A rope running in a V groove has a short life.

A rope that is allowed to ride, chafe on its own part or to overlap, will be almost immediately crippled.

The sign of an overloaded rope is excessive stretching.

Flexible Rope.
6 strands, each 12 wires		Extra Flexible
Rope.
6 strands, each
24 wires		Special Extra
Flexible Rope.
6 strands, each
37 wires
Size
Circum.		Diam. of barrel
or sheave round
which it may be
worked at a
slow speed		Guaranteed
Breaking Strain		Guaranteed
Breaking Strain		Guaranteed
Breaking Strain
InchesInchesTonsTonsTons
11⁄2 9 4 71⁄2 8
13⁄4 101⁄2 51⁄2 93⁄4 11
2 12 7 13 141⁄2
21⁄4 131⁄2 9 161⁄4 171⁄2
21⁄2 15 12 201⁄2 22
23⁄4 161⁄2 15 24 261⁄2
3 18 18 281⁄2 321⁄4
31⁄4 191⁄2 22 34 371⁄2
31⁄2 21 26 39 43
33⁄4 221⁄2 29 451⁄2 50
4 24 33 511⁄2 561⁄2
41⁄4 251⁄2 36 59 65
41⁄2 27 39 65 701⁄2
43⁄4 74 79
5 821⁄2 88
(Bullivant & Co. Ltd.)

Chains.—The strength of a chain depends upon the diameter and quality of the iron of which the links are formed, governed by good workmanship. The safe load for working can be calculated approximately by the following method:—

Square the number of eighths of an inch which are contained in the diameter of the iron of which the link is made, and strike off the last figure as a decimal.

For example, where the iron is of 1⁄2-inch diameter, square the number of 1⁄8 in the diameter, i.e. 4 × 4 = 16 = 1·6 tons.

Generally before leaving the factory, chains are tested up to half the weight they should break under, and which is about double the load they are intended to carry in practice. This test cannot be relied upon for the future working of the chain, as any stretching of a link, which would ultimately result in fracture, would probably not be apparent under it. The links should therefore be examined periodically for any appearance of weakness or stretching.

A stretched link should at once be cut out, as it may break with much less load than that which it was first tested to carry. A chain during use also deteriorates in quality, and it is a good rule to have it periodically annealed.

The links should then be re-tested up to double the weight they are again required to carry.