Page:The New International Encyclopædia 1st ed. v. 17.djvu/313

* ROPE. 285 ROPE. rojic-walk ami tlic ciuls of the yarns from theui air passed tliroufili holes in an "iron fc'aufje plate, known as the face plate, and then llirough a east- iron tul)('. which acts to collect the separate yarns into a closely laid cylindrical bunitle. After being passed through the tube the yarns are fastened on a hook of the forming machine, which runs on a track the entire length of the walk, and which at the same time twists the yarns Ictt-handed into a strand. To lay these strands into a rope, two laying macliines are re- quired, one at ea<-li end of the walk, which are known as the upjier and lower machines. As many of the strands as are required for the rope are stretched at full length along the walk and are attached to the hooks on the laying machines. The upper machine has but one hook, to which all the strands are attached and which o|)erates in one direction; while the lower machine has as many hooks as there are strands and operates in the opposite direction. To keep the strands equidistant the- are placed in the grooves of a conical wooden block called a "top," which is at- tached to an upright post on a car called a top stud. The top is pushed up close to the upper laying machine at the beginning of the twisting process, and, as the twisting proceeds, the strands closing in behind it gradually force it down the walk until the lower laying machine is reached and the rope completed. .Machine Rope-Making. The greater part of medium-size rope is made by rope-making ma- chines, as distinguished from the rope-walk. In describing rope-making by machines reference will be had particularly to the working of Ma- nila hemp, the material most extensively used, but Russian, Sisal, and other hemps are manipu- lated in essentially the same manner. The treat- ment of jute requires a rather different process, owing to its shorter and weaker fibre. The bales of Manila hemp, averaging in weight about 270 pounds each, are opened, and, after the fibre has been lightly shaken apart, it is placed in layers which are sprinkled lightly with oil to soften and to lubricate the fibre previous to its passage through the machines. The first mechanical operation is called 'scutching,' and consists in l)assing the hemp over revolving cylinders bris- tling with sharp steel prongs or teeth, which straighten out the fibres and remove the coir, or fine broken particles, the dirt, and other foreign substances. It is then passed on to the break- ers, which are large frames each about 2.5 feet long, consisting of two endless chains covered with long steel pins. The first chain feeds the fibres to the second, which runs much slower, the effect being to comb or straighten out the fibres and draw them into a continuous ribbon or sliver. Following this operation comes the passage of the hemp through the spreaders and drawing frames, machines similar to the breakers, but smaller, and furnished with steel pins and teeth of gradually increasing fineness, which still further comb and straighten out the fibres — a number of slivers being put together behind each machine and drawn down to one sliver again at the end of each machine. This drawing is re- peated several times through machines of vari- ous degrees of fineness, in order to make the sliver even, without which it would be impossi- ble to spin fine even yarns. This process is completed on a very fine drawing frame called a finisher, and from this the material eniprgpii in complete readiness for spinning. 'I'lie Npinning is doni' on spinning machines or jennies, encli op- erating two spindles, moving at about l."iOO revo- lutions per minute. The spinning twists the fibre right-handed into yarn, almut lOOt) yards of which are wound upon each bobl)iii. 'Ihe' next process is to •form' the yarn into strands and ■lay' the stran<ls into rope, and this is |H-rfornied upon machines known as formers and layers. For the larger sizes of rope theri' are iismillv separate machines, but for ro[H' 'j in<'li in iliani- eter and less the former and layer are combined into a single machine. The former consists of u circular iron disk, at the centre of which is erected a perpendicular shaft, carrying ut ita end a 'head' or die. The plane of the disk nujy be either horizontal or vertical. .Around the edge of the disk are spaced several bobbins or spools full of yarn, the number of spoids used depending upon the nuiiilier of yarns in the final strand. The free end of the yarn from each spool is carried to the head, where, by a revolving mo- tion of the disk, they aie twisted together and wound otf on to a spool or drum. If we substi- tute for the s|iools of yarn just described spools filled with twisted strands we have in its essen- tials a layer. When former and layer are com- bined, each spool on the large disk is rei>laced by a small disk and head, which twists a strand, the several strands being led to the head of the main disk and there twisted into completed rope, which is wound oil onto a drum or reel. SpEtlAl, Roi'ES. Cables for drilling oil and water wells have to be made unusually long and run all the way from 1,400 feet to .■i,.500 feet in length, and from 1% inches to 2li inches in diameter. They are composed of three strands of manila ropes, laid together with a very bard lay, so that they will not untwist when used for drilling, and also will resist the continual wear and rubbing against the side of the casing and the wall of the well. Cables of this kind are always made on machines and not in Ihr rope- walk. These machines have to be exceedingly large and heavy to carry this amount of rope, and only a few mills in the world are e<|Uip|>ed for making well-drilling cables. For making tarred rope the yarns are first run through cop- per tanks filled with heated tar: the yarns enter through holes in an iron plate and are drawn through the tank by machinery. .s the yarns emerge from the tank the superlluous tar is re- moved by means of pressing rollers. Tarred ropo may be made any size by the methods already de- scribed, but a large proportion of tarred yarn ia made into small cordage. Strength of Rope. The strength of rope varies with the material of which it is made, the weight of the rope per fathom, etc. The fol- lowing figures compiled from Kent's Mirhtiniciil Eniiiiieer's I'ockrl Book (New York, 1900) give some general information on this matter: MATERIALS Untarred hemp Tarred hemp. Cotton rope... Manila rope... Circ. in iucbes l.Ktto 6.9 l.« to 7.12 2.48 to 6.51 1.19 to 8.9 Weljrht. lbs. per fathom 0.42 to 7.77 0.38 to 10.39 1.(18 to 8.17 0.2 to 11.4 Strength, Itia. 1.67C1I.I :i;i.-"~ 1.040 to :)1...|'' 3,ati9 to 'U.-i!* 1,280 to ee.Mo The comparative strength of hemp, iron, nml steel ropes is indicated in a general way by the