374 | APPLIED MECHANICS 
angle of the groove in which the rope runs is 60°, and the coefficient of friction 
may be taken as 0:25, and the rope is in contact with the pulley for half the 
circumference. Find also the centrifugal tension in thé rope if the fly-wheel is 
10 feet in diameter, and the reduction in the horse-power transmitted due to this 
tension. Weight of rope for 1 foot of length=0-28 lb. [B.E.] 
26. Calculate the horse-power transmitted by a wire rope under the following 
conditions. The driving pulley is 12 feet in diameter, and it runs at 150 revolu- 
tions per minute. The rope consists of six strands, each strand having seven 
wires, and each wire having a diameter of 0°064 inch. The rope embraces half 
the circumference of the pulley, and the coefficient of friction between the rope 
and the pulley is 0°25. The weight of the rope is 0°56 ib. per foot of length. The 
working stress is 21.000 lbs. per square inch of wire section, and the modulus of 
elasticity E is 29,000,000 lbs. per square inch. 
27. If the bending stress is not to exceed 12,000 lbs. per square inch, find the 
minimum diameter of the driving pulley for a wire rope made up of wires 
No. 15 I.8.W.G. (0°072 inch diameter), the modulus of elasticity of the wire being 
29,000,000 lbs. per square inch. 
28. Adhering to the conditions given in Exercise 26, except as regards the 
speed of the pulley, determine the velocity of the rope, in feet per second, when 
the horse-power transmitted is a maximum, and find the maximum horse-power. 
29. A wire rope made up of 72 wires each 0°048 inch diameter is used to 
transmit power. Taking the maximum working stress in the wires at 25,000 Ibs. 
per square inch, the bending stress at 13,000 lbs. per square inch, w=4-16, and 
n=0'4, plot the horse-power transmitted, and v the velocity of the rope in feet 
per second, between the limits »=0, and v=200. State the maximum horse- 
power and the corresponding value of vy. Scales.—Horse-power, 1 inch to 40 
horse-power ; velocity, 1 inch to 40 feet per second. 
30. A chain of uniform pitch transmits motion from a sprocket wheel having 
15 teeth to another having 10 teeth. What is the mean velocity ratio? Express 
the difference between the possible maximum and the possible minimum velocity 
ratio as a percentage of the mean. 
