A GOVERNOR FOR TELEPHONE DIALS 



1289 



respect, the speed attained with oil in the case shows a value of /x = 0.06 

 which is very close to the ^l = 0.05 taken as the lower limit. 



To produce a decrease in governor speed one must increase the \aliie 

 of /x. This is difficult to do on a controlled basis, since it is brought about 

 by the progressive action of wear particles and foreign material scoring 

 the surface of the brass case during the life of the go\'ernor. The the- 

 oretical analysis indicates that when the coefficient of friction increases 

 to ju = 0.35 the speed of the governor w^ill decrease from 10.00 to 9.65 

 pulses per second. This assumes that there would be no speed change 

 due to wear in any part of the governor. In practice of course the gover- 

 nor studs Avear as the case is scored and, therefore, are made progres- 

 sively shorter. For this condition the increased outward motion of the 

 weight required for stud-to-case contact produces an increase in the 

 spring force, Fs , acting on the weights. The speed change which results 

 from increasing the spring force is in the direction to compensate for the 

 loss in speed due to increase in coefficient of friction. Therefore, con- 

 sidering only stud friction and wear as effective in causing change in 

 speed, generally the governor and dial speed should increase from its 

 initially adjusted value during life. 



It can be concluded from the experimental and theoretical evidence 

 that there is the possibility of a speed change due to varying coefficient 



z 

 o 

 ,"r! 13 



D- 12 



0.10 0.15 0.20 0.25 030 03b 

 COEFFICIENT OF FRICTION, ju 



0.40 0.45 



Fig. 12 — • Dial speed versus coefficient of friction. 



