Part 6 (1/2)

From _A_ as a center and with our dividers set at 5”, eep the arc _f_ Frorees on each side of the line _A B_ on the arc _f_, and establish the points _g h_ Froh the points just established we draw the radial lines _A g'_ and _A h'_ The angular extent between these lines defines the limit of our roller action

Noe lay off on the arc _f_ six degrees each side of its intersection with the line _A B_, we define the extent of the jewel pin; that is, on the arc _f_ we establish the points _l h the points _l m_ draw, from _A_ as a center, the radial lines _A l'_ and _A m'_ The extent of the space between the lines _A l'_ and _A m'_ on the circle _a_ defines the size of our jewel pin

TO DETERMINE THE SIZE OF A JEWEL PIN

[Illustration: Fig 56]

To ed drawing of the lines defining the jewel pin at Fig 56 At the intersection of the line _A B_ with the arc _a_ we locate the point _k_, and froh the intersection of the lines _A l'_ and _A m'_ with the arc _a_ We divide the radius of the circle _i_ on the line _A B_ into five equal parts, as shown by the vertical lines _j_ Of these five spaces we assu away that portion to the right of the heavy vertical line at _k_

[Illustration: Fig 57]

We will now proceed to delineate a fork and roller as the parts are related on first contact of jewel pin with fork and initial with the co a pallet The position and relations are also the same as at the close of the act of i 57, as before, by drawing the line _A B_ and the arcs _a_ and _b_ to represent the pitch circles We also sweep the arc _f_ to enable us to delineate the line _A g'_ Next in order we draw our jewel pin as shown at _D_ In drawing the jewel pin we proceed as at Fig 56, except we let the line _A g'_, Fig 57, assu 56; that is, we delineate the jewel pin as if extending on the arc _a_ six degrees on each side of the line _A g'_, Fig 57

THE THEORY OF THE FORK ACTION

To aid us in reasoning, we establish the point _ 57, and proceed to delineate another and iinary jewel pin at _D'_ (as we show in dotted outline) A brief reasoning will show that in allowing thirty degrees of contact of the fork with the jewel pin, the center of the jewel pin will pass through an arc of thirty degrees, as shown on the arcs _a_ and _f_ Now here is an excellent opportunity to iular rees on the arc _f_ is of more than twice the linear extent as on the arc _a_

Before we co the jewel pin _D_, shown at full line in Fig 57, ill come to perfectly understand what mechanical relations are required As previously stated, we assu 57, is in the act of encountering the inner face of the horn of the fork for the end or purpose of unlocking the engaged pallet Now if the inner face of the horn of the fork was on a radial line, such radial line would be _p B_, Fig 57 We repeat this line at _p_, Fig 56, where the parts are drawn on a larger scale

To delineate a fork at the instant the last effort of impulse has been imparted to the jewel pin, and said jewel pin is in the act of separating fro of the fork--ould also call attention to the fact that relations of parts are precisely the same as if the jewel pin had just returned fro the inner face of the prong of the fork in the act of unlocking the escapement

We mentioned this matter previously, but venture on the repetition toclear and easily understood We co it in four equal parts, as on previous occasions, and from _A_ and _B_ as centers draw the pitch circles _c d_

By methods previously described, we draw the lines _A a_ and _A a'_, also _B b_ and _B b'_ to represent the angular motion of the two mobiles, viz, fork and roller action As already shown, the roller occupies twelve degrees of angular extent To get at this conveniently, we lay off on the arc by which we located the lines _A a_ and _A a'_ six degrees above the line _A a_ and draw the line _A h_

Now the angular extent on the arc _c_ between the lines _A a_ and _A h_ represents the radius of the circle defining the jewel pin From the intersection of the line _A a_ with the arc _c_ as a center, and with the radius just na 58, which represents our jewel pin; we afterward cut ao-fifths and draw the full line _D_, as shown We show at Fig 59 a portion of Fig 58, enlarged four times, to show certain portions of our delineations ive the subject a th of the prong _E_ of the lever fork is lith as will allow the jewel pin _D_ to pass it

HOW TO DELINEATE THE pronGS OF A LEVER FORK

[Illustration: Fig 58]

[Illustration: Fig 59]

To delineate this length, from _B_ as a center eep the short arc _f_ so it passes through the outer angle _n_, Fig 59, of the jewel pin

This arc, carried across the jewel pin _D_, li of the fork The outer face of the prong of the fork can be drawn as a line tangent to a circle drawn frole _n_ of the jewel pin Such a circle or arc is shown at _o_, Figs 58 and 59 There has been a good deal said as to whether the outer edge of the prong of a fork should be straight or curved

To the writer's , like frole roller, while a fork with a curved prong will be best adapted for a double roller This subject will be taken up again e consider double-roller action The extent or length of the outer face of the prong is also an open subject, but as there is but one factor of the proble on it, e name this and see this requirement satisfied we have made an end of this question The function perfor of a fork is to prevent the engaged pallet fro hollow

The inner angle _s_ of the horn of the fork must be so shaped and located that the jewel pin will just clear it as it passes out of the fork, or when it passes into the fork in the act of unlocking the escapes a trifle is allowed, that is, the fork is th to allow for safety in this respect

THE PROPER LENGTH OF A LEVER

We will now see how long a lever must be to perform its functions perfectly Now let us deter _E'_ the jewel pin parts froes on its return

To do this we draw a line fro 59) of the jewel pin, so as to les, and the point _t_ so established on the line _e_ is where contact will take place between the jewel pin and fork