Watch and Clock Escapements Part 12

The hollow cone end _m_ of _I_ should also be hardened, but this is best done after the hollow cone is turned in. The hardening of both ends should only be at the tips. The sliding center _I_ can be held in the V-shaped groove by two light friction springs, as indicated at the dotted lines _s s_, Fig. 115, or a flat plate of No. 24 or 25 sheet bra.s.s of the size of _H_ can be employed, as shown at Figs. 116 and 117, where _o_ represents the plate of No. 24 bra.s.s, _p p_ the small screws attaching the plate _o_ to _H_, and _k_ a clamping screw to fasten _I_ in position. It will be found that the two light springs _s s_, Fig. 115 will be the most satisfactory. The wire legs, shown at _L_, will aid in making the device set steady. The pillar _E_ is provided with the same slides and other parts as described and ill.u.s.trated as attached to _D_.

The position of the pillars _D_ and _E_ are indicated at Fig. 110.

[Ill.u.s.tration: Fig. 117]

[Ill.u.s.tration: Fig. 118]

We will next tell how to flatten _F_ to keep _H_ exactly vertical. To aid in explanation, we will show (enlarged) at Fig. 118 the bar _F_ shown in Fig. 109. In flattening such pieces to prevent turning, we should cut away about two-fifths, as shown at Fig. 119, which is an end view of Fig. 118 seen in the direction of the arrow _c_. In such flattening we should not only cut away two-fifths at one end, but we must preserve this proportion from end to end. To aid in this operation we make a fixed gage of sheet metal, shaped as shown at _I_, Fig. 120.

[Ill.u.s.tration: Fig. 119]

ESCAPEMENT MATCHING DEVICE DESCRIBED.

[Ill.u.s.tration: Fig. 120]

In practical construction we first file away about two-fifths of _F_ and then grind the flat side on a gla.s.s slab to a flat, even surface and, of course, equal thickness from end to end. We reproduce the sleeve _G_ as shown at Fig. 113 as if seen from the left and in the direction of the axis of the bar _F_. To prevent the bar _F_ turning on its axis, we insert in the sleeve _G_ a piece of wire of the same size as _F_ but with three-fifths cut away, as shown at _y_, Fig. 121. This piece _y_ is soldered in the sleeve _G_ so its flat face stands vertical. To give service and efficiency to the screw _h_, we thicken the side of the sleeve _F_ by adding the stud _w_, through which the screw _h_ works. A soft metal plug goes between the screw _h_ and the bar _F_, to prevent _F_ being cut up and marred. It will be seen that we can place the top plate of a full-plate movement in the device shown at Fig. 109 and set the vertical centers _I_ so the cone points _n_ will rest in the pivot holes of the escape wheel and pallets. It is to be understood that the lower side of the top plate is placed uppermost in the movement holder.

[Ill.u.s.tration: Fig. 121]

If we now reverse the ends of the centers _I_ and let the pivots of the escape wheel and pallet staff rest in the hollow cones of these centers _I_, we have the escape wheel and pallets in precisely the same position and relation to each other as if the lower plate was in position. It is further to be supposed that the balance is in place and the c.o.c.k screwed down, although the presence of the balance is not absolutely necessary if the banking screws are set as directed, that is, so the jewel pin will just freely pa.s.s in and out of the fork.

HOW TO SET PALLET STONES.

We have now come to setting or manipulating the pallet stones so they will act in exact conjunction with the fork and roller. To do this we need to have the sh.e.l.lac which holds the pallet stones heated enough to make it plastic. The usual way is to heat a piece of metal and place it in close proximity to the pallets, or to heat a pair of pliers and clamp the pallet arms to soften the cement.

Of course, it is understood that the movement holder cannot be moved about while the stones are being manipulated. The better way is to set the movement holder on a rather heavy plate of gla.s.s or metal, so that the holder will not jostle about; then set the lamp so it will do its duty, and after a little practice the setting of a pair of pallet stones to perfectly perform their functions will take but a few minutes. In fact, if the stones will answer at all, three to five minutes is as much time as one could well devote to the adjustment. The reader will see that if the lever is properly banked all he has to do is to set the stones so the lock, draw and drop are right, when the entire escapement is as it should be, and will need no further trial or manipulating.

CHAPTER II.

THE CYLINDER ESCAPEMENT.

There is always in mechanical matters an underlying combination of principles and relations of parts known as "theory." We often hear the remark made that such a thing may be all right in theory, but will not work in practice. This statement has no foundation in fact. If a given mechanical device accords strictly with theory, it will come out all right practically. _Mental conceptions_ of a machine are what we may term their theoretical existence.

When we make drawings of a machine mentally conceived, we commence its mechanical construction, and if we make such drawings to scale, and add a specification stating the materials to be employed, we leave only the merest mechanical details to be carried out; the brain work is done and only finger work remains to be executed.

With these preliminary remarks we will take up the consideration of the cylinder escapement invented by Robert Graham about the year 1720. It is one of the two so-called frictional rest dead-beat escapements which have come into popular use, the other being the duplex. Usage, or, to put it in other words, experience derived from the actual manufacture of the cylinder escapement, settled the best forms and proportions of the several parts years ago. Still, makers vary slightly on certain lines, which are important for a man who repairs such watches to know and be able to carry out, in order to put them in a condition to perform as intended by the manufacturers. It is not knowing these lines which leaves the average watchmaker so much at sea. He cuts and moves and s.h.i.+fts parts about to see if dumb luck will not supply the correction he does not know how to make. This requisite knowledge does not consist so much in knowing how to file or grind as it does in discriminating where such application of manual dexterity is to be applied. And right here let us make a remark to which we will call attention again later on. The point of this remark lies in the question--How many of the so-called practical watchmakers could tell you what proportion of a cylinder should be cut away from the half sh.e.l.l? How many could explain the difference between the "real" and "apparent" lift? Comparatively few, and yet a knowledge of these things is as important for a watchmaker as it is for a surgeon to understand the action of a man's heart or the relations of the muscles to the bones.

ESSENTIAL PARTS OF THE CYLINDER ESCAPEMENT.

The cylinder escapement is made up of two essential parts, viz.: the escape wheel and the cylinder. The cylinder escape wheel in all modern watches has fifteen teeth, although Saunier, in his "Modern Horology,"

delineates a twelve-tooth wheel for apparently no better reason than because it was more easily drawn. We, in this treatise, will consider both the theoretical action and the practical construction, but more particularly the repair of this escapement in a thorough and complete manner.

At starting out, we will first agree on the names of the several parts of this escapement, and to aid us in this we will refer to the accompanying drawings, in which Fig. 122 is a side elevation of a cylinder complete and ready to have a balance staked on to it. Fig. 123 shows the cylinder removed from the balance collet. Figs. 124 and 125 show the upper and lower plugs removed from the cylinder. Fig. 126 is a horizontal section of Fig. 122 on the line _i_. Fig. 127 is a side view of one tooth of a cylinder escape wheel as if seen in the direction of the arrow _f_ in Fig. 126. Fig. 128 is a top view of two teeth of a cylinder escape wheel. The names of the several parts usually employed are as follows:

_A._--Upper or Main Sh.e.l.l.

_A'._--Half Sh.e.l.l.

_A''._--Column.

_A'''._--Small Sh.e.l.l.

_B B' B''._--Balance Collet.

_G._--Upper Plug.

_H._--Lower Plug.

_g._--Entrance Lip of Cylinder.

_h._--Exit Lip of Cylinder.

_c._--Banking Slot.

_C._--Tooth.

_D._--U arm.

_E._--Stalk of Pillar.

_I._--U s.p.a.ce.

_l._--Point of Tooth.

_k._--Heel of Tooth.

The cylinder escapement has two engagements or actions, during the pa.s.sage of each tooth; that is, one on the outside of the cylinder and one on the inside of the sh.e.l.l. As we shall show later on, the cylinder escapement is the only positively dead-beat escapement in use, all others, even the duplex, having a slight recoil during the process of escaping.

When the tooth of a cylinder escape wheel while performing its functions, strikes the cylinder sh.e.l.l, it rests dead on the outer or inner surface of the half sh.e.l.l until the action of the balance spring has brought the lip of the cylinder so that the impulse face of the tooth commences to impart motion or power to the balance.

[Ill.u.s.tration: Fig. 122]

[Ill.u.s.tration: Fig. 123]

[Ill.u.s.tration: Fig. 124]

[Ill.u.s.tration: Fig. 125]

[Ill.u.s.tration: Fig. 126]

[Ill.u.s.tration: Fig. 127]

[Ill.u.s.tration: Fig. 128]

Most writers on horological matters term this act the "lift," which name was no doubt acquired when escapements were chiefly confined to pendulum clocks. Very little thought on the matter will show any person who inspects Fig. 126 that if the tooth _C_ is released or escapes from the inside of the half sh.e.l.l of the cylinder _A_, said cylinder must turn or revolve a little in the direction of the arrow _j_, and also that the next succeeding tooth of the escape wheel will engage the cylinder on the outside of the half sh.e.l.l, falling on the dead or neutral portion of said cylinder, to rest until the hairspring causes the cylinder to turn in the opposite direction and permitting the tooth now resting on the outside of the cylinder to a.s.sume the position shown on the drawing.

The first problem in our consideration of the theoretical action of the cylinder escapement, is to arrange the parts we have described so as to have these two movements of the escape wheel of like angular values. To explain what we mean by this, we must premise by saying, that as our escape wheel has fifteen teeth and we make each tooth give two impulses in alternate directions we must arrange to have these half-tooth movements exactly alike, or, as stated above, of equal angular values; and also each impulse must convey the same power or force to the balance. All escape wheels of fifteen teeth acting by half impulses must impel the balance during twelve degrees (minus the drop) of escape-wheel action; or, in other words, when a tooth pa.s.ses out of the cylinder from the position shown at Fig. 126, the form of the impulse face of the tooth and the shape of the exit lip of the cylinder must be such during twelve degrees (less the drop) of the angular motion of the escape wheel. The entire power of such an escape wheel is devoted to giving impulse to the balance.

The extent of angular motion of the balance during such impulse is, as previously stated, termed the "lifting angle." This "lifting angle" is by horological writers again divided into real and apparent lifts. This last division is only an imaginary one, as the real lift is the one to be studied and expresses the arc through which the impulse face of the tooth impels the balance during the act of escaping, and so, as we shall subsequently show, should no more be counted than in the detached lever escapement, where a precisely similar condition exists, but is never considered or discussed.

We shall for the present take no note of this lifting angle, but confine ourselves to the problem just named, of so arranging and designing our escape-wheel teeth and cylinder that each half of the tooth s.p.a.ce shall give equal impulses to the balance with the minimum of drop. To do this we will make a careful drawing of an escape-wheel tooth and cylinder on an enlarged scale; our method of making such drawings will be on a new and original system, which is very simple yet complete.

DRAWING THE CYLINDER ESCAPEMENT.

All horological--and for that matter all mechanical--drawings are based on two systems of measurements: (1) Linear extent; (2) angular movement.

For the first measurement we adopt the inch and its decimals; for the second we adopt degrees, minutes and seconds. For measuring the latter the usual plan is to employ a protractor, which serves the double purpose of enabling us to lay off and delineate any angle and also to measure any angle obtained by the graphic method, and it is thus by this graphic method we propose to solve very simply some of the most abstruce problems in horological delineations. As an instance, we propose to draw our cylinder escapement with no other instruments than a steel straight-edge, showing one-hundredths of an inch, and a pair of dividers; the degree measurement being obtained from arcs of sixty degrees of radii, as will be explained further on.