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(1898) on the Springing and Adjusting of Watches

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(1898) on the Springing and Adjusting of Watches http://stores.ebay.com/information4all www.amazon.com/shops/information4allwww.amazon.com/shops/information4all http://stores.ebay.com/information4allhttp://stores.ebay.com/information4allEx Libris C. K. OGDEN www.amazon.com/shops/information4allwww.amazon.com/shops/information4all http://stores.ebay.com/information4allhttp://stores.ebay.com/information4all www.amazon.com/shops/information4allwww.amazon.com/shops/information4all ON THK Springing AND fidlasting Watches Beini;' a description of the Balance Spring and the Compensation Balance with Directions for applying the Spring and Adjustii' Isochronism and Temperature. J . BRITTEN, Author of the Watch & Clock Makers' Handbook, Former Clock and Watch .Makers, &c. fLonUon : K. & F. N. SroN, 125, STRAND, W.C. fjorfc : Srox & CiiAMiiKKi.Aix, 12, Cortlandt Street. 1898. rrserved. \All rights \ PREFATORY NOTE. To meet many enquiries for a book of moderate price explanatory of the springing and adjusting of watches, this little work is submitted. It is intended for those tolerably conversant with watch- making generally, yet who desire guidance in this particular branch, rather than for beginners, and therefore a knowledge of many elementary facts is assumed. The examination of modern watch escapements is dealt with because it belongs particularly to the art of the adjuster. For drawings of the escapements, particulars of their action, " and other details, the student is referred to the Watch and Clock Makers' Handbook," to which this volume may be regarded as supplementary. A brief historical notice of the balance spring and is a compensation balance included here ; comprehensive " account of the early craftsmen may be found in Former Clock and Watch Makers and their Work." If springs and balances of nickel-steel alloy answer all expectations it may be that, in the future, adjustment for varying temperatures will be unnecessary. But in such an event so many springs and balances of other material will remain as to justify the inclusion of those pages devoted to compensation, even apart from their historical interest. F.J. B. 35, Northampton Square, London, E.C. CONTENTS CHAPTER I. Introduction and Effect of Various Springs. CHAPTER II. Theoretically Correct Terminal Curves. Effect of Disturbing Influences. CHAPTER III. Compensation for Varying Temperature. CHAPTER IV. Method of Procedure in Springing and Adjusting. CHAPTER V. The Manufacture of Balance Springs. CHAPTER VI. Non-magnetic Material and Material insensible to Changes of Temperature. CHAPTER VII. Gauges. CHAPTER VIII. Observatory Tests, and Note on Timing Repeating Carriage Clocks. CHAPTER IX. Examination of Escapements. Revolving Escapements. 1077183 ON THK SPRINGING AND ADJUSTING OF WATCHES, CHAPTER I. The vibrating wheel of a watch or chronometer which, in conjunction with the balance spring, regulates the progress of the hands is called the balance. The time in which a balance will vibrate cannot be predicated from its dimensions alone. A pendulum of a given length always vibrates in the same time as long as it is kept at the same distance from the centre of the earth, because gravity, the force that it, is the but the want of impels always same ; constancy in the force of the balance spring, that in watches and chronometers takes the place of gravity, and governs the vibrations of the balance is one of the chief diffi- culties of the timer. There is another point of difference between the pendu- lum and the balance. The time of vibration of the former is unaffected by its mass, because every increment of mass carries with it a proportional addition to the influence of gravity : but by adding to the mass of a balance, the strength of the balance spring is not increased at all, and therefore the vibrations of the balance become slower. There are three factors upon which the time of the vibration of the balance depends : (1) The weight, or rather the mass of the balance.* (2) The distance of its centre of gyration from the centre of motion, or, to speak roughly, the diameter of the balance. From these two factors the moment of inertia may be deduced. f (3) The strength of the balance spring, or, more strictly, its power to resist change of form. I append the usual formula for ascertaining the time of vibration of a balance, though it is difficult of -application in actual practice : T = A /~ALM A being the moment of inertia of the balance, M the moment of elasticity of the spring, L the length of the spring, and TT 3-14159. The Moment of Elasticity of a spring is its power of resistance. It varies directly as the modulus of elasticity of the material, and as the breadth and cube of the thick- ness of the spring when its section is rectangular. Mo = E is a usual formula, E representing the modulus of elasticity, b the breadth, and / the thickness of the spring. The moment of elasticity must not be confounded with the bending moment. The bending moment is a measure of the resistance a spring offers to bending, and of the amount of bending which has been produced, which varies directly as the angle wound through, and inversely as the length of the spring. ' -~ M L is a formula for ascertaining the bending moment, E being the modulus of elasticity, b the breadth, t * The mass of a body is the amount of matter contained in that body, and is the same irrespective of the distance of the body from the centre of the earth. But its weight, which is mass multiplied by gravity, varies in different latitudes. t The centre of gyration is that point in a rotating body in which the whole of its energy may be concentrated. A circle drawn at seven-tenths of its radius on a circular rotating plate ot unilortn thickness would represent its centre oi gyration. The moment of inertia or the controlling power of balances varit-s as their mass and as the square of the distance of their centre of gyration from their centre of motion. Although not Strictly accurate, it is practically quite near enough in the comparison of plain balances to take their weight and the square of their diameter measured t the middle of the rim. the thickness, and L the length of the spring, and A the angle through which it is wound. This formula also determines the value of the force which has produced the bending, for if the forces are in equilibrium, the moment of the resisting force must be exactly equal to the moment of the bending force. The Modulus of Elasticity is a constant, represented by E, whfch is used for ascertaining what proportion of its length material is strained when subjected to stress. If the body is stretched, the strain is a lengthening, and if it is compressed, a shortening of its original dimensions. In Young's formula, which is usually accepted, the stress in pounds per square inch of section, divided by E, gives the strain the force in Ibs. that would stretch a rod ; E being one square inch in section to twice its original length, supposing its elasticity to remain perfect all the time. Young gives 29,000,000 as E for steel, but Mr. Robert Gardner considers this too high for the average quality of steel used in balance springs, and places it at 23,000,000. One end of the balance spring is fixed to a collet fitted friction tight on the balance staff, and the other to a stud attached to the balance cock or to the watch plate. The most ordinary form of balance spring is the volute or flat spiral, like Fig. 2. An overcoil or Broguet spring is a volute with its outer end bent up above the plane of the body of the spring, and carried in a long curve towards the centre, near which it is fixed. (Fig. 3.) For marine chronometers helical springs, in which both ends curve inwards, are universally used. Either helical or Breguet springs are as a rule applied to pocket chronometers, although a " form of spring called duo Flat Fig. 2. -Ordinary in unfl."' invented, I Fig. 3. believe, with balance spring. spring by Mr. Hammersley, is overcoil. sometimes preferred. The bottom of this spring is in the form of a volute, from the outer coil of which the spring the end is curved is continued in the form of a helix ; upper in towards the centre as in the ordinary helical spiing. Elevation. Plan. Fig. 4. Helical spring. Among fancy shapes, which may be dismissed in a few words, are spherical springs, introduced by Frederic Houriet no to be ; they present superiority, and having prepared on a solid spherical block are difficult to harden " except by exposure to a high temperature. Bird cage springs," having a helical body with top and bottom terminals formed into volutes, were another short lived con- ceit, with no advantage except the difficulty of making them. The introduction of the balance spring which marks such an important epoch in the manufacture of watches is due to the investigations of Dr. Robert Hooke. He discovered that the potential energy of a spring is pro- portional to the angle through which it has been wound, " and propounded the whole theory in the sentence, Ut tensio sic vis," meaning that the force is proportionate to the tension. He proposed to patent his discovery in " 1660, and to quote his own words, Sir Robert Moray drew me up the form of a patent, the principal part whereof, viz., the description of the watch, is his own handwriting, which I the I in have yet by me ; discouragement met with the progress of this affair made me desist for that time." Derham describes the earliest of Hooke's essa) 7 s in this " direction as a tender straight .spring, one end whereof played backward and forward with the ballance." It is stated that several watches were made under Hooke's supervision at this period, and one of the first to which the balance spring was applied he is said to have presented to Dr.
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