[Ill.u.s.tration: Fig. 126.]
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(16). +Twist Or Plait Knot+.--Another method of shortening a small handy rope is known as the twist or plait knot.
Arrange the rope in such a manner that the amount to be taken up forms a bight as in Fig. 127.
[Ill.u.s.tration: Fig. 127. Fig. 128.]
Then by taking _a_ over _b_ and _c_ over _b_, and so on, taking the outside one on each side alternately over the middle one, the plait is formed. To keep the plait clear, the end has to be continually dipped through the first bight made (Fig. 128).
{72}
HOW TO HANDLE WIRE ROPE, ETC.
+The following article by a Wire Specialist will be read with interest+:--
When uncoiling Wire Rope it is important that no kinks are allowed to form, as once a kink is made no amount of strain can take it out, and the rope is unsafe to work. If possible a turn-table should be employed (an old cart wheel mounted on a spindle makes an excellent one); the rope will then lead off perfectly straight without kinks.
(See Fig. 129.)
[Ill.u.s.tration: Fig. 129. Fig. 130.]
If a turn-table is not available the rope may be rolled along the ground as shown in Fig. 130.
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In no case must the rope be laid on the ground and the end taken over (as in Fig. 131), or kinks will result, and the rope will be completely spoiled.
[Ill.u.s.tration: Fig. 131.]
The life of Wire Rope depends princ.i.p.ally upon the diameter of drums, sheaves, and pulleys; and too much importance cannot be given to the size of the latter. Wherever possible the size of the pulleys should be not less than 700 times the diameter of the largest wire in the rope, and never less than 300 times. The diameters of drums, sheaves, and pulleys should increase with the working load when the factor of safety is less than 5 to 1.
The load should not be lifted with a jerk, as the strain may equal three or four times the proper load, and a sound rope may easily be broken.
Examine ropes frequently. A new rope is cheaper than the risk of killing or maiming employees.
{74}
One-fifth of the ultimate strength of the rope should be considered a fair working load.
In shafts and elevators where human life is constantly raised and lowered, the working load should not be more than one-tenth of the ultimate breaking strength of the rope.
To increase the amount of work done, it is better to increase the working load than the speed of the rope. Experience has shown that the wear of the rope increases with the speed.
Wire Rope should be greased when running or idle. Rust destroys as effectively as hard work.
Galvanized Wire Rope should never be used for running rope. One day"s use will wear off the coating of zinc, and the rope will soon begin to rust.
Great care should be taken that the grooves of drums and sheaves are perfectly smooth, ample in diameter, and conformed to the surface of the rope. They should also be in perfect line with the rope, so that the latter may not chafe on the sides of the grooves.
+Set of Wire Rope Splicing Tools+.
To produce the best work, the splicer should have at his disposal a set of tools similar to those in the accompanying ill.u.s.tration.
The Tool set consists of--1 Tucker for Small Strands Splicing; 1 Marlin Spike, Round; 1 Marlin Spike, Flatted; 1 Pair Special Steel Wire Cutters; 1 Serving Mallet. All of best Cast Steel, Hand Forged.
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[Ill.u.s.tration: Fig 132.]
These Sets may be had at prices varying from 15/6 to 46/-.
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+Directions for Splicing+.
TO MAKE AN ENDLESS SPLICE.--Clamps are applied to the rope sufficiently far back from the ends to allow plenty of room for the splice, and the men to operate in. The two ends are then drawn together by means of blocks and tackle, until they overlap each other for a s.p.a.ce of twenty to thirty feet, according to the size of the rope. At a point from each end midway of the lap, the rope must be bound with a good serving of No. 18 or No. 20 annealed wire. The serving at the extreme ends is then cut off, the strands untwisted to the new serving, and the hemp cores also cut off so as to abut when the open bunches of strands are brought together, and the opposite strands interlaced regularly with each other, presenting the appearance as near as can be shown (Fig.
133).
[Ill.u.s.tration: Fig. 133.]
After these are all correctly interlaced, pull the ropes tightly together, so that the cores abut against one another. Next take {77} strand No. 1, and as it is being unlaid, follow it up with strand A, which must be laid into its place tightly until within five feet from the end. Strand No. 1 is then cut off, leaving it five feet long, same length as A strand. The remaining strands are treated the same way, three alternate strands being laid towards the right hand and three to the left. The strands being now all laid in their places, the ends are cut off, as with the first strands, to five feet. The appearance of splice will now be the same as in Fig. 134.
[Ill.u.s.tration: Fig. 134.]
The next thing is to tuck in the ends, and this is where the skill comes in. Before doing this, _care should be observed to see that the spliced portion of the rope is perfectly limp, or free of tension, otherwise this operation cannot be well performed_. The core is then cut and pulled out on the side corresponding with the end to be tucked in for a distance equal to the length of the end which is to replace it. It is desirable, especially if the rope is composed of small wires, to tie the ends of the strands with soft twine or threads of jute yarn in order to keep the wires well bunched. A marlin spike is then pa.s.sed over +1+ and under two of the strands, when the core is cut off at the proper point, and by moving the spike along the rope spirally with the strands, the loose end +1+ is pa.s.sed into the core s.p.a.ce and the spike withdrawn. {78} Then pull out the core on the other side, pa.s.s the marlin spike over A and under two strands as before, cut off the core, and tuck in the end A in precisely the same manner, after which the rope is twisted back again as tightly as possible, and the clamps or other appliances that may be used are removed to the next pair of projecting ends. Any slight inequality in the symmetrical shape of the rope may be taken out by pounding with a wooden mallet. Some prefer to tuck in first all the ends projecting in one direction, and then the ends projecting the other way; it is immaterial in what order they are tucked in.
If these directions are implicitly followed, the spliced portion of the rope will be of uniform diameter with other portions, and will present a smooth and even appearance throughout. After running a day or two, the locality of the splice cannot be readily detected, and the rope will be quite as strong in this portion as any other.
+Splicing Thimbles+.
UNDER AND OVER STYLE--Ordinary type of Wire Rope. Serve the rope with wire or tarred yarn to suit the circ.u.mference of the thimble, bend round thimble and tie securely in place with temporary lashing till splice is finished (as in Fig. 135). Open out the strands (as in Fig.
136), taking care to keep the loose end of the rope to the left hand (see Fig. 136). Now insert marlin spike, lifting two strands (as shown in Fig. 137), and tuck away towards the right hand (that is inserting the strand at the point, and over the spike) strand No. 1, pulling the strand well home. Next {80} insert marlin spike through next strand to the left, only lifting one strand, the point of the spike coming out at the same place as before. Tuck away strand No. 2 as before.
[Ill.u.s.tration: Fig. 135. Fig. 136. Fig. 137. Fig. 138.]
The next tuck is the locking tuck. Insert marlin spike in next strand, and, missing No. 3, tuck away strand No. 4 from the point of the spike towards the right hand. Now, without taking out the spike, tuck away strand No. 3 behind the spike towards the left hand (as shown in Fig.
138). Now insert spike in next strand, and tuck away strand No. 5 behind and over the spike. No. 6 likewise. Pull all the loose strands well down.
[Ill.u.s.tration: Fig. 139. Fig. 140.]
This completes the first series of tucks, and the splice will, if made properly, be as Fig. 139. Now, starting with strand No. 1 and taking each strand in rotation, tuck away under one strand and over the next strand till all the strands have been tucked four times. If {81} it is intended to taper the splice, the strands may at this point be split, and half of the wires being tucked away as before, the other half cut close to the splice. Fig. 127 [Transcriber"s note: 140?] shows the finished splice ready for serving over.
[Ill.u.s.tration: Fig. 141.]