WHY MEASURE MOMENT OF INERTIA?

The MOI of simple shapes may be calculated by well known methods. However, reducing complex shapes or compound objects to an assemblage of simple objects and summing the moments of inertia can lead to large errors. It is more practical and faster to accurately determine the MOI of complex objects or of objects with varying density by direct measurement.

Measuring MOI directly has these advantages:

Greater Accuracy - Typical errors in calculated MOI can range to over 30% due to simplifying the part shape, or making assumptions about average density. If hanging wire or trifilar pendulums are used to measure MOI, large errors result from multiple mode oscillations.

Cost Savings - Measurements can generally be made in a small fraction of the time required for exact MOI calculations. Cost savings in engineering time alone can quickly pay for the instrument. Furthermore, calculations do not account for manufacturing variations.

Quality Assurance - Military and industrial specifications frequently set limits on MOI (and CG location), where these parameters are critical to the performance of rockets, projectiles, and re-entry components.

Space Electronics offers the most complete line of moment of inertia measurement instruments.