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WIRE ROPE TRANSMISSION. 343
Solution
d: 0.00009 X 400 X 400 = 14.4 feet.
When the rope is new it is always put on with more
tension than is necessary to transmit the power, because new
rope will stretch. It is, therefore, very important when de-
signing such transmission to calculate the maximum pressure
which the rope will exert on the bearings when put on with the
least deflection ever wanted, and calculate size of bearings and
shafting for pulleys according to this stress, with due considera-
tion not only for strength but also for heat and wear. (See page
360 and page 367.) The correct amount to allow for stretch will
vary with different kinds of rope and also with the tempera-
ture. If a rope is spliced on a warm summer day it must be
made slacker than if it was spliced on a cold winter day, as the
length of the rope will be changed considerably by the difference
in temperature ; the only guide is practical experience and good
judgment. As a general rule, it may be safe to allow about half
of the deflection as previously calculated when splicing a new
rope, provided that the shafts and bearings are constructed so
as to allow such tension. The rope is always strong enough.
The splicing of the rope should be done by a man ex-
perienced in that kind of work. The splice itself is usually
made at least 240 times the diameter of the rope.
TABLE No. 38.—Giving Suitable-Sized Pulleys for Different Sizes of
Wire Rope, Weight of Rope, Horse=Power which Different Sizes
of Wire Rope nay Transmit at Different Velocities, the least Stress
at which it may be done and the Least Corresponding Pressure on
the Bearings ; also, the Ultimate Average Strength of Wire Rope.
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7 V?, 0.31 8000 330 330 660 495 990 25 30 40 50
8 H 0.57 12000 517 517 1034 775.5 1551 39 47 62 78
10 u 0.92 18000 636 636 1272 954 1908 56 67 90 112
12 V* 1.12 24000 1012 1012 2024 1518 3036 77 92 122 153
14 1 1.50 32000 1320 1320 2640 1985 3960 100 120 160 200
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