Part 9

The utility of a Public Clock is considerably enhanced by its being provided with a dial marking the time in the simplest and most unmistakeable lines, so that it may readily be ascertained at any reasonable distance from the clock-tower what is the hour either by day or night. In order that this important requisite may be attained, it is of course necessary that the dial shall be so constructed as to be visible both by night and day, and so arises the necessity for providing illuminating power either from within or from without. Now the simplest method, and perhaps also in the end the least objectionable, is that followed at the Horse Guards, where the dial forms part of the tower itself, and is lighted not from within, but from without. The advantage of this arrangement is, that the architect can make the dial harmonize with the character of the building, that the illuminating power is kept apart from the clock, and if the centre of the dial be slightly sunk the hands may be brought quite close to the face, so as to prevent any seeming error in time, as is sometimes caused by the convexity of a copper dial. The figures too, having been once carefully divided and cut into the stone, are renewed, so to speak, by merely being painted over.

+----------------------------------------------------------------------+ | [Illustration: Memorial Turret Clock Dial.] | +----------------------------------------------------------------------+

Dials may be made of any material, wood, stone, slate, iron, brass, copper, and coloured or semi-opaque glass. Copper dials possess many advantages, and these have been of late years preferred, except where more ornamental dials are required, in which case slate and skeleton frames are used with good effect. The large dial of my great clock which was placed over the principal entrance of the International Exhibition Building in the Cromwell Road was of slate, elaborately enamelled with white and gold on a blue ground. Another kind of dial having a good effect is that erected by myself some time since for Sir Moses Montefiore, at the Synagogue, Ramsgate, consisting of a skeleton or framework of iron fitted with Minton or encaustic tiles. A dial such as this can thus be made with comparatively little expense during the erection of the tower, and the architect can then, as I have said, design it so as to be in keeping with the edifice; the Minton tiles have also the advantage of being almost indestructible, and of being made of any pattern or colour. The chief points to remember are that the dials should be slightly sunk in the centre so as to allow the hour hand to traverse in the sinking point close to the disc and the figures, and especially that the dial should be made large enough to distinctly show the hour. Properly the dial should never be less in diameter than one-tenth of the number of feet which it is distant from the ground, and in all cases where it is possible I should recommend it to be much larger than this. The dials of St Paul's and Westminster are larger than they would be under the above rule, and they are certainly not too large. As to the colour of the dials, figures, and hands, there is not much choice; dark ground and gilt figures, or white ground with black figures, or a skeleton frame with gilt figures are the chief in use. In the white semi-transparent dials with opaque figures used for illuminated clocks, the time, which is seen with sufficient distinctness by night when the light is behind the figures, is not as clearly indicated by day. To remedy this defect an invention has been applied by which the dial when illuminated at night throws out a beautiful transparent light admirably marking the position of the figures and hands, which being black or dark blue, or even strongly gilt, can also be distinctly seen by day, even as clearly as the long-approved copper dials painted black with gilt figures.

THE HANDS

should be most carefully made, and like the figures should be painted of a colour which shall most powerfully contrast with that of the dial. The hands are almost invariably made of copper strengthened by diaphragms, and poised from the inside. In some old-fashioned clocks in which the hands have been poised from the outside the effect has been produced of a third hand, and numerous mistakes caused thereby. As to the shape of the hands, there is but one simple rule, namely, that the less of ornamentation in them the better. The minute hand should be perfectly plain, with a tapering but not too fine point, extending to the top of the figures; the hour hand should be of equal breadth and plainness, but its point should be more marked by perhaps an arrowhead or heart-shaped tip only reaching to the bottom of the figures. With large hands counterpoises are found necessary, and these should be placed inside the dial if possible, for they are when outside sometimes mistaken for the point of the hour hand. If a counterpoise must be placed outside, it is better to arrange that it shall be as little as possible, and that the inside counterpoise make up the difference, giving to the latter perhaps two thirds, and one third to the former,--but in any case care has to be taken to prevent the counterpoise appearing like a hand.

THE FRAME.

The old-fashioned clock-frame, known in the trade as the 'bedstead,' is now generally superseded by the horizontal frame originally introduced by the French, which possesses the special advantage of not only being durable and strong, but that it allows of any part of the clock which may have been injured, or may require cleaning, being easily taken out and replaced without interfering with other portions of the mechanism,--any wheel can be separately handled and removed. In the old upright frame which is even now still in use by some of the more ancient firms of clockmakers, if any part of the clock be injured the entire machine must be taken to pieces.

THE FIXING

of a Turret Clock requires much careful forethought and experienced labour; because whatever oversight has been made by the architect in planning the clock-room must be made good by the clockmaker who has to fix up a public time-piece. In the first place the latter will take care that the supports of the clock shall be sufficiently strong and free from vibration, and that the movement shall be bolted securely to the iron girders, or strong oak beams provided for the purpose; he will remember that when it is intended that the clock shall strike the hours and quarters, that the bell or bells should be hung as high in the tower as possible, so that when the stroke of the hammer is given by a perfect fall of the weights, the louvres of the tower should be so arranged as to bring out the full sound of the bell, as in the case of the bell at St Paul's cathedral, which, though only weighing 5 tons 4 cwts., is frequently heard on clear nights as far as Windsor. He will in a word require to be acquainted with all the points of importance attached to his rather intricate duty, or he may by failure render nugatory the best workmanship that could be bestowed in clockmaking. The wiser arrangement as to clock-fixing is to intrust the duty to the clockmaker, and he will then necessarily bear the sole responsibility of any mistake.

THE WINDING and keeping in order is, as we have said, a less laborious task as respects modern clocks than those which were made fifty years ago, inasmuch as, although it is the duty of a clock-winder to watch daily the action of the time-piece under his charge, he need not perform his winding duties oftener than once a week. He must be on the alert to observe any effect produced by the action of the wind or the fall of snow upon the hands of the clock, which under certain conditions is not uncommon; he must note by some good regulator any tendency to variation in the Church clock, and he must also observe the Equation of Time, which is the difference between true and mean solar time for each day, and which is not quite the same for every year, because it moves on about a quarter of a day in each year until leap year comes and puts it back again. The Equation may be reckoned by an Equation Table, or by the time mentioned in the Almanacs as 'clock before' or 'clock after sun.' It is obviously a very important requisite for good time-keeping that good horological instruments shall be intrusted to skilful and careful hands. In many instances it has happened that escapements made upon the truest scientific principles, and set going in thorough working order, have been so injured by the mechanical genius of the village (some blundering sexton, or some jack-of-all-trades, whose education in mechanism must be exercised at the parish expense), that the new clock with all its merits has been seriously damaged. In such a case the clockmaker had better be at once consulted.

A MODERN TURRET CLOCK DESCRIBED.

+----------------------------------------------------------------------+ | [Illustration: A Modern Turret Clock.] | | | | [Illustration: Hour-Wheel and Snail.] | +----------------------------------------------------------------------+

The Turret Clock which the highest skill and the best experience of the value of the latest improvements can produce, may be thus described:--

The Bed or Frame is of cast-iron. The Barrel on which the cords are wound possesses a metal cap in front, and a ratchet or toothed wheel at the back end; between this cap and ratchet is a metal drum or tube adapted to the width of the Frame. Passing through the drum is an axle or barrel-arbor, on the back end of which the main or barrel-wheel is fitted so as to allow the line which carries the weight to be wound upon the barrel without moving the wheel, which latter is kept in place by means of a cap or key pinned tight on the arbor. Upon the barrel wheels are fitted clicks and springs, the former falling into the toothed wheel or ratchet, and the latter keeping the clicks in place while the clock is being wound up, for as the weights are wound up the clicks prevent the barrel running back. At each end of the barrel arbor is a pivot in brass bearings fitted in plumber block, and bolted on the bed or frame with bolts and washers. Beyond the pivot on the front of the arbor is a square to receive the winder. The uprights or small frames for carrying the going-train contain the following; first, there is an arbor across the frame at the back of which is a pinion working in the teeth of the barrel-wheel; at the other end of the arbor is the centre-wheel with teeth cut in it, and above this wheel is another pinion running into it with a wheel at the other end, termed the third wheel and pinion. The escape-pinion runs into the third wheel; on this arbor is fitted the escape-wheel, which has very fine teeth cut in it. Above the escape-wheel is an arbor termed the verge arbor, to which are fitted the pallet arms. The pallet bits or pads working in the escape-wheel teeth are of hardened steel polished. At the back end of the verge arbor is fitted the crutch which connects the escapement and the pendulum rod. The escapement is that called the dead-beat or lever escapement, found to be the best for time-keeping, and least likely to get out of order. Upon the set-hand arbor, used for setting the hands on the dial to time, are two springs or keys to keep in place a wheel fitted loosely on the arbor, and working in the teeth of the centre-wheel. The hands are set by means of the set key which fits on the end of the arbor in front. At the back end of the same arbor is a joint by means of which an iron rod connects the clock to the dial, and works the outside hands. The whole of the arbors are turned with suitable pivots into brass bearings screwed into the uprights, and all bolted to the bed or frame by stout bolts and washers. On the front upright is fitted an index or set-dial by which to set the outside hands, and two wheels and pinions, termed the motion or dial-work, fitted on sockets and working on iron studs which are screwed into the upright. Upon the largest wheel, known as the hour-wheel, is fixed a snail having twelve steps in it for regulating the strokes to be given at the different hours. The striking-train consists of a barrel similar to the going-train, only that it has a camm or toothed-wheel fitted on the back of the barrel-wheel for the purpose of raising the hammer which strikes the bell, a lever being used called the hammer-tail. This barrel is fitted into bearings in plummer-block, and bolted on frame. The train of wheels and pinions fitted in arbors, and working in brass bearings, consists of,--the pallet pinion fitted tight in the pallet arbor and working in the teeth of the barrel-wheel; at the front end of this arbor is a pallet of steel working in the teeth of the rack (see next illustration), and gathering it up as the blows of the hammer striking the hours are given on the barrel. Above the pallet arbor is a pinion running into the teeth of the pallet wheel and termed the fly-pinion, as it is used for regulating the blows or strokes. Fans are attached to the fly-pinion to assist in regulating the striking,--the intervals between the strokes being thus made longer or shorter as desired. Fitted to the fly-frame is a ratchet with two clicks and springs, these being used to prevent the train being stopped too suddenly, and the damage likely to arise therefrom. At the right-hand side of the clock frame is an arbor to carry the work for the maintaining power, by means of which work the clock is kept going even while it is being wound up, and injury to the escapement is at the same time prevented. But for this maintaining power during the winding-up, whilst the pendulum is vibrating to and fro, the pallets are liable to catch the teeth of the wheel, and these are so fine as to be readily injured. As properly fixed the clock cannot be wound up unless this maintaining power is put in action by means of a lever passing in front of the barrel-square, so that the winder cannot be put on the square until the lever is raised and puts this power in action. The repeating work for the striking-train is fitted on brass sockets working on wrought-iron studs screwed into the front upright, and consists of the Rack-hook, Warning, Locking, and Lifting pieces. The Rack is a portion of a circle with a number of half-circular teeth cut on its edge; at the end of the Rack is the Rack-arm fitted with a spring having a nib or pin in it, which nib or pin falls upon the steps of the before-mentioned hour-snail, and thus the different strokes are given at the hours; as the nib falls nearer the centre the rack drops a greater number of teeth. The Rack-hook is placed above the rack to catch the rack as it is gathered up by the gathering pallets, and when the proper number of strokes has been given this hook falls into a deep tooth, and then, by means of a locking-piece attached to it, causes the train to be locked with the stop-piece on the fly-pinion arbor, this latter piece forming part of both the locking and warning work. The lifting-piece lifts the rack-hook out of the deep tooth in the rack and locking, by means of a snail or eccentric fitted on the set-hand arbor. On this lifting-piece is also a piece for the warning, fitted on a small stud. The pendulum rod has a brass top, and some adjusting work with a steel suspension spring set in brass, by means of which the clock can be put in beat with great exactness, there being no necessity with this adjustment to bend the crutch as heretofore, for the crutch on the verge arbor has a pin screwed into it which communicates the escapement to the adjusting work or pendulum, and keeps it in motion. At the bottom of the pendulum rod is an iron screw and nut by means of which the pendulum bob is raised or lowered, and the clock made to go faster or slower. The motion or dial work for driving the hands are outside at the back of the dials, and consist of two wheels and pinions working in one another, the larger of the two being fitted to a socket and tube. At the other end of this tube is another socket for the hour hand to be fixed to; and through this tube passes another iron rod, at one end of which rod is fitted one of the pinions and the minute hand, the other wheel and pinion being fitted on a socket worked upon a stud in a cock bolted on a bar called the dial bar. If the clock has to drive more than one pair of dial hands, wheels called bevelled or angle wheels are used, which may be cut to suit any angle, so it will not matter how far off the dials may be fitted, or how many they may be, so long as the proper expansion and universal joints are fitted to them. The Hammer-work consists of an iron frame with an arbor pivoted into brass bearings, and upon this arbor is fitted a lever, one end of the lever holding the hammer-head, and the other end raising the hammer. The lifting of the hammer is done by means of a wire from the hammer-tail previously mentioned. There is also a steel spring attached to the lever to prevent the hammer chattering on the bell.

+----------------------------------------------------------------------+ | [Illustration: The Rack.] | | | | [Illustration: Pendulum Rod.] | | | | [Illustration: Quarter or Chime Clock.] | +----------------------------------------------------------------------+

QUARTER or CHIME CLOCKS differ from the above only in having another barrel and train of wheels to provide the extra power for such striking and chiming.

+----------------------------------------------------------------------+ | [Illustration: GAS WHEEL FOR ILLUMINATED DIALS.] | +----------------------------------------------------------------------+

In instances where it is requisite that the clock face should be visible at a great distance, it is necessary that the dial should be made of semi-transparent glass and be illuminated by gas, which is usually turned as low as possible by day and turned on at night by means of the 24-hour wheel, as shown in the annexed illustration, the time for the turning on being regulated by the man in charge of the clock, who takes out or screws in the pins placed in the rim for that purpose.

+----------------------------------------------------------------------+ | [Illustration: NEST OF BEVELLED WHEELS FOR FOUR DIALS.] | +----------------------------------------------------------------------+

These wheels should be rather large, inasmuch as they have to carry the hands moving upon the face of the dial. The size of these wheels varies of course with the size of the clock, but they are seldom less than five inches and are generally from seven to nine inches wide.

HAMMER AND BELL.

The next engraving exhibits the relative positions of hammer and bell in a turret clock,--the hammer being fixed at right angles to the swing of the bell, so that the blow of the hammer should not drive the bell out of reach of its next blow, and this position least interfering with the ringing of the bell, when the bell is required to be rung. The hammer spring, as shown, is sometimes so adjusted as to allow of the hammer being brought nearer or further from the bell.

+----------------------------------------------------------------------+ | [Illustration: Hammer and Bell.] | +----------------------------------------------------------------------+

THE GREAT CLOCKS OF THE INTERNATIONAL EXHIBITION OF 1862.

BENSON'S GREAT CLOCK.

+----------------------------------------------------------------------+ | [Illustration: Benson's Great Clock.--The Exterior.] | | | | [Illustration: Benson's Great Clock.--The Movement.] | +----------------------------------------------------------------------+

The movement of this clock, next to that at Westminster, is the largest in the world, and, in point of quality of material and finish of workmanship, it is unequalled by any. The three main wheels are each two feet in diameter, and cast in the solid, of the very finest gun-metal, the teeth being afterwards cut by an engine made expressly for that purpose. The frame is of the best wrought-iron planed to a smooth surface, and by means of a contrivance, known to engineers as plumber blocks, any part of the mechanism may be removed without disturbing the remainder. The pendulum, which is self-compensating, is over 15 feet long, and vibrates or beats once in two seconds. The quarter chimes, which are struck on four bells, are a modification of those of S. Mary, Cambridge.

The great weights necessary to drive so large a clock, and which by the friction they would cause might prejudicially influence its performance, are in this case not allowed to act directly upon the pendulum, but are made to wind up a small auxiliary weight once every half-minute, and this weight imparts an exactly uniform impulse to the pendulum at each vibration. This arrangement, which is called the _remontoir_, is supplemented in this clock by a double lever escapement of a novel kind, in connection with that known as Graham's Dead Beat.

A CALENDAR AND WIND-DIAL

are useful additions to some edifices. The CALENDAR indicates on special circles of a large dial--by means of three separate hands--the month of the year, the day of the month, and the day of the week. The peculiarity of this invention is that it needs no correction for the long and short months, nor even for the month of February, with its occasional 29 days; as by means of a wheel cut for the successive months in a period of four years, and which takes that time for a single revolution, the calendar is rendered a perpetual one. The mechanism which directs the pointers to the days of the week and of the month is discharged, by the clock, each night at 12 o'clock, when the levers shift the hands to their proper places on their several dials. On the first of the month all three hands on the dial are moved at the same instant.

The WIND-DIAL is lettered with the four cardinal points of the compass and the 12 intermediates. The hand which points on the dial is connected by rods and bevelled wheels with a vane at the top of the house, placed 20 feet above the roof in order to be affected, not by wind eddies, but by the true current of air. The connecting rods boxed in the wall are broken at every eight feet with universal joints, and hardened steel is used for all pivots and sockets. The dials are generally made of semi-transparent ground glass and are lit by gas after dark. In a set of Clock Calendars which I some time since provided for His Grace the Duke of Portland, the clock showed the time on four illuminated dials five feet nine inches in diameter, chiming quarters, hours, &c. (the well-known Cambridge chimes) on bells of 12 cwt., repeating the hour after the 1st, 2nd, and 3rd quarters. The two sides of an adjoining tower show a calendar similar to the one above mentioned, with the addition of an extra circle on the dial to mark the age of the moon and the equation of time, so that each dial has four circles, besides the circle of the moon, shifted simultaneously at 12 o'clock every night.

SUN-DIALS