THE ANGULAR MOTION OF AN ESCAPE WHEEL.

[Illustration: Fig. 76]

We can also make use of our angle-testing device for measuring our
escape-wheel action, by letting the clasp embrace the arbor of the
escape wheel, instead of the pallet staff. We set the index arc as in
our former experiments, except we place the movable index _D_, Fig. 76,
so that when the engaged tooth rests on the locking face of a pallet,
the index hand stands at the extreme end of our arc of twelve degrees.
We next, with our pointed pegwood, start to move the fork away from the
bank, as before, we look sharp and see the index hand move backward a
little, indicating the "draw" on the locking face. As soon as the pallet
reaches the impulse face, the hand _A_ moves rapidly forward, and if the
escapement is of the club-tooth order and closely matched, the hand _A_
will pass over ten and a half degrees of angular motion before the drop
takes place.

[Illustration: Fig. 77]

We will warn our readers in advance, that if they make such a testing
device they will be astonished at the inaccuracy which they will find in
the escapements of so-called fine watches. The lock, in many instances,
instead of being one and a half degrees, will oftener be found to be
from two to four degrees, and the impulse derived from the escape wheel,
as illustrated at Fig. 76, will often fall below eight degrees. Such
watches will have a poor motion and tick loud enough to keep a policeman
awake. Trials with actual watches, with such a device as we have just
described, in conjunction with a careful study of the acting parts,
especially if aided by a large model, such as we have described, will
soon bring the student to a degree of skill unknown to the old-style
workman, who, if a poor escapement bothered him, would bend back the
banking pins or widen the slot in the fork.

We hold that educating our repair workmen up to a high knowledge of what
is required to constitute a high-grade escapement, will have a
beneficial effect on manufacturers. When we wish to apply our device to
the measurement of the escapement of three-quarter-plate watches, we
will require another index hand, with the grasping end bent downward, as
shown at Fig. 77. The idea with this form of index hand is, the
bent-down jaws _B'_, Fig. 77, grasp the fork as close to the pallet
staff as possible, making an allowance for the acting center by so
placing the index arc that the hand _A_ will read correctly on the