c3 are drums, mounted in the carriage in a plane at right angles to the plane in which the spindles are placed. At top they have a double groove for a cord to run in, and the motion which they receive from the great fly wheel, or rim of the mule (not visible in this view) they impart to the spindles. Such a drum is assigned to every 24 spindles; and therefore a mule of 480 spindles contains 20 drums. In the middle of the carriage is seen the horizontal pulley k3, furnished with three grooves, which stands in a line with the drums c3.
The motion is given to the drums c3, upon the right hand half of the carriage by a single endless band or cord which proceeds from the middle groove of the pulley k3. The rotation of the spindles is produced by a slender cord, of which there are 12 upon each drum c3; because every such cord goes round the drum, and also every two wharves which stand at the same level upon the spindles. It is obvious that the drums, and consequently the spindles, must continue to revolve as long as the main rim of the mule is turned, whether the carriage be at rest or in motion upon its railway.
If we suppose the carriage to be run in to its standing point, or to be pushed home to the spot from which it starts in spinning, its back plank d2 will strike the post q3 upon the fixed frame, and the points of the spindles will be close in front of the roller beam. The rollers now begin to turn and to deliver threads, which receive immediately a portion of their twist from the spindles; the carriage retires from the roller beam with somewhat greater speed than the surface speed of the front rollers, whereby the threads receive a certain degree of stretching, which affects most their thicker and less twisted portions, and thereby contributes greatly to the levelness of the yarn. When the carriage has run out to the end of its course, or has completed a stretch, the fluted rollers suddenly cease to revolve (and sometimes even beforehand, when a second stretch is to be made), but the spindles continue to whirl till the fully extended threads have received the proper seconder after-twist. Then the carriage must be put up, or run back towards the rollers, and the threads must be wound upon the spindles.
This is the order of movements which belong to the mule. It has been shown how the rotation of the spindles is produced.
For winding-on the yarn the carriage has a peculiar apparatus, which we shall now describe. In front of it, through the whole extent to the right hand as well as the left, a slender iron rod, d5, runs horizontally along, in a line somewhat higher than the middle of the copping portion of the spindles, and is supported by several props, such as e5. Upon each end of the two rods, d5, there is an arm, g5; and betwixt these arms an iron wire, called the copping wire, f5, is stretched, parallel with the rod d5. For the support of this wire, there are several slender bent arms h5 extended from the rod d5 at several points betwixt the straight arms g5. The rod d5 has, besides a wooden handle at the place opposite to where the spinner stands, by which it can be readily grasped. This movement is applied at the left division of the machine, and it is communicated to the right by an apparatus which resembles a crane’s bill. The two arms, g5, in the middle of the machine, project over the rods d5, and are connected by hinges with two vertical rods j5, which hang together downwards in like manner with two arms i5, proceeding from a horizontal axis k5.
By means of that apparatus the yarn is wound upon the spindles in the following manner. As long as the stretching and twisting go on, the threads form an obtuse angle with the spindles, and thereby slide continually over their smooth rounded tips during their revolution, without the possibility of coiling upon them. When, however, the spinning process is completed, the spinner seizes the carriage with his left hand and pushes it back towards the roller beam, while with his right hand he turns round the handle of the rim or fly wheel, and consequently the spindles. At the same time, by means of the handle upon the rod d5, he moves the copping-wire, f5, so that it presses down all the threads at once, and places them in a direction nearly perpendicular to the spindles; as shown by the dotted line y5. That this movement of the copping wire, however, may take place without injury to the yarn, it is necessary to turn the rim beforehand a little in the opposite direction, so that the threads may get uncoiled from the upper part of the spindles, and become slack; an operation called in technical language, the backing off. The range upon which the threads should be wound, in order to form a conical cop upon the spindle, is hit by depressing the copping wire to various angles, nicely graduated by an experienced eye. This faller wire alone is not, however, sufficient for the purpose of winding-on a seemly cop, as there are always some loose threads which it cannot reach without breaking others.
Another wire called the counter-faller, l5, must be applied under the threads. It may be raised to an elevation limited by the angular piece p5; and is counterpoised by a very light weight m5, applied through the bent lever n5, which turns upon the fulcrum o5. This wire, which applies but a gentle pressure, gives tension to all the threads, and brings them regularly into the height and range of the faller f5. This wire must be raised once more, whenever the carriage approaches the roller beam. At this instant a new stretch commences; the rollers begin again to revolve, and the carriage resumes its former course. These motions are performed by the automatic machinery.
There is a little eccentric pulley mechanism for moving the guide beam to and fro with the soft yarns, as they enter between the back rollers. On the right hand end of the back roller shaft, a worm screw is formed which works into the oblique teeth of a pinion attached to the end of the guide beam, in which there is a series of holes for the passage of the threads, two threads being assigned to each fluted roller. In the flat disc of the pinion, an eccentric pin stands up which takes into the jointed lever upon the end of the guide beam, and as it revolves, pushes that beam alternately to the left and the right by a space equal to its eccentricity. This motion is exceedingly slow, since for each revolution of the back roller, the pinion advances only by one tooth out of the 33 which are cut in its circumference.
After counting the number of teeth in the different wheels and pinions of the mule, or measuring their relative diameters, it is easy to compute the extension and twist of the yarns; and when the last fineness is given to ascertain their marketable value. Let the ratio of speed between the three drawing rollers be 1 : 13⁄22 : 71⁄2; and the diameter of the back and middle roller three quarters of an inch: that of the front roller one inch; in which case the drawing is thereby increased 11⁄3 times, and 71⁄2 × 11⁄3 = 10. If the rovings in the creel bobbins have been No. 4. the yarn, after passing through the rollers, will be No. 40. By altering the change pinion (not visible in this view) the fineness may be changed within certain limits, by altering the relative speed of the rollers. For one revolution of the great rim or fly wheel of the mule, the front roller makes about 6-tenths of a turn, and delivers therefore 22·6 lines or 12ths of an inch of yarn, which, in consequence of the tenfold draught through the rollers, corresponds to 2·26 lines of roving fed in at the back rollers. The spindles or their whorls make about 66 revolutions for one turn of the rim. The pulleys or grooved wheels on which the carriage runs, perform 0·107 part of a turn while the rim makes one revolution, and move the carriage 24·1 lines upon its rails, the wheels being 6 inches in diameter.
The 22·6 lines of soft yarn delivered by the front rollers, will be stretched 11⁄2 lines by the carriage advancing 24·1 lines in the same time. Let the length of the railway, or of each stretch be 5 feet, the carriage will complete its course after 30 revolutions of the rim wheel, and the 5 feet length of yarn (of which 561⁄2 inches issue from the drawing rollers, and 31⁄2 inches proceed from the stretching) is, by the simultaneous whirling of the spindles, twisted 1980 times, being at the rate of 33 twists for every inch. The second twist, which the threads receive after the carriage has come to repose, is regulated according to the quality of the cotton wool, and the purpose for which the yarn is spun. For warp yarn of No. 40 or 50, for example, 6 or 8 turns of the rim wheel, that is, from 396 to 528 whirls of the spindles for the whole stretch, therefore from 7 to 9 twists per inch will be sufficient. The finished yarn thus receives from 40 to 42 twists per inch.