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Product of inertia (POI) is the characteristic of an object that causes dynamic unbalance. Knowing the POI of an object is essential to determine some of its flight characteristics, such as its tendency to wobble. Knowing POI in all planes allows determining the principal axes of a payload. How to measure product of inertia? Product […]

This page describes a new low-speed vertical axis aerospace balance machine that takes advantage of recent advances in technology. This machine measures moment of inertia (MOI) in addition to product of inertia (POI) and center of gravity (CG) offset. Spin speeds as low as 15 RPM yield useful results. This machine has a number of […]

Product of inertia is generally measured using a spin balance machine. In this type of machine, the object is rotated at a speed of about 100 RPM, and the reaction forces against the upper and lower spindle bearings are measured. Product of inertia is then calculated automatically by the machine’s on line computer, using formulas […]