Accession Number : ADA290503

Title :   Dynamics of a Split Torque Helicopter Transmission.

Descriptive Note : Technical memo.,

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

Personal Author(s) : Krantz, Timothy L.

PDF Url : ADA290503

Report Date : JUN 1994

Pagination or Media Count : 69

Abstract : Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.

Descriptors :   *TORQUE, *TRANSMISSIONS(MECHANICAL), MATHEMATICAL MODELS, FREQUENCY, SIMULATION, POSITION(LOCATION), OPTIMIZATION, MANUFACTURING, MODELS, DYNAMICS, MATRICES(MATHEMATICS), STIFFNESS, PATHS, MESH, TIME, VARIATIONS, TRANSMITTANCE, SHARING, HELICOPTERS, COEFFICIENTS, SYMMETRY, ERRORS, BALANCE, GEOMETRY, INDEXES, POWER, SHAFTS(MACHINE ELEMENTS), SIDEBANDS, SPLITTING, EQUATIONS, ROTORS, FRICTION, GEARS, HELIXES, LAGRANGIAN FUNCTIONS, TEETH, GEAR TEETH.

Subject Categories : Helicopters
      Jet and Gas Turbine Engines

Distribution Statement : APPROVED FOR PUBLIC RELEASE