Determination of Maximum Loads for Drive Train Components in Thrusters Using Flexible Multibody-System Models

The usage of modern thrusters allows to combine the functions of the drive and the ship rudder in one assembly, which are separated in conventional ship propulsions. The horizontally oriented propeller is supported in a vertically rotatable nacelle, which is mounted underneath the ship hull. The propeller can directly or indirectly driven by an electric motor or combustion engine. The direct drive requires the installation of a low speed electric motor in the nacelle. The present paper concentrates on indirect drives where the driving torque is transferred by bevel gear stages and shafts from the ship to the propeller. Due to the closed and inaccessible construction high demands on the reliability have to be achieved. Especially for the design of the highly loaded bevel gear stages accurate information to the occurring loads are required. The available experience to the operation of thrusters show, that primarily rarely occurring special load cases must be considered in the design process. Such operational conditions can only be determined by expensive long-term measurements. By means of a detailed multibody system simulation model of the thruster it is already possible to develop a basic knowledge to the dynamic properties of the drive train and to determine design loads for drivetrain components.