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Chronographs, Calendars, Etc.

( Originally Published 1918 )

Stop Watches.—These are merely centre seconds watches with a slide at the side of the case, operating a lever on the pillar plate. The lever has an upright thin brass wire, which comes into contact with the balance rim or the roller edge and stops the watch. Pulling the slide back releases the balance, and the watch starts again. An improved form of stop watch has the stopping mechanism operated by pressing the keyless winding button.

The Independent Centre Seconds watch was introduced to enable the seconds hand to be stopped and restarted without stopping the watch at all. These watches had two mainsprings and two trains of wheels. One was the going train, the other the centre seconds train, and its sole business was to drive the seconds hand. The scape pinion had always six leaves, there-fore one leaf came round per second. The last pinion of the independent train was a fly pinion, with a light arm that just caught the leaves of the scape pinion. Every time a leaf passed, the arm of the fly pinion was allowed to pass, and the fly made one revolution. This caused the centre seconds hand to beat dead seconds. A few showed fifths of seconds by a small hand making one revolution per second. The independent train was stopped and started by a slide at the case side, as in stop watches. The slide worked a lever which caught the fly pinion arm. Independent centre seconds watches are no longer made, their place being taken by chronographs with a " start stop and fly back action quite independent of the going train.

Centre seconds watches have the minute hand driven by, motion wheels. If the depths of these wheels are a little shallow, they allow the minute hand too much shake. Very often the amount of shake is equal to as much as one minute division on the dial. This renders the time uncertain to that amount. To reduce the error, some watches have a very thin and light spring acting on the teeth of the cannon pinion to hold it back, as in Fig. 202. Such a spring can with advantage be fixed to a good watch of this kind having shaky motion work. Its back pressure is so slight that it does not interfere at all with the going of the watch.

Chronographs.—The first chronographs really marked the time. A seconds hand was used whose point held a small drop of ink. On pressing the button, this was caused to mark the dial with a dot without stopping the hand. Modern chronographs start the hand with the first push of the button, stop it by the second, and cause it to fly back to zero by a third push. When not in use as a chronograph the hand rests at zero.

Starting Mechanism.—They are arranged in many ways, but all contain the same general mechanism and act on the same principles. A centre seconds hand is mounted on an axis with a fine-toothed wheel. Another wheel the same size is mounted on the fourth pinion of the going train, or the fourth wheel itself used. An intermediate wheel between the two is so arranged that it can be put into or out of gear by a slight movement. When in gear the centre seconds hand runs. When out of gear the hand stands still.

Fig. 203 is an illustration of one method adopted, in which the fourth wheel itself drives the small intermediate wheel A. A has two sets of teeth. One set gears with the fourth wheel B, and the other, very fine set, gears with the centre seconds wheel C. A is mounted in a frame, E, turning on a pivot at D. It has a very slight movement, just enough to engage and disengage the fine teeth. B is the fourth wheel, with which A is always running ; C is the centre seconds wheel. In Fig. 204, B is a fine wheel mounted on the fourth pinion ; C is the centre seconds wheel ; A is the intermediate wheel running in a frame like a lever, pivoted at the fourth pinion. A very slight movement of the lever D suffices to throw A into gear with C. In other watches the wheels have bevel teeth, and the intermediate wheel, or the wheel C, throws into and out of gear by a rise and fall motion.

So far as the starting is concerned, it is effected by a press of the button moving the frame E (Fig. 203) or the lever D (Fig. 204) so as to throw A into gear with C.

Stopping Mechanism.—The stopping is effected by the second push throwing the intermediate wheel A out of gear again, and simultaneously applying a brake to the rim or teeth of C to hold it still and steady where stopped. In Fig. 2o5, A is the brake. It works on a pivot, B, and is applied by the light spring D. A very slight movement lifts it clear of C or applies it to hold C steady.

Fly-back Mechanism.—A third push of the button lifts the brake clear of C, and at the same time brings C back to zero. This is effected as in Fig. 206. C, the centre seconds wheel, has a steel heart fixed to it. The lever B comes down sharply upon the heart, which is really a part of a spiral, and by its pressure on the polished edge of the heart causes C to fly round until B rests upon the hollow and holds C steady at zero. B is pivoted at D, and is brought down sharply by a spring, E.

The fourth push of the button commences the cycle of operations again, and lifts B (Fig. 206) clear of A, and simultaneously throws A (Figs. 203 and 204) into gear with C. The button, upon its being pushed in, depresses the lever A, working on a stud or pivot at B. At its other end is a hook, C, which engages with the ratchet wheel D. Each time A is depressed D is hooked round one tooth. D is held in position by the click F. Upon D are four projecting pieces of steel, E. It takes three pushes of A to bring each block E round, forming a complete cycle. Against the blocks E rest the tail ends of the levers applying the brake, throwing the intermediate wheel into gear and bringing the heart to zero. D is therefore the main controlling wheel of the entire mechanism. Each lever has its spring, holding its tail end against the blocks E. As a block comes round it raises one tail end, as at G, and then allows it to fall into the space again.

Minute Recorders.—Most chronographs are furnished with a minute recorder.

The wheel C or A (Fig. 204) is fitted with a short finger, which comes round at the end of one minute and moves the minute recording wheel round one tooth. A hand on the dial indicates the number of minutes run since the hand was started. Generally the recording hand reads up to thirty minutes, and therefore the wheel has thirty teeth. Minute recording mechanism varies very much in design, but is always fairly simple and easily seen. Some minute recording hands are slowly travelling all the time the hand is running. The minute recording wheel is furnished with a heart piece, and is brought to zero by the same lever as the centre seconds wheel, and in the same manner.

Double Fly-back Hands.—Some chronographs have a double seconds hand, the second one being just underneath the first. A push piece in the case enables it to be stopped any-where while the first runs on. A second push causes it to rejoin the first hand. The mechanism of this is simple, though very delicate.

The wheel C (Fig. 206) is furnished with another small steel heart over the one shown. A light wheel runs over it, with a pipe outside the pipe of the wheel C. In Fig. 208, A is the wheel supporting the second hand. It is furnished with a pivoted friction roller (generally of ruby), which presses against the edge of the heart, and, if left to itself, will always find the lowest point, as shown, holding the wheel lightly. The slightest pressure on its rim will stop it, and the wheel C (Fig. 206) underneath it, with the heart, will continue to travel without it. The small ruby roller meanwhile runs round the heart. A (Fig. 208) has a smooth rim with no teeth.

The stopping mechanism for the wheel A consists of a double brake like a pair of scissors, as at B. These are allowed to close a little by a spring and grip the rim of A. This stops the hand. When B is opened the wheel A is released, and the small ruby roller and spring, acting on the heart on C, causes A to return to its original position on C and travel with it again.

The brakes B are alternately opened and closed by a square between their outer ends. When two angles are presented to B, they open ; when two flats, they close. They are closed by a spring. The square is worked round by a ratchet and a hooked lever actuated by a case push piece, as shown in Fig. 208, very much resembling the mechanism shown in Fig. 207.

Cleaning.—To clean a chronograph, take out the balance for safety ; then remove the chronograph work, and take all to pieces, being careful to keep each spring with its lever, etc., to avoid confusion. In putting together, put on the chronograph work last, preferably when the watch is in its case. Oil the pivot of the wheel D (Fig. 207), all the lever pivots, and the blocks E. Oil where each spring makes contact with its lever.

When the chronograph hand is mounted on a long, slender pivot coming through the centre pinion, and its wheel is on the back of the watch, oil its pivots. But when the hand is mounted on the pipe of its wheel, which runs outside the cannon pinion or centre arbor, the pipe must be absolutely clean inside, and not oiled. The slightest oil or dirt here will stop it. These remarks apply still more forcibly to the second hand of a double fly back. Its pipe and ruby roller must be clean and free. Some chronograph hands do not always go back exactly to zero, but vary about 1/5 second each time. To remedy this, many are fitted with a light spring, which just catches the point of the heart and holds it exactly true each time. While the hand is running the point of the heart just touches the tip of this spring at each revolution and passes it. Fig. 209 shows the arrangement. A is the spring that holds the heart-point.

The fine-toothed wheels are very delicate. They must be brushed clean in the teeth, as the slightest dirt completely fills up the fine-cut spaces. The depth between A and C (Figs. 203 and 204) is a very particular one. In some watches A is simply kept pressed into C by a light spring, and the depth has no shake at all, one wheel following the inequalities of the other. In these watches starting the seconds hand nearly always takes off some of the power, and causes the action of the balance to fall off very much. In other watches the lever carrying A is pressed against an adjustable stop (D, Fig. 204), and can approach C no further. In these the depth can be set to a nicety with a strong eyeglass, so as to have just a little shake all round. It causes the point of the hand to move a little loosely, but avoids dragging the watch.

Double fly-back chronographs are very delicate, and seldom work perfectly for many months together. The slightest dirt will cause sticking of the hands, and prevent them flying back properly to zero. Great care must always be taken in putting the hands on to see that they are all free of each other in any position they may take up.

There is one form of Swiss chronograph often met with in which the chronograph hand and dial are both at the back of the watch. In these the chronograph wheel C (Fig. 20k) is driven direct by the wheel B, on the fourth wheel axis, and there is no need for an intermediate wheel. Both these wheels, B and C, are bevel wheels, and C throws into gear by a rise and fall or "pump" action. They are so arranged that by turning two or three dog screws at the edge, the whole of the chronograph work can be removed bodily without disturbing its parts, and, if necessary, the going part of the watch can be cleaned and repaired without doing the chronograph work.

Simple Calendars.—In these the day of the month is shown, and the watch automatically changes it at midnight each 24 hours. The date dial is divided up to 31 days, and for the months having that number of days is correct. For the 28, 29, or 30 day months the hand requires correction. Some calendars show in addition the day of the week, the month, and the age of the moon.

In these simple calendars the day of the week, the month, and the moon dials will need no alteration so long as the watch is wound (except for a small error that accumulates with the moon disc), the date only requiring correction.

The calendar wheels are driven from the hour wheel, which turns once in 12 hours. This is made to drive two wheels of exactly twice the size, turning in 24 hours. A pin, B, in one of these wheels moves the day of the week wheel, C (Fig. 210), one tooth. This wheel has 7 teeth, and is mounted on a fixed stud in the watch plate, and held in position by a spring or jumper, A. The other 24-hour wheel similarly moves the date wheel, made and mounted as in Fig. 210, but with 31 teeth. A pin or finger on the date wheel moves the month wheel (12 teeth) one tooth at each revolution. A second pin on one of the 24-hour wheels moves the moon wheel one tooth per day. In cleaning these watches, leave all calendar wheels and studs dry, but oil the springs where they touch. When putting together, set the watch at 12 o'clock; then put on all calendar wheels in such a position that they just begin to change. As a rule, each hand and wheel can be set by jumping it round with a push in the case side. Take out and clean all these pushes, as dirt is apt to accumulate and fix them.

Perpetual Calendars never want altering, unless the watch stops. They show the date correctly, and change the month in February, in 30 and 31 day months, and even give February 29 days in leap year. But as they all failed in the year 1900, they can scarcely be called perpetual ! Still, it will be many a year before they need go wrong in this way again.

As before remarked, it is the date wheel that causes the difficulty. Instead of being moved by a simple pin set in a 24-hour wheel, it has to be moved by a jumper. This is a steel lever that is drawn back a certain distance, and in going forward pushes the date wheel on one tooth. An arrangement is made by which, at the end of April, June, September, and November, the juniper is drawn back more, and in going forward moves the wheel two teeth. In February it moves it four teeth, except in leap year, when it only moves three.

There are many different ways of effecting it. In some there is a wheel of 48 teeth, moving one tooth per month and making a revolution in four years. It has shallow slots in its rim for the 30)-day months, a deeper one for one February of 29 days, and three still deeper ones for February of 28 days. These slots regulate the distance the jumper is drawn back. There are almost as many ways of making perpetual calendar work as there are calendar watches, and any illustrations would be useless.

It is advisable to thoroughly study the action before taking any of it apart, and as a rule little difficulty will be experienced. Take care to leave it on the right month and the right year ; also to see that when the month changes the date hand drops on to the " re" exactly.

In nearly all calendars the work is mounted entirely upon a loose frame, put on over the motion work and held by two or three screws at its edge. This enables it to be all removed together, and replaced last thing in putting the watch together.

Arrangement of Complicated Watches. — Many watches show nearly everything that can be shown and do everything that can be done. The writer has cleaned watches that are (r) clock watches, (2) minute repeaters, (3) double fly-back chronographs, (4) perpetual calendars, and (5) aneroid barometers, all in one. In such watches the pillar plate is very deep and hollow. Next the plate comes the clock watch and repeating mechanism. Above that, supported by bridges and cocks, lies the chronograph work. Above that, in its separate frame screwed on over all, is the calendar work. The barometer has a circular vacuum box in the shape of a ring, and it lies round the movement outside the repeater gongs.

Occasionally a repeater and perpetual calendar has the repeating work on the back of the movement and the calendar work under the dial. Many Swiss chronographs and calendars have the chronograph work at the back and the calendar work under the dial.

Double-time Watches are not very complicated, merely having a double set of motion work and showing two times—say, Greenwich and Paris—on two different circles.

Sidereal Watches have a second pair of hands showing sidereal time. Neither of these last require any special directions. The latter depend on the ratios of the wheels employed, and not on the putting together.

General Remarks.—The cleaning and repairing of complicated watches is not work that should be attempted by a novice.

Careless handling is the cause of innumerable troubles. In putting parts together, if something does not go quite right, an inexperienced workman is tempted to alter this or that piece, to "just take a little off" here or there with a file, in the belief that all will then be right. In such a case it is well to consider first that the man who made the parts in question undoubtedly made them right, and therefore, if the action is not right afterwards, it is either that the mechanism is not correctly put together or suffers from the effects of wear. It is, in fact, much more likely that some parts require a little putting on than that they want any filing off.

A little filed off one part, it will be found, necessitates a little being filed off another, and so on, until the entire action is almost ruined beyond repair.

Therefore, unless a workman is thoroughly at home with this kind of work, or is merely practising on an old and worthless movement, he should not attempt on his own responsibility to alter the form of any part of a complicated watch.

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