Part 2 (1/2)

With this space in the dividers one leg is set at the point _c_,the point _t_ The points _p_ and _t_ are then connected, and thus the impulse face of the entrance pallet _B_ is defined From the point _t_ is drawn the line _t t'_, parallel to the line _b s_, thus defining the inner face of the entrance pallet

DELINEATING THE EXIT PALLET

To delineate the exit pallet, sweep the short arc _u u_ (fro_ as a center) with the dividers set at five inches, and fro j'_ set off eight and one-half degrees and draw the line _g l_ At one degree below this line is drawn the line _g m_

The space on the arc _f_ between these lines defines the locking face of the exit pallet The point where the line _g m_ intersects the arc _f_ is named the point _x_ From the point _x_ is erected the line _x w_, perpendicular to the line _g m_ From _x_ as a center, and with the dividers set at five inches, the short arc _y y_ is swept, and on this arc are laid off twelve degrees, and the line _x z_ is drahich line defines the locking face of the exit pallet

Next is taken ten and one-half degrees froree-scale, and from the point _d_ on the arc _n_ the space named is laid off, and thus is established the point _v_; and froh the point _v_ It will be evident on a little thought, that if the tooth _A'_ ile of the pallet must extend down to the point _v_, on the arc _v' v'_; consequently, we define the i a line from point _x_ to _v_ To define the outer face of the exit pallet, we draw the line _v e_ parallel to the line _x z_

There are no set rules for drawing the general for to about ould deem appropriate, and to accord with a sense of proportion and ance Ratchet-tooth pallets are usually made in what is termed ”close pallets”; that is, the pallet jewel is set in a slot sawed in the steel pallet arest and most serviceable form of pallet made We shall next consider the ratchet-tooth lever escaperees of pallet action

DELINEATING CIRCULAR PALLETS

To delineate ”circular pallets” for a ratchet-tooth lever escape, by locating the point _A_, which represents the center of the escape wheel, at some convenient point, and with the dividers set at five inches, sweep the arc _m_, to represent the periphery of the escape wheel, and then draw the vertical line _A B'_, Fig 19 We (as before) lay off thirty degrees on the arc _m_ each side of the intersection of said arc with the line _A B'_, and thus establish on the arc _h the points so established the radial lines _A a'_ and _A b'_

We erect from the point _a_ a perpendicular to the line _A a_, and, as previously explained, establish the pallet center at _B_ Inasmuch as we are to employ circular pallets, we lay off to the left on the arc _ half of the angular , and thus establish the point _c_, and froh this point the radial line _A c'_ To the right of the point _a_ we lay off five degrees and establish the point _d_ To illustrate the underlying principle of our circular pallets: with one leg of the dividers set at _B_ eep through the points _c a d_ the arcs _c'' a'' d''_

From _B_ as a center, we continue the line _B a_ to _f_, and with the dividers set at five inches, sweep the short arc _e e_ From the intersection of this arc with the line _B f_ we lay off one and a half degrees and draw the line _B g_, which establishes the extent of the lock on the entrance pallet It will be noticed the linear extent of the locking face of the entrance pallet is greater than that of the exit, although both represent an angle of one and a half degrees

Really, in practice, this discrepancy is of little i would secure safety in either case

[Illustration: Fig 19]

The fault we previously pointed out, of the generally accepteda detached lever escapement, is not as conspicuous here as it is where the pallets are draith equidistant locking faces; that is, the inner angle of the entrance pallet (shown at _s_) does not have to be carried down on the arc _d'_ as far to insure a continuous pallet action of ten degrees, as with the pallets with equidistant locking faces Still, even here we have carried the angle _s_ down about half a degree on the arc _d'_, to secure a safe lock on the exit pallet

THE AMOUNT OF LOCK

If we study the large drawing, where we delineate the escape wheel ten inches in diah we clairees lock, we really have only about one degree, inases from the line _B f_, and, as a consequence, the absolute lock of the tooth _C_ on the locking face of the entrance pallet _E_ is but about one degree Under these conditions, if we did not extend the outer angle of the exit pallet at _t_ down to the peripheral line _ree of lock This is true of both pallets We les at _r s n t_ down on the circles _c'' d'_ if ould secure the lock and iht and a half degrees i to adree lock in a sound, well- to allow of a looseness of drawing to incorporate to the extent of one degree in anysuch extreme accuracy as the parts of a watch It has been claireat extent, be re the centers of the pallet staff and escape wheel nearer together We hold that such a course is not htest necessity for such a policy

ADVANTAGE OF MAKING LARGE DRAWINGS

By ested and insisted upon, we can secure an accuracy closely approxiet a lock of one and a half degrees on the locking face of the entrance pallet _E_, we measure down on the arc _c''_ from its intersection with the peripheral line _rees, and establish the point _r_ and thus locate the outer angle of the entrance pallet _E_, so there will really be one and a half degrees of lock; and by rees from its intersection with the peripheral line _m_, we locate the point _s_, which deterle of the entrance pallet, and we know for a certainty that when this inner angle is freed from the tooth it will be after the pallet (and, of course, the lever) has passed through exactly ten degrees of angular le of the exit pallet, we measure on the arc _d'_, froht and a half degrees, and establish the point _n_, which locates the position of this inner angle; and, of course, one and a half degrees added on the arc _d'_ indicates the extent of the lock on this pallet Such drawings not only enable us to theorize to extreive us proportionate measurements, which can be carried into actual construction

THE CLUB-TOOTH LEVER ESCAPEMENT

We will now take up the club-tooth form of the lever escapement This form of tooth has in the United States and in Switzerland almost entirely superceded the ratchet tooth The principal reason for its finding soto the fact that this form of tooth is better able to stand the manipulations of the able-bodied watchth than skill We will not pause noever, to consider the comparative merits of the ratchet and club-tooth forms of the lever escapement, but leave this part of the theiven full instructions for delineating both forms

With the ratchet-tooth lever escapement all of the impulse must be derived from the pallets, but in the club-tooth escapement we can divide the impulse planes between the pallets and the teeth to suit our fancy; or perhaps it would be better to say carry out theories, because we have it in our power, in this fores of the relations of the several parts With the ratchet tooth the principal changes we could s to circular pallets The club-tooth escape wheel not only allows of circular pallets and equidistant lockings, but we can divide the impulse between the pallets and the teeth in such a way as will carry out e of the escapeest the 20 we have selected, as a very excellent exarees fork action and ten and a half degrees of escape-wheel action

It will be noticed that the pallets here are coeneral use; this condition is acco the principal part of the i planes placed on the teeth As relates to the escape-wheel action of the ten and one-half degrees, which gives irees are utilized by the driving planes on the teeth and five by the irees of fork action, four and a half degrees relate to the irees to lock, and four degrees to the driving plane of the pallets

In delineating such a club-tooth escape the center of the escape wheel at _A_, and with the dividers set at five inches sweeping the arc _a a_ Through _A_ we draw the vertical line _A B'_ On the arc _a a_, and each side of its intersection with the line _A B'_, we lay off thirty degrees, as in forh the points so established on the arc _a a_ we draw the radial lines _A b_ and _A c_ From the intersection of the radial line _A b_ with the arc _a_ we draw the line _h h_ at right angles to _A b_ Where the line _h_ intersects the radial lines _A B'_ is located the center of the pallet staff, as shown at _B_ Inasrees of escape-wheel action, we take a space of two and a half degrees in the dividers, and on the arc _a a_ lay off the said two and a half degrees to the left of this intersection, and through the point so established draw the radial line _A g_ Froh the point of intersection of the arc _a_ with the line _A g_