If the electric motor of Problem 3.74 is to be mounted at the free end of a steel cantilever beam of length \(5 \mathrm{~m}\) (Fig. 3.65), and the amplitude of vibration is to be limited to \(0.5 \mathrm{~cm}\), find the necessary cross-sectional dimensions of the beam. Include the weight of the beam in the computations.

Data From Problem 3.74:-

A fixed-fixed steel beam, of length \(5 \mathrm{~m}\), width \(0.5 \mathrm{~m}\), and thickness \(0.1 \mathrm{~m}\), carries an electric motor of mass \(75 \mathrm{~kg}\) and speed \(1200 \mathrm{rpm}\) at its mid-span, as shown in Fig. 3.64. A rotating force of magnitude \(F_{0}=5000 \mathrm{~N}\) is developed due to the unbalance in the rotor of the motor. Find the amplitude of steady-state vibrations by disregarding the mass of the beam. What will be the amplitude if the mass of the beam is considered?

Transcribed Image Text:

wot Fo FIGURE 3.65 Unbalance in the motor supported on cantilever beam.