Watch and Clock Escapements | Page 6

fork action and employing a
double-roller safety action to prevent over-banking.
[Illustration: Fig. 10]
From the point e, which represents the center of the pallet staff, we
draw through b the line e f. At one degree below e f we draw the line e
g, and seven and one-half degrees below the line e g we draw the line e
h. For delineating the lines e g, etc., correctly, we employ a degree-arc;

that is, on the large drawing we are making we first draw the line e b f,
Fig. 10, and then, with our dividers set at five inches, sweep the short
arc i, and on this lay off first one degree from the intersection of f e
with the arc i, and through this point draw the line e g.
From the intersection of the line f e with the arc i we lay off eight and
one-half degrees, and through this point draw the line e h. Bear in mind
that we are drawing the pallet at B to represent one with eight and
one-half degrees fork-and-pallet action, and with equidistant lockings.
If we reason on the matter under consideration, we will see the tooth A
and the pallet B, against which it acts, part or separate when the tooth
arrives at the point _c_; that is, after the escape wheel has moved
through ten and one-half degrees of angular motion, the tooth drops
from the impulse face of the pallet and falls through one and one-half
degrees of arc, when the tooth _A''_, Fig. 10, is arrested by the exit
pallet.
To locate the position of the inner angle of the pallet B, sweep the short
arc l by setting the dividers so one point or leg rests at the center e and
the other at the point c. Somewhere on this arc l is to be located the
inner angle of our pallet. In delineating this angle, Moritz Grossman, in
his "Prize Essay on the Detached Lever Escapement," makes an error,
in Plate III of large English edition, of more than his entire lock, or
about two degrees. We make no apologies for calling attention to this
mistake on the part of an authority holding so high a position on such
matters as Mr. Grossman, because a mistake is a mistake, no matter
who makes it.
We will say no more of this error at present, but will farther on show
drawings of Mr. Grossman's faulty method, and also the correct method
of drawing such a pallet. To delineate the locking face of our pallet,
from the point formed by the intersection of the lines _e g b b'_, Fig. 9,
as a center, we draw the line j at an angle of twelve degrees to _b b''_.
In doing this we employ the same method of establishing the angle as
we made use of in drawing the lines e g and e h, Fig. 10. The line j
establishes the locking face of the pallet B. Setting the locking face of
the pallet at twelve degrees has been found in practice to give a safe

"draw" to the pallet and keep the lever secure against the bank. It will
be remembered the face of the escape-wheel tooth was drawn at
twenty-four degrees to a radial line of the escape wheel, which, in this
instance, is the line _b b'_, Fig. 9. It will now be seen that the angle of
the pallet just halves this angle, and consequently the tooth A only rests
with its point on the locking face of the pallet. We do not show the
outlines of the pallet B, because we have not so far pointed out the
correct method of delineating it.
METHODS OF MAKING GOOD DRAWING INSTRUMENTS.
Perhaps we cannot do our readers a greater favor than to digress from
the study of the detached lever escapement long enough to say a few
words about drawing instruments and tablets or surfaces on which to
delineate, with due precision, mechanical designs or drawings.
Ordinary drawing instruments, even of the higher grades, and costing a
good deal of money, are far from being satisfactory to a man who has
the proper idea of accuracy to be rated as a first-class mechanic.
Ordinary compasses are obstinate when we try to set them to the
hundredth of an inch; usually the points are dull and ill-shapen; if they
make a puncture in the paper it is unsightly.
Watchmakers have one advantage, however, because they can very
easily work over a cheap set of drawing instruments and make them
even superior to anything they can buy at the art stores. To illustrate, let
us take a cheap pair of brass or German-silver five-inch dividers and
make them over into needle points and "spring