A 6 x 36 (14 – 7 + 7 – 7 – 1) wire rope construction is a Parallel or Equal Laid Construction in which all wires in a strand have the same Lay Length and the wires of any two superimposed layers remain parallel to each other resulting in a linear contact amongst constituent wires all along the length. The linear contact leads to an optimal stress distribution. A 6 x 37 ( 18/ 12/ 6 – 1) wire rope construction is a Cross ( Non-parallel ) Laid construction in which all wires in a strand have Unequal Lay length and hence wires of superimposed wire layers cross one another and make point contacts through out the length. The High Stress concentration at the cross over points leads to relatively earlier internal failure.

A brief comparison between 6 x 36 and 6 x 37 construction wire rope is given below.

ROPE BEHAVIOUR	6 X 3	6 X 37
Life	Higher because of optimal stress distribution.	Inter nicking amongst the wires at cross over points leads to relatively early wire breakages during use.
Flexibility	High	High
Resistance to Crushing	Higher due to parallel laid wires.	Less due to cross laid wires
Resistance to abrasion	Higher due to higher diameter of outer wires [14 in nos.] Also compact and relatively stable construction.	Relatively lower because diameter of outer wires lesser[18 in Nos.]
Breaking Strength	Higher Breaking Strength Example- Min Breaking Strength of 20 mm dia 6x36 1770 N/mm2 rope with Fibre Core is 234kN & same with Steel core is 252 kN	Relatively less. Equivalent values for 6x37 construction wire rope are 209 kn & 225 kN
Fatigue Life	Higher	Relatively less
In view of the above mentioned facts a 6x36 is considered as a recommended rope construction for almost all general engineering applications.

View Usha Martin Letter Advantage of 6x36