*Project Gutenberg*. Public domain.

The reader is urged to make the drawings for himself
on a large scale, say, an escape wheel 10” pitch
diameter. Such drawings will enable him to realize
small errors which have been tolerated too much in
drawings of this kind. The drawings, as they
appear in the cut, are one-fourth the size recommended,
and many of the lines fail to show points we desire
to call attention to. As for instance, the pallet
center at *B* is tangential to the pitch circle
*a* from the point of tooth contact at *f*.
To establish this point we draw 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 intersection of the vertical line
*i* (passing through the centers *A B*)
with the arc *a*, and then laying off two and
a half degrees on *a* and establishing the point
*f*, and through *f* from the center *A*
draw the radial line *A f’*. Through
the point *f* we draw the tangent line *b’
b b’’*, and at the intersection of the
line *b* with *i* we establish the center
of our pallet staff at *B*. At two and a
half degrees from the point *c* we lay off two
and a half degrees to the right of said point and
establish the point *n*, and draw the radial
line *A n n’*, which establishes the extent
of the arc of angular motion of the escape wheel utilized
by the pallet arm.

[Illustration: Fig. 90]

We have now come to the point where we must exercise
our reasoning powers a little. We know the locking
angle of the escape-wheel tooth passes on the arc
*a*, and if we utilize the impulse face of the
tooth for five degrees of pallet or lever motion we
must shape it to this end. We draw the short
arc *k* through the point *n*, knowing that
the inner angle of the pallet stone must rest on this
arc wherever it is situated. As, for instance,
when the locking face of the pallet is engaged, the
inner angle of the pallet stone must rest somewhere
on this arc (*k*) inside of *a*, and the
extreme outer angle of the impulse face of the tooth
must part with the pallet on this arc *k*.

HOW TO LOCATE THE PALLET ACTION.

With the parts related to each other as shown in the
cut, to establish where the inner angle of the pallet
stone is located in the drawing, we measure down on
the arc *k* five degrees from its intersection
with *a*, and establish the point *s*.
The line *B b*, Fig. 90, as the reader will see,
does not coincide with the intersection of the arcs
*a* and *k*, and to conveniently get at
the proper location for the inner angle of our pallet
stone, we draw the line *B b’*, which passes
through the point *n* located at the intersection
of the arc *a* with the arc *k*. From
*B* as a center we sweep the short arc *j*
with any convenient radius of which we have a sixty-degree