WHEN POWER IS LOST IN THE LEVER ESCAPEMENT.
If we use a ratchet-tooth escape wheel we must allow at least one and a
half degrees drop to free the back of the tooth; but with a club-tooth
escape wheel made as can be constructed by proper skill and care, the
drop can be cut down to three-quarters of a degree, or one-half of the
loss with the ratchet tooth. We do not wish our readers to imagine that
such a condition exists in most of the so-called fine watches, because
if we take the trouble to measure the actual drop with one of the little
instruments we have described, it will be found that the drop is seldom
less than two, or even three degrees.
If we measure the angular movement of the fork while locked, it will
seldom be found less than two or three degrees. Now, we can all
understand that the friction of the locking surface has to be counted as
well as the recoil of the draw. Locking friction is seldom looked after
as carefully as the situation demands. Our factories make the impulse
face of the pallets rounded, but leave the locking face flat.
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