To find the strength of a rope, or the weight it will support.
First method.—Square the circumference, and divide by 5, for the number of tons which it will bear suspended from it.[46]
Example.—What weight will 3-inch rope of the best description support?
(3 × 3) 5 = 9/5 = 1⅘ ton, or 4030 lb. Weight required.
Second method.—Multiply the square of the circumference by 2, the product will give the practical weight in cwts. that may be lifted by it, or about half the breaking weight.
Example.—What number of cwts. may be lifted by a 3-inch rope?
32 × 2 = 18 cwts. Weight required.
| The strain, | in pounds, | a rope | will bear safely | = girt2 × 200} | nearly. |
| ” | ” | a cable | ” ” | = girt2 × 120} |
CHAINS.
To find the weight of chains.