OF THE HYDROSTATIC PRESS. 135 



therefore, by comparison, we have 

 P ct 



consequently, by multiplying and substituting the cohesive power of 

 cast iron, we have 



(*4-r)P:=13076D 2 f. (111). 



Let 4r 2 , be substituted in this equation, instead of D 2 its equivalent, 

 and we shall obtain 



consequently, the pressure in tons, is 



52304 r*t _ 23.35 r*t 

 ~2240(*+r)~- (f+r) ' (112). 



From which it appears, that by knowing the interior radius of the 

 cylinder and the thickness of the metal, the power of the press can 

 easily be ascertained ; the following is the rule for that purpose. 



RULE. Multiply 23.35 times the thickness of metal by the 

 square of the radius of the cylinder, and divide the product 

 by the radius plus the thickness of metal, and the quotient 

 will give the power of the press in tons. 



145. EXAMPLE 16. A Hydrostatic Press is so constructed, as to 

 have the interior radius of its cylinder equal to 3 inches, and the 

 thickness of metal 4 inches ; now this press is designed for packing 

 flax, and is estimated to stand a pressure of 180 tons; query if its 

 power is not overrated ? 



According to the above rule, it is 



consequently, the power of the press is overrated by about 60 tons, 

 being one third less than the estimated pressure according to the 

 question. 



The thickness of metal necessary to resist a pressure of 180 tons or 

 403200 Ibs. is equal to 17.9 inches nearly, and the proposed thickness 

 is only 4 inches, being less than one fourth of the thickness which is 

 really necessary to resist the strain ; hence we infer that the press in 

 its present state, is entirely unfitted for its intended purpose, and 

 altogether inconsistent with safety and precision of operation. Here 

 follows the description of a press when completely furnished in all its 

 parts and fit for immediate action. 



