Let us further suppose the diameter of our actual
escape wheel to be .26”, and we were constructing
a watch after the lines of our drawing. By “lines,”
in this case, we mean in the same general form and
ratio of parts; as, for illustration, if the distance
from the intersection of the arc *a* with the
line *b* to the point *B* was one-fifteenth
of the diameter of the escape wheel, this ratio would
hold good in the actual watch, that is, it would be
the one-fifteenth part of .26”. Again,
suppose the diameter of the escape wheel in the large
drawing is 10” and the distance between the
centers *A B* is 5.78”; to obtain the actual
distance for the watch with the escape wheel .26”
diameter, we make a statement in proportion, thus:
10 : 5.78 :: .26 to the actual distance
between the pivot holes of the watch. By computation
we find the distance to be .15”. These
proportions will hold good in every part of actual
construction.

All parts—thickness of the pallet stones,
length of pallet arms, *etc*.—bear the
same ratio of proportion. We measure the thickness
of the entrance pallet stone on the large drawing
and find it to be .47”; we make a similar statement
to the one above, thus: 10 : .47 ::
.26 to the actual thickness of the real pallet stone.
By computation we find it to be .0122”.
All angular relations are alike, whether in the large
drawing or the small pallets to match the actual escape
wheel .26” in diameter. Thus, in the pallet
*D*, Fig. 93, the impulse face, as reckoned from
*B* as a center, would occupy four degrees.

MAKE A LARGE ESCAPEMENT MODEL.

Reason would suggest the idea of having the theoretical keep pace and touch with the practical. It has been a grave fault with many writers on horological matters that they did not make and measure the abstractions which they delineated on paper. We do not mean by this to endorse the cavil we so often hear—“Oh, that is all right in theory, but it will not work in practice.” If theory is right, practice must conform to it. The trouble with many theories is, they do not contain all the elements or factors of the problem.

[Illustration: Fig. 94]

Near the beginning of this treatise we advised our
readers to make a large model, and described in detail
the complete parts for such a model. What we
propose now is to make adjustable the pallets and fork
to such a model, in order that we can set them both
right and wrong, and thus practically demonstrate
a perfect action and also the various faults to which
the lever escapement is subject. The pallet arms
are shaped as shown at *A*, Fig. 94. The
pallets *B B’* can be made of steel or
stone, and for all practical purposes those made of
steel answer quite as well, and have the advantage
of being cheaper. A plate of sheet brass should
be obtained, shaped as shown at *C*, Fig. 95.
This plate is of thin brass, about No. 18, and on
it are outlined the pallet arms shown at Fig. 94.