## strands

06.11.2021 Wire Rope

# Number of strands

From three to nine strands are used to make a rope. Apart from some special cases, practically all ropes are made of six strands as a balanced construction. However, when used for elevators where special flexibility is required, eight strands are used. Also, Two or more layers of strands are used when non-torque is required. For ropes of the same diameter, generally, the more the number of strands the smaller is the diameter of each strand. In such cases, the rope may gain flexibility but, on the other hand, the strength will drope and the rope will become inferior in corrosion resitance and deformation.

# Lay of the strands（number of wires and position）

One strand is normally made up of seven to several tens of wires with simillar or differing, diameters in single or multi-layers. In the method where the wires are positioned to form more than two layers, there is the cross lay where the wires of each layer are in the same lay angle, and the parallel lay where one process is used to lay the wires so that wires of each layer will be of the same pitch. For strands of the same diameter, the more the number of wires, smaller will be the diameter of each wire and the greater will be the flexibility of the strand. However, the rope will become inferior in its wear resistance and deformation resistance.

## (1)Cross lay

The cross lay is also called as the point contact lay, as each wire is in contact with each other. The laying of the wires is carried out in such a way that the lay angle will be almost equal for each layer of wire of the same diameter. The length of the wires in each layer will also be the same and the wires of each layer will be in contact with each other.

## (2)Parallel lay

Parallel lay is also called as the equal lay. It is also called one operation lay from the number of stranding processes and also as linear contact lay as each wire is in contact with each other. Moreover, at this company, the parallel lay rope has the product name of Super Rope. In the parallel lay, the wires of each layer are positioned in such a way that there will be no space between them and so that the upper layer wires will fit neatly into the groove of the lower wires of the strand. For this, wires of differing diameters are positioned at the same time so that each wire layer will have the same pitch and will be in contact with each other. Therefore, differing from the cross lay rope, although the lay angle of each wire layer and the length of the wires are not uniform, as each wire is in contact with each other, it is superior in its fatigue resistance. Moreover, the 6xFi(25),6xWS(36) and the 8xS(19) belong to this lay method.

### ・Basic types

As the basic parallel lay, there are the following three types.

#### (a)Seale type

The number of wires of each leyer is shown as 1+n+n and the number of wires of the inner and outer layers is the same. The wires of the outer layer fit completely into the grooves of the inner layer wires. The outer layer wires of this Seale type rope is thicker when compared to other parallel lays and so it is superior, particularly in its wear resistance and is mainly used for elevators.

#### (b)Warrington type

The number of wires of each layer is indicated as 1+n+(n+n) and there are two kinds of wires for the outer layers, one being large and the other small. The number of wires of the outer layer is double that of the inner layer and combination of the inner and outer layers fill the spaces between the wires. This Warrington type rope is seldom being used recently.

#### (c)Filler type(with filler wire)

The number of wires of each layer is indicated as 1+n+(n)+2n and the number of wires of the outer layers is double that of the inner layer. The inner wires and the same number of thin filler wires are used to fill the spaces in the inner and outer layers. This filler type rope has a good balance between the flexibility, fatigue resistance and wear resistance and has the widest range of use among parallel lay ropes.

### ・Combination types

Apart from the above three basic types, there are combinations of these types. Among these, the following two types are used the most.

#### (a)Semi-seale type

This is a combination between the cross lay and the parallel lay and around the center 7 wiers, 2 layers of simillar number wires are positioned in a Seale type. This semi-Seale type rope has a comparatively good fatigue resistance nature and has a wide range of uses.

#### (b)Warrington Seale type

This is a combination between the Warrington type and the Seale type and is extremely superior in its fatigue resistance. It also abounds in flexibility and is superior in its wear resistance and so has a wide range of uses.

### ・Flat type

The strands are combined in such a way that the outer circumference of the rope will be flat in shape. This rope has a smooth surface and specific pressure is small so it is superior in its abrasion resistance. In general, the triangular strand and the clam shaped strand are major type and flat strand type is partially seen.

#### (a)Triangular strand type

Up to now, an outer layer wire was positioned around the triangular wires but, recently, a single layer or two layers of wires are stranded around a triangular core made of round wires to form a round wire triangular core strands.

#### (b)clam shaped strand type

The cross sectional view of this type is in the shape of shell and this rope is usually in three strands, or four strands. Also, apart from the fatigue resistance, it also has a non-twisitng nature. The Mono-Rope of this company which is widely used belongs to this type.

#### (c)Flat strand type(oval strand type)

There is the type where two layers of strands in which the wires are stranded in an oval shape are positoned around a fiber core(Sinking Rope) and the type where the core is a multiple layer of wires around which 6 to 10 strands are positioned(Concentric Rope).

Cooperated by：Tokyo Rope Manufacturing

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