When Push Comes to Shove, Select the Right Strength Members for Your Cable Application

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Posted On:
July 29, 2016
Cable Legend

Northwire launches Extreme Materials – Robust Performance from Cable to Connector. This white paper merges decades of Northwire cable design engineering expertise and innovative LEMO connector leadership. These subject matter experts share knowledge about the design and manufacturing of custom interconnect solutions.

Strength Members

Featured in Extreme Materials white paper are the inside out details about cable construction and the important role strength members bring to the cable assembly design.

Fortifying a cable design with push strength, pull strength, mechanical strength, and rigidity, strength members provide both a functional and protective role in the world of connectivity. Together, Northwire custom cable and LEMO connector design engineers gather a full understanding of the cable assembly end application and environmental considerations: underwater cable, medical cable, or ruggized industrial cable to determine the material and components needed and assembly design requirements.

Download White Paper

Within the Extreme Materials white paper, Northwire subject matter experts summarize the three most common types of cable strength members:

  1. Fiberglass Rods

  2. Steel Strength Members

  3. Aramid Fiber

Northwire’s Director of R&D, Kevin DePratter, provides insight for the utilization of fiberglass rods and notes, “We use fiberglass rods when a cable has to be extremely rigid because the cable is being pushed through the pipe. One extreme application is for sewer system inspections where there is a camera and connector on the cable. The rod enables the cable to stand straight out. This gives the cable great compressive properties and a lot of push/pull strength.”

The advantages of steel strength members are explained within the NWI-LEMO white paper, noting its use in cable and wire applications where pulling strength and compressive strength are needed. Steel strength members (or steel cords) are incorporated within LEMO and Northwire’s SMPTE HD AV offerings. Varying requirements for weight and durability dictate the type of steel strength member utilized within the cable design. The characteristics of stainless steel strength members include exceptional strength at only 3/16th of an inch while galvanized steel provides pull strength of approximately 500 Newtons without breaking as well as superior compressive strength.

An extreme material, aramid fiber (or DuPont’s brand, Kevlar®), regularly used for protective apparel, excels in providing extreme pulling strength in cable and can be stranded in various configurations to deliver different levels of strength. A bundle of four strands provides 450-600 Newtons of pull strength. While it is not rigid, it does offer high compressive strength without adding significant weight. If aramid fiber is used in a cable system, special attention must be given to the cable’s termination, as incorrect termination can lead to weak points in the fiber.

When determining a strength member for a cable design, NWI SMEs advise asking:

  1. What type(s) of strength are required?

  2. Does this cable need to be rigid or flexible?

  3. What is the plan for termination and connectorization?

Discover the questions you should ask when selecting a cable and connector assembly for your application. Download the Extreme Materials white paper. 

Download White Paper

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