56 NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE
HOW TO HANDLE WIRE ROPE.
When uncoiling wire rope it is important that no kinks are allowed
to form, as once a kink is made no amount of strain can take it out,
and the rope is unsafe to work. If possible a turn-table should be em-
ployed (an old cart wheel mounted on a spindle makes an excellent
one); the rope will then lead off perfectly straight without kinks.
If a turn-table is not available the rope may be rolled along the
ground.
In no case must the rope be laid on the ground and the end taken
over or kinks will result, and the rope will be completely spoiled.
The Me of wire rope depends principally upon the diameter of
drums, sheaves, and pulleys; and too much importance cannot be given
to the size of the latter. Wherever possible the size of the pulleys
should be not less than 700 times the diameter of the largest wire in the
rope, and never less than 300 times. The diameters of drums, sheaves
and pulleys should increase with the working load when the factoi
of safety is less than 5 to 1.
The load should not be lifted with a jerk, as the strain may equal
three or four times the proper load, and a sound rope may easily be
broken.
Examine ropes frequently. A new rope is cheaper than the risk
of killing or 'maiming employees.
One-sixth of the ultimate strength of the rope should be considered
a fair working load.
To increase the amount of work done, it is better to increase the
working load than the speed of the rope. Experience has shown that
the wear of the rope increases with the speed.
Wire rope should be greased when running or idle. Rust destroys
as effectively as hard work.
Great care should be taken that the grooves of drums and sheaves
are perfectly smooth, ample in diameter, and conform to the surface
of the rope. They should also be in perfect line with the rope, so that
the latter may not chafe on the sides of the grooves.
Wire is manufactured in various grades to suit different requirements,
the breaking strengths being given in tables issued by the makers; a safp
working load is about one-sixth of its ultimate strength.
A table issued by Messrs. Bullivant & Co. is given on page 37 but,
when tables are not available, an estimated breaking stress for the
flexible steel wire rope generally used for cargo wort is given by 20\