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WIRE ROPE TRANSMISSION. 341
The tension of the rope may be calculated from its de-
flection when at rest (see Fig. 2), and for a rope running hor-
izontally the usual formula is :
p _ WK \/a* + P
P = K*l (very nearly)
a
P = Force in pounds at f.
W= Weight of rope in pounds from d to f, which is half
the span.
b = Half the span in feet.
a = Twice the deflection in feet.
Note.—(See Fig. 2.) If the length of the line a represents
the weight of the part of the rope from dtof, the length of the
line x represents the tension in the rope at/"; therefore the ten-
sion will be as many times the weight as the length of line a is
contained in the line x.
Example.
The horizontal distance between two pulleys is 200 feet
;
when standing still the deflection in a wire rope of %"
diameter is 5 feet. What is the tension in the rope ?
Solution
:
In Table No. 38 the weight of %" wire rope is given as 1.12
pounds per foot; therefore, 100 feet of %" rope will weigh 112
pounds.
112 X V1002
+ 102
_ 112 X 100.5
P
10 10
1125.6 pounds.
This is the tension in each part of the rope ;
therefore the
force against the pulley, due to the weight of the rope, is 1125.6
X2 = 2251.2 pounds. If this is supported by a bearing on each
side of the pulley, the pressure on each bearing, if both are the
same distance from the pulley, will be 1125.6 pounds.
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