228 



APPENDIX. 



28. To find the pressure of the steam in the cylinder. 



RULE. Determine the resistance to traction by the last rule; add to it an eighth part for 

 the additional friction it causes on the engine, and 6 Its. per ton of the weight of the engine 

 for its own separate friction. The sum will express the whole force or resistance to be 

 . overcome by the engine. Multiply this resistance at the circumference of the wheel by its 

 diameter in inches, and then divide by the product of the square of the diameter of the 

 cylinder into the length of the stroke. The quotient will express the effective pressure on 

 the piston in fts. per square inch ; and, adding 14*7 ft>s. for the pressure of the atmosphere, 

 the result will be the pressure of the steam in Tbs. per square inch. 



Example 1. The weight of the engine is 12 tons, the tender 7 tons, the train 50 tons, the 

 diameter of the driving wheels 54 inches, the diameter of the cylinder 12 inches, and the 

 length of the stroke 18 inches. It is required to find the pressure of steam in the cylinder to 

 sustain an uniform velocity up an incline of 1 in 140. 



tons. Gross load 69 



2240 



Horizontal traction 552 Its. 



20160 

 13440 



140) 154560 (1104 Its. effect of gravity. 

 140 



145 

 140 



560 

 560 



Gravity 1104 Ibs. 

 Horizontal traction 552 



Diameter 

 cylinder / 



Inclined traction 1656 up the plane. 

 Additional friction 207 one-eighth. 

 Engine 72 



12 

 12 



Resistance 1935 

 Wheel 54 



144 

 Stroke 18 



1152 

 144 



2592) 104490 ( 40-3 fl5s. effective pressure. 

 10368 14'7 atmospheric 



Divisor 2592 



8100 

 7776 



324 



55'0 Ibs. pressure of steam per square 

 inch. 



The consumption of water may hence be calculated by No. 25. 



