. Watch and clock escapements; . eep the arc g. The space between the lines B f and B i on the arc g definesthe extent of the locking face of the entrance pallet C. The inter-section of the line B f with the arc g we denominate the point o,and from this point as a center sweep the short arc p with a 5radius ; and on this arc, from its intersection with the radial lineA b, lay off twelve degrees, and through the point so established, 36 Watch and Clock Escapements. from o as a. center, draw the radial line o m, said line defining thelocking face of the entrance pallet C. It will be seen that th
. Watch and clock escapements; . eep the arc g. The space between the lines B f and B i on the arc g definesthe extent of the locking face of the entrance pallet C. The inter-section of the line B f with the arc g we denominate the point o,and from this point as a center sweep the short arc p with a 5radius ; and on this arc, from its intersection with the radial lineA b, lay off twelve degrees, and through the point so established, 36 Watch and Clock Escapements. from o as a. center, draw the radial line o m, said line defining thelocking face of the entrance pallet C. It will be seen that this gives a positive draw of twelvedegrees to the entrance pallet ; that is, counting to the line B /.In this escapement as delineated there is perfect tangential the locking face of the entrance-pallet stone at C was made toconform to the radial line A b, the lock of the tooth D at o wouldbe dead; that is, absolutely neutral. The tooth D would pressthe pallet C in the direction of the arrow x, toward the center of the. Fig. 22 pallet staff B, with no tendency on the part of the pallet to turn onits axis B. Theoretically, the pallet with the locking face cut tocoincide with the line A b would resist movement on the center Bin either direction indicated by the double-headed arrow y. A pallet at C with a circular locking face made to conform tothe arc g, would permit movement in the direction of the double-headed arrow y with only mechanical effort enough to overcomefriction. But it is evident on inspection that a locking face on theline A b would cause a retrograde motion of the escape wheel, andconsequent resistance, if said pallet was moved in either directionindicated by the double-headed arrow y. Precisely the same con-ditions obtain at the point u, which holds the same relations to theexit pallet as the point o does to the entrance pallet C. The Detached Lever Escapement. 37 ANGULAR MOTION OF ESCAPE WHEEL DETERMINED. The arc (three and a half degrees) of the circl
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