CHAPTER XIII.

THE DETACHED LEVER ESCAPEMENT AS APPLIED TO CLOCKS.

As the clock repairer is almost of necessity a watchmaker, or hopes to become one, and as he must enter deeply into the study of all questions pertaining to the detached lever in its various forms before he can make any progress at all in watchmaking, it would seem unnecessary to repeat in these pages that which has already been so well said and so perfectly drawn, described and illustrated by such authorities as Moritz Grossman, Britten, Playtner and the various teachers in the horological schools, to say nothing of an equally brilliant and more numerous coterie of writers among the French, Germans and Swiss, so that the reader is referred to these writers for the mathematics and drawings which already so fully cover the technical and theoretical properties of the detached lever escapement. A few words as to its adaptation to clocks may, however, not be out of place.

Anyone who sees the clocks of to-day would be inclined to suppose that the first clocks were constructed with pendulums, because this is evidently the most simple and reliable system for clocks, and that the employment of the balance has been suggested by the necessity for portable time pieces. This is, however, not the case, for the first clocks had a verge escapement with a crude balance consisting of two arms, carrying shifting weights for regulation. The pendulum was not used until about three hundred years after the invention of the first clock.

After the invention of the dead beat escapement, with its great gain in accuracy by the reduction of the arc of pendulum oscillation, attempts were made to combine its many virtues with the necessarily large vibrations of a balance and thus get all the advantages of both systems. By placing the lever on the arbor of the anchor, it was possible to multiply the small angle of impulse on the pallets very considerably at the balance, and to make all connection between them cease immediately after the impulse had been given. The dead beat escapement was thus converted into the detached lever escapement and the latter made available for both watches and clocks. Another important feature of this escapement is that when properly proportioned it will not set on the locking or lifting, but will start to go as soon as power is applied to the escape wheel through the train. This cannot be said of the cylinder, duplex, or detent escapements, and it will be seen at once that this has an important influence upon the cost of construction, which must always be considered in the manufacture of cheap clocks in enormous quantities.

The lever escapement with pins for pallets and the lifting planes on the teeth of the escape wheel, which is the one usually put into cheap clocks, is from the theoretical point of view a very perfect form, because its lifting and locking take place at exactly the same center distance and at the same angles, which again allows for greater latitude in cheap construction, while still maintaining a reasonably accurate rate of performance. These are the main reasons why the pin anchor has such universal use in cheap clocks.

As this escapement is generally centered between the plates, banking pins are dispensed with by extending the counterpoise end of the lever far enough so that its crescent shaped sides will perform that office by banking against the scape wheel arbor; see Fig. 61. The fork end of the lever engages with an impulse pin carried in the balance and the balance arbor is cut away to pass the guard point or dart, thus doing away with the roller table. In other constructions the roller table is supplied in the shape of a small brass collet which carries the pin and has a notch for the guard point, thus making a single roller escapement.

The diameter of the lifting pins is generally made equal to 2½ degrees of the scape wheel, which gives a lift of 2 degrees on the pallet arms, and the remainder of the lift, 6½ degrees, must be performed by the lifting planes of the wheel teeth. The front sides of the wheel teeth are generally made with 15 degrees of draw and the lever should bank when the center of the pin is just a little past the locking corner of the tooth. Other details of the pin anchor escapement coincide with the ordinary pallet form, as used in watches, and the reader is referred for them to the works of the various authors mentioned previously.

The trouble with the majority of these clocks is in the escapement and balance pivots, and to these parts are we going to direct particular attention, for often, be it ever so clean, the balance gets up a sort of “caterpillar motion” that is truly distressing, and if no more is done we may expect a “come back” job in a very short time. In taking down the movement the face wheels are left in place, but sometimes it may be necessary to remove the “set wheel” of the alarm in order to proceed as we do. Remove the screws or pins that hold the plates together in the vicinity of the escapement, leaving the others, though if screws they may be loosened slightly; pry up the corner of the plate over the lever to loosen one pivot of same and let it drop away from the scape wheel sufficiently to let the wheel revolve until it is locked by a wire or pegwood previously inserted in the train, after which the plates can be pried apart more conveniently to permit the lever being removed entirely, also the scape wheel and the one next following. As nickel clocks differ in make-up, the operator must, of course, exercise judgment as to the work in hand to accomplish this.

Have ready a straight-sided tin pail, with cover, that will hold at least one-half gallon of gasoline and of diameter large enough to receive the largest brass clock; remove the wire or pegwood and immerse the clock into the fluid and allow it to run down; this will loosen all the dirt and gummy oil and clean the clock very effectually. Let it remain long enough for all the dirt to settle to the bottom of the pail; then remove and wipe as dry as possible with a soft rag; by having no binder on the spring it is permitted to uncoil to its full, and thereby remove all gummy oil between its coils. Now peg out the holes of the wheels removed and of the lever and that portion of our work is complete.

Polish or burnish the pivots of wheels either in a split chuck in the lathe, or by holding in a pin vise, resting the pivot on a filing block (an ivory one is best), and revolving between the fingers, using a smooth back file for burnishing, after the manner of pointing up a pin tongue, only let the file be held flat, so as to maintain a cylindrical pivot as nearly as possible. The scape wheel is now polished, i. e., the teeth, with a revolving bristle wheel on a polishing lathe, charged with kerosene oil and tripoli. This will smooth up the teeth in fine form, especially those wheels that work into a lever with pin pallets. Clean the scape wheel by dipping into gasoline to remove all the oil and tripoli. The other wheel may simply be brushed in the gasoline or dipped and then brushed dry.

We now turn our attention to the lever and closely examine the pallets with a glass; if there are the least signs of wear upon them they must be removed. Of the lever with pin pallets it is better to remove the steel pins and insert new ones. See if the holes in the anchor where they are inserted will admit a punch to drive them out from the back; if not, open these holes with a drill until the ends of the pins are reached. Put a hollow stump with a sufficiently large hole in the staking tool, and by placing the pins in the stump they can be driven out successively, being sure that the driving punch is no larger than the pins; drive or insert into their places a couple of needles of the proper size, and then break off at correct lengths; this completes the job in this particular style of lever.

With the other style the job is not quite so easy; with a pair of small round-nose pliers grasp the brass fork close up to the staff and bend it back from the pallets till it lays parallel with the staff; treat the counter poise of the fork in like manner; place a thin zinc lap into the lathe, charged with flour of emery, and with the fingers holding the pallets grind off all wheel teeth marks on both the impulse and locking faces of the pallets. Then polish with a boxwood lap charged with diamantine. It is surprising how speedily this can be done if laps are at hand. The only care necessary is not to round off the corners of the pallets, and as they are so large they can be easily held flat against the laps with the thumb and finger as before stated. Bend back the fork and counterpoise to their original position. The fork must now be attended to; see that no notches are worn in the horns of the fork by the steel impulse pin in the balance; if they appear they must be dressed out and polished, also examine and smooth if necessary the ends of the horns that bank against the balance staff. These may seem small matters, but they are often what cause all the trouble.

We now come to the balance staff and the hardened screws in which the staff vibrates; their irregularities are often the source of much vexation, and there is only one way to go at it and that is with a will and determination to make it right. Examine the points of the staff and see if they are in their normal shapes and are sharp and bright; if so they will probably do their work. But we will suppose we have a bad case in hand and will therefore treat it thoroughly according to our method. We find the staff is large in diameter and the ends are very blunt; the notch in the center has a burr on each side as hard as glass, making an admirable cause for catching the horns of the fork in some of the vibrations or in a certain position; also the round part of the staff back of the notch is rough and looks as if it never had been finished, and, in fact, it has not, for it truly appears as if half, if not all, the nickel clocks are made to be finished by the watchmaker. Remove the hairspring and place the staff between the jaws of your bench vise, with the jaws close up to the staff, but not gripping it, the balance “hub” resting on the jaws with the impulse pin also down between the jaws. Have a block of brass about one-fourth inch square; rest it on top of the staff, or on its pivot end, if it may so be called, holding it with the thumb and finger of the left hand. Strike this block with a hammer and drive out the staff; a hollow punch is apt to be split in doing this, and as the pivot is to be re-pointed no harm will be done to the pivot or to the end of the staff. Draw the temper so it will work easily, insert into a split chuck and turn up new points; have them long and tapering, that is, turn the points to a long slant from the end of the staff to the body of same, or at least twice as much taper as they generally have; polish off the back of the notch or round part of the staff with an oil stone slip. Remove from the chuck, smear all over with powdered boracic acid by first wetting the staff in water, and then heat to a bright red and plunge straight into water; it will now be white and hard; draw the temper from the staff in the vicinity of the notch, leaving the pivot points hard as before; re-insert into the chuck and with diamantine polish the points and also around the staff in the vicinity of the notch. The drawing of the temper from the center of the staff to a spring temper is to make it less liable to breakage while driving on the balance. Fasten the staff tight in the vise and with a rather stout brass tube, large enough to step over the largest staff, drive on the balance to its former position.

If the workman has a pivot polisher with a large lap, the job may be done, without softening the staff or removing the balance, by grinding the pivots. In turning the staff we often find it almost impossible to hold true. We straighten the best we can and then turn up our pivots, and as long as the untruth of the staff will not cause the balance to wabble to such an extent as to give us a headache or cause us to look cross-eyed it will do. We do not wish to be misunderstood or to give the impression that we go on the principle of “good enough”; but as gold dollars cannot be bought for seventy-five cents, neither can a workman devote the time to have everything perfect for fifty cents; and for this very reason do they come in such an unfinished state from the manufacturers.

Next see if the two screws in which the balance vibrates have properly cut countersinks; if rough or irregular, better at once draw the temper, re-drill with a sharp-angled drill and again harden.

Occasionally a bunch of these clocks will come in with both pivots and cones badly rusted. This has generally been caused by acid pickling, or some sort of chemical hardening at the factory; the acid or alkali gets into the pores of the steel and comes out after the clock has been shipped. They are generally made in such quantities that fifty or a hundred thousand of them have been distributed before finding out that they were not right and then it is a matter of two or three years before the factory hears the last of it. The trouble is attributed to bad oil, or to anything else but the hardening, which is the real cause, and the expense of taking back and refitting the balance arbors and cones, paying freight both ways and standing the abuse of disgruntled jewelers, goes on until life becomes anything but a bed of roses. Every jeweler should warn the factory immediately on finding rust in the cones of a shipment of new clocks and not attempt to fix them himself, as such a fault cannot be discovered at the factory and every day it continues means more thousands of clocks distributed that will give trouble.

Our clock is now ready to be put together. Wind up the spring and slip on the binder; then put in the wheels and lever; then adjust the balance and hairspring to their proper places, slightly wind the mainspring and then see (by bringing either horn against the staff) whether it sticks and holds the balance; if so, shorten the fork slightly by bending; try this until the balance and fork act perfectly free and safe. Slightly oil the balance pivots; an excess will only gather dust and prove detrimental, as the countersinks form an admirable place for holding the dust. Now oil the remaining parts and we are sadly mistaken if our clock does not make a motion that will be gratifying.

The foregoing process may seem tedious and uncalled for and too close mention made of the lesser portions of the work, but we must not “despise the day of small things,” and as we are watchmakers, we are expected to do this work, even though troublesome and the pay small; we should also bear in mind that if we only make a nickel clock run and keep fair time, it will be a large advertisement, and possibly repay tenfold. It takes only an hour to do this job complete, while in many cases only the balance staff needs attention.

Sometimes such a clock will be apparently all right mechanically but will continue to lose time; then it is probable that the balance does not make the proper number of vibrations, which causes the clock to lose time. There is one way to tell this, which will soon locate the trouble: count the train to ascertain the number of vibrations the balance should make in one minute. You do this by counting the number of teeth in the center wheel, which we will say is 48; third wheel 48; fourth wheel, 45; escape, 15. Multiply all teeth together, which give us 48 × 48 × 45 × 15 = 1,555,200. Now count the leaves in the third wheel pinion, which is 6; fourth, 6; escape, 6. Multiply these together, 6 × 6 × 6 = 216; now divide the leaves into the teeth, 1,555,200 ÷ 216 = 7,200, which is the number of whole vibrations some Ansonia alarm clocks make in one hour. Dividing 7,200 by 60 gives us 120, the number of vibrations per minute. Now the balance must make 120 vibrations in one minute, counting the balance going one way. If the balance only vibrates 118, the clock will lose time and the hairspring must be taken up or made shorter, until it makes the required number of vibrations. If it should vibrate 122 the clock would gain and the hairspring should be let out.

Find out the number of vibrations your balance should make and work accordingly; and if you find that the balance makes the proper number of vibrations in one minute, then the trouble must lie in the center post, which has not enough friction to carry the hands and dial wheels, or the wheel that gears into the hour wheel and regulates the alarm hand is too tight and holds back the hands. You should find some trouble about these wheels or center post, for where a balance makes the proper number of vibrations in one minute, the minute hand cannot help going around if everything else is correct.

Fig. 62 illustrates the escapement of the Western Clock Manufacturing Company for their cheap levers. It has hardened steel pallets placed in a mould and the fork cast around them, thus insuring exact placing of the pallets, and the company claim that they thus secure a detached lever escapement with all the advantages of hardened and polished pallets at a minimum cost.

Mr. F. Dauphin, of Cassel, Germany, on page 387 of Der Deutsche Uhrmacher Zeitung, 1905, has described a serious fault of some of the cheap American alarm clocks in the depthings of the escapements and how he remedied it by changing the position of the pins. It is to be regretted that Mr. Dauphin did not state the measurements of the parts as nearly as possible in this article and also give the manufacturer’s name, simply to enable others not as skilled as he is to do what I would do in such a case; namely, to return it to the jobber and get a new and correct movement in its stead _free of charge_. The American clock manufacturers are very liberal in this respect and never hesitate to take back a movement that was not correct when it left the factory, even when the customer, in the attempt to correct it, has spoiled it; spoiled or not, it goes to the waste pile anyway, when it reaches the factory. I seriously doubt the ability of the average watch repairer to correctly change the position of the pins as suggested; and to change the center of action of the lever is certainly a desperate job. I herewith give a correct drawing of an escape wheel and lever, such as are used in the above cited clocks, made from measurements of the parts of a clock. The drawing is, of course, enlarged. The measurements are: Escape wheel, actual diameter, 18.11 mm.; original diameter, 17 mm.; lever, from pin to pin, outside, 9.3 mm.; distance of centers of wheel and lever, 10.0 mm. I found that all these measurements almost exactly agree with Grossmann’s tables, and I do not doubt at all that they were taken from them. There is only one mistake visible, which is in the shape of the escape teeth, and I fail to see why this was overlooked by those in charge at the factory; _the draw is insufficient_. It is only from seven to eight degrees, when it should be fifteen degrees. I show this at tooth A, in the drawing, where you can see both dotted lines, measuring the angle of draw; line C as it is and line B as it should be.

Notwithstanding the deficient draw, this escapement will work safely as long as the pivot holes are not too large, or worn sideways; but if you want to make it safe you should file the locking faces of teeth slightly under; even if you do not make a model job, you have remedied the fault. Make a disk of 18.11 mm. diameter, put it on the arbor of the wheel and lay a straight edge from the point of the tooth to the center of the disk, so as to see how much it needs to be filed away. Even if this undercutting is not very true it will go.

TO MEASURE WHEELS WITH ODD NUMBERS OF TEETH.—This is a job that so frequently comes to the watchmaker who has to replace wheels or pinions that the following simple method should be generally appreciated. It depends upon the fact that the radius of a circle, R, Fig. 64, equals the versed sine E (dotted) plus the cosine B. If we stand such a wheel on the points of the teeth, A C, and measure it we shall get the length of the line T B only, when what we really need is the length of the lines T B E, to give us the real diameter for our wheel, and E we find has been cut away, so that we cannot measure it. Say it is a 15-tooth escape wheel, then by standing the old wheel up on the anvil of a vertical micrometer, resting it on two of its teeth, as shown in Fig. 64, the measuring screw can be brought in contact with the tooth diametrically opposite the space between the two teeth on the anvil, and a measurement taken, which will be less than the full diameter by the versed sine of 12 degrees (half the angle included between two adjoining teeth). By bringing each tooth in succession to the top, such a wheel could be measured in fifteen different directions, which would vary slightly, owing to the fact that some of the teeth may be bent a little, but the mean of these measures should be what the wheel would measure were the teeth in their original shape. If a tooth was badly bent the three measures in which it was involved could be rejected, and the mean of the other twelve measures taken as the correct value and found to be, we will say, 0.732 inch. Consulting a table of natural sines the cosine of 12 degrees is found to be 0.97815, which subtracted from 1 gives 0.02185 as the versed sine. Multiplying this by 0.36 inch (practically one-half of our measured 0.732) to get the approximate radius of the wheel, we get 0.008 inch, the amount to be added to the micrometer measurement in order to get the diameter of the blank.

At first sight it may appear like a vicious principle that we must know the radius of the wheel before we can determine the value of the correction in question, but we only need to know the radius approximately in order to determine the correction very closely, an error of ¹/₂₀ inch in the assumed value of the radius producing an error of only 0.001 inch in the value of the correction.

This method can of course be applied to all wheels and pinions to get the size of the blank; with other wheels than escape wheels, where the pitch line and the full diameter do not coincide, the addendum may be subtracted from the full diameter to get the pitch line.

CUTTERS FOR CLOCK TRAINS.—In cutting escape wheels or others with wide space between the teeth, it is a matter of some difficulty with many people to enable them to set the cutter properly.

Mr. E. A. Sweet calls attention to the fact that if a cutter be set so that its center touches the circumference of the wheel to be cut, said cutter will be in the proper position for work. For instance, if an escape wheel is to be cut, it is sufficient to set the cutter in such a manner that that portion of the cutter forming the bottom of the cut touch the circumference of the blank at the center of the cutter. It may then be backed off and fed in with the certainty of being properly placed.