Experimental Characterization of a Pericyclic Mechanical Transmission
Open Access
- Author:
- Mc Govern, Jeremy
- Graduate Program:
- Aerospace Engineering (MS)
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 16, 2024
- Committee Members:
- Edward Smith, Thesis Advisor/Co-Advisor
Robert Charles Bill, Special Signatory
Amy Pritchett, Program Head/Chair
Hans DeSmidt, Special Signatory
David K Hall, Committee Member
Jose Palacios, Committee Member - Keywords:
- Rotorcraft
Drive System
Vibrations - Abstract:
- From its conception in 1970’s, the nutating, now pericyclic, mechanical transmission has undergone several years of rigorous analysis to address common drivetrain considerations of noise, maintenance, and power density. These analytical studies have led to the fabrication of a 50 HP 32:1 reduction ratio prototype. The objective of this thesis is to perform a series of high-speed tests on the prototype, beginning with its assembly and static testing procedure. High-speed experiments of the prototype first require static testing to verify the transmission’s functionality. Slow-roll testing was used to analyze contact pattern development and load sharing behavior. Favorable contact patterns across the meshes confirmed preliminary calculations of backlash and apex point tolerances. Equivalent strain readings across both pericyclic gear sets validated housing installation procedures and the system’s load sharing capability. Successful results from static testing verified the prototype’s assembly procedure. The prototype’s integration into the high-speed test stand required fabrication of mounting and shaft coupling components. An auxiliary lubrication system was also assembled to supply the test article with a circulating bath of oil. Thermocouples monitored input and output shaft bearing temperatures through fixtures in the housing. 3-axis accelerometers were embedded into the shaft support blocks to capture the transmission’s dynamic behavior. Finally, the strain gauges used in static testing captured load sharing data. This thesis concludes with a characterization of the prototype through high-speed testing data. Power transmission data validated the pericyclic reduction ratio model. Accelerometer data demonstrated the transmission’s capability to operate at low vibration, with peak amplitudes of 1.2 and 2.5 inches per second on the pericyclic gear train and output shaft respectively. Acoustic emission data captured the first 5 harmonics of the shaft speed and gear mesh frequencies. The thermal profile showed the shaft bearings remained below 180 °F throughout testing, implying safe operating conditions. Finally, strain and vibration data showed the pericyclic gear train maintained load sharing throughout the entire operating envelope, further validating static testing and assembly procedures. The results of the experiments demonstrate the technological readiness of pericyclic mechanical transmissions.