The Weakest Link

Posted on Monday, June 3, 2013 in UEA Blog

There is an old adage concerning a chain only being as good as its weakest link. This is true in a variety of situations and applications from a team sport to a human body to virtually any man-made machine or piece of equipment. An often over-looked factor in the function and life of a cable reel is the selection of the cable to be used for extension and retraction on the reel. Many things can affect the 'life' of this cable, including the environment it is subjected to, but the majority of early cable failures are caused by incorrect specification of the cable to meet the bend radius imposed by the reel sheave or hub and/or the frequency of the extension and retraction cycles the cable must endure.

Multiple conductor cables are built for a wide variety of environments and applications including wide temperature extremes, UV resistance, abrasion resistance and electrical shielding. Many of the applications for these cables are static and the cables are never moved once installed or at least very infrequently. Other applications, such as some cable chains or robotics, can require millions of bending and/or twisting cycles. For such applications the cables are designed with different jacketing and insulating materials and often with lubrication of some type between the individual wires within the cable. Most cable manufacturers have a specified minimum bend radius for each cable model and if the cable is acceptable for flexing applications the recommended bend radius is virtually always higher for the dynamic application compared to that for static use.

UEA Customer Service tries very hard to determine the actual expected usage for the reel when a call or RFQ is received for a new cable reel application. The environment and cycling information are very important to help in the selection of a cable if the cable is not already customer specified. If the customer has specified the cable to be installed on the reel they are reminded to verify the cable specifications for acceptability for a reeling application. Once the cable is determined the correct reel hub size can be selected based upon the cable diameter and the minimum allowed bend radius of the cable. Cable extension length and reel function, such as horizontal or vertical operation and latching or constant tension, are factors in determining the spring to be used in spring reel applications. For hand-crank or motorized reels the reel model is based upon the cable length and diameter once the correct cable is identified for the application.

Many factors can affect the overall life of a cable reel but it is always important to start with the proper cable to prevent it from being the 'weakest link' in the system.

Brent Jensen

Engineering Manager