326 APPLIED SCIENCE 



PART II. 



THE HORIZONTAL STEAM-ENGINE. 



31. IN a previous paragraph (29) the loaded dynamic frame 

 (Fig. 38) for one position of a direct-acting horizontal steam- 

 erigine has been described, and the mode of drawing that frame 

 explained, on the assumption that the loads L a , L 6 , L n L^ are 

 known : it was stated that these loads had been calculated for 

 one particular engine. The present paper gives the varying 

 effort which this engine is capable of exerting at each part of its 

 stroke with given pressures (both constant and varying) in the 

 cylinder, and given constant velocities of the crank-axle. The 

 same calculations show the efficiency of the engine at each part 

 of the stroke, and its total efficiency under the same circum- 

 stances. This problem has, it is believed, never hitherto been 

 solved so as to take into account all the circumstances of mass, 

 weight, and friction. 



32. No pains have been taken in the choice of the particular 

 example. The object of the paper is not so much to draw 

 general conclusions as to all steam engines which, indeed, 

 differ too much in arrangement to make this feasible as to 

 show how, by a method of no great complexity, full information 

 can be obtained as to any particular engine or class of engines. 



The following are the particulars of the engine : Stroke, 

 16 in. ; diameter of cylinder, 8 in. ; length of connecting rod, 

 41 in. ; centre of gravity of connecting rod, 20 in, from the 

 crank pin ; mass of connecting rod 34 Ibs. ; mass of piston and 

 piston rod, 46 Ibs. ; mass of balanced crank and that part of the 

 fly-wheel which is borne by the main bearings, 200 Ibs. ; the 

 mass of the frame fixed to the earth is indefinitely large ; dia- 

 meter of crank-shaft in bearings, 4^ in. ; diameter of crank pin, 

 2-4"; diameter of pin at crosshead, 1'8". The position of the 

 resistance overcome (Fig. 17, Part I.) is that of a tangent to 

 an imaginary circle of 18 in. radius, concentric with the crank 



