Steel rope: classification and selection criteria for rope. Types of ropes

Rice. 1: a – TK (6x19 + s.); b – LK-O (6x19 + 7x7); V – LK-R (6x19 + s.); G – LK-RO (6x36 + s.); d – LK-Z (6x25 + 7x7); e – TLK-O (6x37 + s.)

Depending on the core material there are ropes with an organic core made of bast (hemp) or synthetic (nylon, nylon) fibers, and when working in conditions of elevated temperatures or chemically aggressive environments - from asbestos fibers and ropes with a metal core, which is also used as a double lay wire rope (Fig. 65, b, d). Ropes with a metal core are used for multi-layer winding on a drum, since this rope does not lose its shape under the influence of load from overlying turns, as well as under sharply changing loads and when working in conditions of high temperatures, which preclude the use of ropes with an organic core. A rope with a metal core, although it has a higher coefficient of filling the cross section with metal, due to the different operating conditions of the core strands and the rope strands, practically does not become stronger. Ropes with an organic core are more flexible than ropes with a metal core, and hold the lubricant better, since the lubricant comes to the wires not only from the outside (during operation, the ropes are regularly lubricated), but also from the core, impregnated with lubricant.

Classification of ropes by type of lay

Based on the type of laying of the wires in the strands, the following are distinguished:

TK type ropes(Fig. 1, a) with point contact of individual wires between layers of strands;

ropes type LK with a linear touch of the wires in the strands. Ropes type LK have several varieties:

• LK-O (Fig. 1, b), where the wires of individual layers of the strand have the same diameter;

  LK-R (Fig. 1, c), in which the wires in the upper layer of the strand have different diameters;

  LK-RO (Fig. 1, d) - the strands contain layers composed of wires of the same diameter and of wires of different diameters;

  LK-Z (Fig. 1, e) - filling wires of smaller diameter are placed between two layers of wires.

ropes type TLK-O and TLK-R with combined point-linear contact between the wires in the strand (Fig. 65, e).

TK type ropes with point contact of wires are used only for non-stressful operating modes, when the service life is determined mainly not by the quality of the rope, but by the conditions of its use. Ropes with linear touch have better section filling, they are more flexible and wear-resistant. Their service life is 30–100% higher than the service life of TK type ropes. Due to better filling of the section, they have a slightly smaller diameter at the same breaking load.

Classification of ropes by type of lay

By lay type ropes divided into:

regular or unwinding ropes(in these ropes, the wires and strands tend to straighten after the ends are removed);

non-unwinding ropes, twisted from pre-deformed wires and strands: their shape corresponds to their position in the rope. The wires of non-unwinding ropes in an unloaded state do not experience internal stress. These ropes have a significantly longer service life. The tensile load in them is more evenly distributed between the strands and between the wires in the strands. They have greater resistance to variable bending. Broken wires in them retain their previous position and do not come out of the rope - this facilitates its maintenance and reduces wear on the surface of the drum and block due to broken wires.

non-rotating ropes- these are multi-layer ropes that have the opposite direction of lay of the strands in individual layers. However, when bending around the block, individual layers easily shift relative to each other, which sometimes leads to bulging of the strands and premature failure of the rope.

Attaching ropes to structures.

Blocks on pulleys

tall lifting mechanisms, the main parts of which are a wheel with a circumferential groove (pulley) and a rope or cable; are used for lifting heavy objects with the application of small forces (or with the application of forces in a comfortable position of the worker) both as working parts of lifting machines (winches, hoists, cranes), and independently of them. Typically, a block is a device consisting of one pulley in a frame with a suspension and one cable; chain hoist - a combination of pulleys and cables. The operating principles of these mechanisms are explained in the figures. In Fig. 1a, a load weighing W1 is lifted using a single block with a force P1 equal to the weight. In Fig. 1b, the load W2 is lifted with the simplest multiple pulley system, consisting of two blocks, with a force P2 equal to only half the weight of W2. The impact of this weight is divided equally between the branches of the cable on which pulley B2 is suspended from pulley A2 by hook C2. Consequently, in order to lift the load W2, it is sufficient to apply a force P2 equal to half the weight of W2 to the branch of the cable passing through the groove of the pulley A2; Thus, the simplest chain hoist gives a double gain in strength. Fig. 1,c explains the operation of a pulley with two pulleys, each of which has two grooves. Here the force P3 required to lift the load W3 is only a quarter of its weight. This is achieved by distributing the entire weight of W3 between the four suspension cables of block B3. Note that the multiple of the gain in strength when lifting weights is always equal to the number of cables on which the movable block B3 hangs. In its principle of operation, a pulley block is similar to a lever: the gain in force is equal to the loss in distance with theoretical equality of the work performed. In the past, the cable for pulleys and pulleys was usually flexible and durable hemp rope. It was woven with a braid of three strands (each strand, in turn, was woven from many small strands). Hemp rope pulleys were widely used on ships, agricultural farms, and in general where an occasional or periodic application of force was required to lift a load. The most complex of these pulleys (Fig. 2) were apparently used on sailing ships, where there was always an urgent need for them when working with sails, spar parts and other moving equipment. Later, for frequent movements of large loads, steel cables, as well as cables made of synthetic or mineral fibers, began to be used, as they are more wear-resistant. Pulley hoists with steel cables and multi-groove pulleys are integral components of the main lifting mechanisms of all modern hoisting and transport machines and cranes. The pulleys of the blocks usually rotate on roller bearings, and all their moving surfaces are forcibly lubricated.

Rice. 1. PRINCIPLE OF OPERATION OF THE BLOCK AND PULLEY. a - single block (with one cable stretched along the groove of a single pulley); b - a combination of two single blocks with a single cable covering both pulleys; c - a pair of double-groove blocks, through four paired grooves of which a single cable passes.

Rice. 2. PULLEYS with various combinations of three types of blocks: on the left - a pair of double blocks; in the center there is a triple block with a double block; on the right is a pair of triple blocks. In a triple pulley, the end of the cable to which the pulling force is applied passes through the central groove; in this case, the lower - movable - block is fastened with a thimble so that its axis is perpendicular to the axis of the upper - fixed - block.

Classification of construction machines. General requirements for machines

Based on production (technological) characteristics, all construction machines and mechanisms can be divided into the following main groups: -

1) lifting;

2) transporting;

3) loading and unloading;

4) for preparatory and auxiliary work;

5) for excavation work;

6) drilling;

7) pile drivers;

8) crushing and screening;

9) mixing;

“10) machines for transporting concrete mixtures and solutions; " 11) machines for laying and compacting concrete mixtures;

12) road; - 13) finishing; 14) power tool.

Road and other construction machines not listed are not considered in the textbook, since their study in the course “Construction machines and their operation” is not provided for.

Each of these groups of machines, in turn, can be divided according to the method of performing work and the type of working body into several subgroups, for example, machines for excavation work can be divided into the following subgroups:

a) earth-moving and transport machines: bulldozers, scrapers, motor graders, grader-elevators, etc.;

b) single-bucket and multi-bucket excavators; earthmoving and milling machines, levelers with a telescopic boom, etc.;

c) equipment for the hydromechanical method of soil development: hydraulic monitors, suction and dredging equipment, etc.

d) soil compaction machines: rollers, vibratory compaction machines, rammers, etc.

The operating conditions of construction machines are somewhat complex. Construction machines must provide the necessary productivity in the open air, in any weather, at any time of the year; move along dirt roads and off-road conditions, in cramped conditions of a construction site. Therefore, based on specific operating conditions, a number of requirements are imposed on a particular machine, and the more fully the machine meets all operating requirements, the more suitable it is for use in construction production.

Each machine must be reliable, durable and adaptable to changing operating conditions; must be convenient to operate, easy to maintain, repair, install, dismantle and transport, economical to operate, i.e., consume a minimum amount of electricity or fuel per unit of output. The machine must ensure labor safety and ease of work for operating personnel, achieved by appropriate placement of instruments, controls, good visibility of the work front, automatic cleaning of the cab sight glasses, a pneumatic or hydraulic control system that helps reduce the effort on the control levers, insulation of the cab from the effects of noise, vibration and dust. The machine must have beautiful external shapes, good finishing and durable color.

Machines operating in conditions of low or, conversely, elevated temperatures must be adapted to work in the given conditions.

Frequently relocated non-self-propelled construction vehicles must have minimal weight and be easy to install, dismantle and transport.

For self-propelled machines that frequently change jobs, the mandatory requirements include maneuverability, vehicle maneuverability and stability.

Maneuverability (mobility) of a machine is the ability to move and turn around in cramped conditions, as well as move around the construction site and outside it at a speed sufficient for production conditions.

The cross-country ability of a vehicle is the ability to overcome uneven terrain and shallow water obstacles, pass through wet and loose soils, snow cover, etc. Cross-country ability is determined mainly by the specific pressure on the ground, the amount of ground clearance (clearance) - with longitudinal Ri and transverse Yag the passability radii of wheeled vehicles (1), the minimum turning radius.

The stability of a machine is the ability to withstand the forces that tend to overturn it. The lower the machine's center of gravity and the larger its support base, the more stable the machine.

Machine productivity is the amount of product (expressed in weight, volume, or pieces) produced per unit of time - hour, shift, year. Productivity is distinguished: theoretical (calculated, structural), technical and operational.

Machine design. Requirements for the working body and drive of the machine

Transmissions

Transmission (power train) - in mechanical engineering, a set of assembly units and mechanisms connecting the engine (motor) with the drive wheels of a vehicle (car) or the working part of a machine, as well as systems that ensure the operation of the transmission. In general, the transmission is designed to transmit torque from the engine to the wheels (working body), change traction forces, speeds and direction of movement. The transmission is part of the power unit

The vehicle transmission includes:

Clutch;

Transmission;

Intermediate cardan shaft;

Transfer case;

cardan shafts to drive axles;

Main gear;

Differential;

• Constant velocity joints;

  Power take-off.

The transmission of tracked vehicles (for example, a tank) generally includes:

Main clutch (clutch);

Input gearbox (“guitar”);

Transmission;

Rotation mechanism;

Final drive.

Plant ropes used on sea vessels, according to the material from which they are made, as well as by design and classification. approved by the State All-Union Standards (GOST), are indicated on the previous pages of the site.
Recently, on sea vessels they have been using nylon and nylon cables, made from synthetic fiber. Nylon cables They are characterized by high tensile strength, low water absorption, high tensile elongation, good elasticity and chemical resistance. Nylon cable can withstand temperatures up to +220° C.
Nylon has valuable properties of increased technical strength (for example, the tensile strength of dry nylon reaches 6300 kg/cm2). Nylon is elastic, resistant to moisture and abrasion, and is used for durable fishing gear.
The disadvantage of nylon cables is the melting of the threads (fibers) from friction against the surface of the winch drum, windlass or bollards.

General information

Most often, three-strand cable is used on ships. A four-strand cable is 20-25% weaker than a three-strand cable of the same thickness.
Cable work cables are used as tugs and mooring lines, although their strength is 25% lower than the strength of cable work cables. Their positive qualities include better drying of a wet cable.
Cables with a thickness of 100 to 150 mm are called ropes, from 150 to 350 mm cables and over 350 mm ropes.
Hemp cable is being produced white (unresined) and resinous.
Resined cable weighs approximately 12% more than white cable, and its strength is 25% lower than that of white cable. Resinized cable lasts longer than white cable due to better weather protection.
The dark matte color of the cable means that the cable is stale and of little use. This cable has an unpleasant odor.
Manila cable is more flexible and lightweight than hemp cable.
Manila cable gets wet a little and floats on the surface of the water, which is valuable when used as tugs, moorings and rescue lines.
Coconut cable is elastic, has a strength approximately four times less, and weighs half as much as resin hemp cable of the same thickness.
Sisal cable floats on the surface of the water, but is inferior in strength to Manila cable.
Liktros is a soft cable with a gentle descent, which is used to trim the edges of the sails.
Often used for towing combined cable, such as “Hercules”, in which its individual strands consist of galvanized steel wires covered with sisal hemp yarn. The strands are twisted around a soft core. The Hercules cable is produced in four-strand and six-strand.
All plant cables must be evenly twisted along the entire length and have no defects in the strands (kinks, knots, etc.).
The new cable is stretched without losing its strength, up to approximately 8-9%
its original size.
Mold loosens the cable by about 10-15%. The steeper the cable is, the weaker it is. A wet cable is weaker than a dry one.

Hemp tench

A plant cable with a circumference of less than 25 mm is called a tench. A tench with two threads (white and resinous) is called shkimushgar. A tench with three threads (white and tarred) is called yuzen. Special purpose lines include: l aglin, lotlin, diplotlin, signal halyards etc. White lotlin, 18 threads, three strands. The diplot line descends with cable work and has 27 threads with three strands. All other lines of cable work.
Laglines for mechanical logs and signal halyards are made of wicker and made from the best quality hemp.

Measuring plant ropes

The thickness of the plant cables is measured along the circumference. Usually 10 measurements are taken at different places on the cable. The arithmetic mean of these measurements will determine the size of the cable circumference.

Care of plant cables

Cables must be stored in dry, ventilated areas. Plant cables are resistant to fire, heat, smoke, as well as various types of oils and acids. A wet cable must be dried, since an insufficiently dried cable laid in a bay will rot and prematurely lose its strength. Cables that become soiled with silt during use must be thoroughly washed before drying.
It is recommended to rinse plant ropes that have become wet in salt water with fresh water before drying; for better drying, they should be stored on wooden banquets.

Calculation of plant cables

Approximate service life (in operation) of the plant cable:
a) cable work - 3 years;
b) perline - 2 years;
c) other cables - 1 year.

The cable required for the job can be selected by calculating its breaking strength using the formula
R = P r (π d 2 / 4) (1)
where
d = Ö(4R / Pr * π) ,
where R is the breaking strength, kg;
d - cable diameter, cm;
P r- permissible design tensile strength of the cable (usually P r accept no more than 100 kg/sq. cm with a cable block diameter of 10d and no more than 80 kg/sq. cm for smaller diameters). Usually, when calculating cables, the load from the cable’s own weight, the force of mass acceleration during the initial period of lifting the load, and the additional tension when bending around the pulleys of the drums are neglected.

For lifting heavy objects, the selection of the required cable can be made using the approximate formula
Р = nR, (2)
where P is the working strength of the cable;
n - safety factor (safety factor);
R - breaking strength of the cable.

Example 1. Select a hemp cable to lift a load weighing 1500 kg. The load Q is suspended by one free block on two cables.
Solution. We carry out the calculation according to formula (2), taking a 6-fold safety factor. The tensile force to which the cable is subjected is equal to
R = Q / 2 = 1500 / 2 = 750 kg.
Taking a 6-fold safety margin, we obtain the working strength of the cable
P = 750 kg * 6 = 4500 kg.

To check this calculation, we select a white hemp cable from the GOST 483-41 table, looking for a number close to 4500 kg in the “cable breaking strength” column. For a high-strength cable, this breaking strength is equal to 4477 kg and corresponds to a cable for which d = 31.8 cm. Then, indicating the permissible design tensile strength of the cable in kg/sq. cm, through P r, according to formula (1)
P r = R / ( π d 2 / 4) = 750 / ( π * 3,18 2 / 4)
we obtain a calculated tensile strength equal to 93 kg/sq. cm, which is quite acceptable.

The breaking and permissible working strength of plant cables can be approximately calculated using the formula
R = k С 2, (3)
where R is the breaking strength, kg;
k - strength coefficient (Table 2);
C - cable circumference, mm.

table 2

Strength factor for plant cables

Table 3

Determining the weight of the plant rope

Name of the cable	Weight per meter	Note
Hemp with a circumference of more than 10 cm	Q = C 2 / 112	Q- weight of 1 linear meter of cable, kg C - cable circumference, cm
Hemp with a circumference of less than 10 cm	Q = C 2 / 106
Manila	Q = C 2 / 137
Sisal	Q = C 2 / 145

Table 4

Lapel cables (ropes), cable work

(GOST 483-55)

Rope size, mm		Elevated			Normal
circumferentially	by diameter	total number of heels in the rope	weight of 1 meter of rope, g		total number of heels in the rope	weight of 1 meter of rope, g	total strength of rope heels, kg
150	47,8	201	1710	11658	201	1710	10653

Table 5

Sisal and Manila cables (ropes), three-strand drive, cable work

Cable size, mm		the total number of turns of all cable strands in a linear meter	number of heels in the cable	weight of 1 meter of cable at a humidity of 12%, g	average breaking force of 1 cable heel, kg	total rope strength by heels, kg	breaking strength of the cable as a whole, kg
by diameter	circumferentially
25	78,5	42	66	420	73	4818	3760
30	94,5	35	96	610	73	7008	5250
35	110	30	132	840	73	9636	6830
40	126	26	174	1100	73	12702	8510
45	141	24	216	1370	73	15768	10550
50	157	21	270	1700	73	19710	12800
55	173	19	327	2070	73	23871	15050

Table 6

Cables (ropes) Manila ordinary three-strand cable work

(GOST 1088),

Size, mm

Elevated

Normal

circumferentially

by diameter

number of heels in the cable

number of heels in the cable

weight of 1 meter of cable at a humidity of 12%, g

average breaking force of 1 cable heel, kg

total rope strength by heels, kg

breaking strength of the cable as a whole, kg

Table 7

Ordinary sisal cables (ropes), three-strand cable work

Size, mm

the total number of turns of all cable strands in a linear meter

Elevated

Normal

number of heels in the cable

weight of 1 meter of cable at a humidity of 12%, g

average breaking force of 1 cable heel, kg

total rope strength by heels, kg

breaking strength of the cable as a whole, kg

number of heels in the cable

weight of 1 meter of cable at a humidity of 12%, g

average breaking force of 1 cable heel, kg

total rope strength by heels, kg

breaking strength of the cable as a whole, kg

Table 8

Main characteristics of nylon ropes
Cable dimensionsmm		Weight 10 linear m cable,kg	Bursting Fortress,kg
circumferentially	by diameter
12.7	4.0	0,13	294,6
19,1	6.4	0,26	543,6
25.4	7,9	0,45	906,8
31,8	10,3	0,66	1451,4
33,1	11.1	1, 0	2087,9
44.5	14,3	1,34	2834.6
50.8	15,9	1, 78	3657.6
57,2	18.2	2,13	4572,0
63,5	20,6	2,77	5588, 0
69,8	22,2	3,27	6807.2
76.2	23.8	3,92	8128,0
82.6	27.0	4,56	9448,8
88,9	28.6	5.39	10972,8
95.3	30.2	6,14	12700,0
101,6	31,8	7,03	14427,2
114,3	36.5	8.80	18288,0
127,0	39,7	10,94	22555,2
139,7	44.5	13,28

Vegetable and synthetic cables come from the manufacturer in coils. Depending on the thickness of the cable, up to four to five separate pieces of cable can be laid in the bay. Cables thicker than 100 mm are laid in a coil in one piece. There must be a manufacturer's stamp on the tags attached to the coils and on the cable certificates. The cable being accepted onto the ship must be carefully inspected. During inspection, the uniformity and density of the lay and the integrity of the strands are checked. Plant cables must be free from traces and odor of mold and rot. It is necessary to check the thickness of the cable and its design and compare it with the data indicated on the tag and in the certificate. The thickness is measured around the circumference in at least ten places along the entire length of the cable. In order to make sure that there are no internal defects, you need to slightly untwist the strands in a small area and inspect them. Cables that have been manufactured for a long time should be especially carefully inspected. To completely unravel the coil for the purpose of inspecting the cable or cutting it into pieces of the required length, it is recommended to place it on a cross suspended on a cable to a swivel, and unravel the cable from the outer end. To unravel the coil of plant cable and unwind a small piece, you should bring the inner end of the cable out and unravel the coil from the inside. A coil of synthetic cable is rolled out across the deck and unraveled from the outer end. The cable unraveled from the coil is stretched across the deck and cut into pieces of the required length. To protect the cable from unwinding, marks from a heel, skimushgar or sailing thread are first placed on it on both sides of the cut points. The free ends of the synthetic cable are melted with a blowtorch. The cable intended for moorings is sealed at both ends with ogons (hashes) and wound on mooring views or laid in coils on lattice wooden stands - banquettes. The cables must be laid in the coils in a twisted manner, i.e. direct descent cables - clockwise, and reverse descent cables - counterclockwise. Plant ropes stored on views or banquettes on the deck should be covered with covers in wet weather, and ventilated in dry weather. Synthetic cables must be protected from sunlight.

Cables not in use should be stored clean and dry in well-ventilated areas. Synthetic cables should be stored in rooms with an air temperature of no more than 30°C and a relative humidity of no more than 70%. To reduce the hygroscopicity of plant cables, which increases due to the deposition of salts on them, cables wet in sea water should be washed with fresh water and then dried. Synthetic cables are not afraid of moisture, so drying them is not necessary. However, if the cable will be stored on a view, it should be dried in the shade to prevent rusting of the view and the cable. Steel cables are supplied to the ship in small coils or in standard length pieces wound on spools. Each cable reel is supplied with a tag and a certificate, which indicates the main characteristics of the cable and its dimensions, as well as the date of manufacture and the name of the manufacturer. To completely unravel the cable from the reel, pass a crowbar through the middle and secure it on vertical stands. To unravel a small coil of cable, it is rolled out along the deck, starting from the outer hoses. During an external inspection of the cable, it is necessary to compare its design data with those indicated on the tag and in the certificate, and check the diameter of the cable with a caliper. The cable must not have dents, broken wires, cracks or other damage to the galvanization. The cable strands should fit tightly together. Before cutting a steel cable, marks made of soft wire or plant cable heels are placed on the cable on both sides of the cut to protect it from unwinding. Steel cables that are not in use must be stored in a dry room, lubricated and neatly laid in coils. Mooring ropes on views should be covered, and in dry weather - open for ventilation.

In all devices, only serviceable cables should be used. The plant cable must be replaced if there is a rupture of the heels, rot, significant abrasion or deformation. To avoid flattening and structural damage, the cables should not be subjected to sharp bends under load. Therefore, all parts of ship equipment through which cables pass must be rounded. Plant cables shorten by 10-12% when wet, and lengthen when dry. Therefore, in wet weather, tightly stretched cables must be loosened to avoid their breakage.

The outer fibers of vegetable and especially synthetic cables are not sufficiently resistant to abrasion. Therefore, in places where they rub against metal surfaces, it is necessary to place mats, canvas, etc. Considering that synthetic cables are susceptible to melting due to friction. Special requirements are imposed on equipment parts: on the surface of drums, bollards, bale strips, rollers there should be no ribs, protrusions and roughness in the form of sharp edges, burrs, cavities, etc. When operating synthetic ropes, sand and other solid particles must not be allowed to enter between the strands, as they cause the cable to break. It is necessary to protect the cable from coal tar, drying oil, grease, varnishes and paints, as well as organic solvents. Synthetic ropes used on tankers, gas carriers or ships intended for the transportation of flammable and chemical cargo in bulk must undergo treatment to remove static electricity charges, which consists of soaking the rope in a 2% salt solution (20 kg of table salt per 1 m3 of water ) during the day. Cables in service should be doused on deck with sea water at least once every 2 months. The steel cable should not have knots or pegs, or broken or protruding wires. The pegs should be spaced in advance, the broken wires should be cut short, and the cable should be braided in these places. If, according to working conditions, the steel cable must be in sea water, then it is recommended to first lubricate it with a boiled hot mixture of equal parts of tree resin and lime, and after work, rinse it with fresh water, dry it and lubricate it. When working with cables, precautions must be taken. It should be remembered that the steel cable does not have great elasticity under a load close to the breaking force; it elongates by only 1-2%. Therefore, it is almost impossible to foresee the moment of its rupture, and this obliges people working with the cable to be extremely careful. When cutting steel cables with a chisel, you must wear safety glasses. Work with steel cables must be carried out using gloves. Working with synthetic ropes poses a great danger due to their high elasticity. It must be borne in mind that the critical limit after which there is a danger of rupture is the elongation of polyamide cables by 40, polyester and polypropylene - by approximately 30%. When broken, the synthetic cable contracts with great force, its ends rapidly fly off in the direction of tension to the attachment point, which creates a danger for people nearby.

Steel rope - rope structures can contain one or many strands (Table 5.1), (Fig. 5.1). Strands consist of wires that are divided into equally normal cross-section structure (all wires with the same cross-section) and different diameters (combined cross-section structure). The breaking force of a rope mainly depends on its diameter. With the same diameters, a rope with a larger number of wires is more flexible.

Rice. 5.1 Double lay steel rope
1 - wire; 2 - strand; 3 - core

Table 5.1 Types of strands
(1 - wire, 2 - strand, 3 - core)

Name	Image
Closed design with two layers of wedge wire, one layer of Z-wire and TK type core

The ropes vary in design

Single lay (spiral)- consisting of one, two or three layers of wire twisted into concentric spirals (Fig. 5.2)

Rice. 5.2 Single lay (spiral)

Double lay - consisting of six or more strands twisted into one concentric layer (Fig. 5.3).

Fig.5.3 Double lay

Triple lay - consisting of strands twisted in a spiral into one concentric layer (Fig. 5.4).

Rice. 5.4 Triple lay

According to the type of contact of the wires between the layers, ropes are distinguished:

With point touch (type TK)- lays of wires have different steps along the layers of the strand, and the wires intersect between layers. This arrangement of elements increases their wear during shear during operation, creates significant contact stresses that contribute to the development of fatigue cracks in the wires, and reduces the coefficient of filling of the rope section with metal.

With linear touch (LK type)- such strands are produced in one technological step, while the constancy of the wire laying pitch in all layers of the strand is maintained. To obtain a linear touch, the diameters of the wire and strand are selected depending on the design of the latter. Thus, in the top layer of rope strands of type LK-0, wires of the same diameter are used in layers, strands of type LK-R have wires of different diameters in the outer layer, and in strands of type /7/S-Z, wires are used that fill the space between wires of different diameters . There is a type of rope with a linear touch of the wire between the layers and having layers in the strands with wires of both different and identical diameters - LK-RO. In three-layer linear touch strands, there are various combinations of the above types of strands. It should be noted that the performance of ropes with linear contact of wires in strands, with the correct choice of rope design, is much higher than the performance of ropes with point contact of wires.

With point-linear touch (TLK type)- strands of point-linear touch are obtained by replacing the central wire in strands of linear touch with a seven-wire strand: in this case, a layer of wires of the same diameter with a point touch is laid on a two-layer strand of the LK type. The design of these strands makes it possible to produce them on spinning machines with a relatively small number of bobbins. In addition, TLC strands, with appropriate selection of laying parameters, have increased non-twisting properties;

Based on the core material, ropes are distinguished:

With organic core (OC). Most rope designs use lubricated organic cores of hemp, manila, sisal or cotton yarn as the core at the center of the rope, and sometimes at the center of the strands, to provide the required flexibility and resilience. The use of cores made of asbestos cord and artificial materials (polyethylene, nylon, nylon, etc.) is also allowed.

Metal Core (MC). It is advisable to use a metal core in cases where it is necessary to increase the structural strength of the rope when multilayer winding it on a drum, to reduce the structural elongation of the rope during tension, and also when operating the rope under conditions of elevated temperature. One of the most common designs of this type is a double lay rope made of 6-7 wire strands located around a central seven-wire strand. The metal core can be made of ordinary rope or soft wire with a tensile strength of no more than 900 N/mm2.

According to the combination of laying directions of strands and rope:

Rope single-sided lay- with the same direction of lay of the wires in the strands and the strands in the rope (Fig. 5.5).

Rice. 5.5 Single lay rope

Rope cross lay- with the opposite direction of laying of strands and rope (Fig. 5.6).

Externally, a cross lay rope differs in that the wires on its surface are located parallel to the axis of the rope. The wires of a one-way lay rope are located at an angle to its axis.

One-way laid ropes are less rigid, but are prone to unwinding. In crane mechanisms, as well as for the manufacture of slings, they are used.

cross lay nuts, more rigid, but not prone to unwinding under load. Non-unwinding ropes twisted from pre-deformed wires, which will be described below.

According to the laying method, ropes are divided:

Unwinding- the wires are not freed from internal stresses arising during the process of laying wires into strands and strands into a rope. Strands, strands and wires in this case do not retain their position in the rope after removing the bandages from its ends;

Non-unwinding (N)- when laying wires into a strand and strands into a rope, internal stresses are relieved by straightening and preliminary deformation in such a way that after removing the dressings from the end of the rope, the strands and wires retain the given position. Non-unwinding ropes have a number of advantages compared to unwinding ones: somewhat greater flexibility and a more uniform distribution of tensile forces on the strands and wires, increased resistance to fatigue stress, and no tendency to disrupt straightness when unfolding.

According to the degree of twist, ropes are divided:

Rotating;

Low-rotating (MK). These ropes should be distinguished from non-unwinding ones. In low-twist ropes, thanks to the selection of laying directions of individual layers of wires (in spiral ropes) or strands (in multi-layer double lay ropes), rotation of the rope around its axis is eliminated when the load is freely suspended. A low-twist rope can be made either non-unwinding or unwinding. A prerequisite for the manufacture of low-twisting ropes is the arrangement of the strands in two or three concentric layers with the opposite direction of lay of each concentric row of strands. In this case, the rotational moments of all strands of the rope are balanced, which prevents the overall rotation of the rope around its axis.

The review will look at the main (most common) types of synthetic ropes. Their advantages and disadvantages. Basic information is provided - difficulty level - beginner.

You can read about the types of materials used in the production of ropes in the article: Comparison of materials. Synthetic ropes: what are they made of?

1. Twisted ropes

Most common twisted three-strand ropes (Laid three-stand)
The design is simplified - three individually twisted strands (in one direction) are then twisted all together (in the other direction).

Depending on the final number of torsions there may be
-soft– small number of twists. In this case, the greatest strength of the rope and the lowest elongation are achieved structurally. In this case, there will be low resistance to abrasion and a high tendency to snagging and pulling out strands (formation of “tufts”)
-hard- a large number of twists. Lowest strength, highest elongation and high abrasion resistance.
-medium hardness– average number of twists. The most common of the three designs.

Such ropes are made from natural fibers, metal wire, synthetic - multifilament, monofilament threads. Combined - synthetic/synthetic, synthetic/natural fibers, synthetic/metal

Pros:
- easy to manufacture (cheap)
-convenient for splicing (weaving - splish, fire).

Disadvantages include:
- tendency to “unwind” (it is necessary to fix the ends of the rope)
- tendency to form loops (and knots) when the rope is unloaded, in a free state

Other types of twisted ropes will not be considered in this article due to their relatively low prevalence. A general comparison of performance with other types of ropes can be seen in the conclusions.

2. Braided ropes

The general characteristic is the yarn count of the rope, i.e. the number of strands from which it is braided. The yarn count corresponds to (or is a multiple of) the number of bobbins on the braiding machine.

Braided ropes without core

All ropes in this group will have an internal cavity. The higher the spunness, the larger the diameter of the cavity. For example, for 8-strand ropes the cavity is insignificant, and by touch it is very difficult to distinguish them from a rope with a core. But a 24-strand rope without a core will already resemble a stocking (easily wrinkled to a flat state).

8-strand L type ropes. (plaited rope).

The figure shows that this rope structure is achieved by interweaving double strands. The strength and linear weight of such ropes are comparable to three-strand twisted ones (with the same diameters). However, they are not prone to the formation of loops and twists.

Simple hollow n-strand ropes (hollow single-braid)
They are ordinary braided ropes. Below is an 8-strand rope. This structure is achieved by simply interweaving the strands. In general, the braiding machine uses 8 bobbins with thread, four of which move clockwise and four counterclockwise. Such ropes are simple to make and easy to use.

Twill braid ropes
Similar to the previous type, they have a void in the center. Visually, they are easily distinguishable from simple wicker ones.
This structure is achieved by interweaving the strands with an offset. For example, a machine uses 12 bobbins of thread, six of which move clockwise and the remaining six move counterclockwise. However, unlike the previous look, each left strand is “covered” by two right strands. And vice versa, each right strand is “covered” by two left ones.

Diagonal braided ropes have a slightly thicker braid than similar simple braided ones.

Solid braid ropes
Can be separated into a separate group. Thanks to the special type of machines on which such ropes are produced, it turns out to be filled with thread inside, i.e. without voids. Such ropes are widespread in America.

Braided ropes with core

Bundles of threads, braided cores, twisted cores can be used as a core. There are also more complex designs; they are used for special-purpose ropes.
The core and braid can be made of different materials. This combination is used to obtain certain properties. For example, abrasion-resistant material can be used in the braid, and a lighter or stronger material can be used in the core.

Ropes with a braided core (Double-braid, braid-of-braid rope)

As a rule, a braided 8- or 12-strand fast-pulling rope is used as a core. The braid consists of a larger number of strands (usually 16 strands or more) and has a dense weave.

Ropes with parallel twisted strands (parallel stand rope)

They are ropes in which the core strands are located parallel to the central axis of the rope. One of the most common examples in this group is Kermantle rope - safety ropes. The core consists of three-strand twisted cords, the braid is usually 24, 32 or 48 strands. Ropes of this type are very effective (the strength of the threads is used by 80-90%, while on simple braided ropes only about 60%) and at the same time they do not have the disadvantages of conventional twisted ropes.

Results
As a result, you can display a comparison table (you must understand that this information is conditional, and the ropes being compared must be of the same diameter and made of the same material).