176 



STEAM ENGINES 



long pipes will cause considerable resistance to the flow of the 

 steam. The pipe connections between the indicator and the 

 engine should be short and direct, and care should be taken 

 to see that the piston at the end of the stroke does not cover 

 the hole tapped for the attachment of the indicator pipe. 

 Before attaching the indicator, it is advisable to open the cock 

 slightly, to blow out any dirt or rust that may have accumu- 

 lated in the pipe. 



Pendulum Reducing Motion. The motion of the drum cord 

 is usually obtained from the crosshead. As the stroke of the 



FIG. 4 



FIG. 5 



engine is nearly always greater than the circumference of the 

 drum, the cord cannot be attached directly to the crosshead, 

 and an arrangement called a reducing motion is used. A pen- 

 dulum reducing motion is shown in Fig. 3. The upright a is 

 fastened to the engine frame, and the lever b is pivoted at c 

 to the upright. Another upright d is fastened to the cross- 

 head or to the piston rod near the crosshead, and the link e 

 is connected at / to the piece d and at g to the lever b. The 

 cord, which should be parallel to the axis of the cylinder, is 

 attached to the point h on the lever b, which point must be 

 on the straight line connecting c and g. 



