1296 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1954 



use in telephone dials which is an improvement over the conventional 

 fly-bar type governor. Fine regulation is provided by the drive-bar 

 governor for a given change in the coefficient of friction between the studs 

 and case. This is achieved by locating the studs as close to the weight 

 pivot as manufacturing techniciues will permit. Improved speed regula- 

 tion is provided for varying input torque in the new governor as com- 

 pared with the fly-bar governor. The experimental data shows the new de- 

 sign able to control speed approximately twice as well. It is an effective 

 non-forcing governor, prohibiting excessive increase in dial speed as a re- 

 sult of forcing the fingerwheel during rundown. This nonforcing feature is 

 achieved by applying the driving torcjue to the weights at a point to 

 develop a moment about the weight pivot. This drive-bar moment assists 

 the centrifugal force in maintaining pressure of the friction stud against 

 the case for friction governoring. 



Having established a design which provided the degree of dial speed 

 regulation considered necessary, it was then possible to investigate the 

 second requirement of noise free operation. Application of the chatter 

 theory to the drive-bar governor indicated the design to be unstable. 

 This situation was controlled by using the ends of the drive-bar to limit 

 the fall of the governor weights. This configuration of parts allows only 

 small movement of the weights during the unstable period and provides 

 damping as the weights close on the arms. The small motion and friction 

 damping in the assembly results in a governor which is relatively free 

 from noise during operation. Experience with dials ecjuipped with drive- 

 bar governors indicate that the chattering effect has been controlled. 



ACKNOWLEDGMENT 



The unpublished work of C. R. Moore covering the theory of fly-ball, 

 fly-bar and band type governors has served as a foundation for this 

 paper and the experimental work of R. E. Prescott aided considerably in 

 determining the final drive-bar governor design. The writer also wishes 

 to express appreciation to Mr. Prescott and H. F. Hopkins for their 

 helpful comments and suggestions during preparation of this paper. 



Appendix I 



DERIVATION OF THE DRIVE-BAR TYPE GOVERNOR SPEED EQUATION 



Referring to Fig. 4, as the governor mechanism rotates in a clockwise 

 direction each weight tends to move outward vuider the influence of 

 centrifugal force and the torque force, F. The centrifugal force, Fm , 



