What is transmissibility?

Transmissibility T is the ratio of transmitted to exciting force. T less than 1 means isolation occurs. For undamped systems T=1/(r squared minus 1) where r=f/fn.

How to determine unbalance force?

F = mu times e times omega squared, where mu times e is unbalance in kg m and omega is angular velocity in rad/s.

What transmissibility to target?

T=0.10 (90 percent) for general machinery, T=0.05 (95 percent) for sensitive equipment, T=0.20 (80 percent) for non-critical.

Why force increases at resonance?

At resonance r approximately 1, amplification equals 1/(2 zeta). Damping limits peak but reduces high-frequency isolation.

How to handle uneven weight distribution?

Distribute mount stiffness proportionally to CG location using the lever rule for asymmetric machines.

Free Engineering Tool #067

Machine Vibration Isolation Calculator

Complete isolation design. Enter machine mass, speed, unbalance force, number of mounts, and target transmissibility.

TransmissibilityForce IsolationAuto-Calc

Results

Transmitted Force

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Total Stiffness

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Per Mount

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Natural Frequency

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Static Deflection

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Freq Ratio r

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Transmissibility (undamped)

Required Natural Frequency

Stiffness and Deflection

Transmitted Force

Example – Pump 800 kg at 1500 RPM

Given: m=800 kg, 1500 RPM (25 Hz), F0=500 N, T=0.10, 4 mounts

r = sqrt(1/0.10 + 1) = 3.317, fn = 25/3.317 = 7.54 Hz

k = 800 x (2pi x 7.54)^2 = 1795 kN/m = 449 N/mm per mount

delta = 4.37 mm, Ftrans = 50 N

Machine passes through resonance during startup. Ensure adequate mount damping for transient amplification.

Machine Vibration Isolation Calculator | Free Tool #067

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

Transmissibility (undamped)

Required Natural Frequency

Stiffness and Deflection

Transmitted Force