Watch and Clock Escapements - A Complete Study in Theory and Practice of the Lever, Cylinder and Chronometer Escapements, Together with a Brief Account of the Origin and Evolution of the Escapement in Horology by Anonymous
page 16 of 243 (06%)
page 16 of 243 (06%)
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From the point _e_, which represents the center of the pallet staff, we
draw through _b_ the line _e f_. At one degree below _e f_ we draw the line _e g_, and seven and one-half degrees below the line _e g_ we draw the line _e h_. For delineating the lines _e g_, etc., correctly, we employ a degree-arc; that is, on the large drawing we are making we first draw the line _e b f_, Fig. 10, and then, with our dividers set at five inches, sweep the short arc _i_, and on this lay off first one degree from the intersection of _f e_ with the arc _i_, and through this point draw the line _e g_. From the intersection of the line _f e_ with the arc _i_ we lay off eight and one-half degrees, and through this point draw the line _e h_. Bear in mind that we are drawing the pallet at _B_ to represent one with eight and one-half degrees fork-and-pallet action, and with equidistant lockings. If we reason on the matter under consideration, we will see the tooth _A_ and the pallet _B_, against which it acts, part or separate when the tooth arrives at the point _c_; that is, after the escape wheel has moved through ten and one-half degrees of angular motion, the tooth drops from the impulse face of the pallet and falls through one and one-half degrees of arc, when the tooth _A''_, Fig. 10, is arrested by the exit pallet. To locate the position of the inner angle of the pallet _B_, sweep the short arc _l_ by setting the dividers so one point or leg rests at the center _e_ and the other at the point _c_. Somewhere on this arc _l_ is to be located the inner angle of our pallet. In delineating this angle, Moritz Grossman, in his "Prize Essay on the Detached Lever Escapement," makes an error, in Plate III of large English edition, of more than his entire lock, or about two degrees. We make no apologies for calling attention to this mistake on the part of an authority holding so high a |
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