Wire Rope
Click here to download Wire Rope Selection Procedure and Sample Problem Presentation
Wire rope, is a type of cable which consists of several strands of metal wire laid (or 'twisted') into a helix. The term cable is often used interchangeably with wire rope. However, in general, wire rope refers to diameters larger than 3/8 inch. Sizes smaller than this are designated as cable or cords.
Advantages / Why wire rope drives
Ropes furnish smooth, continuous action.
Rope Drives are low in cost of installation and high in efficiency.
The ratio of revolutions can easily be changed by a new small pulley.
Changes of pulley alignment which are so destructive to gears or belts do not affect ropes.
Freedom from shut downs by accidents is assured. The breaking of a tooth is serious; a temporary overstraining of ropes does very little harm.
Rope Drives are noiseless.
The engine or motor may be located away from the grit and dust of the mill.
Freedom from shocks is obtained, as ropes are elastic.
Efficiency of Rope Drives varies from 87 % to 97%
Strand
Groups of strand wrapped in a uniform helix around a core.
Strand is two or more wires wound concentrically in a helix. They are usually wound around a center wire.
Wire Rope
7 x 19 describes seven groups of nineteen wires
Lay
The lay of the strand, wire rope or cable, is the direction in which the helix of the wires orbit the core. An easy way to determine the lay is to hold the specimen vertically in front of you and observe whether the strands or wires travel up and to the right or up and to the left.
Materials of Wire Ropes
Wrought Iron
Cast Steel
Copper
Bronze
Stainless steel
Wire Rope Selection - Using PSG Design Data Book
Step:1
Selection of wire rope type
Select a wire rope (6 x 19 or 6 x 37) from PSG Design Data Book P. No: 9.1 based on the type of application
Step:2
Calculation of design load
Design Load = 2.5 x Load to be lifted x Assumed factor of safety
Select factor of safety from PSG Design Data Book P. No: 9.1 based on the rope application
Step:3
Wea - Effective Load
Wd - Direct Load (load to be handled)
Wb - Bending Load
Wa - Acceleration Load
E' - Take it from PSG Design Data Book P. No: 9.1
v1 = 0 (initial velocity)
Selection of wire rope diameter (d)
Assuming the design load as breaking load select the wire rope diameter from PSG Design Data Book P. No: 9.4 to 9.5
Step:4
Calculation of sheave diameter or Drum Diameter (D)
Using the selected type of wire rope select D/d ratio from PSG Design Data Book P. No: 9.1 and calculate D
Step:5
Selection of useful cross sectional area (A)
Using the formula for "A" in PSG Design Data Book P. No: 9.1 calculate cross sectional area
Step:6
Calculation of wire diameter (dw)
i = Number of strands x number of wires in each strand
Step:7
Selection of weight of rope (Wr)
For the selected diameter of wire rope in PSG Design Data Book P. No: 9.4 to 9.5 select the weight of rope
Step:8
Calculation of Effective Load (Wea)
Wea = Wd + Wb + Wa
Wd = W + Wr
Step:9
Calculation of factor of safety
If the working factor of safety is greater than the recommended factor of safety then the design is safe.
If its not safe calculate how many wires can be used to handle the load using the next step.
Step:10
Calculation of number of wires