Problem 11: Dynamic Analysis for Vibration of an Unbalanced Mass


A 65 Kg industrial sewing machine has a rotating unbalanced mass of 0.15 Kg-m. The machine operates at 125 Hz and is mounted on a foundation of equivalent stiffness 2x106 N/m and damping ratio 0.12. What is the machine's steady state amplitude?

Figure 1.

Entities Validated

  • Rigid body
  • Revolute joint
  • Translational joint
  • Force_Spring damper – translational

Type of Analysis

  • Dynamic


Schaum’s Outline of, Theory and Problem of Mechanical Vibrations, First Edition by S Graham Kelly: 82 (ISBN 0-07-034041-2)

Model Files

  • rotating_unbalance_mass.mdl - MotionView Model
  • rotating_unbalance_mass.xml - MotionSolve Deck

Graphical Results

Figure 2.

Result Comparison

Output Analytical MotionSolve % Error
Steady state amplitude of machine (mm) 2.43 2.43 0 %


MotionSolve results compare well with analytical results.