(277) The rollers are in three lines, and are borne in brackets or stands fastened to longitudinal iron “roller beams,” sustained at intervals by light frames or “spring pieces.” The lower lines of rollers are finely fluted, and are made of the same superior quality of iron as those used in the roving frames. Their diameter is usually an inch, but this varies with the staple to be spun. The front line of top rollers are generally of Leigh’s loose boss type, cloth and leather covered, and are weighted by a saddle, stirrup, and lever weight. The middle and back lines are “common rollers,” also covered in the same manner. The front lines of the right and left-hand set in each mule are coupled by a short shaft, and the second and third are driven from the first.
Fig. 149.
Fig. 150.
(278) The carriage has a rectangular frame, being built with strong longitudinal timbers, securely tied together by cross pieces. These carry, as was shown, the bolster and footstep rails. On the cross cast-iron “muntins” the bearings for the tinroller shafts are fastened. The carriages at each side of the headstock are coupled by a strong iron frame, to which they are securely fastened. This is known as the “square,” and carries some of the mechanism for giving motion to the spindles and building the cop.
(279) The tin roller is generally six inches in diameter, and consists of a series of cylinders made from sheets of tinned iron, securely soldered together. In each end of the rollers so formed an iron disc is fastened, and the lengths are coupled by means of short shafts. The whole of the lengths are thus connected, and a bearing is placed at each junction, so that the tin roller is well sustained throughout. The rollers in each of the two carriages are coupled by a short shaft, extending across the square, and carried by means of pedestals, fixed to the latter. On this short length of shaft the driven tin roller pulley is secured, as will be hereafter fully described.
(280) The spindle is made of steel, and is from 131⁄2 to 18 inches long, according to the class of material being dealt with. For coarse counts and for “twist” yarn a larger cop is made, and the spindle is of necessity longer. For 32’s twist yarn a spindle about 17 inches long is used, and its diameter varies from 3⁄8ths inch to less than 1⁄8th inch. The part between the two bearings is called the “haft,” and that above the bolster—on which the cop is wound—the “blade.” The spindle is thickest in the haft, terminating in a small foot, but the blade is tapered throughout. Great care is taken with the spindles to ensure their accuracy, and they can, therefore, be run at velocities as high as 11,000 revolutions per minute without vibration. The extra diameter of the haft ensures the necessary resistance to flexure caused by the pull of the driving band. The latter is a thin cotton cord-made of the best grades of cotton—passed tightly over the spindle warve and the tin roller. It is highly important that the bands should not be either too tight or too slack. In the one case the friction generated would be excessive and detrimental, and in the other the twist would not be fully put into the roving, which would be said to be “slack twisted.” Varying atmospheric conditions materially alter the tension of the bands, and their proper piecing is only to be mastered after long practice. The spindle is disposed in the carriage at a varying angle, to suit the material being spun.