Читать книгу The Modern Clock. A Study of Time Keeping Mechanism; Its Construction, Regulation and Repair онлайн

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Conversion Table of Inches, Millimeters and French Lines.

Inches expressed in Millimeters and French Lines. Inches. Equal to Millimeters. French Lines. 1 25.39954 11.25951 2 50.79908 22.51903 3 76.19862 33.77854 4 101.59816 45.03806 5 126.99771 56.29757 6 152.39725 67.55709 7 177.79679 78.81660 8 203.19633 90.07612 9 228.59587 101.33563 10 253.99541 112.59516 Millimeters expressed in Inches and French Lines. Millimeters. Equal to Inches. French Lines. 1 0.0393708 0.44329 2 0.0787416 0.88659 3 0.1181124 1.32989 4 0.1574832 1.77318 5 0.1968539 2.21648 6 0.2362247 2.65978 7 0.2755955 3.10307 8 0.3149664 3.54637 9 0.3543371 3.98966 10 0.3937079 4.43296 French Lines expressed in Inches and Millimeters. French Lines. Equal to Inches. Millimeters. 1 0.088414 2.25583 2 0.177628 4.51166 3 0.266441 6.76749 4 0.355255 9.02332 5 0.444069 11.27915 6 0.532883 13.53497 7 0.621697 15.79080 8 0.710510 18.04663 9 0.799324 20.30246 10 0.888138 22.55829 11 0.976952 24.81412 12 1.065766 27.06995

Center of Gravity.—The watchmaker is concerned only with the theoretical or timekeeping lengths of pendulums, as his pendulum comes to him ready for use; but the clock maker who has to build the pendulum to fit not only the movement, but also the case, needs to know more about it, as he must so distribute the weight along its length that it may be given a length of 60 inches or of 44 inches, or anything between them, and still beat seconds, in the case of a regulator. He must also do the same thing in other clocks having pendulums which beat other numbers than 60. Therefore he must know the center of his weights; this is called the center of gravity. This center of gravity is often confused by many with the center of oscillation as its real purpose is not understood. It is simply used as a starting point in building pendulums, because there must be a starting point, and this point is chosen because it is always present in every pendulum and it is convenient to work both ways from the center of weight or gravity. In ssss1 we have two pendulums, in one of which (the ball and string) the center of gravity is the center of the ball and the center of oscillation is also at the center (practically) of the ball. Such a pendulum is about as short as it can be constructed for any given number of oscillations. The other (the rod) has its center of gravity manifestly at the center of the rod, as the rod is of the same size throughout; yet we found by comparison with the other that its center of oscillation was at two-thirds the length of the rod, measured from the point of suspension, and the real length of the pendulum was consequently one-half longer than its timekeeping length, which is at the center of oscillation. This is farther apart than the center of gravity and oscillation will ever get in actual practice, the most extreme distance in practice being that of the gridiron pendulum previously mentioned. The center of gravity of a pendulum is found at that point at which the pendulum can be balanced horizontally on a knife edge and is marked to measure from when cutting off the rod.