LAYING OUT ESCAPE-WHEEL TEETH.
To "lay out" or delineate our escape-wheel teeth, we continue our
drawing shown at Fig. 6, and reproduce this cut very nearly at Fig. 8.
With our dividers set at five inches, we sweep the short arc _a a'_ from
_f_ as a center. It is to be borne in mind that at the point _f_ is
located the extreme point of an escape-wheel tooth. On the arc _a a_ we
lay off from _p_ twenty-four degrees, and establish the point _b_; at
twelve degrees beyond _b_ we establish the point _c_. From _f_ we draw
the lines _f b_ and _f c_; these lines establishing the form and
thickness of the tooth _D_. To get the length of the tooth, we take in
our dividers one-half a tooth space, and on the radial line _p f_
establish the point _d_ and draw circle _d' d'_.
To facilitate the drawing of the other teeth, we draw the circles _d' c'_,
to which the lines _f b_ and _f c_ are tangent, as shown. We divide
the circle _n n_, representing the periphery of our escape wheel, into
fifteen spaces, to represent teeth, commencing at _f_ and continued as
shown at _o o_ until the entire wheel is divided.
Pages:
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27