CHAPTER XVIII.

SNAIL STRIKING WORK, ENGLISH, FRENCH AND AMERICAN.

While the majority of snail striking movements made in America are on the French system, because they are cheaper when made in that way, still this system is so condensed and so difficult to illustrate, with all its mechanism packed in a small space between the plates, that the student will gain a much better idea of the rack and snail and its principles by first making a study of an English snail striking clock, which has the whole of the counting and releasing levers placed outside the front plate, where they can occupy all the room that may be necessary. The calculation and planting of the striking train do not differ from those using the count wheel, up to and including the single toothed pinion or gathering pallet. The stopping of the train after striking is different and the counting is divided, being dependent upon four pieces acting in conjunction in an hour strike of the simplest order, which number may run to a dozen in a repeating clock.

As the count wheel system had the defect of getting out of harmony with the hands when the latter are turned backward, so the snail system has its defects, which are the displacement of the rack and failure to stop the striking in some clocks if the striking train runs down before the time side and is then rewound, and a most puzzling inaccuracy of counting, resulting from slight wear and inaccuracy of adjustment. We mention these things here because they have an influence on the construction of the clock and an advance knowledge of them will serve to make clearer some of the statements which follow.

HOUR AND HALF-HOUR SNAIL STRIKING WORK.—Fig. 104 is a view of the front plate of an English fusee striking clock, on the rack principle. The going train occupies the right and center and the striking train the left hand. The position of the trains is indicated in dotted lines, the trains having barrels and fusees as shown by the squared arbors, all the dotted work being between the clock plates, and that in full lines being placed on the outside of the front plate, under the dial. The connection between the going train and the striking work is by means of the motion wheel on the center arbor, and connection is made between the striking train and the counting work by the gathering pallet, F, which is fixed to the arbor of the last wheel but one of the striking train, and also by the warning piece, which is shown in black on the boss of the lifting piece, A. This warning piece goes through a slotted hole in the plate, and during the interval between warning and striking stands in the path of a warning pin in the last wheel of the striking train. The motion wheel on the center arbor, turning once in an hour, gears with the minute wheel, E, which has an equal number of teeth. There are two pins opposite each other and equidistant from the center of the minute wheel, which in passing raise the lifting piece, A, every half hour. Except for a few minutes before the clock strikes, the striking train is kept from running by the tail of the gathering pallet; F, resting on a pin in the rack, C. Just before the hour, as the boss of the lifting piece, A, lifts the rack hook B, the rack C, impelled by a spring in its tail, falls back until the pin in the lower arm of the rack is stopped by the snail, D. This occurs before the lifting piece, A, is released by the pin in the minute wheel, E, and in this position the warning piece stops the train. Exactly at the hour the pin in the minute wheel, E, gets past the lifting piece, A, which then falls, and the train is free. For every blow struck by the hammer the gathering pallet, F, which is really a one-toothed pinion, gathers up one tooth of the rack, C, which is then held, tooth by tooth, by the point of the hook, B. After the pinion, F, has gathered up the last tooth, its tail is caught by the pin in the rack, which stops and locks the train, and the striking ceases.

The snail, O, is mounted on a twelve-toothed star wheel, placed on a stud in the plate, so that a pin in the motion wheel on the center arbor moves it one tooth for each revolution of the motion wheel, and it is then held in position by the click and spring as shown. The pin, in moving the star wheel, presses back the click, which not only keeps the star wheel steady, but also completes its forward motion after the pin has pushed the tooth past the projecting center of the click. The steps of the snail are arranged so that at one o’clock it permits only sufficient fall of the rack for one tooth to be gathered up, and at every succeeding hour gives the rack an additional motion equal to one extra tooth. It will be seen that where a star wheel is used a cord or wire attached to A and run outside the case, so that A may be lifted, will cause the clock to repeat the hour whenever desired.

The lower arm of the rack, C, and the lower arm of the lifting piece, A, are made of brass, and thin, so as to yield when the hands of the clock are turned back; the lower extremity of the lifting piece, A, is a little wider, and bent to a slight angle with the plane of the arm, so as not to butt as it comes into contact with the pin when this is being done. If the clock is not required to repeat, the snail may be placed upon the center arbor, instead of on a stud with a star wheel as shown, and this is generally done with the cheaper class of hour striking clocks; but the position of the snail is not then so definite, owing to the backlash of the motion wheels, so that it will not repeat correctly, as the pin of the rack may fall on a slope of the snail and, besides, a smaller snail must be used, unless it is brought out to clear the nose of the minute wheel cock, or bridge if one be used.

HALF-HOUR STRIKING.—The usual way of getting the clock to strike one at the half-hour, is by making the first tooth of the rack, C, lower than the rest, and placing the second pin in the minute wheel, E, a little nearer the center than the hour pin, so that the rack hook, B, is lifted free of the first tooth only at the half hour. But this adjustment is too delicate after some wear has occurred and the action is then liable to fail altogether or to strike the full hour, from the pin getting bent or from uneven wear of the parts. The arrangement shown in Fig. 104 is generally used in English work, as it is much safer. One arm of a bell-crank lever rests on a cam fixed to the minute wheel, E. This arm is shaped so that just before the half-hour the other extremity of the bell-crank lever catches a pin placed in the rack, C, and permits it to release the train and fall the distance of but one tooth. This is the position shown in Fig. 104. After the half-hour has struck, the cam carries the hook free from the pin in C.

DIVISION OF THE HOUR SNAIL.—The length of the rack tail, from the center of the stud hole in the rack to the center of the pin, should be equal to the distance between the center of the stud hole and the center of the snail. The difference between the radius of the top and the radius of the bottom step of the snail may be obtained by getting the angular distance of twelve teeth of the rack from center to pin. See A B, C D, E F, Fig. 105, which show the total distances for twelve steps of the snail for rack tails of different lengths. Divide the circumference of a piece of brass into twelve parts and draw radial lines as shown in Fig. 106. Each of these spaces is devoted to a step of the snail. Draw circles representing the top and bottom step. Divide the distance, A B or E F, Fig. 105, between these two circles, into eleven equal parts, and at each division draw a circle which will represent a step of the snail. The rise from one step to another should be sloped as shown, so as to raise the pin in the rack arm if the striking train has been allowed to run down, and it should be resting on the snail when it is desired to turn the hands back. The rise from the bottom to the top step is bevelled off, so as to push the pin in the rack arm on one side, by springing the thin brass of the arm and allow it to ride over the snail if it is in the way when the clock is going. It should also be curved to avoid interference with the pin. Clockmakers making new snails when repairing generally mark off the snail on the clock itself after the rest of the striking work is in position. A steel pointer is fixed in the hole of the lower rack arm, and the star wheel jumped forward twelve teeth (one at a time) by means of the pin in the motion wheel. After each jump a line is marked on the blank snail with the pointer in the rack arm by moving the rack arm. These twelve lines correspond to the twelve radial lines in Fig. 106. The motion wheel is then turned sufficiently to carry the pin in it free of the star wheel and leave the star wheel and blank snail quite free on their stud. The rack hook is placed in the first tooth of the rack, and while the pointer in the rack arm is pressed on the blank snail, the latter is rotated a little, so that a curve is traced on it. The rack hook is then placed in the second, and afterwards in the succeeding teeth consecutively, and the operation repeated till the twelve curves are marked. There is one advantage in marking off the snail in this way. Should there be any inaccuracy in the division of the teeth of the rack, the steps of the snail are thus varied to suit it. This frequently occurs in old clocks which have had new racks filed up by hand by some watchmaker.

Reference to the drawing, Fig. 105, will show that the rack is laid out as a segment of a wheel with teeth occupying two degrees each, with a few teeth added for safety. Fourteen to sixteen teeth are generally provided, for the following reasons: If the first tooth is used to strike the half hours, it may in time become worn so that it can no longer be stretched to its proper length. In such cases moving the pin two degrees nearer the rack teeth will allow us to use the teeth from the second to the thirteenth in striking twelve, which makes a cheap and easy repair, as compared to inserting a new tooth or making a new rack.

Weight driven snail clocks should have the weight cords of the striking side long enough so that the striking train will not run down before the time train, as in such a case the rack tail is pushed to one side by the progress of the snail (which is carried on the time train and is still running); then the rack will drop clear out of reach of the gathering pallet and when the striking train is wound that train will continue striking until it runs down, or the dial is removed and the rack replaced in mesh with the gathering pallet. This happens with short racks and with large, old-fashioned snails. By leaving a few more teeth in the rack the rack tail will strike the stud, or hour wheel sleeve, before the rack teeth get out of reach of the gathering pallet.

Many watchmakers put a stud or pin in the plate to stop the rack from falling beyond the twelfth step, to prevent troubles of this kind.

The rack tail is friction-tight on its arbor and should be adjusted so that the proper tooth shall come in mesh with the gathering pallet for each step of the snail, or irregular striking will result. Such a clock may strike one, two, three and four correctly and then strike six for five, or seven or nine for eight, or thirteen for twelve, or it may strike one or two hours wrong and the rest correctly. This is because the gathering pallet, F, Fig. 104, does not carry the rack teeth safely past the edge of the rack hook, B, owing to the tail of the rack not being properly adjusted. The teeth should all be carried safely past the edge of the hook and then be dropped back a little as the hook engages; this is the more necessary to watch with hand-made racks and snails, or after putting in a new, and therefore larger, pin in the rack tail to replace one which is badly worn.

The snail should be put on so that the pin in the rack tail will strike the center of each step, or there is danger of irregular striking, or of failure to strike twelve, owing to the pin striking the surface of the cam midway between one and twelve and thus preventing the rack from falling the requisite number of teeth. When this occurs the clock will jam and stop.

The rack hook, B, Fig. 104, should be lifted far enough so that the rack will fall clear of the hook without the teeth catching and making a rattling noise as they pass the hook. In many old hour strikes the first tooth of the rack is left longer than the rest to ensure this freedom of passage when the rack is released.

The gathering pallet, F, is the weakest member of the system and will be very likely to be split or worn out in clocks brought in for repair. It should be squared on its arbor, or pinned, but many are not. If split, and the arbor is round, where the pallet is put on, it may cause irregular striking by opening on the arbor and permitting the train to run when the tail strikes the pin in the rack. A new one should be made so as to lift one tooth and a very little of the next one at each revolution. It is necessary to cause the gathering pallet to lift a little more than one tooth of the rack, and let it fall back again, to insure that one will always be lifted; because if such was not the case the clock would strike irregularly, and would also be liable sometimes to strike on continually till it ran down. If the striking part is locked by the tail of the gathering pallet catching on a pin in the rack, the tail should be of a shape that will best prevent the rack from falling back when the clock warns for striking the next hour; and of course the acting faces of the pallet must be perfectly smooth and polished.

The teeth of the rack may require dressing up in some cases and to allow this to be done the rack may be stretched a little at the stem, with a smooth-faced hammer, on a smooth anvil; or, if it wants much stretching, take the pene of the hammer and strike on the back, with the front lying on the smooth anvil. The point of the rack hook, B, will probably be much worn, and when dressing it up it will be safe to keep to the original shape or angle. The point of the rack hook is always broader than the rack, and the mark worn in it will be about the middle of the thickness; so enough will be left to show what the original shape or angle was.

After cleaning, particularly if it be French, look for dots on the rims of the wheels, and for pinions with one end of one leaf filed off slantingly. When putting it together, place the pin wheel (that is the one with the pins) and the pinion it engages with so that the leaf of the pinion (which you will find filed slanting at one extremity) enters between the two teeth of the wheel, opposite which you will find a countersunk mark, on the side of the wheel. See also that the gathering pallet, F, which lifts the rack, does so at the same time that the gong hammer falls. Then place the hour and minute wheels and cannon pinion so that the countersunk marks on each line with each other. Neglect of the marks on a marked train generally means that you will have to take the clock down again and set it up properly before it will run; therefore pay attention to these marks the first time.

QUARTER CHIMING SNAIL STRIKES.—Fig. 107 shows the counting mechanism and trains of an English, fusee, quarter-strike work. The time train occupies the center, the hour striking train the left and the chiming train the right. All the train wheels are between the plates and are dotted in as in Fig. 104, while the counting mechanism is on the front plate, behind the dial and is drawn in full lines, to show that it is outside.

GOING TRAIN. Fusee Wheel 96 Pinion 8 Center Wheel 84 Pinion 7 Third Wheel 78 Pinion 7

STRIKING TRAIN. Fusee Wheel 84 Pinion 8 Pin Wheel, 8 pins in Pin Wheel 64 Pinion 8 Pallet Wheel 70 Pinion 7 Warning Wheel 60 Fly Pinion 7

CHIMING TRAIN. Fusee Wheel 100 Pinion 8 Second Wheel 80 Pinion 8 Pallet Wheel 64 Pinion 8 Chiming Wheel 40 Warning Wheel 50 Fly Pinion 8

The reader will see a marked resemblance between the hour and time trains of Fig. 104 and the same trains of Fig. 107. The hour rack hook in 107, however, is hung from the center and the hour warning lever is raised by a spring instead of a lifting piece.

The minute wheel of Fig. 107 carries a snail of four steps, corresponding to the four teeth of the quarter rack, and the tail of the quarter rack is bent upwards towards the rack, to engage with the quarter snail. The quarter rack carries a pin which projects on both sides of the rack; one side of this pin stops the tail of the quarter gathering pallet and therefore locks the train as fully described in Fig. 104. The other side of the same pin acts on the tail of the hour warning lever, so that whenever the quarter rack falls the hour warning lever is released and its spring moves it into the path of the hour warning pin. This goes on whether the hour rack hook is released or not. Behind the quarter snail, there are four pins in the minute wheel; these pins raise the quarter lifting piece, which raises the quarter rack hook and the quarter warning lever at the same time, thus warning and dropping the quarter rack; as soon as the lifting piece drops, the warning lever and rack hook are released and the quarter train starts.

One, two, three, or four quarters are chimed according to the position of the quarter snail, which turns with the minute wheel. At the time for striking the hour (when the quarter rack is allowed to fall its greatest distance), the pin in it falls against the bent arm of the hour rack hook, and releases the hour rack and hour warning lever. As the last tooth of the quarter rack is gathered up, the pin in the quarter rack pulls over the hour warning lever, and lets off the hour striking train. The position of the pieces in the drawing is as they would be directly after the hour was struck.

Figs. 108, 109 and 110 are three views of the New Haven eight-day snail strike, which is on the French system. As nearly all American strikes utilize this system and the work is between the plates, this may be considered a typical American snail strike.

As will be seen in Fig. 108, by the two pins at the center arbor, immediately behind the snail, this is a half-hour strike; and as the rack hook has for its lower step a little more than twice the depth of the other steps in the snail, it will readily be perceived that this rack hook may be pushed almost out and thus release the train without dropping the rack. This is the method pursued in striking half hours.

Figs. 109 and 110 show the parts more clearly than in 108. They are drawn a little larger than actual size and we will discover that the rack is the only portion of this system that works by gravity, all the others being spring operated. We see here the pins J K, which are used to push out the lever M sufficiently far so that the upper portion, which is bent at right angles to form a stop, will free the warning pin O and allow the train to run. The rack hook and the locking lever L are mounted on the same arbor and are kept in position by a coiled spring on the arbor until they are pushed out by the lower projection at the upper end of M for either the half-hour or hour strike.

As shown in Fig. 109, the lever M and the rack hook are pushed out by J far enough to pass the warning pin O and to unlock the train, which is normally locked by the pin N and the lever L. G is the gathering pallet, which is a long pin in a lantern pinion as in the ordinary count wheel strike. H is the hammer tail and P the pin wheel; R is the rack and T the rack tail. The rack arm is curved to pass the center arbor when dropping for twelve and the rack tail is bent toward the teeth in order that it may admit of a longer rack in a small movement, thus permitting of a large snail and consequently less liability of disarrangement. The same necessity of the proper adjustment of the rack tail T with the snail exists as has already been spoken of in regard to the English form of the snail strike.

In Fig. 110 will be seen the rack dropped clear with the tail resting clear of the snail at one stroke from the snail. In other words, the train is now in position to give eleven more strokes, having struck the first stroke of twelve. By comparison with Fig. 109, it will be seen that the spring actuated arm M has been thrown forward so that its dog is resting on the center arbor, after having been released from the hour pin K. This holds M out of the way of the warning pin O and the rack hook and allows the parts to operate as fully described with the English rack.

The gathering pallet G must have as many teeth as there are teeth between the pins in the pin wheel P. The train is locked by L coming in contact with N, the locking pin on the wheel on the same arbor as the gathering pallet. In setting this train up, it should stop so that the warning pin O should be near the fly.

As all the parts are operated by springs on the arbor, as shown by the hammer-spring H, it will be seen that this strike mechanism will work in any position, while that which is operated by gravity must be kept upright. A loose fly will cause the clock to strike too fast and may cause it to strike wrong. Careless adjustment of the rack tail T with the snail will also induce wrong counting, although this is somewhat easier to adjust than the English form of strike. The hook should safely clear the rack teeth just as the gathering pallet G lets go of a tooth. If attention is paid to this point in adjusting the rack tail there will generally be little trouble.

The cam bearing the pins J K on the center arbor may be shifted with a pair of pliers to secure accurate register of hands and strike, as is the case with most American strikes. In putting in the pin wheel it should be set so that the pins may have a little run before striking the hammer tail, as this hammer tail is very short, and if the spring is strong the pins may not be able to lift the hammer tail without sufficient run to get the train thoroughly under motion. The half-hour strike should also be tested so that the pin J will release the warning pin O from the lever M without releasing the rack hook from the rack, as shown in Fig. 109. The parts of the train when at rest will be readily discerned in Fig. 108, where the hook L has locked the train by the pin N and the freedom between the pins and the hammer tail is about what it should be.

The relative position of the locking lever L and the rack hook is also very clearly shown in Fig. 108; that is, when the rack hook is pressed clear home at the lower notch of the rack, the lever L should safely lock the train and the lever M be resting with its link against the center arbor.