XVII
XVII
Thesplicing of a transmission rope is an important matter; the points on which the success of the splice, and incidentally the drive, depend being the length of the splice, which in turn depends upon the diameter of the rope and which is given in the table (Fig. 97a);the diameter of the splice, which should be the same as the diameter of the rope; the securing of the ends of the strands of the splice, which must be so fastened that they will not wear or whip out or cause the overlying strands to wear unduly; and the workmanship of the splice, which should be the best it is possible to secure. When splicing an old and a new piece of rope, the new piece should be thoroughly stretched, for, at best, it is an exceedingly difficult task on account of the stretch and difference in diameter of the rope.
Data Relative to Manila Transmission Rope and Sheaves
Length of Splicein FeetABCDEFGHIJ1/2.25.1217505062010605/8.2906.162730806249703/4.5625.20395011268277607/8.7656.265400153683265011..347000200710143657011/81.2656.438900253710164051011/41.5625.6310,900312710164546011/22.25.7715,700450812185438013/43.06251.0421,400612812186333024.1.3628,000800914207229021/45.06251.7335,4001012914208125521/26.252.1343,700125010162290230
Fig. 97a.
Key to above table
ADiameter of Rope in InchesBSquare of DiameterCApproximate Weight per Foot, PoundsDBreaking Strength, PoundsEMaximum Allowable Tension, PoundsF3-StrandG4-StrandH6-StrandISmallest Diameter of Sheaves in InchesJMaximum Number of Revolutions per Minute
The illustrations and instructions for making standard rope splices are taken, by the courtesy of the American Manufacturing Company, from their "Blue Book of Rope Transmission."
There are many different splices now in use, but the one that experience has proved best is what is known as the English transmission splice. In describing this we take for our example a four-strand rope, 1¾ inches in diameter, as spliced on sheaves in the multiple system. The rope is first placed around sheaves, and, with a tackle, stretched and hauled taut; the ends should pass each other from six to seven feet, the passing point being marked with twine on each rope. The rope is then slipped from the sheaves and allowed to rest on shafts, to give sufficient slack for making the splice.
Fig. 98.
Fig. 98.
Unlay the strands in pairs as far back as the twinesM,Mâ², crotch the four pairs of strands thus opened (Fig. 98), cores having been drawn out together on the upper side. Then, having removed markingtwineM, unlay the two strands 6 and 8, still in pairs, back a distance of two feet, toA; the strands 1 and 3, also in pairs, being carefully laid in their place. Next unlay the strands 5 and 7 in pairs, toAâ², replacing them as before with 2 and 4. The rope is now asshown in Fig. 99. The pair of strands 6 and 8 are now separated, and 8 unlaid four feet back toB, a distance of six feet from center, strand 6 being left atA. The pair of strands 1 and 3 having been separated, 3 is left atA, as companion for 6, strand 1 being carefully laid in place of strand 8 until they meet at pointB. The two pairs of strands 2-4 and 5-7 are now separated and laid in the same manner, every care being taken, while thus putting the rope together, that original twist and lay of strand is maintained. The protruding cores are now cut off so that the ends, when pushed back in rope, butt together.
Fig. 99.
Fig. 99.
The rope now appears as shown in Fig. 100, and after the eight strands have been cut to convenient working lengths (about two feet), the companion strands are ready to be fastened together and "tucked"; this operation is described for strands 2 and 7, the method being identical for the other three pairs. Unlay 2 and 7 for about twelve to fourteen inches, divide each strand in half by removing its cover yarns (see Fig. 101), whip with twine the ends of interior yarns 2â² and 7â²; then, leaving cover 2, relay 2â² until near 7 and 7â², here join with simple knot 2â² and 7â², Fig. 102. Divide cover yarns 7, and pass 2â² through them, continuing on through the ropeunderthe two adjacent strands, avoiding the core, thus locking 2â², Fig. 103.In no event pass 2â² over these or any other strands.Half-strand 7â² must now be taken care of; at the right of the knot made with 2â² and 7â², 2â² is slightly raised with a marlin spike, and 7â² passed or tucked around it two or three times, these two half-strands forming in this way a whole strand. Half-strand 7â² is tucked until cover 2 is reached, whose yarns are divided and 7â² passed through them and drawn under the two adjacent strands, forming again the lock. The strand ends at both locks are now cut off, leaving about two inches, so that theyarns may draw slightly without unlocking. This completes the joining of one pair of strands, Fig. 104. The three remaining pairs of strands are joined in the same manner.
Fig. 100.
Fig. 100.
Fig. 101.
Fig. 101.
Fig. 102.
Fig. 102.
Fig. 103.
Fig. 103.
Fig. 104.
Fig. 104.
After the rope has been in service a few days, the projecting ends at locks wear away, and if tucks have been carefully made, and the original twist of yarns preserved, the diameter of the rope will not be increased, nor can the splice be located when the rope is in motion.