Adjust the bubble level so that it is centered when the cradle is empty.
Step 2. Measure and record the calibration bar's diameter and length. Weigh and record the weight of the calibration bar.
Using the formula given in the mathematical solution section, calculate and record the calibration bar's moment of inertia.
Step 3. Place the calibration bar in the cradle as shown in the picture at left. Adjust the position of the bar so that the the bubble level returns to reading level, indicating that the calibration bar is centered on the cradle.
Step 4. Twist the pendulum and calibration bar, slightly (15-20 degrees or so), and release, to produce an oscillation. At a conveniently determined point in the swing, begin timing with a stop watch. Time at least ten oscillations, and stop the time precisely on an exact number on periods. Record the number of oscillations and total time. Divide the total time by the number of oscillations timed to determine the average period.
Step 5. Repeat Steps 1 - 4 with the pendulum empty.
Step 6. Using the calibration bar's moment of inertia and the average periods for the calibration bar on the pendulum and for the empty cradle, determine the torsional stiffness of the pendulum's spring, and the pendulum's moment of inertia. Record these values for use in future gun MOI measurements.