*Project Gutenberg*. Public domain.

*c*, measuring down on the arc

*c’*and establishing the point

*t*. The points

*p*and

*t*are then connected, and thus the impulse face of the entrance pallet

*B*is defined. From the point

*t*is drawn the line

*t t’*, parallel to the line

*b s*, thus defining the inner face of the entrance pallet.

## DELINEATING THE EXIT PALLET.

To delineate the exit pallet, sweep the short arc
*u u* (from *g* as a center) with the dividers
set at five inches, and from the intersection of this
arc with the line *g j’* set off eight and
one-half degrees and draw the line *g l*.
At one degree below this line is drawn the line *g
m*. The space on the arc *f* between
these lines defines the locking face of the exit pallet.
The point where the line *g m* intersects the
arc *f* is named the point *x*. From
the point *x* is erected the line *x w*,
perpendicular to the line *g m*. From *x*
as a center, and with the dividers set at five inches,
the short arc *y y* is swept, and on this arc
are laid off twelve degrees, and the line *x z*
is drawn, which line defines the locking face of the
exit pallet.

Next is taken ten and one-half degrees from the brass
degree-scale, and from the point *d* on the arc
*n* the space named is laid off, and thus is
established the point *v*; and from *g* as
a center is swept the arc *v’ v’*
through the point *v*. It will be evident
on a little thought, that if the tooth *A’*
impelled the exit pallet to the position shown, the
outer angle of the pallet must extend down to the point
*v*, on the arc *v’ v’*; consequently,
we define the impulse face of this pallet by drawing
a line from point *x* to *v*. To define
the outer face of the exit pallet, we draw the line
*v e* parallel to the line *x z*.

There are no set rules for drawing the general form of the pallet arms, only to be governed by and conforming to about what we would deem appropriate, and to accord with a sense of proportion and mechanical elegance. Ratchet-tooth pallets are usually made in what is termed “close pallets”; that is, the pallet jewel is set in a slot sawed in the steel pallet arm, which is undoubtedly the strongest and most serviceable form of pallet made. We shall next consider the ratchet-tooth lever escapement with circular pallets and ten degrees of pallet action.

## DELINEATING CIRCULAR PALLETS.

To delineate “circular pallets” for a
ratchet-tooth lever escapement, we proceed very much
as in the former drawing, by locating the point *A*,
which represents the center of the escape wheel, at
some convenient point, and with the dividers set at
five inches, sweep the arc *m*, to represent
the periphery of the escape wheel, and then draw the
vertical line *A B’*, Fig. 19. We
(as before) lay off thirty degrees on the arc *m*
each side of the intersection of said arc with the
line *A B’*, and thus establish on the
arc *m* the points *a b*, and from *A*
as a center draw through the points so established
the radial lines *A a’* and *A b’*.