RULES FOR CALCULATING THE STEAM ENGINE. 213 



THE CONICAL PENDULUM OR GOVERNOR. 



The vertical distance between the point of suspension and the plane in which the balls 

 revolve is the height of the governor. 



13. To find the height for any proposed number of revolutions per minute. 



RULE. Divide the number 375 by twice the number of revolutions per minute, and the 

 square of the quotient will be the required height of the governor in inches. (263.) 



Example. What ought to be the height of the governor so that the number of revolutions 

 may be 42 per minute ? 



42 



2 



84) 375 (4-46 



336 4-46 



4-46 

 390 



336 2676 



1784 

 540 1784 



19-8916 

 Height 19-9 inches. 



14. The height being known, it is required to find the number of revolutions per minute. 

 RULE. Divide 375 by twice the square root of the height in inches, and the quotient will 

 be the number of revolutions per minute. (263.) 



Example. Take the same example and let the height be 19-9 inches, to find the revolutions 

 per minute. 



Square root of 19'90 = 4-46 



2 



8-92 

 8-92) 375-00 (42 revolutions per minute. 



3568 



1820 

 1784 



36 



ECCENTRIC. 



15. The length of the levers being given, to find the requisite throw of the eccentric. 



RULE. Multiply the length of the stroke of the valve by the length of the lever on the 

 weight shaft for the eccentric rod, and divide the product by the length of the lever which 

 works the valve, and the quotient will be the throw required. 



2 e 



