Part 8 (1/2)
We arn our readers in advance, that if theydevice they will be astonished at the inaccuracy which they will find in the escapements of so-called fine watches The lock, in rees, will oftener be found to be frorees, and the i 76, will often fall below eight degrees Such watches will have a poor h to keep a policeman awake Trials with actual watches, with such a device as we have just described, in conjunction with a careful study of the acting parts, especially if aided by a largethe student to a degree of skill unknown to the old-style workman, who, if a poor escape pins or widen the slot in the fork
We hold that educating our repair worke of what is required to constitute a high-grade escapement, will have a beneficial effect on manufacturers When ish to apply our device to the measurement of the escapement of three-quarter-plate watches, ill require another index hand, with the grasping end bent doard, as shown at Fig 77 The idea with this forrasp the fork as close to the pallet staff as possible,the index arc that the hand _A_ will read correctly on the index _D_ Suppose, for instance, we place the jaws _B'_ inside the pallet staff, we then place the index arc so the hand reads to the arc indicated by the dotted arc _ 78, and if set outside of the pallet staff, read by the arc _o_
[Illustration: Fig 78]
HOW A BALANCE CONTROLS THE TIMEKEEPING OF A WATCH
We think a majority of the fine lever escapements made abroad in this day have what is terains to be derived fro the arc of fork and roller action; (2) reducing the friction of the guard point to a minimum While it is entirely practicable to use a table roller for holding the jewel pin with a double-roller action, still a departure from that forregate weight of a balance should be kept as far froht as well consider here as elsewhere, the relation the balance bears to the train as a controlling power Strictly speaking, _the balance and hairspring are the ti only two purposes: (_a_) To keep the balance in motion; (_b_) to classify and record the number of vibrations of the balance Hence, it is of paramount importance that the vibrations of the balance should be as untra the arc of connection between the balance and fork to one as brief as is consistent with sound results With a double-roller safety action we can easily reduce the fork action to eight degrees and the roller action to twenty-four degrees
Inasmuch as satisfactory results in adjustment depend very much on the perfection of construction, we shall noell to sothe arc of engagement between the fork and roller, we lessen the duration of any disturbing influence of escapement action
To resume the explanation of why it is desirable to make the staff and all parts near the axis of the balance as light as possible, ould say it is the ularity of the intervals of vibration To illustrate, suppose we have a balance only 3/8” in diahteen-size movement We can readily see that such a balance would require but a very light hairspring to cause it to give the usual 18,000 vibrations to the hour We can also understand, after a little thought, that such a balance would exert asforce on its pivots as a balance of the saer hairspring There is another factor in the balance problem which deserves our attention, which factor is atmospheric resistance This increases rapidly in proportion to the velocity
HOW BAROMETRIC PRESSURE AFFECTS A WATCH
The ical mechanics have decided that a balance18,000 vibrations per hour, is not desirable, because of the varying atmospheric disturbances as indicated by baroht as near the periphery as is consistent with strength, is what is to be desired for best results It is the ainst the elastic force of the hairspring, which we have to depend upon for the regularity of the tiht of matter from our roller table and place them in the rie against the hairspring, we have disposed of these two grains so as to increase the efficiency of the controlling power and not increase the stress on the pivots
[Illustration: Fig 79]
We have deduced from the facts set forth, two axioht of our balance as th; (_b_) avoid excessive size fro 79, the shape of the piece which carries the jewel pin As shown, it consists of three parts: (1) The socket _A_, which receives the jewel pin _a_; (2) the part _A''_ and hole _b_, which goes on the balance staff; (3) the counterpoise _A'''_, which ht of the jewel socket _A_, neck _A'_ and jewel pin This counterpoise also uard roller _B_, Fig 80 As the piece _A_ is always in the same relation to the roller _B_, the poise of the balance must always remain the same, no matter how the roller action is placed on the staff We once saw a double roller of nearly the shape shown at Fig 79, which had a sold screw placed at _d_, evidently for the purpose of poising the double rollers; but, to our thinking, it was a sort of hairsplitting hardly worth the extra trouble Rollers for very fine watches should be poised on the staff before the balance is placed upon it
[Illustration: Fig 80]
We shall next give detailed instructions for drawing such a double roller as will be adapted for the large model previously described, which, as the reader will rerees of roller action We will also point out the necessary changes required toto urge again the advantages to be derived fro such aexperience in escapereat many nerinkles they never dreamed of previously
It is ihly master the theory of the lever escapeht the faults and errors in such escapements, which, in the every-day practice of his profession, coe more required than in fork and roller action We are led to say the above chiefly for the benefit of a class of workmen who think there is a certain set of rules which, if they could be obtained, would enable thehts any and all escapements It is well to understand that no such system exists and that, practically, we must make one error balance another; and it is the ”kno” to make such faults and errors counteract each other that enables one workman to earn more for himself or his employer in two days than another workman, who can file and drill as well as he can, will earn in a week
PROPORTIONS OF THE DOUBLE-ROLLER ESCAPEMENT
The proportion in size between the two rollers in a double-roller escaperee on it
Grossmann shows, in his work on the lever escape roller; (2) two-thirds of the size of the acting roller The chief fault urged against a ser horns to the fork to carry out the safety action Longer horns mean more metal in the lever, and it is the conceded policy of all recent ht as possible Another fault pertaining to long horns is, when the horn does have to act as safety action, a greater friction ensues
In all soundly-constructed lever escapements the safety action is only called into use in exceptional cases, and if the watch was lying still would theoretically never be required Where fork and pallets are poised on their arbor, pocket motion (except torsional) should but very little affect the fork and pallet action of a watch, and torsional ht to act on a watch to an extent to make it worthy of much consideration In the double-roller action which we shall consider, we shall adopt three-fifths of the pitch diameter of the jewel-pin action as the proper size Not but what the proportions given by Grossood service; but we adopt the proportions naht fork, and still the friction of the guard point on the roller is but little uard roller of half the dia roller is employed
The fork action we shall consider at present is ten degrees, but subsequently we shall consider a double-roller action in which the fork and pallet action is reduced to eight degrees We shall conceive the play between the guard point and the safety roller as one degree, which will leave half a degree of lock reed pallet
THEORETICAL ACTION OF DOUBLE ROLLER CONSIDERED
In the drawing at Fig 81 we show a diagram of the action of the double-roller escapement The small circle at _A_ represents the center of the pallet staff, and the one at _B_ the center of the balance staff
The radial lines _A d_ and _A d'_ represent the arc of angular motion of fork action The circle _b b_ represents the pitch circle of the jewel pin, and the circle at _c c_ the periphery of the guard or safety roller The points established on the circle _c c_ by intersection of the radial lines _A d_ and _A d'_ ill denominate the points _h_ and _h'_ It is at these points the end of the guard point of the fork will ter for construction, we show the guard enough short of the points _h h'_ to allow the fork an angular ree, from _A_ as a center, before said point would come in contact with the safety roller
[Illustration: Fig 81]
We draw through the points _h h'_, fro'_ Wethe short arc _i_ with any of the radii we have used for arc measurement in forrees To give ourselves a practical object lesson, let us iuard point rests on the circle _c_ at _h_ Suppose we uard roller represented by the circle _c_, to aduard point, and then commence to revolve the circle _c_ in the direction of the arrow _j_, letting the guard point rest constantly in such notch When the notch _n_ in _c_ has been carried through thirty degrees of arc, counting frouard point, as relates to _A_ as a center, would only have passed through an arc of five degrees We show such a guard point and notch at _o n_ In fact, if a jewel pin was set to engage the fork on the pitch circle _b a_, the escapement would lock To obviate such lock iden the notch _n_ to the extent indicated by the dotted lines _n'_, allowing the guard point to fall back, so to speak, into the notch _n_, which really represents the passing hollow It is not to be understood that the extended notch at _n_ is correctly drawn as regards position, because when the guard point was on the line _A f_ the point _o_ would be in the center of the extended notch, or passing hollow We shall next give the details of drawing the double roller, but before doing so we deeuard points more fully than has been done heretofore