FARM MACHINERY 



termine the area of the diagram when the point is passed 

 around it. To obtain the mean height and the average 

 draft it is only necessary to divide the area of the diagram 

 by its length. This can only be done when distances 

 along the paper are proportional to the distance passed 

 over by the implement. 



36. Steam and gas engine indicators. The indicator, 

 although not used much in connection with farm engines, 



FIG. 14 THE STEAM OR GAS ENGINE INDICATOR. AN INSTRUMENT USED 

 TO OBTAIN A RECORD OF THE PRESSURE IN THE ENGINE CYLINDER 

 AT VARIOUS POINTS OF THE STROKE 



should be mentioned at this point under a discussion of 

 the methods of measuring work. 



Fig. 14 illustrates a steam engine indicator complete, 

 and also a section of it showing the mechanism inside. In 

 brief, the indicator consists in a drum, upon which a paper 

 card is mounted to receive the record or diagram, and a 

 cylinder carefully fitted with a piston upon which the 

 pressures of the steam or gases from the engine cylinder 

 act. The drum by a mechanism called a reducing motion 

 is given a motion corresponding to that of the engine 



