Wire Rope Basics: Everything You Need to Know

Wire rope is a versatile alternative to chain used in a variety of applications such as overhead lifting, rigging, lashing, towing, and construction. Wire rope can be found in elevators, bridges, cranes, aircraft, and anywhere a strong and dependable method of transferring mechanical force is required.

Wire rope is a complex mechanism with many interconnected parts that is frequently used in assemblies with wire rope hardware and other lifting and rigging equipment.

By no means comprehensive, this article serves as a surface-level introduction to the basics of wire rope.

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Anatomy of Wire Rope

Wire rope consists of three core components:

The Core

The core is the center of the wire rope and serves as the foundation to hold the rope together. There are three types of cores:

• Fiber — synthetic or sisal; the weakest core type
• Strand — the core is a wire strand, identical to the other strands of the rope
• Independent Wire Rope Core (IWRC) — a separate wire rope core; the strongest of the three types

The Wire

The wire is the basic unit of the wire rope. Wires form the strand. Most wire is high-carbon steel, though other material types are available.

The Strand

The strand is made up of a specific number of wires laid helically around a wire core.

The most common type used in industry is 6 × 19 — six strands comprised of approximately 19 wires, but may have 16 through 26 wires per strand. It offers a good combination of flexibility and wear resistance.

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Rope Lay

The term rope lay signifies the direction of rotation of the wires and the strand. Rotation is either to the right (clockwise) or left (counterclockwise). The standard is right regular lay. Left-lay rope is reserved for special-purpose applications. The lay-length is the distance measured along a rope in which a strand makes one complete revolution around the axis.

How Lay Affects Performance

• Regular lay — more stable and more resistant to crushing
• Lang lay — more fatigue-resistant and abrasion-resistant; use is normally limited to single-layer spooling and when the rope and load are restrained from rotation

Wire rope should be protected with softeners or blocking when used at corners or sharp bends — especially when the load approaches the capacity of the rigging.

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Fatigue Resistance

Fatigue resistance refers to the ability of the wires to repeatedly bend under stress — such as when a rope passes over a sheave. Smaller wires have a greater ability to bend, so a rope made of many smaller wires will have greater fatigue resistance than one made of fewer, larger wires.

To avoid fatigue, ropes should never be bent over sheaves or drums with a diameter so small that it kinks or excessively bends the wires. Specific recommendations exist for sheave and drum sizes to accommodate all rope sizes and types. Because every rope is subject to metal fatigue from bending stress, its strength gradually decreases with use.

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Strength

The strength of wire rope is typically measured in tonnes of 2,000 pounds. Engineers assign the rope a nominal strength called Breaking Strength in the catalogue. When tensioned on a test device, new ropes will break at a figure equal to or greater than the catalogue figure. A rope should never be used at its full catalogue strength.

A rope gradually loses strength over its useful life due to natural causes such as surface wear and metal fatigue. As a result, a Factor of Safety is applied during rope selection to build service life into a rope installation.

No Single Wire Rope Can Do It All

All wire ropes feature design property trade-offs. Increasing fatigue resistance (more, smaller wires) reduces abrasion resistance, and vice versa. Choose your wire rope like any other piece of machinery — carefully, with all operating conditions in mind.

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Featured Wire Rope Products

Below are a few wire rope options available from Hercules. Click any product to view full specifications and pricing.

Product Description	Image
Wire Rope 1-3/8" 6×36 IWRC RRL EIPS BRT SKU: wr22636wc12b17ax | $10.71/ft 6×36 construction with Independent Wire Rope Core (IWRC). Right regular lay, Extra Improved Plow Steel (EIPS), bright finish. Excellent fatigue resistance for heavy-duty lifting applications.
Wire Rope 20mm 19×7 WC RRL EEIPS Galvanized SKU: wr20mm197wc13g3x | $3.15/ft 19×7 rotation-resistant construction with Wire Core (WC). Right regular lay, Extra Extra Improved Plow Steel (EEIPS), galvanized finish. Ideal for crane applications requiring rotation resistance.
Wire Rope 7/8" 6×26 FC RRL EIPS BRT SKU: wr14626fc12b1ax | $2.11/ft 6×26 construction with Fiber Core (FC). Right regular lay, Extra Improved Plow Steel (EIPS), bright finish. A flexible, cost-effective option for general rigging and lifting.

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Definitions

Metallurgy is the art, science, and technology of turning metals and alloys (i.e., materials consisting of two or more metals) into forms suitable for practical use.

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