ROUGH-AND-Tt MDLE ENGINEER i 



feet the piston travels per minute; divide the product by 

 33,000; the result will be the horse power of the engine. 



Q. How will you find the area of pi>tn? 



A. Square the diameter of piston and multiply it by 



7854. 



Q. What do you mean by squaring the diann 



A. Multiplying it by itself. If a cylinder is < 

 in diameter, 36 multiplied by .7854, gives the area in 

 are inches. 



Q. What do you mean by average pressure ? 



A. If the pressure on boiler is 60 pounds, and tlu- 

 engine is cutting off at y 2 stroke, the pressure for the full 

 stroke would be 50 pounds. 



Q. Why do you say less 5 pounds ? 



A. To allow for friction and condensation. 



Q. What is the power of a 7x10 engine, running 200 

 revolutions, cutting off at ]/ 2 stroke with 60 pounds of 

 steam ? 



A. 7x7 = 49x7854 = 38.4846. The average pres- 

 sure of 60 pounds would be 50 pounds less 5 = 45 

 pounds; 38.4846x45 = 1731. 8070x^33 1-3 (the number 

 of feet the piston travels per minute) = 577,269.0000 

 divided by 33,000= 17^2 horse power. 



Q. What is a high pressure engine? 



Tt is an engine using steam at a high pressure and 

 exhausting into the open air. 



Q. What is a low pressure engine? 



