximations for each clutch component including; centrifugal stress, torque and bending stress, axial clutch engagement loads and clutch disk thermal stresses. The clutch disk temperature rise and power dissipation are evaluated using a constant load torque clutch engagement model. The results show that the carbon-carbon clutch achieves significant weight savings compared with an equivalent steel clutch due to its higher allowable clutch temperature rise. The design procedure presented in this paper offers a rapid approach for overall sizing of multi-disk clutch systems.

Analysis of Pericyclic Mechanical Transmission with Straight Bevel Gears

A design methodology for a Pericyclic mechanical transmission utilizing straight bevel gears has been presented. By virtue of its very high reduction ratio in a single meshing stage, the pericyclic transmission holds promise for significant transmission weight reduction compared to state-of-the-art concepts. Assembly, gear geometry and kinematics of the drivetrain leading to a high reduction ratio while having a very high contact ratio (~8-10 teeth in contact) has been discussed. Tooth contact behavior has been studied in detail. A load distribution model has been developed that can be easily generalized to any internal-external bevel gear mesh. A rolling/ sliding velocity analysis has also been carried out, taking nutational motion into account. This is further used to determine the elastohydrodynamic lubrication characteristics of the meshing gear pairs. The methodology was applied to a conceptual design, resulting in acceptable levels of predicted contact stress and transmission efficiency.