A safe general rule for all ropes is, one fourth the square of the circumference gives the breaking weight in short tons.
TABLE OF WEIGHTS THAT MANILLA ROPE IN DAILY USE WILL SUSTAIN.
| Circumference, in. | 1 | 1¼ | 1½ | 1¾ | 2 | 2¼ | 2½ | 2¾ | 3 | 3¼ | 3½ | 3¾ | 4 |
| Weight, lbs. | 540 | 844 | 1215 | 1654 | 2160 | 2734 | 3375 | 4084 | 4860 | 5704 | 6415 | 7594 | 8640 |
| Circumference, in. | 4¼ | 4½ | 4¾ | 5 | 5¼ | 5½ | 5¾ | 6 | 6¼ | 6½ | 6¾ | 7 | 8 |
| Weight, lbs. | 9753 | 10935 | 12184 | 13500 | 14884 | 16635 | 17954 | 18252 | 19805 | 21421 | 23100 | 24843 | 32448 |
To Preserve White Rope.—Dip when dry into a bath containing 20 grms. (about seven tenths of an ounce) of sulphate of copper per litre (a little over one quart) of water; soak for four days and dry. Then soak in a solution of 100 grms. (3.5 oz.) of soap per litre of water.
Iron-wire Rope.—Its breaking weight in tons is about equal to the square of the circumference in inches.
Steel-wire Rope.—It is from 2 to 2½ times stronger than iron-wire rope. Wire rope can be safely worked in field service to one half its breaking weight.
To Preserve Wire Rope.—Apply linseed-oil with a piece of sheepskin, wool inside; or mix the oil with equal parts of Spanish brown and lampblack. If used underground or in water, take mineral or vegetable tar, add one bushel of fresh-slaked lime to barrel of tar, boil it well, and then saturate the rope with the boiling tar.
Chains.—Chains, when used in place of ropes, should be examined to see that every link is free from flaws and not too much worn. The chain should have no kinks in it, and each return, when more than one is used, should bear its proper strain. Do not work a chain over a windlass of small diameter; the iron of the links breaks by bending, not by tensile strength. Lubricate freely.