A handbook on the teeth of gears, their curves, properties, and practical construction (1890)
Grant, George B. (George Barnard), 1849-1917 · Lexington, Mass., Lexington Gear Works · leaf 69
ARS 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 line at right angles to the line… … Case IV. Wlien the focal distance is finite and negative, the curves arehyperbolas. The opposite focus about which one hyperbola turns is now ontlie other side of the curve, which becomes a negative or internal pitch line,as in Fig IV. The linli is of finite length and can be practically…
Gearing
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
