me445_hw4 - is transmitted to the ground when the fan is...

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ME 445 Mechanical Vibrations // Fall 2009 Homework #4 Due: 19.11.2009 1. Consider the effect of variable mass on an aircraft landing suspension system by modeling the landing gear as a moving base problem as shown. The mass of a regional jet is 13,236 kg empty and its maximum takeoff mass is 21,523 kg. Compare the maximum deflection for a wheel motion of magnitude 0.50 m and frequency of 35 rad/s, for these two different masses. Take the damping ratio to be 1 . 0 = ζ and the stiffness to be 4.22 x 10 6 N/m. 2. A fan of 45 kg has an unbalance that creates a harmonic force. A spring-damper system is designed to minimize the force transmitted to the base of the fan. A damper is used having a damping ratio of 2 . 0 = . Calculate the required spring stiffness so that only 10% of the force
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Unformatted text preview: is transmitted to the ground when the fan is running at 10,000 rpm. 3. (p. 3.28) An electric motor of mass 68 kg is mounted on an isolator block of mass 1200 kg and the natural frequency of the total assembly is 160 cpm with a damping factor of ζ =0.1 (see below). If there is an unbalance in the motor that results in a harmonic force of F=100 sin 31.4t, determine the amplitude of vibration of the block and the force transmitted to the floor. 4. (p. 3.29) A sensitive instrument with mass 113 kg is to be installed at a location where the acceleration is 15.24 cm/s2 at a frequency of 20 Hz. It is proposed to mount the instrument on a rubber pad with the following properties: k=2802 N/cm and ζ =0.10. What acceleration is transmitted to the instrument?...
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