(225) The sliver as left by the drawing frame consists of a number of fibres arranged in a parallel order, and contains a little twist introduced by the coiler. It is not practicable to carry the parallelising process much further, as the drawn slivers are so attenuated that very little more draught would pull the fibres asunder. As, however, it is essential, in order to produce a yarn of the requisite fineness, that a further reduction shall be effected, it is the practice to gradually introduce into the sliver a small amount of twist. This is done by stages, and at each stage the partially twisted fibre is subjected to the action of drawing rollers. The machines about to be described, therefore, have a dual action, and, in most cases, are three in number, known respectively as slubbing—second slubbing or intermediate—and roving frames. While this is the rule, it is not the universal practice. In spinning coarse counts, for instance, only the first and third of the series are sometimes employed, while the production of very fine yarns is aided by the use of a fourth machine, known as a “jack” frame. Whatever may be the number of steps by which the process is completed the object is the same—to reduce the sliver to an even round thread of such proportions that it can be readily twisted into yarn of the requisite diameter. The introduction of a slight twist binds the fibres together, and enables them to be drawn as required without breakage. The thread finally produced is technically known as a “roving.” The various machines being practically identical in their details, varying only in correspondence with the increasing fineness of the thread, it is only necessary to give a description of one of the series.

(226) In Fig. 128 a front view of a slubbing frame, and in Fig. 134 a back view of a roving frame, as made by Mr. John Mason, are shown. The sliver is brought from the drawing frame in the cans in which it is coiled, these being placed at the back of the slubbing machine. It is drawn from the cams over a guide roller, and is then conducted to the drawing rollers. After being treated in the slubbing frame the bobbins produced are placed upon wooden pegs, pointed at both ends, which are sustained in bearings in the light frame S shown in Fig. 134, this being known as a “creel.” The bobbins are borne in an almost vertical position, and revolve easily as the slubbing is being drawn off. There may be two or three rows placed in the creel, which is described as a one, two, or three height creel accordingly. In either case the material is conducted as in the slubbing frame to the drawing rollers. Of these there are usually three, but sometimes four lines, their construction being generally similar to those used in the drawing frame, the back set of top rollers being ordinarily heavier than the front ones. The rollers are carried in brass bearings, fixed to the roller beam, and are weighted as in the drawing frame. Top clearers are fitted above the rollers, which are quite covered by polished cast-iron covers. The bottom rollers are kept clean by the aid of a revolving clearer kept closely pressed against them by a two-armed spring, the ends of the arms being grooved to form bearings for the axes of the clearer roller. The “under clearer” spring is attached to the roller beam, and is usually made of flat steel, stamped out of a sheet. A better form, made from round bright wire, has been recently introduced by Mr. C. H. Pugh, of Birmingham, which has the great merits of catching less fly and being more easily cleaned. As was said in the previous chapter, the absolute cleanliness of the rollers is essential, as otherwise the sliver will adhere to them—this being known as “licking”—and will be wrapped round them, thus producing “roller laps.” The drawing action having been fully described in the preceding chapter, it is not necessary to go over the same ground. The diameter of the front rollers in the slubbing frame are about 1¹⁄₄ inch, and in the roving frame 1¹⁄₈ inch. The weights are heavier in the slubbing frame, and in all the series the back rollers are more lightly weighted than the front. Thus the weights used for the front, middle, and back lines in the slubbing frame are respectively 18, 14, and 10lbs; in the intermediate frame 14, 10, and 8lbs.; and in the roving frame (with single bossed rollers) 10, 8, and 6lbs; and (with double bossed rollers) 18, 14, and 12lbs.

(227) The mode of constructing the spindles A, is illustrated in sectional elevation in Fig. 129. The spindles are made from round steel from ⁹⁄₁₆ inch to ⁷⁄₈ inch diameter, and are arranged in two rows, one behind the other, with their centres alternating thus _ -_ - _. This arrangement permits of more spindles being fitted into the space at liberty. Usually the distance from centre to centre of adjoining spindles denotes the “gauge” of a machine, but in the series of machines now being dealt with, the peculiar setting of the spindles prevents this. The “gauge” in this case is denoted by the number of spindles in a defined number of lineal inches. Thus, to take an illustration from actual practice, a slubbing frame may have 4 spindles in 17¹⁄₂ inches, that being its gauge; an intermediate, 6 in 19¹⁄₂ inches; or a roving frame 8 in 20¹⁄₂ inches. The spindles are accurately ground so as to be quite round, and vary in length from 28 to 42 inches. At the “foot” the diameter of the spindle is reduced, and the extreme lower end or “toe” is conical, being borne by a brass footstep fixed in a longitudinal rail. Immediately below the bobbin is an upper bearing or bolster, fixed in a similar rail. On the top of the spindle a flyer B is placed, this being of the shape shown, and constructed of steel. The legs are oval in section, and may be either tubular or solid, being made as light as possible. At the centre of the bridge connecting the legs is a circular double boss C, which is bored throughout, the hole so formed being carefully rounded and polished at its upper orifice. At a point near the top a hole is bored penetrating to that in C, and being also well rounded and polished. The lower portion of C constitutes a socket, into which the upper end of the spindle fits, the latter passing above the point at which the bridge is attached to the boss. A slot is cut across the upper end of the spindle, and a round pin, engaging with the slot, is fixed in the socket of the flyer, which is thus positively driven.

(228) Attached to one or both legs of the flyer are two snugs or projections D D¹ acting as bearings for pressure fingers or “pressers” E. The latter are round rods, hooked at their upper ends and bent at right angles at their lower ends. The hooked portion can be dropped into a socket in the upper snug D, and the presser thus oscillates freely on the centre of the bearings D D¹. The inner end of the finger E is flattened and curved so as to correspond with the surface of the bobbin F, being formed with a guide-eye, as shown. It is made of such a length as always to press upon the surface of the bobbin during the rotation of the flyer, which it is caused to do by the centripetal action set up by the latter. The amount of pressure exerted depends entirely on the rate of the revolution of the flyer, and the practical effect is that the roving is more tightly wound on the body than it would otherwise be. It was at one time customary to use two pressers with each flyer, but it is more generally the practice now to employ one only. Great care is taken to balance the flyer, and, when single pressers are used, one leg is made solid and the other tubular, the presser being fitted to the latter. The sliver, after leaving the rollers, is passed through the upper part of the boss C, emerging by the small hole referred to, being then wrapped round the presser two or three times, and finally conducted through the guide-eye in the finger to the bobbin F. Both the inner and outer surface of the flyer must be absolutely smooth, as otherwise it catches the fibre and forms “fly.” For this reason, steel, as a constructive material, has entirely superseded the fine iron formerly used.

(229) The spindle is borne, as was shown, by a bolster and footstep. In order to give steadiness and reduce friction it is the practice to fit in the former a collar or tubular bearing. This is either “short” or “long.” Formerly short collars were the rule, these merely acting as a somewhat longer bearing, the bobbin in its vertical movement sliding upon the spindle. Mr. John Mason then introduced the “long” collar which is shown in Fig. 128. The collar I is of sufficient length to extend from the bolster, bearing upwards through the bobbin to a point within the flyer. It is recessed internally, so as not to bear the entire length, but simply to be in contact with the spindle at two points. The latter is thus sustained high up, in addition to being borne, as usual, at the two lower points. The effect is that a much less amount of vibration is set up, and the flyer revolves with greater steadiness. This has an important bearing upon the operation, as it diminishes considerably the risk of breakage.

(230) Another method which, in many respects, is superior to any other, is that shown in Figs. 130 and 131 in vertical section and elevation. This is the plan previously adopted by Messrs. William Higgins and Sons, and now made by Messrs. Crighton and Sons, and Shepherd and Ayrton. In this case the spindle A is carried in a long tube I, which extends downwards until it is formed, as shown, into a footstep for the spindle toe. In short, the spindle is sustained in a kind of tubular cradle, being to a certain extent entirely free of the fixed bearing rails J K. To these the tube I is attached by swivel joints, so arranged that they are universal, thus allowing the spindle A and flyer B to adjust themselves as required to compensate for any unevenness of balance which may exist in the bobbins or flyers. The tube I is recessed for a certain part of its length, so as to form an oil chamber and reduce the friction set up during work. The advantages arising from this arrangement are that, even when the spindle is running at high velocities, any untrueness in the balance of the spindle merely causes it to find its true centre of gravity, and thus avoid vibration or wear. Spindles constructed in this manner can be worked for many years without showing any wear which is at all detrimental, and on this account higher velocities are attainable with ease than can be reached with the ordinary methods of construction.

(231) The spindles are positively driven as shown in Fig. 130, by means of bevel wheels fastened near the foot. In the arrangement shown in these drawings the spindle pinions F are formed with square holes, into which the spindles, similarly shaped, are fitted. This allows the spindle to be easily lifted out when required for examination. Usually the pinions F are fastened to the spindle by means of a set screw. In either case they engage with a bevel wheel G fastened on a shaft H, carried in brackets fixed to the framing, and extending longitudinally along the frame. The spindles being set zig-zag, as described, there are two lines of them, and consequently there must be two shafts H to drive them, and in order to distinguish between the two, they are supposed to be shown in position in Fig. 131, and the back wheels are marked F¹ G¹. The shafts H are geared so as to revolve at the same velocity, but in opposite directions, and, as it is imperative that the spindles shall revolve in the same direction, this is attained by gearing the pinions F F¹ on different sides of the centres of the wheels G G¹, as clearly shown. To enable this to be done, the teeth of the wheels are cut at a special angle or “skew” to suit.

(232) The bobbin L rests upon a flange of the bevel pinion M placed on the collar, and driven by the wheel N. The pinions are, as shown in Fig. 129, fixed in the “bobbin rail,” or, as in Fig. 130, carried on the top of a bearing sustained by the swivel joint. The upper flange of each pinion has formed on it oblong “snugs” or projections, which take into corresponding slots made in the bottom of the bobbins. The wheels N are keyed on the shafts O, which also extend the whole length of the machine, and are suitably borne by brackets fastened to the underside of the bobbin rail. Thus the latter sustains both the driving shafts and the bevel pinions which, as in the case of the spindles, are driven by wheels gearing at different sides of the centre.

(233) This mode of construction lends itself very easily to the formation of the bobbin or spool of roving, which, at its completion, is of the shape shown in Fig. 128, cylindrical with conical ends. In order to wrap the yarn upon the bobbin L it is necessary to give the latter not only a rotary but a vertical movement. It is, of course, possible to give this motion to the spindle and flyer and not to the bobbin, but this is not a convenient method in the case of machines like those under notice, for many reasons. The rail, therefore, which carries the bobbin pinions and bobbin, known as the “bobbin rail,” receives a vertical traverse to an extent which is determined by the class of material to be dealt with. This traverse is a reciprocal one, and is technically known as the “lift,” a machine being said to have a lift of so many inches according to the extent of the vertical movement of the bobbin rail. This varies from 10 or 12 inches in the case of the slubbing frame to 5 or 6 inches in the roving frame, and is obtained in a manner which will be presently described. While it is taking place the bobbins are slid upon the spindle, the presser eye continuing to revolve in the same horizontal plane. From this it follows that any yarn drawn through the eye by the rotation of the bobbin is of necessity wound upon a fresh portion of the surface of the latter. It only remains now to point out, before proceeding to deal with the machine in detail, that it has been shown the spindles and bobbins are driven independently, and may, if desired, rotate at various and different speeds; and that provision is also made for the maintenance of the vertical position of the spindles and flyers while permitting that of the bobbin to be altered. These, added to the regular delivery of sliver by means of the rollers, constitute the essential features of these machines, but the effective manipulation of them gives rise to a number of interesting mechanical problems.

(234) It has been pointed out that the action of the rollers in attenuating the sliver is identical with that of those in the drawing frame, so that no special description need be given of them. But these machines are the first in which the process of twisting is carried out, and the rollers form an important part of the mechanism for this purpose. In introducing twist into any strand or sliver it is necessary that one end of it should be held, while the other is also held and turned at a higher or lower speed. If this is done the strand will be twisted, and the amount of twist is strictly defined by the number of times it is turned. In actual working it is not practicable to continue so to twist the strand without at the same time submitting it to the action of the spindles continuously. Unless it was so delivered it would be broken because of the shortening which takes place during twisting, and it is therefore necessary to furnish a fresh portion of the sliver to the action of the twisting mechanism. For this reason the sliver, while being firmly held by the nip of the front rollers, is also delivered by them at a definite rate, which depends on their size and rate of revolution. Now, assuming that no such delivery takes place, and that a length of sliver of 10 inches is turned 100 times, there would be in each inch of it 10 turns or twists. Suppose, now, that another 10 inches was delivered and the same number of turns made, a similar result would be obtained. It does not matter whether the delivery is constant or intermittent, provided only that the ratio of the length delivered and the number of revolutions of the twisting mechanism remain the same. Intermittent delivery would, however, be very inconvenient in practice in producing rovings, and thus it is requisite to provide for a steady and regular delivery of yarn, as well as a uniform speed of the spindle and flyer. Granting the attainment of these conditions, it is easy to define the amount of twist put into any thread, it being in the same ratio as the number of revolutions made by the twisting mechanism during the delivery of one inch of sliver or roving. Twists are always defined as being so many “turns” per inch, and are arrived at in the way just indicated. As a matter of fact there is a little slip in the rollers, which does not, however, to any large extent modify the rule enunciated. The constants in a machine of this kind are therefore the rate of revolution of the spindles and front rollers; and, generally speaking, the amount of twist increases as the roving becomes finer. This can be attained by an increase of spindle speed or a decrease of that of the rollers, as will be readily understood, but considerations of a mechanical nature generally lead to the latter course being pursued. The spindle speeds in a slubbing intermediate, and roving frame, dealing with the same class of roving, would be approximately 700, 800, and 1,100 revolutions per minute. A table of productions, speeds, etc., is given on page 174, which will throw some light on this point.

(235) It has been already noticed that the bobbin receives a vertical traverse, while the spindle is vertically stationary, and that, in consequence, the yarn is wrapped upon the bobbin in spiral coils. The speed of this traverse is carefully regulated so that each layer is quite free from any overlap, while, at the same time, no space should be left between the coils. When the bobbin has wrapped round it for the whole of its length one layer of roving, its diameter is increased by an amount equal to double the thickness of the roving. Thus its circumference is enlarged, and every revolution it makes requires a longer length of material to cover the surface than it did when it was bare. This extra amount must either be fed to the bobbin, or its speed must be reduced, and as the rollers deliver at a constant rate, the latter is the course pursued. Further, the length of roving wrapped upon the bare bobbin during the whole lift is, of necessity, less than that which would be wrapped upon it after a layer has been wound on if the lift were constant. It is essential that the length of each complete layer should be as nearly as possible equal, and for this reason the traverse of the bobbin is shortened slightly after each of its reciprocal movements. The amount of the diminution in lift is in exact correspondence with the excess of length which would be taken up if it remained constant. The increase in the diameter of the spool has thus an important bearing on the lift, and it is of equal moment in relation to another function of the machine.

(236) A reference to Fig. 129 will show that the flyer and bobbin rotate round the same centre, and the roving delivered by the rollers is passed on to the bobbin through the presser eye, as pointed out. If it be assumed that the yarn passes on to the bobbin at some imaginary point in the circumference of the latter, and that this occupies during its rotation a definitely relative position to that of the flyer eye during its revolution in a concentric circle, it follows that no roving can pass from the flyer to the bobbin. A little thought will make this clear, but Fig. 132 will serve to illustrate it. In this figure, A is the spindle, B the circumference of the bobbin, and C the path of the flyer eye. Now, as A and C are attached in the manner previously described, they must of necessity revolve at the same speed. On the other hand, the rate of rotation of B is capable of variation by reason of its independent driving. Let D and E represent respectively the points at which the yarn leaves the flyer C find passes on to the bobbin B. It is obvious that if the relative position of D and E remain unchanged—that is, if they travel at equal speeds, so that the line between them is always alike—there can be no passage of roving from D to E; or, in other words, there can be no winding. But if the point E makes a complete revolution in less time than D does, or vice versâ, winding will take place. In the first case the quicker motion of E would result in the bobbin B taking up roving from D; and in the second the greater velocity of D would cause it to wrap the roving round the bobbin. To make this clear, suppose the lines A D and A E to represent radial lines drawn through the points D E at the commencement of winding, and that at the termination of say three revolutions, the position of these lines relatively is the same. It is perfectly clear that the line D E will have remained unaltered, and no passage of the roving will have occurred. But now assume that the flyer C had moved so much faster than the bobbin B, that the radial lines through D and E were in the position shown in Fig. 133. It will at once be seen that C will have drawn forward a certain length of roving corresponding to its gain, and that the portion of its circumference between the point where the material from D passes on to it and the point E will be covered by the roving. In the event of B moving faster than C, the effect is identical with that described, although it is obtained in an entirely different way.

(237) This statement of the general principle is sufficient to show the conditions under which winding is successfully effected. The gain either of the bobbin or flyer upon the other is technically called the “lead,” and thus a frame is said to be constructed with a bobbin or flyer “lead.” The determination of the amount of lead is very simple, and is fixed by the speed of the rollers, it being manifestly impossible to take up more yarn than is delivered. It follows, therefore, that the excess of the surface speed of the bobbin or spool at any stage of its development must accurately correspond with that of the front rollers. If this condition be departed from, either by the lead given being too great or too little, the result will be broken yarn; in the first case by stretching, and in the second by the production of slack places which become entangled and broken. It may here be stated that it is now almost universally the practice to let the bobbin lead, as, with the flyer leading, a certain amount of stretch is put into the yarn, which is very injurious. This defect is especially noticeable in starting the frame, and it is entirely remedied by giving the lead to the bobbin.

(238) Assuming, then, that the bobbin leads, it is necessary to consider the effect of the gradual increase in the size of the bobbin, caused by the winding on of the yarn. This difficulty is rendered acute by reason of the positive driving of the bobbin. In flyer frames, used for spinning or doubling, the bobbin has a little slip which can be easily adjusted, but which is not obtainable in this case. The slip of the bobbin is caused by the drag of the yarn, a procedure which at this stage is practically impossible. Every traverse of the bobbin rail is, as has been seen, accompanied by an increase of the circumference of the bobbin corresponding to the diameter of the roving. Thus, to take an extreme case, assuming the diameter of the empty tube to be 1¹⁄₂ inch, it would take up at each revolution 4·7 inches of yarn. If the yarn was ¹⁄₈ inch thick, the diameter of the bobbin would be 1³⁄₄ inch after one layer, and each revolution would take up 5·5 inches of yarn. This is, of course, assuming that the flyer is absent, and that the bobbin was winding. As the surface velocity of the bobbin and front roller must correspond, and no more sliver is delivered at one time than at another, it follows that the rate of revolution of the bobbin must diminish in exact proportion to the increase of its circumferential speed. It is, therefore, easy to calculate the exact amount of retardation at each traverse by a knowledge of the diameter of the yarn, or the number of layers to be wound on any spool.

(239) It is thus easy to see that with the bobbin leading it should gradually diminish in speed, and it is consequently the practice to run it at a much higher speed at the beginning than at the termination of winding. For instance, an empty spool 1 inch diameter takes up per revolution 3·1416 inches of roving, while one 3 inches diameter would take up 9·42 inches. It thus becomes imperative to reduce the speed of the bobbin wheels, and these being constantly geared with their driving wheels, it is necessary to reduce the velocity of the bobbin shafts. These are driven, as described hereafter, by a train of gearing from the main shaft, and special means are adopted to compass the reduction. The spindles are running at a constant speed, and it follows, in consequence, that the bobbin must run at the same rate, plus the number of revolutions necessary to take up the length of yarn delivered in any given time. If, for instance, the spindles made 100 revolutions while 10 inches of yarn was being delivered, the bobbin must revolve 100 times plus the number necessary to take up the 10 inches of yarn.

(240) When the flyer leads, the application of this principle is not quite so clearly seen at first sight, but a little reflection will make it understood. In this case the winding is effected by the excess of the speed of the flyer over that of the bobbin. This is exactly the reverse of the practice when the bobbin leads, but the essential condition is, as before, the preservation of the relative surface speeds of the bobbin and roller. Suppose that, in starting, the diameter of these two are the same, then the bobbin must lag behind the flyer to the extent of one revolution for each revolution of the roller. But as the bobbin increases in diameter, it requires more yarn to cover its surface, and a less difference in speed is needed, as, if the bobbin continues to lag one revolution, the difference between the speed of delivery and that of winding become so great as to stretch and break the roving. Instead of wrapping it round, for instance, a circumference of three inches it has eventually to be wound on one of six inches, and it is obvious that if the speed of the bobbin remains constant the roving will be drawn and broken. It is, therefore, necessary to gradually increase the speed of the bobbin so that for every inch of yarn delivered, an inch of the circumference will be covered by it. The difference between this and the former case consists in the fact that the roving is wrapped on a concentric surface, revolving in the same direction at a slower speed, while, with the bobbin leading, the surface on which the roving is wound, moving in excess of the speed of the flyer, draws the roving through the flyer eye at a rate equal to that of its delivery. In other words, it is in one case wrapped on by the excess of the flyer speed or the drag of the bobbin, while, in the other, it is drawn on by the excess of speed of the bobbin. The conclusion is thus arrived at that when the flyer leads, the bobbins must start at their slowest speed, and gradually increase; while, when the bobbin leads, it must begin at its highest speed and gradually diminish.

(241) Having thus explained the principle of the machine, it now remains to describe the mechanism by which it is carried into effect, referring for this purpose to Fig. 134. The driving, or “jack,” shaft A has a fast and loose pulley on its outer end, and has fastened on it two spur wheels. One of these drives, by means of a carrier wheel, a wheel fixed on one of the spindle shafts, and motion is given to the spindles in the way previously described. The speed of the spindles, being independently obtained, can be changed without reference to the other motions. The pinion C is known as the “twist wheel,” and is made as large as convenient. It drives, by the intervention of a carrier wheel, a pinion D fixed on the shaft on which the cone E is also keyed. The shaft carrying D has also fastened on it, within the framing, a pinion which directly gears into a wheel fixed on the roller axis. Thus the twist wheel C drives the cone E and the rollers, so that if it is replaced by a smaller wheel, both of these revolve at a lower speed, or vice versâ. This is important, because as the speed of the rollers and that of the bobbins are both regulated from the twist wheel, the alteration of their velocities is made simultaneously.

(242) This part of the mechanism is easily understood and involves no difficulty, but the driving of the bobbins gives rise to a complex problem which necessitates the employment of some ingenious mechanism. The upper cone E drives, by means of a strap or band, the lower cone E¹. The circumferences of each of these cones are accurately turned to corresponding, but converse, parabolic curves, one cone being convex and the other concave. They must be exactly the same in their largest and smallest diameters, and are turned in lathes fitted with “former” plates, by which the slide rest is guided in its correct path. The lower cone is carried in bearings B, formed in two arms connected by a tubular stay, oscillating on a shaft (M, Fig. 134), on which is the pinion H. This arrangement is shown separately in plan and elevation in Figs. 135 and 136. A pinion G is fixed on the spindle of the lower cone, and gears with a spur wheel F fastened on the shaft named. Thus, when the cone E¹ is raised or lowered, the pinion G rolls round its engaging wheel F, being always fully in gear. This arrangement is utilised to keep the strap tight, the lower cone being coupled by an adjustable connecting rod or chain I to a disc fixed on the cross shaft shown, the former being preferable. By revolving the shaft J, the cone E¹ can be raised or lowered, and the tension on the strap can be regulated by means of a right and left-handed nut which couples the two parts of the connecting rod I, Fig. 134. Motion is given to the pinion H, as will be easily understood, from the cone E¹, and from it to the shaft K by the carrier pinion which gears with H¹ on K. On K also is fixed a spur pinion L¹ driving the plate wheel L, and the worm which engages with the worm-wheel on the upright shaft M. The latter is thus revolved, its precise function being explained hereafter.

(243) The wheel L forms a part of the ingenious winding, or, as it is sometimes called, “the differential motion,” invented by Mr. Henry Holdsworth. This is one of the class of epicyclic wheel trains, of which many instances are known and which are very interesting. Fig. 137 is a drawing on an enlarged scale of this motion, the reference letters, with the exception of L and N, being used for this figure specially. Upon the shaft A a fixed cast-iron tube is placed, upon which the wheel L and the compound wheel D N revolve. The jack shaft A revolves in the tube, and on the shaft is fastened a bevel wheel B which gears with similar pinions C and E. These are carried in bearings formed in the wheel L at equal distances from its centre, and have perfect freedom of revolution. They also engage with the bevel wheel D, cast in one piece with the spur wheel N, which is known as the “bobbin wheel.” The latter gears with a spur pinion carried in a double swing frame O O¹ (Fig. 134), centred on the jack shaft and attached at its other end to the bobbin rail. In this way, as the latter rises and falls, the swing frame or “swing”—as it is shortly called—oscillates on its centre, and the spur pinion rolls round the bobbin wheel N, being always in full gear. By means of a carrier wheel—also borne by the swing—the motion of the bobbin wheel is communicated to a spur wheel on one of the bobbin shafts, and by equal sized pinions on each shaft to the other. Thus, the bobbins are driven by a train of wheels, which are always in gear, no matter what the vertical position of the bobbin may be. The bobbin wheel and its compound bevel run loose upon the cast-iron tube, as previously stated.

(244) The foregoing description of the winding motion will serve to show the principle of its construction, and its mode of action can now be explained. Suppose first, that the bearings of the pinions C and E are fixed instead of revolving with the wheel L, and that the shaft A is revolved, it is obvious that the revolution of the wheel B would be communicated to C and E. These would rotate on their axes, and would consequently drive the wheel D N at the same speed as B, but in the opposite direction. This may be called one pole of the operation of this motion. The other is reached when the plate wheel L is rotated in the same direction as B at an equal velocity, the wheel D N being then carried round in the same direction, and at the same speed as B. But if the relative velocity of L is reduced, there will be a lessened speed communicated to the wheel D N in the proportion of two revolutions less than that of B for every revolution of L. That is to say, if B was running at 20 revolutions per minute and L in the same time made one revolution, D N would make 18 revolutions. This gives rise to a curious result in working. When the number of revolutions made by L is half of those made by B, the motion of D N entirely ceases, but as the proportion is varied so as to be slower than B, the velocity of D N is reduced as described, but its direction of rotation will be different. That is, if L makes more than half as many revolutions as B, the wheel D N will move in the same direction as B; but if it makes less than half, D N will rotate in the opposite direction to B. This motion is admirably treated in Professor Goodeve’s “Elements of Mechanism,” where its rationale is fully described, and where the student will find ample explanations of the operation of this class of mechanism. It is sufficient for the present purpose, however, to reiterate that the loss of motion in the bobbin wheel D N, is equal to two revolutions of B for each one of L; and that the direction of motion of D N depends on the speed of L. It may be said, in amplification, that when L revolves at less than half the speed of B, the velocity of D N increases as that of L decreases; while if the plate wheel L makes more than one-half the number of turns of B the speed of D N increases with that of L. The middle point thus becomes a sort of zero, a fact which it is desirable to remember. Treated algebraically, the formula may be stated as follows, where b = the velocity of the driving pinion B, l = that of the plate wheel L, and n that of the bobbin D N, if L revolves in the same direction as the shaft, n = b - 2l; but if in the contrary direction, then n = -b - 2l.

(245) The effect of the application of this formula in the latter case is different entirely to the results already described. If the wheel L revolves at the same speed as B, but in the contrary direction, then n = - 3b, if the value of b be substituted for that of l. If L makes half the number of revolutions that B does, then n = -2b. The relations of B and D N can thus be accurately ascertained, and by the aid of this formula the speed of the bobbin wheel can be easily calculated. It is only necessary to know the value of the entire train of gearing from the fixed wheel B to the plate wheel N to be able to apply the formula given above. Thus, if it is found that the ratio of the velocity of L and the fixed wheel B be, say, as 1: 40, and that B makes 250 revolutions per minute, the speed of D N could be arrived at easily. Substituting the arithmetical value of l and b for those signs, the result would be n = 250 - 2(250÷40) = -262·5. As the changing position of the cone strap is the only variable factor in the problem, it is only necessary to know the diameters at various points to ascertain accurately the reduction or acceleration of speed which will occur during the time it is making the necessary traverse. It should be explained, before passing on to deal at greater length with the practice of the subject, that the minus sign merely indicates that the bobbin wheel revolves in a contrary direction to the wheel B and the shaft A.

(246) The application of this mechanism to the purposes of winding depends, therefore, upon the regulation of the speed of L. It has been seen that the motion of the latter is derived from the bottom cone E¹. Assuming the plate wheel to run in the same direction as the wheel B, it follows that when the bobbin leads, the wheel L must start at its slowest relative speed, and increase as the bobbin fills. It is for many reasons desirable that the speed of the plate wheel should be as low as possible, which is the course generally adopted. If the flyer leads, the opposite plan is pursued. When, as is the case in the machine made by Mr. John Mason, the plate wheel revolves in the reverse direction to that of the wheel B, it commences at its quickest and finishes at its lowest relative speed, with a bobbin lead. Under these circumstances the full value of the special arrangement, illustrated in Fig. 137, is seen. The highest velocity of the cone is obtained when the bobbins are empty and have in consequence the lightest weight. Where spindles are revolving at 800 to 1,000 revolutions per minute, this is undoubtedly a great consideration, because the strain upon the strap is lessened by reason of the decreased velocity at a time when the strap is on the smallest diameter of the driving cone. It is sometimes the practice to run L and D on the bare jack shaft in the contrary direction, this creating a good deal of friction and necessitating extra driving power. For this reason the introduction of a tubular bush, such as is shown in Fig. 137, is attended with considerable advantage. The friction existing when the wheels run upon the bare shaft, but in the contrary direction, is very great, as will be understood when the speed of the wheels—about 400 revolutions per minute—is remembered. Any rotation of one or more of the wheels in the opposite direction to the shaft is therefore equal to an increase of the friction on the latter by the rate of the movement of the former.