A handbook on the teeth of gears, their curves, properties, and practical construction (1887)
Grant, George B. (George Barnard), 1849-1917 · [Boston] · leaf 76
Case II. When the focal distance is finite and positive, the curves areellipses that will roll together if fixed on centers at their opposite foci, as inFig. II. The link is a moving bar connecting the two moving foci. … Ua x<ig. III :baba.bolic gbabs Case III. When the focal distance is infinitely great the curves are parab-olas. One parabola turns about its focus while the other turns about itsopposite focus, but, as the opposite focus is at an infinite distance the sec-ond parabola must move in a straight…
Gearing
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