The line type wizard properties window displays approximate minimum breaking load (MBL) values for ropes and wires which may be useful in setting the allowable tension for the line type.
These MBL values are calculated as follows, where $d$ is rope/wire nominal diameter in metres and the MBL in kN:
| nylon ropes (dry) |
$163950\,d^2$ |
| nylon ropes (wet) |
$139357\,d^2$ |
| polyester ropes |
$170466\,d^2$ |
| polypropylene ropes |
$105990\,d^2$ |
| wire ropes with fibre core |
$584175\,d^2$ |
| wire ropes with wire core |
$633358\,d^2$ |
These formulae were derived from manufacturer's catalogue data consistng of minimum (dry) strength against nominal diameter for each of the five rope/wire constructions. The formulae were obtained by least squares fitting and were found to give good agreement with the manufacturer's data, other than underestimating MBL for small diameter fibre ropes.
| Note: |
Nylon ropes lose some strength when wet; the formula given for wet nylon ropes is based on the manufacturer's statement that they can lose up to 15% of their (dry) strength when wet. |
