Allowable Exciting Force or Moment of Diesel Main Engine

In my previous paper, the estimation of the natural frequencies of hull has been made with the intention of avoiding the resonance with the service rpm of main engine. However, as a Diesel engine is practically selected from the existing types, it is occasionally impossible to keep clear of any resonance.In this paper, allowable exciting force or moment at resonant point is investigated in the case where the acceleration due to hull vibration is restricted to a limitted value.The procedure is as follows, 1) Allowable acceleration in accommodation (a) to be determined principally from a view-point of human sensibility.2) The force at the ship's end causing the acceleration a (Fe) to be estimated.3) The force at the ship's end of the primary order due to the production errors etc. of propeller and engine (Fp) to be deduced from the analyses of measured data.4) The allowable force at the ship's end of main engine derived as the difference of Fe and Fp to be transformed to the force or moment at the position of main engine.Allowable exciting force or moment can be considered to be approximately proportional to L2 and L3 respectively.