1280 THE BELL SYSTEM TECHNICAL JOURXAL, NOVEMBER 1954 

 THEORETICAL OPERATING CHARACTERISTICS 



The sokition of the e(iuatioii of motion for any governor is based on 

 specific design constants and certain assumed and estimated values. Such 

 dimensions as the governor case inside diameter r, and distance from the 

 shaft center to the weight pivot h, are two examples of design constants. 

 These constants establish the arrangement of the various component 

 parts of the mechanisms and are, therefore, subject to practical manu- 

 facturing and space considerations as well as considerations from a speed 

 regulation standpoint. The design constants are in effect static considera- 

 tions. They are not subject to appreciable variation once established, 

 and on any particular governor do not vary significantly over the life of 

 the governor. 



Table IV 



During actual operation there are two factors which directly affect the 

 degree of speed control afforded by a governor; i.e., the coefficient of 

 friction which exists between the governor case and friction studs, and 

 the value of input torque to the governor shaft. Design control over these 

 factors is present, but to a lesser degree than for the design constants 

 mentioned previously. These factors are considered fixed in arriving at a 

 given design but actually vary from governor to governor and over the 

 life of a governor. It is therefore necessary to consider carefullj^ the effect 

 of variations in friction and torque if close regulation of speed is re- 

 c^uired. 



The input torc^ue to the governor shaft vnW vary because of the dimen- 

 sional variations of the motor springs, the tolerance permitted for the 

 driving torque at full windup of the dial, dial friction and the variation 

 in pulsing spring forces. These variables appear at the governor as a 

 range of input torques during iiin-down of the mechanism. For the motor 

 spring used in the 7-type dial, input torque referred to the governor 

 shaft decreases during run-down on the average from 20,000 dyne-cm 

 to 13,000 dyne-cm. Torque required to overcome bearing and gear fric- 



