Wire Rope Stretch

In any cable or wire rope application, stretch may be a concern. There are two forms of stretch in cable and wire rope: Structural Stretch and Elastic Stretch. These events occur within cable loads up to and including the minimum breaking strain (MBS) of the wire rope. Exceeding the certified (static) MBS of any wire rope product can be expected to lead to unrecoverable cable deformation with possible catastrophic failure.

Structural Stretch

Structural stretch is the lengthening of the lay in the construction of cable and wire rope as the individual wires adjust under load. Random sample testing of structural stretch in Low Cost Wire products has indicated less than a 1% change in the total cable length. This form of stretch can be completely removed by applying a cable or wire rope pre-stretching operation – to design specified loads that respect the certified MBS – prior to installation.

Elastic Stretch

Elastic stretch is the actual physical elongation of the individual wires under load. The elastic stretch can be calculated by using the following formula:

Cable Stretch Calculator (E = (W x S) / D²)

Where:

E = Elastic Stretch as a % of Length
W = Weight of load in kilograms
D = Diameter of wire rope in millimeters
S = Stretch Factor (See Chart Below)

Notes:

Values derived from this calculator are approximations
No consideration is made of the grade of the wire rope (and its inherent effect on MBS)
Fiber Core Wires are outside of the scope of the calculator
Assumed Lay of the Wire Rope is RHOL
Calculator is derived from publicly available information sites.

Structural Stretch

Elastic Stretch

Cable Stretch Calculator (E = (W x S) / D2)

Where:

Notes:

Cable Stretch Calculator (E = (W x S) / D²)