212 APPENDIX. 



Diameter 24 inches Safety valve 5 Ifcs. 

 Add 2-5 Atmosphere 14'7 



26-5 Total pressure 197 



26-5 



19iOO) 5J22-05 (0-275 inches 

 38 0-5 for wear 



142 0-775 inches, the re- 

 133 quired thickness. 



90 



PISTON ROD, &c. 



12. To find the diameter of the piston rod, &c. 



RULE. Multiply the square root of the pressure of the steam per square inch in the boiler 

 by the diameter of the cylinder in inches, and divide the product by 



33 for cast iron, 

 36 wrought iron, 

 57 tempered steel ; 



and the quotient will be the diameter of the rod in inches, for a double-acting engine. For a 

 single-acting engine one-half of the result will be sufficient. (24 1 .) 



Example. The force of the steam being 20 fts. per square inch, and the diameter of the 

 cylinder 38 inches ; required the diameter of the piston rod, the material being wrought 

 iron. 



Square root of 20 4-47 



38 



3576 

 1341 



36)169-86(4-7 inches diameter. 

 144 



258 

 252 



Thus, for a double-acting engine the diameter should be about 4| inches ; and for a single- 

 acting engine 2| inches. 



Parallel motion rods should be about half the diameter of the piston rod ; and connecting 

 rods should be about seven-tenths of the diameter of the piston rod. (242.) 



