90 



MOTIVE POWER IN MANUFACTORIES 



V X h X 62-5 

 33,000 



PARAGRAPH XV. 

 MOTIVE POWER IN MANUFACTORIES. 



Motive power is supplied by:- 



(A) ACTUAL ANIMAL POWER said to be used in Texas for running portable sawmills. 



(B) WIND, which furnishes an insufficient and unreliable power. 



(C) WATER. 

 The horse-power of falling water is: 



wherein : — 



V stands for volume of discharge in cubic feet per minute; 

 h stands for height of fall in feet; 

 62'5 represents the weight of a cubic foot of water; 

 33,000 equals one horse- power per minute. 



The engineer measures the velocity of running water not at the surface, but at about 40 per cent of 

 the depth of the water. 



The discharge can be approximated: — 



(a) By comparing the height of the water, at a vertical stake inserted at a poind some five feet 

 above a weir made of plank beveled at its rectangular spillway, by means of a spirit-level with the height 

 of the tip of the rectangle over which the water falls. 



. (b) By measuring the height of the water, over the apex of a right angle (placed vertically with 

 the apex down), which acts as the spillway in a dam across the stream. 



INTERDEPENDENCE 



between the discharge in cubic feet per minute and the head of the water at the spillway. 



Water wheels are either vertical, viz., overshot, breast and undershot wheels, or horizontal, viz., turbines. 



I. Overshot wheel. Effective power is 60 to 70 per cent of possible power. The proper velocity at the 

 circumference of the wheel is 5 feet per second, and is at its best if it is equal to 0"55 of the velocity of 

 the water. 



In falls of 20 feet to 40 feet and over, overshot wheels are more effective than turbines. 



