Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/879

Rh ROPE 845 walk.* In tins way the strength, evenness, and other good qualities of hand-spun yarn are secured. Fig. 2. Twine Manv/acture. The making of twines and small cords forms a distinct branch of the rope trade, the whole of the opera- tions being carried out on a series of machines in which a large number of twines and cords are twisted and otherwise prepared .simultaneously, while in rope-making the machines deal only in general with the material of one rope at a time. , Common twines are twisted from prepared yarns on a twine-twisting frame, the same in principle as the doubling spindle frames of the ordinary textile trade. The bobbins of yarn are placed on pegs in the creel above the twisting spindles, from two to five bobbins being placed over each spindle according to the number of yarns which go to make up the twine. These yarns are passed round a pair of rollers, which pull them off the bobbins and deliver them evenly and with regularity to the flyer of the spindle, by which they are twisted and wound on the bobbin round which they rotate. By a recent improvement the required number of yarns, instead of being drawn from separate bobbins, are first wound together upon one bobbin in a " doubling winding frame." A series of bobbins so filled are placed on spindles in a twisting frame and twisted by inverted flyers ; the twisted twine is drawn off by pairs of conical grooved twist rollers round which it passes, and is wound on taking- up bobbins. Cord or cable laid twine that is, twine twisted first as above and then in strands of three, cabled or twisted in the reverse direction is prepared on cabling machines. At the back of the machine the yarns receive their first twist as above described, and thence the strands from three spindles are drawn off together over a pair of^cone rollers, by which they are laid, and thence they pass to the front of the machine, where there is a range of powerful flyers and spindles by which they are twisted and wound upon a large bobbin. Twines and cords at this stage are rough and bristly in appearance, and for finishing them they undergo a dressing, sizing, and polishing operation in a special polishing machine. From the bobbins they are unwound and passed through a trough of hot water, thence in parallel order over the surface of a set of rubbing rollers covered with strong card cloth revolving at high speed in a contrary direction to that in which the twine is travel- ing. The friction of the strong card wires shaves and smooths the twine, which then passes through the sizing trough contain- ing a hot paste, usually of potato farina. The superfluous paste is squeezed out by passing the twine between rollers, and it is next passed over rollers covered with rough coir, which presses in all fibres yet protruding from the twine, and finally it is dried by passing round a range of steam-heated cylinders, running parallel with which are coir-covered polishing rollers which smooth the twine while it is being dried. The finished twine is wound into balls of a definite weight on a balling machine. Rope-Spinning. The machines required for making ropes from spun yarn consist of a forming flyer for forming the strands and a laying machine for twisting the strands into rope. A cabling machine for uniting three-strand hawsers into a cable is only a second] laying machine of larger and heavier dimensions ; but it is still a common practice to lay the heavy cable on the ropewalk. The two operations of forming strands and laying rope may be per- formed on one combined machine, especially in dealing with light ropes composed of a few yarns ; but as a rule separate machines are preferred for each operation. In a simple machine designed only for a single twisting operation there must be one fixed and one revolving section. If the section which contains the bobbins of yarn to be twisted is fixed, then the section in which is placed the bobbin for receiving the twisted product must be made to revolve. A machine in which the two operations of forming strands and laying rope are combined is of necessity cumbrous in proportion and complex in gearing. It must embrace three form- ing flyers, to form simultaneously three strands which in another part of the machine are laid into one rope. The forming flyers re- volve in one direction to twist the strands, while they move in the opposite direction as a whole with the revolution of the laying section which gives the finishing twist to the rope, and such com- plex inter-revolutions within one frame are somewhat unwieldy. Finally, the machines may be made with their axis of revolution either vertical or horizontal. With all these alternatives there is considerable room for modification in the twisting arrangements. The ordinary form of strand-laying machine is a vertical Hyer (fig. 3). It consists of two or more upright frames or creels a, a, capable of holding ranged above each other a certain number of bobbins, from which the yarn may be easily run off and carried upward to be formed into a strand. The creels are fixed above and below in a stout circular plate and framework bb, to which motion of rotation is given by gearing c, placed on the under side. At the upper end of the revolving framework the yarns from the various bobbins are passed through a register plate d, a circular piece of metal pierced with concentric holes corresponding in number with the bobbins which the creels are fitted to hold. Beyond the register plate d the yarns come together in the trumpet- shaped mouth of the stranding tube. The stranding tube itself varies in gauge according to the diameter of the strand being made, and in it the yarns are caught, rounded, compressed, twisted, and Fig. 3. smoothed, and, passing out, the new-formed strand is drawn over a pulley c around " drawing-off " gear/, and wound on a large bobbin or drum g. The speed at which the drawing-off gear revolves regu- lates the hardness or softness of twist given to the strand, and its rotation can be varied at pleasure by the use of change wheels. In fig. 4 is illustrated a different form of stranding machine, of American origin. In this apparatus the bobbin creel is stationary -A. Fig. 4. and the yarns are drawn through the register plate and twisted in the stranding tube by the revolution of the entire framework in which are placed the drawing-off gear and the large drum or spool on which the finished strand is wound. The advantages claimed for this apparatus are facility of replacing bobbins as the yarns run out, and increased production owing to the rapid and uninter- rupted rotation of the flyer. In the ordinary laying machine there are only three bobbins of strand to deal with ; but, from the fact that it is necessary to give a certain amount of "forehard" or twisting to the strands them- selves while they are being twisted together in an opposite direction for laying, the machine is not without complexity. The three bobbins revolve together within a strong iron frame, and that motion forms the strand into a rope. But each bobbin is at the same time revolving in a contrary direction on its own axis at the rate tempered to the amount of forehard it is desired to put on the rope in laying. Moreover, in order to deliver evenly and in equal quantities the heavy and intractable strands from each bobbin to the laying top, it is necessary to have within each bobbin frame a drawing-off motion, and thus we have three dis-