Accession Number : ADA303657

Title :   Vibration Analysis of a Split Path Gearbox.

Descriptive Note : Technical memo.,

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

Personal Author(s) : Krantz, Timothy L. ; Rashidi, Majid

PDF Url : ADA303657

Report Date : MAY 1995

Pagination or Media Count : 16

Abstract : Split path gearboxes can be attractive alternatives to the common planetary designs for rotorcraft, but because they have seen little use, they are relatively high risk designs. To help reduce the risk of fielding a rotorcraft with a split path gearbox, the vibration and dynamic characteristics of such a gearbox were studied. A mathematical model was developed by using the Lagrangian method, and it was applied to study the effect of three design variables on the natural frequencies and vibration energy of the gearbox. The first design variable, shaft angle, had little influence on the natural frequencies. The second variable, mesh phasing, had a strong effect on the levels of vibration energy, with phase angles of 0 deg and 180 deg producing low vibration levels. The third design variable, the stiffness of the shafts connecting the spur gears to the helical pinions, strongly influenced the natural frequencies of some of the vibration modes, including two of the dominant modes. We found that, to achieve the lowest level of vibration energy, the natural frequencies of these two dominant modes should be less than those of the main excitation sources. (AN)

Descriptors :   *VIBRATION, *TRANSMISSIONS(MECHANICAL), MATHEMATICAL MODELS, LOAD DISTRIBUTION, PARAMETRIC ANALYSIS, EQUATIONS OF MOTION, DYNAMIC RESPONSE, STIFFNESS, HELICOPTER ROTORS, RESONANT FREQUENCY, SHAFTS(MACHINE ELEMENTS), BEARINGS, DESIGN CRITERIA, TIME DOMAIN, FREQUENCY DOMAIN, TRANSMISSION GEARS, TORQUE, TORSION, RUNGE KUTTA METHOD, LAGRANGIAN FUNCTIONS.

Subject Categories : Mechanics
      Helicopters

Distribution Statement : APPROVED FOR PUBLIC RELEASE