Maximum Effect of Machines. 



283 



Table containing the best Proportions between the Velocities of the 

 Impelled and Working Points of a Machine, or between the Lev- 

 ers by which the Power and Resistance act. 



In order to understand the method of using this table, let 

 us suppose that we wish to raise two cubic feet of water in a 

 second, bj means of the power of a stream which affords five 

 cubic feet of water in a second, applied to a wheel and axle, 

 the diameter of the wheel being seven feet. It is required, 

 therefore, to find the diameter which we must give to the axle, 

 in order to obtain a maximum effect. We have obviously p = 5, 



and r =. 2, and since p : r : : 5 : 2, we have p = - r ; but, in 



the above table, r = 10 ; hence p = - 10 = 25. Now it ap- 

 pears from the table, that when p = 25, the diameter of the 

 axle, or d, is 0.8708, D being 1 ; but as D = 7, the diameter 

 of the axle must be 7 X 0.8708 = 6.0956. 



