. Watch and clock escapements; . eader is urged to make the drawings for himself on alarge scale, say, an escape wheel 10 pitch diameter. Such draw-ings will enable him to realize small errors which have been toleratedtoo much in drawings of this kind. The drawings, as they appearin the cut, are one-fourth the size recommended, and many of the The Detached Lever Escapement. 89 lines fail to show points we desire to call attention to. As forinstance, the pallet center at B is tangential to the pitch circle afrom the point of tooth contact at f. To establish this point wedraw the radial lines A
. Watch and clock escapements; . eader is urged to make the drawings for himself on alarge scale, say, an escape wheel 10 pitch diameter. Such draw-ings will enable him to realize small errors which have been toleratedtoo much in drawings of this kind. The drawings, as they appearin the cut, are one-fourth the size recommended, and many of the The Detached Lever Escapement. 89 lines fail to show points we desire to call attention to. As forinstance, the pallet center at B is tangential to the pitch circle afrom the point of tooth contact at f. To establish this point wedraw the radial lines A c and A d from the escape-wheel center A,as shown, by laying off thirty degrees on each side of the intersec-tion of the vertical line i (passing through the centers A B) withthe arc a, and then laying off two and a half degrees on a andestablishing the point /, and through / from the center A draw theradial line A f. Through the point f we draw the tangent lineb b b, and at the intersection of the line b with i we establish the. !« 1 .** X, , Fig. 90 center of our pallet staff at B. At two and a half degrees fromthe point c we lay off two and a half degrees to the right of saidpoint and establish the point n, and draw the radial line A n n,which establishes the extent of the arc of angular motion of theescape wheel utilized by the pallet arm. We have now come to the point where we must exercise ourreasoning powers a little. We know the locking angle of theescape-wheel tooth passes on the arc a, and if we utilize theimpulse face of the tooth for five degrees of pallet or lever motion wemust shape it to this end. We draw the short arc k through thepoint n, knowing that the inner angle of the pallet stone must rest onthis arc wherever it is situated. As, for instance, when the lockingface of the pallet is engaged, the inner angle of the pallet stonemust rest somewhere on this arc (k) inside of a, and the extreme 90 Watch and Clock Escapements. outer angle of the impulse face of
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Keywords: ., bookcentury1900, bookdecade1900, bookidwatchclockes, bookyear1904
