178 



STEAM ENGINES 



The uppermost corner of the parallelogram is pivoted at / to 

 a stationary support, and the indicator cord g is attached to 

 the bar c at the point h, which lies on the straight line joining 

 the points e and /. 



Brumbo Pulley. A familiar form of reducing motion is 

 that shown in Fig. 7, as it is easy to construct. The lever a is 

 connected with the crosshead b by the bar c, pivoted at d and e. 

 At its upper end the lever a is pivoted on a stationary pin / 

 and has firmly fixed to it the sector g. The indicator cord h 

 is fastened to the sector at the corner * and lies against the 

 curved face j of the sector, which is an arc of a circle having 



its center at /. As the crosshead moves back and forth, the 

 cord h is given a similar but reduced . motion by the sector. 



Reducing Wheels. Instead of a reducing motion composed 

 of levers, a reducing wheel may be used. Such a device is 

 illustrated in Fig. 8, as attached to the engine and to the 

 indicator, ready for use. A rigid upright is firmly fastened 

 to the crosshead, and to this upright is tied a cord, th< 

 end of which is wound on the wheel a. As the cr< 

 moves back and forth, the cord rotates the wheel a. Evidently 

 the linear movement of a point on the rim of this wheel in any 

 period is the same as that of the crosshead in that period. 

 Fixed to the wheel a and turning with it on the same shaft is 



