Question

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An electric motor is to be supported by four identical mounts. Each mount can be treated as a linear prevent problems due required that the amplitude of motion should not exceed 0.1 mm per 1 N of unbalance force. The mass of the motor is 120 kg and the operating speed is 720 rpm Use the concept of transfer function to determine the required stiffhess coefficient of each mount.

Answer 1

Given W = 720 rpm = 2pi times 720/60 = 75.4 rad/s Let stiffness of each mouting be k So, For four parallel mouting stiffness = 4k Amplitude(A) = F/Squareroot(Ke - mw^2)^2 + (cw)^2 For negligible damping c = 0 A/F = 1/k_e - mw^2 \r\n A/F = 1/k_e - mw^2 [This is the transfer function where A/F = 0.1 mm/1N] 0.1 times 10^-3 = 1/4k - 120(75.4)^2 4k - 682219.2 = 10, 000 k = 173054.8 N/m = 173.05 N/mm