We have previously given instructions for drawing the pallet locked; and to delineate the pallet after five degrees of angular motion, we have only to conceive that we substitute the line s’ for the line b’. All angular motions and measurements for pallet actions are from the center of the pallet staff at B. As we desire to now delineate the entrance pallet, it has passed through five degrees of angular motion and the inner angle s now lies on the pitch circle of the escape wheel, the angular space between the lines b’ s’ being five degrees, the line b’’ reducing the impulse face to four degrees.
DRAWING AN ESCAPEMENT TO SHOW ANGULAR MOTION.
To delineate our locking face we draw a line at right angles to the line B b’’ from the point t, said point being located at the intersection of the arc o with the line B b’’. To draw a line perpendicular to B b’’ from the point t, we take a convenient space in our dividers and establish on the line B b’’ the points x x’ at equal distances from the point t. We open the dividers a little (no special distance) and sweep the short arcs x’’ x’’’, as shown at Fig. 91. Through the intersection of the short arcs x’’ x’’’ and to the point t we draw the line t y. The reader will see from our former explanations that the line t y represents the neutral plane of the locking face, and that to have the proper draw we must delineate the locking face of our pallet at twelve degrees. To do this we draw the line t x’ at twelve degrees to the line t y, and proceed to outline our pallet faces as shown. We can now understand, after a moment’s thought, that we can delineate the impulse face of a tooth at any point or place we choose by laying off six degrees on the arc m, and drawing radial lines from A to embrace such arc. To illustrate, suppose we draw the radial lines w’ w’’ to embrace six degrees on the arc a. We make these lines contiguous to the entrance pallet C for convenience only. To delineate the impulse face of the tooth, we draw a line extending from the intersection of the radial line A’ w’ with the arc m to the intersection of the arc a with the radial line A w’’.
[Illustration: Fig. 91]
We next desire to know where contact will take place between the wheel-tooth D and pallet C. To determine this we sweep, with our dividers set so one leg rests at the escape-wheel center A and the other at the outer angle t of the entrance pallet, the short arc t’ w. Where this arc intersects the line w (which represents the impulse face of the tooth) is where the outer angle t of the entrance pallet C will touch the impulse face of the tooth. To prove