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Innovations developed by NASA and its industry partners in a wide array of fields.

Machine Design

How-to, in-depth technical articles for machine design engineers

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How OEM's can make their parts better, faster, and more efficient.

Essentials of Manufacturing

Information, coverage of important developments and expert commentary in manufacturing.

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Epicyclic Gear Train

Epicyclic gear trains are powerful when used correctly, but are often misunderstood. Illustrated below is a typical epicyclic gear train. Notice how the planet gears roll on and revolve about the sun gear. The ring gear rolls on the planet gears. Such a gear configuration has useful applications, but the overall gear ratio is quite difficult to intuitively calculate. Please select "Epicyclic Ratio Calc'n" to learn about an effective yet simple method for calculating the overall gear ratio.