It will be noticed that the pallets here are comparatively thin to those
in general use; this condition is accomplished by deriving the principal
part of the impulse from driving planes placed on the teeth. As relates
to the escape-wheel action of the ten and one-half degrees, which gives
impulse to the escapement, five and one-half degrees are utilized by the
driving planes on the teeth and five by the impulse face of the pallet.
Of the ten degrees of fork action, four and a half degrees relate to the
impulse face of the teeth, one and a half degrees to lock, and four
degrees to the driving plane of the pallets.
In delineating such a club-tooth escapement, we commence, as in former
examples, by first assuming the center of the escape wheel at _A_, and
with the dividers set at five inches sweeping the arc _a a_. Through _A_
we draw the vertical line _A B'_. On the arc _a a_, and each side of its
intersection with the line _A B'_, we lay off thirty degrees, as in
former drawings, and through the points so established on the arc _a a_
we draw the radial lines _A b_ and _A c_.
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