If a change in construction is being considered as a means of obtaining longer service on a rope influenced principally by bending stresses, the table of factors may be useful. For example: a change from a 6 x 25 FW with a factor of 1.00 to a 6 x 36 WS with a factor of 1.5 would mean the service life could be expected to increase 1.15 times or 15%.

It must be pointed out, however, that these factors apply only for bending stresses. Other factors which may contribute to rope deterioration have not been considered.

Rope Construction Factor
6 x 7 or 7 x 7 Aircraft
19 x 7 R.R.
18 x 7 R.R.
6 x 19 S		 .60
.70
.80
6 x 19 W
6 x 21 FW
6 x 26 WS
6 x 25B FS
6 x 27H FS
6 x 30G FS
6 x 31V FS		 .90
7 x 21 FW
6 x 25 FW
6 x 31 WS
8 x 19S		 1.00
8 x 21 FW 1.10
Rope Construction Factor
7 x 25 FW
6 x 29 FW
6 x 36 WS
6 x 36 SFW
6 x 43 FWS
7 x 31 WS		 1.15
8 x 25 FW
6 x 41 WS
6 x 41 SFW
6 x 29 SWS
7 x 36 FW		 1.25
6 x 46 SFW
6 x 46 WS
8 x 36 WS
6 x 61 FWS
6 x 57 SFWS		 1.35

*Note: This table, with some modifications, is based on outer wire diameter relationships.

SERVICE LIFE CURVE FOR VARIOUS D/d RATIOS

This service life curve only takes into account bending and tensile stresses. Its applicability can be illustrated by the following example: A rope working with a D/d ration of 26 has a relative service life of 17. If the same rope works over a sheave that increases its D/d ratio to 35, the relative service life increases to 32. In short, this rope used on a larger sheave, increases its service life from 17 to 32 or 88%.